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  • 1.
    Andersson, Jens
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Claessen, D
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    De Roos, A. M.
    Stabilization of population fluctuations due to cannibalism promotes resource polymorphism in fish2007In: American Naturalist, Vol. 169, p. 820-829Article in journal (Refereed)
  • 2.
    Ask, Jenny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Per
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Terrestrial organic matter and light penetration: Effects on bacterial and primary production in lakes2009In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 54, no 6, p. 2034-2040Article in journal (Refereed)
    Abstract [en]

    We investigated productivity at the basal trophic level in 15 unproductive lakes in a gradient ranging from clear-water to brown-water (humic) lakes in northern Sweden. Primary production and bacterial production in benthic and pelagic habitats were measured to estimate the variation in energy mobilization from external energy sources (primary production plus bacterial production on allochthonous organic carbon) along the gradient. Clear-water lakes were dominated by autotrophic energy mobilization in the benthic habitat, whereas humic lakes were dominated by heterotrophic energy mobilization in the pelagic habitat. Whole-lake (benthic + pelagic) energy mobilization was negatively correlated to the light-extinction coefficient, which was determined by colored terrestrial organic matter in the lake water. Thus, variation in the concentration of terrestrial organic matter and its light-absorbing characteristics exerts strong control on the magnitude, as well as on the processes and pathways, of energy mobilization in unproductive lakes. We suggest that unproductive lakes in general are sensitive to input of terrestrial organic matter because of its effects on basal energy mobilization in both benthic and pelagic habitats.

  • 3.
    Ask, Jenny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Per
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Whole-lake estimates of carbon flux through algae and bacteria in benthic and pelagic habitats of clear-water lakes2009In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 90, no 7, p. 1923-1932Article in journal (Refereed)
    Abstract [en]

    This study quantified new biomass production of algae and bacteria in both benthic and pelagic habitats of clear-water lakes to contrast how carbon from the atmosphere and terrestrial sources regulates whole-lake metabolism. We studied four small unproductive lakes in subarctic northern Sweden during one summer season. The production of new biomass in both benthic and pelagic habitats was calculated as the sum of autotrophic production by algae and heterotrophic production by bacteria using allochthonous organic carbon (OC). Whole-lake production of new biomass was dominated by the benthic habitat (86% +/- 4% [mean +/- SD]) and by primary production (77% +/- 9%). Still, heterotrophic bacteria fueled by allochthonous OC constituted a significant portion of the new biomass production in both benthic (19% +/- 11%) and pelagic habitats (51% +/- 24%). In addition, overall net production (primary production minus respiration) was close to zero in the benthic habitats but highly negative (-163 +/- 81 mg C.m(-2).d(-1)) in pelagic regions of all lakes. We conclude (1) that allochthonous OC supported a significant part of total production of new biomass in both pelagic and benthic habitats, (2) that benthic habitats dominated the whole-lake production of new biomass, and (3) that respiration and net CO2 production dominated the carbon flux of the pelagic habitats and biomass production dominated the benthic carbon flux. Taken together, these findings suggest that previous investigations have greatly underestimated the productivity of clear-water lakes when benthic autotrophic production and metabolism of allochthonous OC have not been measured.

  • 4.
    Ask, Jenny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rowe, Owen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Brugel, Sonia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Strömgren, Mårten
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Importance of coastal primary production in the northern Baltic Sea2016In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 45, no 6, p. 635-648Article in journal (Refereed)
    Abstract [en]

    In this study, we measured depth-dependent benthic microalgal primary production in a Bothnian Bay estuary to estimate the benthic contribution to total primary production. In addition, we compiled data on benthic microalgal primary production in the entire Baltic Sea. In the estuary, the benthic habitat contributed 17 % to the total annual primary production, and when upscaling our data to the entire Bothnian Bay, the corresponding value was 31 %. This estimated benthic share (31 %) is three times higher compared to past estimates of 10 %. The main reason for this discrepancy is the lack of data regarding benthic primary production in the northern Baltic Sea, but also that past studies overestimated the importance of pelagic primary production by not correcting for system-specific bathymetric variation. Our study thus highlights the importance of benthic communities for the northern Baltic Sea ecosystem in general and for future management strategies and ecosystem studies in particular.

  • 5.
    Ask, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Competition mediated coexistence of invading intermediate consumer, ninespine stickleback, and a resident omnivorous top predator, Arctic charManuscript (preprint) (Other academic)
    Abstract [en]

    Climate change results in changes in the geographical distribution of species. Species invasion success into a new area is dependent both on the dispersal ability of species as well as the strength and identity of biotic interactions between resident and invading species. Coexistence in intraguild predation (IGP) systems depends on the relative strength of predation and competition interactions which in turn are temperature dependent. We investigated the effects of introducing an intermediate consumer, ninespine stickleback (Pungitius pungitius), into allopatric populations of the omnivorous top predator Arctic char (Salvelinus alpinus). Introductions were performed in lakes with different climate regimes, two tundra lakes and two forest lakes that differed in average summer temperatures with 1.4 ± 0.5 ºC (average ± 1SD). We found that sticklebacks were able to invade and increase in density in both tundra and forest lakes. Sticklebacks had strong negative effects on resource densities which also was reflected in a decreased growth of small char. Increasing stickleback density had a positive effect on growth of large adults and on the maximum size of char. We conclude that stickleback presence is not limited by biological interactions in these systems but rather by dispersion ability. We suggest that the size dependency in the response of char to the invasion of sticklebacks is fundamental for the successful invasion of sticklebacks, and that size dependent interactions including cannibalism play important roles for coexistence in natural IGP-systems.

  • 6.
    Ask, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Temperature mediated effects on top consumer populations in subarctic lakesManuscript (preprint) (Other academic)
    Abstract [en]

    The effects of temperature on top consumer populations in subarctic lake communities were studied by contrasting two lake pairs in different climate regimes: one pair on the low alpine tundra and one pair in the subalpine birch forest. We measured zooplankton and macroinvertebrate biomasses over the season and estimated population density and size structure of the top consumer Arctic char (Salvelinus alpinus). Furthermore, we modelled char growth using literature data on temperature dependent search rate, handling time and metabolic demands. The forest lakes were warmer than the tundra lakes. Char in the forest lakes were larger and had a higher individual growth compared to char in the tundra lakes, while population density and biomasses of char were not different between the forest and the tundra lakes. There were no differences in macroinvertebrate and zooplankton resource levels available for char between lake pairs. Our modeling of char growth revealed that higher temperature increased growth of char at the observed resource densities, suggesting that the higher temperature in the forest lakes was primarily the cause of the higher growth of char in these lakes. We suggest that cannibalism in char may regulate char recruitment and thereby population density and biomass of char leading to effects of increasing temperature on consumer biomass and consumer individual growth different from what is expected in pure consumer-resource systems. Our results emphasize the importance of feedbacks within ecosystems when addressing effects of climate change and increasing temperature on lake communities.

  • 7.
    Byström, P
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Andersson, J
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Size-dependent foraging capacities and intercohort competition in an ontogenetic omnivore (Arctic char)2005In: Oikos, Vol. 110, p. 523-536Article in journal (Refereed)
  • 8.
    Byström, P
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Andersson, J
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Persson, L
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    De Roos, A M
    Size-dependent resource limitation and foraging-predation risk trade-offs: growth and habitat use in young arctic char2004In: Oikos, Vol. 104, p. 109-121Article in journal (Refereed)
  • 9.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Recruitment pulses induce cannibalistic giants in Arctic char.2006In: J Anim Ecol, ISSN 0021-8790, Vol. 75, no 2, p. 434-44Article in journal (Refereed)
  • 10.
    Byström, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Andersson, J
    Kiessling, A
    Eriksson, L O
    Size and temperature dependent foraging capacities and metabolism: consequences for winter starvation mortality in fish2006In: Oikos, Vol. 115, p. 43-52Article in journal (Refereed)
  • 11.
    Byström, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Per
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Jens
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Preference for cannibalism and ontogenetic constraints in competitive ability of piscivorous top predators2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 7, p. e70404-Article in journal (Refereed)
    Abstract [en]

    We experimentally show that the piscivorous top predator Arctic char (Salvelinus alpinus) have higher attack rates on cannibal prey compared to the interspecific prey species ninespine stickleback (Pungitius pungitius), and that sticklebacks are more efficient competitiors for zooplankton resources compared to juvenile char. We also conducted a literature survey that together with our experiments showed that piscivorous top consumers selected cannibal prey over interspecific prey in 9 out of 10 cases. Our literature survey also showed that specialist prey species are competitively superior compared to juvenile piscivorous species within the zooplankton niche. We discuss our results in relation to omnivory in fish communities and we suggest that the observed general preference for cannibal prey over interspecific prey in piscivores and the competitive advantage of prey species over juvenile piscivores may be major mechanisms for coexistence in fish communities.

  • 12.
    Byström, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bergström, Ulf
    Hjälten, Alexander
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ståhl, Sofie
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jonsson, David
    Olsson, Jens
    Declining coastal piscivore populations in the Baltic Sea: where and when do sticklebacks matter?2015In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, no Suppl 3, p. S462-S471Article in journal (Refereed)
    Abstract [en]

    Intraguild predation interactions make fish communities prone to exhibit alternative stable states with either piscivore or prey fish dominance. In the Baltic Sea, local declines of coastal piscivores like perch (Perca fluviatilis) have been observed to coincide with high densities of sticklebacks (Gasterosteus aculeatus). Mechanisms behind this shift between piscivore and stickleback dominance were studied both experimentally and in field. Results showed that predation by sticklebacks has a strong negative effect on perch larvae survival, but this effect rapidly decreases with increasing perch size, likely due to gape limitations and digestion constraints in sticklebacks. Large spatial and temporal variations in patterns of stickleback migration into perch spawning sites were observed. Whether or not high density of sticklebacks will cause declines in coastal piscivore populations is suggested to depend on the availability of spawning sites in which sticklebacks do not migrate into or arrive late in the reproduction season of coastal piscivores.

  • 13.
    Byström, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hedström, Per
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hotchkiss, Erin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rodríguez, Patricia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Austral Centre for Scientific Research (CADIC-CONICET), 9410 Ushuaia, Tierra del Fuego, Argentina.
    Vasconcelos, Rivera Francisco
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Warming decrease fish population densities and biomassManuscript (preprint) (Other academic)
    Abstract [en]

    Temperature impact all biota and ecosystems through its direct effect on the vital rates of primary producers and consumers. Still, how these changes in rates translates through ecosystem feed backs to the population level of top consumers are poorly understood. Here, we studied effects of temperature increase (+ 3 ̊C during ice free season) on fish population dynamics in a replicated large scale pond ecosystem experiment over 3 years. Increased temperature had no significant effect on whole ecosystem gross primary production while top down effects of warming on intermediate consumers changed from negative to positive due to negative effects of warming on fish population abundance. Total fish density and biomass and abundance of both mature and old fish decreased with warming, while proportion of young fish increased, with warming. The effects of warming on fish population demographics were likely due to that temperature increased cohort competition and fish energy requirements relative to resource production. Our results suggest that global warming may increase competition, favor young individuals and overall decrease fish population densities and biomass. 

  • 14.
    Byström, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Huss, Magnus
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ontogenetic constraints and diet shifts in Perch (Perca fluviatilis): mechanisms and consequences for intra-cohort cannibalism2012In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 57, no 4, p. 847-857Article in journal (Refereed)
    Abstract [en]

    1. In many populations, sufficient size variation to allow for cannibalism may develop not only among age cohorts but also within them. Here, we used data on resource dynamics, consumer body size distribution and gape size limitation to unravel mechanisms promoting cannibalism within cohorts of young-of-the-year (YOY) perch (Perca fluviatilis). 2. Perch are strongly gape limited when feeding on large zooplankton during early ontogeny. As a consequence, only initially large fish were able to shift to feeding on abundant large invertebrates, necessary to sustain fast growth. 3. We suggest that a combination of high initial size variation and exclusive access to resources for individuals with an initial size advantage is a prerequisite for the development of a size distribution sufficient for intra-cohort cannibalism to occur. 4. During the time when cannibalism was observed, growth of the largest individuals in YOY perch cohorts was faster than that of smaller individuals. However, the energy gain from cannibalism did not increase growth rate enough to reach a size necessary to feed on more abundant size classes of victims, and therefore, the effect of cannibalism on overall cohort density was minor. 5. In addition to a high energy gain from cannibalism allowing for fast growth, strong resource limitation and slow growth rates of small individuals (i.e. potential victims) are a prerequisite not only for the development of intra-cohort cannibalism but also for its persistence.

  • 15.
    Byström, Pär
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Per
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Van Kooten, Tobias
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Olofsson, Frans
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Substitution of top predators: effects of pike invasion in a subarctic lake2007In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 52, no 7, p. 1271–1280-Article in journal (Refereed)
    Abstract [en]

    1. Invasions of top predators may have strong cascading effects in ecosystems affecting both prey species abundance and lower trophic levels. A recently discussed factor that may enhance species invasion is climate change and in this context, we studied the effects of an invasion of northern pike into a subarctic lake ecosystem formerly inhabited by the native top predator Arctic char and its prey fish, ninespined stickleback.

    2. Our study demonstrated a strong change in fish community composition from a system with Arctic char as top predator and high densities of sticklebacks to a system with northern pike as top predator and very low densities of sticklebacks. A combination of both predation and competition from pike is the likely cause of the extinction of char.

    3. The change in top predator species also cascaded down to primary consumers as both zooplankton and predator-sensitive macroinvertebrates increased in abundance.

    4. Although the pike invasion coincided with increasing summer temperatures in the study area we have no conclusive evidence that the temperature increase is the causal mechanism behind the pike invasion. But still, our study provides possible effects of future pike invasions in mountain lakes related to climate change. We suggest that future pike invasions will have strong effects in lake ecosystems, both by replacing native top consumers and through cascading effects on lower trophic levels.

  • 16. Calboli, Federico C. F.
    et al.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Merila, Juha
    A test for within-lake niche differentiation in the nine-spined sticklebacks (Pungitius pungitius)2016In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 6, no 14, p. 4753-4760Article in journal (Refereed)
    Abstract [en]

    Specialization for the use of different resources can lead to ecological speciation. Accordingly, there are numerous examples of ecologically specialized pairs of fish species in postglacial lakes. Using a polymorphic panel of single nucleotide variants, we tested for genetic footprints of within-lake population stratification in nine-spined sticklebacks (Pungitius pungitius) collected from three habitats (viz. littoral, benthic, and pelagic) within a northern Swedish lake. Analyses of admixture, population structure, and relatedness all supported the conclusion that the fish from this lake form a single interbreeding unit.

  • 17.
    Degerman, Rickard
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Lefébure, Robert
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Båmstedt, Ulf
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Larsson, Stefan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF). Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Food web interactions determine energy transfer efficiency and top consumer responses to inputs of dissolved organic carbon2018In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 805, no 1, p. 131-146Article in journal (Refereed)
    Abstract [en]

    Climate change projections indicate increased precipitation in northern Europe, leading to increased inflow of allochthonous organic matter to aquatic systems. The food web responses are poorly known, and may differ depending on the trophic structure. We performed an experimental mesocosm study where effects of labile dissolved organic carbon (DOC) on two different pelagic food webs were investigated, one having zooplankton as highest trophic level and the other with planktivorous fish as top consumer. In both food webs, DOC caused higher bacterial production and lower food web efficiency, i.e., energy transfer efficiency from the base to the top of the food web. However, the top-level response to DOC addition differed in the zooplankton and the fish systems. The zooplankton production increased due to efficient channeling of energy via both the bacteria land the phytoplankton pathway, while the fish production decreased due to channeling of energy mainly via the longer and less efficient bacterial pathway. We conclude that the added DOC either acted as a subsidy by increasing the production of the top trophic level (mesozooplankton), or as a sink causing decreased top consumer production (planktivorous fish).

  • 18.
    Diehl, Sebastian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Thomsson, Gustaf
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Wickman, Jonas
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Vasconcelos, Francisco R.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Uszko, Wojciech
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Resource and consumer control of cross-habitat trophic interactions in shallow lakesManuscript (preprint) (Other academic)
  • 19.
    Hamdan, Mohammed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hotchkiss, Erin R.
    Al-Haidarey, Mohammed J.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Carbon dioxide stimulates lake primary production2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 10878Article in journal (Refereed)
    Abstract [en]

    Gross primary production (GPP) is a fundamental ecosystem process that sequesters carbon dioxide (CO2) and forms the resource base for higher trophic levels. Still, the relative contribution of different controls on GPP at the whole-ecosystem scale is far from resolved. Here we show, by manipulating CO2 concentrations in large-scale experimental pond ecosystems, that CO2 availability is a key driver of whole-ecosystem GPP. This result suggests we need to reformulate past conceptual models describing controls of lake ecosystem productivity and include our findings when developing models used to predict future lake ecosystem responses to environmental change.

  • 20.
    Hedström, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bystedt, David
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bokma, Folmer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Brownification increases winter mortality in fish2017In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 183, no 2, p. 587-595Article in journal (Refereed)
    Abstract [en]

    In northernclimateswinter is a bottleneck for many organisms. Low light and resource availability constrain individual foraging rates,potentially leading tostarvation and increasedmortality.Increasinginput of humic substances to aquatic ecosystems causesbrownification of water and hence a further decreaseof light availability,which may lead tofurther decreased foraging ratesand starvation mortality during winter.To test this hypothesis, we measured the effectsof experimentally increased humicwaterinput on consumption and survival of young-of-the-year (YOY) three-spined stickleback (Gasterosteus aculeatus) over winterin largeoutdoor enclosures. Population densitieswereestimated in autumn andthefollowing springand food availabilityand consumptionwere monitoredoverwinter. As hypothesized,mortality washigher underhumic(76%)as compared to ambientconditions (64%).Also, body condition and ingested prey biomass werelower under humic conditionseven thoughresource availability wasnotlower under humic conditions. Light conditions were significantly poorer under humic conditions. This suggeststhat increased mortality and decreased body condition and ingested prey biomasswasnot due to decreased resource availability but due todecreasedsearch efficiencyin this visual feeding consumer. Increased future brownification of aquatic systems may therefore negatively affect both recruitment and densities of fish.

  • 21.
    Hedström, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rodríguez, Patricia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Austral Centre for Scientific Research (CADIC-CONICET), 9410 Ushuaia, Tierra del Fuego, Argentina.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vasconcelos, Rivera Francisco
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Population and size dependent responses in fish production to climate changeManuscript (preprint) (Other academic)
    Abstract [en]

    Climate change is predicted to increase water temperatures and export of terrestrial dissolved matter (TDOM) to aquatic ecosystems with concomitant effects on ecosystem productivity and production of consumers at the top of the food web. Here we study how increased level of TDOM and temperature alone or in combination affect benthic and pelagic primary production and biomass production of fish in replicated large scale outdoor pond experiment. We increased temperature (+3 ̊C) and TDOM concentrations (×2.5) using natural high TDOM water from a small creek and used naturally reproducing three-spine sticklebacks (Gasterosteus aculeatus) populations as model fish species. Gross primary production (GPP) was similar to ambient control conditions in all treatments although increased TDOM concentrations deceased benthic but stimulated pelagic GPP, presumably as a result of decreased light availability and increased nutrient availability, respectively. The production of young-of-the-year (YOY), older, and total fish population were negatively affected by warming, whereas increased TDOM caused decreased YOY and total fish production. Effect of temperature on fish production were likely a result of increased metabolic cost in relation to resource production and intake rates whereas the negative effect of TDOM on fish production was likely a result of decreasing benthic resource production. However, the combined effect on fish production of warming and TDOM was only intermediate compared to individual treatments. Our study suggest climate change will lead to decreased fish production and that the effect may be most pronounced in clear systems dominated by benthic GPP . 

  • 22.
    Hedström, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rodríguez, Patricia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Austral Centre for Scientific Research (CADIC-CONICET), 9410 Ushuaia, Tierra del Fuego, Argentina.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vasconcelos, Rivera Francisco
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Warming but not increased terrestrial doc has negative effects on fish recruitmentManuscript (preprint) (Other academic)
    Abstract [en]

    Water temperature and export of terrestrial dissolved organic carbon (DOC) to recipient aquatic ecosystems have strong impacts on ecosystem productivity. Increased DOC concentration causing brownification of water is argued to reduce fish production by decreasing light availability for autotrophic production. On the other hand, higher temperatures have been shown to correlate positively with fish recruitment. This increase has been related to increased growth rates and survival of young-of-the-year (YOY) fish with warming. However, whether or not increased temperature results in higher growth depends on resource availability, suggesting a relationship between individual gain and recruitment mediated via the interplay between resource production and temperature. In a replicated, large scale experimental pond ecosystem, we tested the effects of increased temperature (+3oC) and terrestrial DOC concentrations (+4 mg/l) on recruitment (size, density and biomass) of three-spined sticklebacks over one growth season. Gross primary production (GPP) was similar between treatments, whereas zooplankton and benthic invertebrate biomass were negatively affected by increased temperature and if any higher at increased DOC levels. Increased temperature had no effect on individual size but negative effects on body condition and recruitment of YOY sticklebacks, while increased DOC concentration had no effect on recruitment. No positive effect of temperature increase on GPP and decreased resource levels in combination with higher metabolic costs, are suggested to increase starvation mortality and to be the main mechanism behind observed negative effects of warming on recruitment. Based on our results, we suggest that climate change may, counter intuitively, have negative effects on fish recruitment due to decreased carrying capacity of nursery habitats as a consequence of increased energy requirements in juvenile fish in relation to the net effects on resource production and ecosystem productivity. 

  • 23.
    Huss, Magnus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Effects of ontogenetic scaling on resource exploitation and cohort size distributions2010In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 119, no 2, p. 384-392Article in journal (Refereed)
    Abstract [en]

    Variation in growth rates among individuals leading to the formation of broad size distributions is commonly observed in animal cohorts. Here we use laboratory derived size-scaling relationships to identify mechanisms driving changes in size distribution patterns within cohorts during early ontogeny. We introduced young-of-the-year perch (Perca fluviatilis) cohorts with different variation in body size distributions in pond enclosures. We kept the exploitative competitive environment constant by adjusting the number of introduced fish such that metabolic requirements were constant between different treatments. Based on modelling results we theoretically derived relative growth rates of differently sized fish when only taken exploitative competitive interactions into account. In agreement with predictions we found that initial variation in body size was negatively correlated with subsequent changes in body size variation in the pond experiment. Corresponding results were obtained in a field study covering 13 studied young-of-the-year perch cohorts in a small lake. Besides having a lower maximum growth capacity, initially large fish also suffered more from resource limitation in our experiment. The results suggest that exploitation competition is a major factor behind growth patterns in young fish cohorts, generally leading to size convergence. To explain the commonly observed pattern of size divergence in animal cohorts, including fish, we suggest that differential timing of diet shifts or mechanisms not related to exploitative interactions must be taken into account. For diet shifts to lead to size divergence we suggest that individuals with an initial size advantage need access to an exclusive prey which has a high growth potential. This, in turn, allows initially larger individuals to surf on a wave of growing prey while individuals only capable to feed on a depressed initial resource experience low growth rates.

  • 24.
    Huss, Magnus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Growing through predation windows:: effects on body size development in young fish2010In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 119, p. 1796-1804Article in journal (Refereed)
    Abstract [en]

    Th e degree to which growth in early life stages of animals is regulated via density-dependent feedbacks through preyresources is much debated. Here we have studied the infl uence of size- and density-dependent mechanisms as well as sizeselectivepredation pressure by cannibalistic perch Perca fl uviatilis on growth patterns of young-of-the-year (YOY) perchcovering several lakes and years. We found no infl uence of initial size or temperature on early body size development ofperch. In contrast, there was a negative relationship between reproductive output and the length of YOY perch at fi ve weeksof age. However, rather than an eff ect of density-dependent growth mediated via depressed resources the relationship wasdriven by positive size-selective cannibalism removing large individuals. Hence, given a positive correlation between thedensity of victims and predation pressure by cannibals, size-dependent interactions between cannibals and their victimsmay wrongly be interpreted as patterns of density-dependent growth in the victim cohort. Overall, our results support theview that density-dependent resource-limitation in early life stages is rare. Still, patterns of density-dependent growth mayemerge, but from variation in size-selective predation pressure rather than density as such. Th is illustrates the importanceof taking overall population demography and predatory interactions into account when studying growth patterns amongrecruiting individuals.

  • 25.
    Huss, Magnus
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Resource heterogeneity, diet shifts and intra-cohort competition: effects on size divergence in YOY fish2008In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 158, no 2, p. 249-257Article in journal (Refereed)
    Abstract [en]

    Most organisms exhibit a substantial size variation among individuals due to individual differences in experienced biotic and abiotic environmental conditions and because individuals undergo growth and development during most of their life time. One important issue in this context is how size variation within cohorts may develop over time. Here we tested the hypothesis, in gape-limited animals such as fish, that size divergence among individuals within a cohort depends on the opportunity to undergo size-dependent diet shifts, by allowing initially larger individuals to make an early diet shift when the first resource becomes limiting. We used young-of-the-year perch (Perca fluviatilis) as our study organism. Competitive intensity and the opportunity to undergo a diet shift from zooplankton to macroinvertebrates affected both mean growth rates and the extent to which inter-individual variation in growth was manifested. As predicted, increased competition combined with the presence of both zooplankton and benthic macroinvertebrates increased the degree of size variation. However, size divergence was also observed among individuals when only the initial resource, zooplankton, was available. We argue that only non-exploitative interactions, such as dominance structures and social interactions could have caused this latter pattern, as exploitative competition is expected to lead to size convergence due to the superior competitive ability of smaller individuals. Our results suggest that diet shifts are not a prerequisite for size divergence in animal cohorts and that dominance and social interactions may have similar effects on size variation within cohorts. Finally, development of size variation is suggested to have strong implications for overall cohort performance.

  • 26.
    Huss, Magnus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Strand, Åsa
    Eriksson, Lars-Ove
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Influence of growth history on the accumulation of energy reserves and winter mortality on young fish2008In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 65, no 10, p. 2149-2156Article in journal (Refereed)
    Abstract [en]

    In seasonal environments accumulated energy reserves are important to avoid starvation mortality during periods of low resource levels. Here we investigated patterns of energy accumulation and the importance of growth history for winter survival in young-of-the-year Eurasian perch (Perca fluviatilis). Under simulated winter conditions in aquaria’s we showed that high winter mortality most likely relate to the depletion of energy reserves in small perch. Correspondingly in a field study, using 4 lakes covering 3-6 lake years each, overwinter survival within cohorts was positively related to individual size. However, average size in autumn did not explain the variation in overwinter survival between cohorts. Instead we showed that seasonal growth history is an important factor. High growth rates late in season may increase cohort survival over winter irrespective of average size, related to a positive growth dependent increase in allocation to energy reserves when approaching winter. Mechanisms regulating within-season temporal dynamics of growth rates are therefore suggested to be important for overall cohort performance.

  • 27.
    Huss, Magnus
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    The origin and development of individual size variation in early pelagic stages of fish2007In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 153, no 1, p. 57-67Article in journal (Refereed)
    Abstract [en]

    Size variation among individuals born at the same time in a common environment (within cohorts) is a common phenomenon in natural populations. Still, the mechanisms behind the development of such variation and its consequences for population processes are far from clear. We experimentally investigated the development of early within-cohort size variation in larval perch (Perca fluviatilis). Specifically we tested the influence of initial variation, resulting from variation in egg strand size, and intraspecific density for the development of size variation. Variation in egg strand size translated into variation in initial larval size and time of hatching, which, in turn, had effects on growth and development. Perch from the smallest egg strands performed on average equally well independent of density, whereas larvae originating from larger egg strands performed less well under high densities. We related this difference in density dependence to size asymmetries in competitive abilities leading to higher growth rates of groups consisting of initially small individuals under high resource limitation. In contrast, within a single group of larvae, smaller individuals grew substantially slower under high densities whereas large individuals performed equally well independent of density. As a result, size variation among individuals within groups (i.e. originating from the same clutch) increased under high densities. This result may be explained by social interactions or differential timing of diet shifts and a depressed resource base for the initially smaller individuals. It is concluded that to fully appreciate the effects of density-dependent processes on individual size variation and size-dependent growth, consumer feedbacks on resources need to be considered.

  • 28.
    Jonsson, Micael
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hedström, Per
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Stenroth, Karolina
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hotchkiss, Erin R
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vasconcelos, Francisco Rivera
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Climate change modifies the size structure of assemblages of emerging aquatic insects2015In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 60, no 1, p. 78-88Article in journal (Refereed)
    Abstract [en]

    Climate change is expected to not only raise water temperatures, but also to cause brownification of aquatic ecosystems via increased inputs of terrestrial dissolved organic matter. While efforts have been made to understand how increased temperature and brownification separately influence aquatic food webs, their interactive effects have been less investigated. Further, although climate change effects on aquatic ecosystems likely will propagate to terrestrial consumers via changes in aquatic insect emergence, this has rarely been studied. We investigated the effect of climate change on aquatic insect emergence, in a large-scale outdoor pond facility where 16 sections - each containing natural food webs including a fish top-consumer population - were subjected to warming (3 degrees C above ambient temperatures) and/or brownification (by adding naturally humic stream water). Aquatic insect emergence was measured biweekly over 18weeks. We found no effect of warming or brownification on total emergent insect dry mass. However, warming significantly reduced the number of emergent Chironomidae, while numbers of larger taxa, Trichoptera and Ephemeroptera, remained unchanged. On average, 57% and 58% fewer Chironomidae emerged from the warmed clear and humic pond sections, respectively. This substantial decrease in emergent Chironomidae resulted in a changed community structure and on average larger individuals emerging from warm sections as well as from humic sections under ambient conditions. There was also a weak influence of fish biomass on the size structure of emergent aquatic insects, with a positive relationship between individual insect size and total fish biomass, but effects of fish were clearly subordinate to those of warming. Climate change impacts on aquatic systems can have widespread consequences also for terrestrial systems, as aquatic insects are ubiquitous and their emergence represents an important resource flow from aquatic to terrestrial environments. While we found that neither warming nor brownification quantitatively changed total aquatic insect emergence biomass, the warming-induced decrease in number of emergent Chironomidae and the subsequent increase in average body size will likely impact terrestrial consumers relying on emergent aquatic insect as prey.

  • 29.
    Karlsson, J
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Byström, P
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Littoral energy mobilization dominates energy supply for top consumers in subarctic lakes2005In: Limnol. Oceanogr., Vol. 50, p. 538-543Article in journal (Refereed)
  • 30.
    Karlsson, Jan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Berggren, M.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jonsson, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Laudon, H.
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Response to Comment: Terrestrial support of pelagic consumers in unproductive lakes- Uncertainty and potential in assessments using stable isotopes2014In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 59, no 5, p. 1800-1803Article in journal (Refereed)
  • 31.
    Karlsson, Jan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Berggren, Martin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jonsson, Anders
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Laudon, Hjalmar
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Terrestrial organic matter support of lake food webs: Evidence from lake metabolism and stable hydrogen isotopes of consumers2012In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 57, no 4, p. 1042-1048Article in journal (Refereed)
    Abstract [en]

    We quantified the utilization of terrestrial organic matter (OM) in the food web of a humic lake by analyzing the metabolism and the consumers' stable isotopic (C, H, N) composition in benthic and pelagic habitats. Terrestrial OM inputs (3 g C m(-2) d(-1)) to the lake greatly exceeded autochthonous OM production (3 mg C m(-2) d(-1)) in the lake. Heterotrophic bacterial growth (19 mg C m(-2) d(-1)) and community respiration (115 mg C m(-2) d(-1)) were high relative to algal photosynthesis and were predominantly (> 85%) supported by terrestrial OM in both habitats. Consequently, terrestrial OM fueled most (85%) of the total production at the base of the lake's food web (i.e., the sum of primary and bacterial production). Despite the uncertainties of quantitatively estimating resource use based on stable isotopes, terrestrial OM clearly also supported around half the zooplankton (47%), macrozoobenthos (63%), and fish (57%) biomass. These results indicate that, although rates of terrestrial OM inputs were around three orders of magnitude greater than that of autochthonous OM production, the use of the two resources by higher trophic levels was roughly equal. The disproportionally low reliance on terrestrial OM at higher trophic levels, compared with its high rates of input and high support of basic biomass production in the lake, suggests that autochthonous resources could not be completely replaced by terrestrial resources and indicates an upper limit to terrestrial support of lake food webs.

  • 32.
    Karlsson, Jan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bergström, Ann-Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gudasz, Cristian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rodriguez, Patricia
    Hein, Catherine
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Terrestrial organic matter input suppresses biomass production in lake ecosystems2015In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 96, no 11, p. 2870-2876Article in journal (Refereed)
    Abstract [en]

    Terrestrial ecosystems export large amounts of organic carbon (t-OC) but the net effect of this OC on the productivity of recipient aquatic ecosystems is largely unknown. In this study of boreal lakes, we show that the relative contribution of t-OC to individual top consumer (fish) biomass production, and to most of their potential prey organisms, increased with the concentration of dissolved organic carbon (DOC; dominated by t-OC sources) in water. However, the biomass and production of top consumers decreased with increasing concentration of DOC, despite their substantial use (up to 60%) of t-OC. Thus, the results suggest that although t-OC supports individual consumer growth in lakes to a large extent, t-OC input suppresses rather than subsidizes population biomass production.

  • 33.
    Karlsson, Jan
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Ask, Jenny
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Ask, Per
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Jansson, Mats
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Light limitation of nutrient-poor lake ecosystems2009In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 460, p. 506-509Article in journal (Refereed)
    Abstract [en]

    Productivity denotes the rate of biomass synthesis in ecosystems and is a fundamental characteristic that frames ecosystem function and management. Limitation of productivity by nutrient availability is an established paradigm for lake ecosystems1, 2, 3. Here, we assess the relevance of this paradigm for a majority of the world's small, nutrient-poor lakes, with different concentrations of coloured organic matter4, 5. By comparing small unproductive lakes along a water colour gradient, we show that coloured terrestrial organic matter controls the key process for new biomass synthesis (the benthic primary production) through its effects on light attenuation. We also show that this translates into effects on production and biomass of higher trophic levels (benthic invertebrates and fish). These results are inconsistent with the idea that nutrient supply primarily controls lake productivity, and we propose that a large share of the world's unproductive lakes, within natural variations of organic carbon and nutrient input, are limited by light and not by nutrients. We anticipate that our result will have implications for understanding lake ecosystem function and responses to environmental change. Catchment export of coloured organic matter is sensitive to short-term natural variability and long-term, large-scale changes, driven by climate and different anthropogenic influences6, 7. Consequently, changes in terrestrial carbon cycling will have pronounced effects on most lake ecosystems by mediating changes in light climate and productivity of lakes.

  • 34.
    Lagesson, Annelie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Brodin, Tomas
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Fahlman, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Fick, Jerker
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jonsson, Micael
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, J.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    No evidence of increased growth or mortality in fish exposed to oxazepam in semi-natural ecosystems2018In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 615, p. 608-614Article in journal (Refereed)
    Abstract [en]

    An increasing number of short-term laboratory studies on fish reports behavioral effects from exposure to aquatic contaminants or raised carbon dioxide levels affecting the GABAAreceptor. However, how such GABAergic behavioral modifications (GBMs) impact populations in more complex natural systems is not known. In this study, we induced GBMs in European perch (Perca fluviatilis) via exposure to a GABA agonist (oxazepam) and followed the effects on growth and survival over one summer (70 days) in replicated pond ecosystems. We hypothesized that anticipated GBMs, expressed as anti-anxiety like behaviors (higher activity and boldness levels), that increase feeding rates in laboratory assays, would; i) increase growth and ii) increase mortality from predation. To test our hypotheses, 480 PIT tagged perch of known individual weights, and 12 predators (northern pike, Esox lucius) were evenly distributed in 12 ponds; six control (no oxazepam) and six spiked (15.5 ± 4 μg l− 1 oxazepam [mean ± 1 S.E.]) ponds. Contrary to our hypotheses, even though perch grew on average 16% more when exposed to oxazepam, we found no significant difference between exposed and control fish in growth (exposed: 3.9 ± 1.2 g, control: 2.9 ± 1 g [mean ± 1 S.E.], respectively) or mortality (exposed: 26.5 ± 1.8 individuals pond− 1, control: 24.5 ± 2.6 individuals pond− 1, respectively). In addition, we show that reduced prey capture efficiency in exposed pike may explain the lack of significant differences in predation. Hence, our results suggest that GBMs, which in laboratory studies impact fish behavior, and subsequently also feeding rates, do not seem to generate strong effects on growth and predation-risk in more complex and resource limited natural environments.

  • 35.
    Lagesson, Annelie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Fahlman, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Brodin, Tomas
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Fick, Jerker
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jonsson, Micael
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Klaminder, Jonatan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bioaccumulation of five pharmaceuticals at multiple trophic levels in an aquatic food web: Insights from a field experiment2016In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 568, p. 208-215Article in journal (Refereed)
    Abstract [en]

    Pharmaceuticals derived from manufacturing and human consumption contaminate surface waters worldwide. To what extent such pharmaceutical contamination accumulates and disperses over time in different compartments of aquatic food webs is not well known. In this study we assess to what extent five pharmaceuticals (diphenhydramine, oxazepam, trimethoprim, diclofenac, and hydroxyzine) are taken up by fish (European perch) and four aquatic invertebrate taxa (damselfly larvae, mayfly larvae, waterlouse, and ramshorn snail), by tracing their bioconcentrations over several months in a semi-natural large-scale (pond) system. The results suggest both significant differences among drugs in their capacity to bioaccumulate and differences among species in uptake. While no support for in situ uptake of diclofenac and trimethoprim was found, oxazepam, diphenhydramine, and hydroxyzine were detected in all analyzed species. Here, the highest bioaccumulation factor (tissue:water ratio) was found for hydroxyzine. In the food web, the highest concentrations were found in the benthic species ramshorn snail and waterlouse, indicating that bottom-living organism at lower trophic positions are the prime receivers of the pharmaceuticals. In general, concentrations in the biota decreased over time in response to decreasing water concentrations. However, two interesting exceptions to this trend were noted. First, mayfly larvae (primarily grazers) showed peak concentrations (a fourfold increase) of oxazepam, diphenhydramine, and hydroxyzine about 30 days after initial addition of pharmaceuticals. Second, perch (top-predator) showed an increase in concentrations of oxazepam throughout the study period. Our results show that drugs can remain bioavailable for aquatic organism for long time periods (weeks to months) and even re-enter the food web at a later time. As such, for an understanding of accumulation and dispersion of pharmaceuticals in aquatic food webs, detailed ecological knowledge is required.

  • 36. Larsson, Stefan
    et al.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Berglund, Johnny
    Carlsson, Ulf
    Veneranta, Lari
    Larsson, Sylvia H.
    Hudd, Richard
    Characteristics of anadromous whitefish (Coregonus lavaretus (L.)) rivers in the Gulf of Bothnia2013In: BIOLOGY AND MANAGEMENT OF COREGONID FISHES - 2011, 2013, p. 189-201Conference paper (Refereed)
    Abstract [en]

    In order to study anadromous whitefish spawning river requirements, we sampled 41 rivers in the Gulf of Bothnia for newly hatched whitefish larvae for one to three consecutive years. Chemical and morphological data (e.g. flow rate, topography, pH, estuary fetch and distance to coastal sandy areas) were collected for each river. Newly-hatched whitefish were caught in 19 rivers whereas whitefish were not confirmed present in 22 rivers. By applying partial least squares discriminant analysis (PLS-DA), data for rivers confirmed to support whitefish were contrasted with data for rivers in which whitefish were not found. The single most important factor was annual average water flow rate. Whitefish larvae were observed in 93% of the rivers with annual mean flow rate > 5 m(3) s(-1) (N = 14). In contrast, newly-hatched whitefish were only found in 22% of the smaller rivers (N = 27).

  • 37.
    Lefebure, Robert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Degerman, Rickard
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Larsson, Stefan
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Eriksson, Lars-Ove
    Department of Wildlife, Fish and Environmental Studies, SLU, Umeå, Sweden.
    Båmstedt, Ulf
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Impacts of elevated terrestrial nutrient loads and temperature on pelagic food-web efficiency and fish production2013In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 19, no 5, p. 1358-1372Article in journal (Other academic)
    Abstract [en]

    Both temperature and terrestrial organic matter have strong impacts on aquatic food-web dynamics and production. Temperature affects vital rates of all organisms, and terrestrial organic matter can act both as an energy source for lower trophic levels, while simultaneously reducing light availability for autotrophic production. As climate change predictions for the Baltic Sea and elsewhere suggest increases in both terrestrial matter runoff and increases in temperature, we studied the effects on pelagic food-web dynamics and food-web efficiency in a plausible future scenario with respect to these abiotic variables in a large-scale mesocosm experiment. Total basal (phytoplankton plus bacterial) production was slightly reduced when only increasing temperatures, but was otherwise similar across all other treatments. Separate increases in nutrient loads and temperature decreased the ratio of autotrophic:heterotrophic production, but the combined treatment of elevated temperature and terrestrial nutrient loads increased both fish production and food-web efficiency. CDOM: Chl a ratios strongly indicated that terrestrial and not autotrophic carbon was the main energy source in these food webs and our results also showed that zooplankton biomass was positively correlated with increased bacterial production. Concomitantly, biomass of the dominant calanoid copepod Acartia sp. increased as an effect of increased temperature. As the combined effects of increased temperature and terrestrial organic nutrient loads were required to increase zooplankton abundance and fish production, conclusions about effects of climate change on food-web dynamics and fish production must be based on realistic combinations of several abiotic factors. Moreover, our results question established notions on the net inefficiency of heterotrophic carbon transfer to the top of the food web.

  • 38.
    Lefébure, Robert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Larsson, S
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    A temperature-dependent growth model for the three-spined stickleback Gasterosteus aculeatus2011In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 79, no 7, p. 1815-1827Article in journal (Refereed)
    Abstract [en]

    Specific growth rates of individually reared juvenile three-spined sticklebacks Gasterosteus aculeatus were investigated under laboratory conditions to parameterize a complete temperature-dependent growth model for this species. To test the applicability of experimentally derived optima in growth response rates to natural conditions, the effects of commercial pellets and natural prey on growth rates were investigated. In addition, to test for seasonal effects on growth, laboratory trials were performed in both spring and winter. Growth took place from 5 to 29° C with a temperature for optimum growth reaching a sharp peak at 21° C. Modelled optimal temperature for maximum growth was estimated to be 21.7° C and lower and upper temperatures for growth were estimated to be 3.6 and 30.7° C, respectively. There were no significant differences in growth rates between fish reared on invertebrates or commercial pellets. Seasonal effects on growth were pronounced, with reduced growth rates in the winter despite similar laboratory conditions. On average, 60% higher growth rates were achieved at the optimum temperature in summer compared to the winter. The strong seasonality in the growth patterns of G. aculeatus indicated here reduces the applicability of the model derived in this study to spring and summer conditions.

  • 39.
    Lefébure, Robert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Larsson, S.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Temperature and size-dependent attack rates of the three-spined stickleback (Gasterosteus aculeatus): are sticklebacks in the Baltic Sea resource-limited?2014In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 451, p. 82-90Article in journal (Refereed)
    Abstract [en]

    The three-spined stickleback Gasterosteus aculeatus is a small omnivorous fish, widely distributed in the northern hemisphere. In the Baltic Sea, recently observed increases in their population densities have been attributed to declines of piscivorous predators. Concurrent with this predator release, an alternative hypothesis is that past and present consumption rates and resource limitation thresholds may have contributed to the recent increases in stickleback abundance. To evaluate this hypothesis, we estimated the size- and temperature-dependent attack rate and the critical resource density (CRD) of three-spined sticklebacks. We incorporated laboratory results with time series of zooplankton abundance to estimate historical trends in degrees of resource limitation in sticklebacks and evaluate if increases in individual consumption rates could be a plausible mechanism facilitating the suggested population increase. Attack rates increased with body size and temperature in laboratory experiments. Estimated CRD increased with size but decreased with temperature, suggesting that stickleback scope for individual and population growth might increase at temperatures above 15 degrees C. Our results further suggest that sticklebacks have been living closer to maximum consumption capacity in the coastal areas of the Bothnian Sea (BS) and Bothnian Bay (BB). Moreover, decreasing levels of resource limitation in the corresponding off-shore zones may have facilitated increases in stickleback densities for these areas. However, in the coastal zones of the Baltic proper (BP), resource levels have declined and are approaching the CRD, suggesting that stickleback populations in BP may not increase further. The decrease in CRD with temperature implies that increasing summer temperatures will increase the scope of individual and population growth in the three-spined stickleback and may favor the three-spined stickleback's competitive ability over other species under a warmer climate. (C) 2013 Elsevier B.V. All rights reserved.

  • 40. Macura, Biljana
    et al.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Airoldi, Laura
    Eriksson, Britas Klemens
    Rudstam, Lars
    Stottrup, Josianne G.
    Impact of structural habitat modifications in coastal temperate systems on fish recruitment: a systematic review2019In: Environmental Evidence, ISSN 2047-2382, E-ISSN 2047-2382, Vol. 8, no 1, article id 14Article in journal (Refereed)
    Abstract [en]

    Background: Shallow nearshore marine ecosystems are changing at an increasing rate due to a range of human activities such as urbanisation and commercial development. As a result, an increasing number of structural modifications occur in coastal nursery and spawning habitats of fish. Concomitant to this increase, there have been declines in many coastal fish populations and changes in the composition of fish communities. As requested by Swedish stakeholders, this review aimed to synthesise scientific evidence of the impact on fish recruitment of structural modifications in temperate coastal areas.

    Methods: We searched for peer-reviewed and grey literature on such impacts in English, Dutch, Danish, Finnish, German, Swedish and Spanish. Searches were performed in bibliographic databases, specialist websites, bibliographies of review articles. We also contacted stakeholder to find relevant literature. Eligible studies included small- and large-scale field studies in marine systems and large lakes (> 10,000 km(2)) in temperate regions of the Northern and Southern Hemispheres. Included replicated comparisons of fish recruitment between altered and unaltered control areas, comparisons before and after an alteration, or both. Relevant outcomes (response variables) included measures of recruitment defined as abundance of juvenile fish in coastal habitats. All fish species were considered. Articles were screened for eligibility by title, abstract and full text. Eligible studies were critically appraised based on their external and internal validity. From each eligible study of sufficient validity, we extracted information on study design, measured outcomes, exposure, type of comparator, effect modifiers and study findings. Study findings were synthesised narratively.

    Results: We searched for eligible studies in 15 databases, 24 specialist websites, Google Scholar, and bibliographies of 11 review articles. The review finally included 37 studies that were eligible and of sufficient validity to be considered for final synthesis. Most studies (23 of 37) were from the Northern Hemisphere. Studies varied in design, spatial resolution, target fish species, and type of structural habitat change. This high level of variation did not allow for a quantitative synthesis and prevented us from drawing general conclusions on the impact of structures or structural modifications on fish recruitment. In this review we provide a narrative synthesis of the evidence base and classify eligible studies into six categories (based on type of exposure and comparator). The categories are as follows: the impacts on fish recruitment of: (1) artificial structures in coastal areas, (2) structures designed as fish attractors, (3) large scale urban sprawl, (4) 'novel' habitats, (5) habitat loss, and (6) restoration.

    Conclusions: This review revealed a very limited evidence base for how structural modifications and marine urban sprawl can affect fish recruitment. Thus, there is a substantial mismatch between stakeholder needs and research evidence. Further, the impact and ecological performance of artificial structures depend both on context and species. Clearly, there is a need for more research on the subject, especially on long-term consequences at larger spatial scales.

  • 41. Macura, Biljana
    et al.
    Lonnstedt, Oona M.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Airoldi, Laura
    Eriksson, Britas Klemens
    Rudstam, Lars
    Stottrup, Josianne
    What is the impact on fish recruitment of anthropogenic physical and structural habitat change in shallow nearshore areas in temperate systems?: A systematic review protocol2016In: Environmental Evidence, ISSN 2047-2382, E-ISSN 2047-2382, Vol. 5, no 1, p. 1-8, article id 10Article, review/survey (Refereed)
    Abstract [en]

    Background: Shallow nearshore marine ecosystems are changing at an increasing rate due to a range of human activities such as urbanisation and commercial development. The growing numbers of constructions and other physical and structural alterations of the shoreline often take place in nursery and spawning habitats of many fish and other aquatic species. Several coastal fish populations have seen marked declines in abundance and diversity during the past two decades. A systematic review on the topic would clarify if anthropogenic physical and structural changes of near-shore areas have effects on fish recruitment and which these effects are. Methods: The review will examine how various physical and structural anthropogenic changes of nearshore fish habitats affect fish recruitment. Relevant studies include small- and large-scale field studies in marine and brackish systems or large lakes in temperate regions of the Northern and Southern hemispheres. Relevant studies may be based on comparisons between undisturbed and disturbed areas, before and after disturbance, or both. Relevant outcomes include measures of recruitment defined as abundance of juveniles of nearshore fish communities. Searches will be made for peer-reviewed and grey literature in English, Dutch, Danish, Finnish, German, Swedish and Spanish. All fish species and species groups will be considered in this review. Included relevant studies will be subject to a critical appraisal that will assess study validity. From relevant included studies, we will extract information on study characteristics, measured outcomes, exposure, comparators, effect modifiers and critical appraisal. Data synthesis will contain narrative and summary findings of each included study of sufficient quality. Meta-analysis may be possible in cases where studies report similar types of outcomes.

  • 42.
    Norlin, Linnea
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Climate Impacts Research Centre (CIRC), Department of Ecology and Environmental Science, Umeå University, Abisko, Sweden.
    Johansson, Martin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Liess, Antonia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Climate change will alter amphibian-mediated nutrient pathways: evidence from Rana temporaria tadpoles in experimental ponds2016In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 61, no 4, p. 472-485Article in journal (Refereed)
    Abstract [en]

    1. With global warming, mean temperatures and brownification of many waterbodies are predicted to increase. This may have unknown consequences on aquatic consumer life histories and nutrient content, consumer-mediated nutrient recycling, and nutrient transport between water and land.

    2. Using a large-scale experimental pond facility, we altered temperature (ambient/+ 4 degrees C) and brownification (clear/humic) in a 2 x 2 factorial design (n = 16 pond sections) to test two aspects of climate change on Rana temporaria tadpole life-history traits and on tadpole-mediated nutrient pathways. On day 16 after hatching, we examined tadpole-mediated nutrient recycling by measuring tadpole nutrient excretion and egestion rates and tadpole body nutrient content. We estimated tadpole growth and development rates from hatching to emergence and measured emergent frog body size and body nutrient content.

    3. Brownification increased total pond water nutrient availability and total pond water nitrogen (N) : phosphorous (P) ratios. Warming positively affected tadpole growth and development rates, whereas browning increased tadpole growth rate only under ambient temperatures. Emergent frog body P content decreased with warming, but only in the clear treatments. But despite these variations in body nutrient content, body stoichiometry remained within a relatively narrow stoichiometric range for both emergent frogs (P content: 1.4-1.8%, N content: 11.4-11.8% and carbon [C] content: 46.9-51.3%) and tadpoles (P content: 1.1-1.2%, N content: 10.1-11.7% and C content: 48.0-50.5%). Warming increased tadpole body P content and browning had a positive effect on tadpole body N content and tadpole N excretion rates, probably mediated by the increased pond water total N availability.

    4. We conclude that warming and brownification will interact in changing aquatic consumer growth and body nutrient stoichiometry. In addition, warming has the potential to affect emergent frog body nutrient content and may thus affect nutrient transport from water to land. Last, by increasing pond water N availability, brownification appears to intensify consumer P limitation and thus amplify consumer-meditated N recycling.

  • 43.
    Persson, L
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Byström, P
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Wahlström, E
    Westman, E
    Trophic dynamics in a whole lake experiment: size-structured interactions and recruitment variation2004In: Oikos, Vol. 106, p. 263-274Article in journal (Refereed)
  • 44.
    Persson, L
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Claessen, D
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    De Roos,, A M
    Byström, P
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sjögren, S
    Svanbäck, Richard
    Wahlström, E
    Westman, E
    Cannibalism in a size-structured population: energy extraction and control2004In: Ecological Monographs, Vol. 74, p. 135-157Article in journal (Refereed)
  • 45.
    Persson, Lennart
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    de Roos, André M
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    State-dependent invasion windows for prey in size-structured predator–prey systems: whole lake experiments2007In: Journal of Animal Ecology, Vol. 76, no 1, p. 94-104Article in journal (Refereed)
    Abstract [en]

    1.

    In size-structured communities where individuals grow in size over their life cycle, interactions between species will shift between competitive and predatory interactions depending on size relationships. The outcome of interactions will subsequently depend on the strength of competitive and predatory interactions, respectively.

    2.

    In a whole lake experiment including four experimental lakes, it was tested under which conditions the competing prey, roach Rutilus rutilus, could successfully recruit into systems previously occupied by the predator, perch Perca fluviatilis. Two replicated introduction experiments were carried out 3 years apart.

    3.

    Roach were able to successfully recruit into three of the four experimental lakes of which two were also inhabited by the top predator pike Esox lucius. Resource levels were unrelated to whether roach could successfully recruit into the systems as recruiting roach in all years were feeding close to their maximum rate.

    4.

    High population fecundity of roach and low predation pressure by perch combined were necessary ingredients for successful recruitment and the presence of only one of these conditions did not result in successful recruitment.

    5.

    It is hypothesized that, although roach were able to successfully recruit into one lake with only perch present in addition to the two lakes that also inhabited pike, long-term coexistence of roach and perch depends on the presence of another top predator (e.g. pike) selectively preying on perch. This hypothesis was supported by data on co-occurrence of perch and roach in different lakes.

    6.

    Overall, the results are in accordance with expectation of size-structured life-history omnivory theory suggesting that coexistence between top predator and intermediate consumer is fragile.

  • 46.
    Rodriguez, Patricia
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Geibrink, Erik
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hedström, Per
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vasconcelos, Francisco Rivera
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Do warming and humic river runoff alter the metabolic balance of lake ecosystems?2016In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 78, no 4, p. 717-725Article in journal (Refereed)
    Abstract [en]

    Global warming is expected to influence lake gross primary production (GPP) and ecosystem respiration (R) by increasing water temperature and terrestrial export of organic material and inorganic nutrients from the catchment. We experimentally tested the effects of warming (3 A degrees C) and natural humic river runoff, separately and in combination, on habitat-specific and whole ecosystem net ecosystem production (NEP = GPP - R) in replicated large scale (136 m(3)) experimental pond ecosystems over one open water season. Pelagic NEP was reduced by warming and increased with humic river water addition. Littoral NEP (benthos, macrophytes, periphyton) showed an opposite pattern with increasing NEP following warming and decreasing NEP following humic river water addition. These changes were a result of changes in GPP with warming (negative in pelagic, positive in littoral) and with humic water addition (positive in pelagic, negative in littoral), while no effects were observed on pelagic respiration. As a result of the counteracting effects on NEP in pelagic and littoral habitats, whole ecosystem NEP was not affected by the treatments. The study suggests that climate mediated changes in temperature and river runoff have relatively small effects on the overall metabolic balance of shallow aquatic ecosystems but there may be large habitat-specific effects.

  • 47.
    Rowe, Owen F.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Food and Environmental Sciences, Division of Microbiology and Biotechnology, Viikki Biocenter 1, University of Helsinki, Helsinki, Finland.
    Guleikova, Liudmyla
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Institute of Hydrobiology National Academy of Sciences of Ukraine, UA-04210, Kyiv, Ukraine.
    Brugel, Sonia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Agneta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    A potential barrier to the spread of the invasive cladoceran Cercopagis pengoi (Ostroumov 1891) in the Northern Baltic Sea2016In: Regional Studies in Marine Science, ISSN 0080-0694, E-ISSN 2168-1376, Vol. 3, p. 8-17Article in journal (Refereed)
    Abstract [en]

    The spread of the invasive cladoceran Cercopagis pengoi has been well documented in southern areas of the Baltic Sea, however, little research on this invasive species (nor the zooplankton community) has focused on the Gulf of Bothnia (Bothnian Sea and Bay). We analysed data collected over a 12–13 year period at two main stations, one coastal and one offshore, to examine the occurrence of C. pengoi, invasion dynamics, effects on natural zooplankton communities and associated environmental factors. Nine other stations in the Gulf of Bothnia were also examined and the contribution to three-spined stickleback (Gasterosteus aculeatus) diet was quantified. The zooplankton community response apparently differed between coastal and offshore stations with Bosmina, Eurytemora, and Acartia populations being influenced during peak abundances of C. pengoi. It appears that the native zooplankton community has some resilience, returning to its prior structure outside of peak invasion periods. C. pengoi, where present, contributed significantly to stickleback diet. We explored possible barriers for C. pengoi in the Bothnian Bay, suggesting that the low productive Bothnian Bay ecosystem may be incapable of supporting such a predator. This highlights the need for further studies, especially in the light of global climate change.

  • 48.
    Seekell, David A.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lake morphometry moderates the relationship between water color and fish biomass in small boreal lakes2018In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 63, no 5, p. 2171-2178Article in journal (Refereed)
    Abstract [en]

    Lake morphometry may moderate the effects of water color on fish biomass in boreal lakes, but empirical evidence is scarce because there are a limited number of lakes for which both water color and bathymetry have been measured. We evaluated variations in catch-per-unit-effort (CPUE), an indicator of fish biomass, across orthogonal gradients of light extinction and mean depth in 16 small Swedish lakes (mean depth 1.7-4.8 m, surface area 1-10 ha). Multiple regression coefficients indicated that the effect of light extinction on CPUE was negative, and that the relationship was more negative for deeper lakes than it was for shallower lakes. The pattern was strongest for lakes with mean depths between 2.1 m and 3.5 m. We estimated that 26% of small lakes in boreal Sweden fall within this mean depth range. These results contribute to the growing understanding of how variations in water color and lake morphometry influence patterns of fish biomass across the boreal landscape.

  • 49.
    van Kooten, Tobias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Jens
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Persson, Lennart
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    de Roos, Andre M.
    Size at hatching determines population dynamics and response to harvesting in cannibalistic fish2010In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 67, no 2, p. 401-416Article in journal (Refereed)
    Abstract [en]

    We hypothesize that size at hatching strongly affects population dynamics of cannibalistic fish species and is a crucial determinant of how populations respond to selective removal of large individuals (harvesting). We use a mechanistic mathematical model to study the relation between hatching size and response to harvesting mortality, using Eurasian perch (Perca fluviatilis) as a model organism. We show how hatching size determines dynamics through its effect on the relative strength of cannibalistic mortality and resource competition as mechanisms of population regulation. In populations with intermediate and large hatching size, cannibalistic mortality is an important determinant of population dynamics. and harvesting destabilizes population dynamics. When hatching size is small, population stability is less sensitive to this type of harvesting. Populations hatching at small size are regulated by competition, and harvesting large individuals affects such populations less. Harvesting can also induce the growth of very large individuals, absent in unharvested populations. Our results show that harvesting in cannibalistic lake fish populations can strongly alter Population dynamics in ways that can only be anticipated on the basis of mechanistic knowledge about how populations are regulated.

  • 50.
    Vasconcelos, Francisco Rivera
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Diehl, Sebastian
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rodriguez, Patricia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Austral Centre for Scientific Research (CADIC-CONICET), 9410 Ushuaia, Tierra del Fuego, Argentina.
    Hedström, Per
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, Jan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Byström, Pär
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Asymmetrical competition between aquatic primary producers in a warmer and browner world2016In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 10, p. 2580-2592Article in journal (Refereed)
    Abstract [en]

    In shallow lakes, pelagic and benthic producers engage in spatially asymmetrical resource competition. Pelagic producers intercept the flux of light to the benthic habitat and benthic producers intercept the flux of sediment-derived nutrients to the pelagic habitat. In boreal and subarctic regions, climate change is affecting this interaction both directly through warming and indirectly through increased loading with colored dissolved organic matter (cDOM) from the catchment (brownification). We use a dynamical ecosystem model to explore the consequences of these changing environmental conditions for lake primary production and compare model predictions with the results of an experiment in which we manipulated water temperature and cDOM supply in a 2x2 factorial design. The experiment was performed in field mesocosms large enough to harbor reproducing fish populations and was run over an entire growing season. In agreement with model predictions, benthic algal production and biomass declined and pelagic algal production and biomass increased with browning. Pelagic nutrient concentrations diverged over time between low and high cDOM treatments, suggesting that browning alleviated pelagic algal nutrient limitation by shading benthic competitors and preventing them from intercepting the release of nutrients from the sediment. Warming considerably reduced benthic and pelagic algal production as well as pelagic algalbiomass and total phosphorus. The warming results are only in partial accordance with model expectations, but can be explained by an indirectly inferred, positive response of macrophyte production (which was not included in the model) to warming. Our study suggests that lake ecosystem responses to climate change are mediated by cross-habitat feedbacks between benthic and pelagic producers.

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