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  • 1. Maaroufi, Nadia, I
    et al.
    Palmqvist, Kristin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bach, Lisbet H.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bokhorst, Stef
    Liess, Antonia
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Rydberg Laboratory of Applied Science, School of Business, Science and Engineering, Halmstad University, Halmstad, Sweden.
    Gundale, Michael J.
    Kardol, Paul
    Nordin, Annika
    Meunier, Cedric L.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Biologische Anstalt Helgoland, Helgoland, Germany.
    Nutrient optimization of tree growth alters structure and function of boreal soil food webs2018In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 428, p. 46-56Article in journal (Refereed)
    Abstract [en]

    Nutrient optimization has been proposed as a way to increase boreal forest production, and involves chronic additions of liquid fertilizer with amounts of micro- and macro-nutrients adjusted annually to match tree nutritional requirements. We used a short-term (maintained since 2007) and a long-term (maintained since 1987) fertilization experiment in northern Sweden, in order to understand nutrient optimization effects on soil microbiota and mesofauna, and to explore the relationships between plant litter and microbial elemental stoichiometry. Soil microbes, soil fauna, and aboveground litter were collected from the control plots, and short- and long-term nutrient optimization plots. Correlation analyses revealed no relationships between microbial biomass and litter nutrient ratios. Litter C:N, C:P and N:P ratios declined in response to both optimization treatments; while only microbial C:P ratios declined in response to long-term nutrient optimization. Further, we found that both short- and long-term optimization treatments decreased total microbial, fungal, and bacterial PLFA biomass and shifted the microbial community structure towards a lower fungi:bacterial ratio. In contrast, abundances of most fungal- and bacterial-feeding soil biota were little affected by the nutrient optimization treatments. However, abundance of hemi-edaphic Collembola declined in response to the long-term nutrient optimization treatment. The relative abundances (%) of fungal-feeding and plant-feeding nematodes, respectively, declined and increased in response to both short-term and long-term treatments; bacterial-feeding nematodes increased relative to fungal feeders. Overall, our results demonstrate that long-term nutrient optimization aiming to increase forest production decreases litter C:N, C:P and N:P ratios, microbial C:P ratios and fungal biomass, whereas higher trophic levels are less affected.

  • 2.
    Meunier, Cedric L.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Alfred-Wegener-Inst., Helmholtz-Zentrum für Polar- und Meeresforschung, Biologische Anstalt Helgoland.
    Boersma, Maarten
    Wiltshire, Karen H.
    Malzahn, Arne M.
    Zooplankton eat what they need: copepod selective feeding and potential consequences for marine systems2016In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 125, no 1, p. 50-58Article in journal (Refereed)
    Abstract [en]

    Herbivores are generally faced with a plethora of resources which differ in quality. Therefore, they should be able to select foods which most closely match their metabolic needs. Here, we tested the hypothesis that copepods of the species Acartia tonsa select prey cells based on quality differences within prey species. We assessed age-specific variation in feeding behaviour and evaluated the potential consequences of such variation for nutrient cycles. Nauplii (young) stages characterized by a low nitrogen to phosphorus (N:P) ratio in their body tissue selected for phosphorus-rich food, while older copepodite stages with higher body N: P selected for nitrogen-rich food. Further, the analysis of a 35-year data set in the southern North Sea revealed a positive correlation between the abundance of nauplii and the ratio of dissolved inorganic N:P, thus suggesting that P-availability for primary producers declines with the population densities of nauplii. Our findings demonstrate that a combination of stage-specific selective feeding and body stoichiometry has the potential to affect cycling of limiting nutrients when consumer populations change in composition.

  • 3.
    Meunier, Cedric L.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gundale, Michael J.
    Sanchez, Irene S.
    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.
    Impact of nitrogen deposition on forest and lake food webs in nitrogen-limited environments2016In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 22, no 1, p. 164-179Article, review/survey (Refereed)
    Abstract [en]

    Increased reactive nitrogen (N-r) deposition has raised the amount of N available to organisms and has greatly altered the transfer of energy through food webs, with major consequences for trophic dynamics. The aim of this review was to: (i) clarify the direct and indirect effects of N-r deposition on forest and lake food webs in N-limited biomes, (ii) compare and contrast how aquatic and terrestrial systems respond to increased N-r deposition, and (iii) identify how the nutrient pathways within and between ecosystems change in response to N-r deposition. We present that N-r deposition releases primary producers from N limitation in both forest and lake ecosystems and raises plants' N content which in turn benefits herbivores with high N requirements. Such trophic effects are coupled with a general decrease in biodiversity caused by different N-use efficiencies; slow-growing species with low rates of N turnover are replaced by fast-growing species with high rates of N turnover. In contrast, N-r deposition diminishes below-ground production in forests, due to a range of mechanisms that reduce microbial biomass, and decreases lake benthic productivity by switching herbivore growth from N to phosphorus (P) limitation, and by intensifying P limitation of benthic fish. The flow of nutrients between ecosystems is expected to change with increasing N-r deposition. Due to higher litter production and more intense precipitation, more terrestrial matter will enter lakes. This will benefit bacteria and will in turn boost the microbial food web. Additionally, N-r deposition promotes emergent insects, which subsidize the terrestrial food web as prey for insectivores or by dying and decomposing on land. So far, most studies have examined N-r-deposition effects on the food web base, whereas our review highlights that changes at the base of food webs substantially impact higher trophic levels and therefore food web structure and functioning.

  • 4.
    Meunier, Cedric L.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Biologische Anstalt Helgoland, Helgoland, Germany.
    Malzahn, Arne M.
    Boersma, Maarten
    A New Approach to Homeostatic Regulation: Towards a Unified View of Physiological and Ecological Concepts2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 9, article id e107737Article in journal (Refereed)
    Abstract [en]

    Stoichiometric homeostasis is the ability of an organism to keep its body chemical composition constant, despite varying inputs. Stoichiometric homeostasis therefore constrains the metabolic needs of consumers which in turn often feed on resources not matching these requirements. In a broader context, homeostasis also relates to the capacity of an organism to maintain other biological parameters (e.g. body temperature) at a constant level over ambient environmental variations. Unfortunately, there are discrepancies in the literature and ecological and physiological definitions of homeostasis are disparate and partly contradictory. Here, we address this matter by reviewing the existing knowledge considering two distinct groups, regulators and conformers and, based on examples of thermo-and osmoregulation, we propose a new approach to stoichiometric homeostasis, unifying ecological and physiological concepts. We suggest a simple and precise graphical way to identify regulators and conformers: for any given biological parameter (e. g. nutrient stoichiometry, temperature), a sigmoidal relation between internal and external conditions can be observed for conformers while an inverse sigmoidal response is characteristic of regulators. This new definition and method, based on well-studied physiological mechanisms, unifies ecological and physiological approaches and is a useful tool for understanding how organisms are affected by and affect their environment.

  • 5.
    Meunier, Cedric Leo
    et al.
    Alfred-Wegener-Institut für Polar- und Meeresforschung, Biologische Anstalt Helgoland, Germany.
    Schulz, Karoline
    Alfred-Wegener-Institut für Polar- und Meeresforschung, Biologische Anstalt Helgoland, Germany.
    Boersma, Maarten
    Alfred-Wegener-Institut für Polar- und Meeresforschung, Biologische Anstalt Helgoland, Germany.
    Malzahn, Arne Michael
    Alfred-Wegener-Institut für Polar- und Meeresforschung, Biologische Anstalt Helgoland, Germany ; Helmholtz-Zentrum Geesthacht Centre for Materials and Coastal Research, Institute for Coastal Research, Geesthacht, Germany.
    Impact of swimming behaviour and nutrient limitation on predator-prey interactions in pelagic microbial food webs2013In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 446, p. 29-35Article in journal (Refereed)
    Abstract [en]

    Heterotrophic dinoflagellates are motile protozoans, important consumers of phytoplankton in aquatic environments. Motility is a main advantage for predators during grazing activities, but can also serve as defence mechanisms against being grazed. Thus, numerous microalgal species are also motile. We hypothesise that the nutrient status of an organism affects its swimming speed and especially that nutrient limitation has a negative impact on cell motility. Such altered motility of both predator and prey should influence feeding success of grazers. We tested those hypotheses by investigating the impact of nutrient (phosphorus) limitation on motility of two algal species, Rhodomonas sauna and Teleaulax sp., and the heterotrophic dinoflagellate Oxyrrhis marina and examined how differences in prey swimming speed affect grazing of O. marina. We show that nutrient limitation had a strong impact, reducing algal swimming speed and escape success and in turn significantly influencing food uptake of O. marina which was maximal for intermediate prey swimming speed. We also tested the importance of algal behaviour on O. marina selective feeding and observed that Teleaulax sp. presented an escape behaviour, which appeared to be an effective defence mechanism against grazing of O. marina. While this study has focused on the trophic interactions between two algal species and one dinoflagellate, the impact of nutrient limitation and escape strategy on feeding success of the predator is likely to be found in the whole range of plankton trophic interactions.

  • 6.
    Meunier, Cédric L.
    et al.
    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. Rydberg Laboratory of Applied Science, School of Business, Science and Engineering, Halmstad University, Halmstad, Sweden.
    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).
    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).
    Paczkowska, Joanna
    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).
    Rahman, Habib
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Skoglund, Björn
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rowe, Owen F.
    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).
    Allochthonous carbon is a major driver of the microbial food web: a mesocosm study simulating elevated terrestrial matter runoff2017In: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 129, p. 236-244Article in journal (Refereed)
    Abstract [en]

    Climate change predictions indicate that coastal and estuarine environments will receive increased terrestrial runoff via increased river discharge. This discharge transports allochthonous material, containing bioavailable nutrients and light attenuating matter. Since light and nutrients are important drivers of basal production, their relative and absolute availability have important consequences for the base of the aquatic food web, with potential ramifications for higher trophic levels. Here, we investigated the effects of shifts in terrestrial organic matter and light availability on basal producers and their grazers. In twelve Baltic Sea mesocosms, we simulated the effects of increased river runoff alone and in combination. We manipulated light (clear/shade) and carbon (added/not added) in a fully factorial design, with three replicates. We assessed microzooplankton grazing preferences in each treatment to assess whether increased terrestrial organic matter input would: (1) decrease the phytoplankton to bacterial biomass ratio, (2) shift microzooplanlcton diet from phytoplankton to bacteria, and (3) affect microzooplankton biomass. We found that carbon addition, but not reduced light levels per se resulted in lower phytoplanlcton to bacteria biomass ratios. Microzooplankton generally showed a strong feeding preference for phytoplanlcton over bacteria, but, in carbon-amended mesocosms which favored bacteria, microzooplankton shifted their diet towards bacteria. Furthermore, low total prey availability corresponded with low microzooplankton biomass and the highest bacteria/phytoplankton ratio. Overall our results suggest that in shallow coastal waters, modified with allochthonous matter from river discharge, light attenuation may be inconsequential for the basal producer balance, whereas increased allochthonous carbon, especially if readily bioavailable, favors bacteria over phytoplankton. We conclude that climate change induced shifts at the base of the food web may alter energy mobilization to and the biomass of microzooplankton grazers.

  • 7.
    Yamamichi, Masato
    et al.
    Kyoto, Japan.
    Meunier, Cedric L.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Peace, Angela
    Knoxville, USA.
    Prater, Clay
    Peterborough, ON, Canada.
    Rua, Megan A.
    Mississippi, USA.
    Rapid evolution of a consumer stoichiometric trait destabilizes consumer-producer dynamics2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 7, p. 960-969Article in journal (Refereed)
    Abstract [en]

    Recent studies have shown that adaptive evolution can be rapid enough to affect contemporary ecological dynamics in nature (i.e. 'rapid evolution'). These studies tend to focus on trait functions relating to interspecific interactions; however, the importance of rapid evolution of stoichiometric traits has been relatively overlooked. Various traits can affect the balance of elements (carbon, nitrogen, and phosphorus) of organisms, and rapid evolution of such stoichiometric traits will not only alter population and community dynamics but also influence ecosystem functions such as nutrient cycling. Multiple environmental changes may exert a selection pressure leading to adaptation of stoichiometrically important traits, such as an organism's growth rate. In this paper, we use theoretical approaches to explore the connections between rapid evolution and ecological stoichiometry at both the population and ecosystem level. First, we incorporate rapid evolution into an ecological stoichiometry model to investigate the effects of rapid evolution of a consumer's stoichiometric phosphorus: carbon ratio on consumer-producer population dynamics. We took two complementary approaches, an asexual clonal genotype model and a quantitative genetic model. Next, we extended these models to explicitly track nutrients in order to evaluate the effect of rapid evolution at the ecosystem level. Our model results indicate rapid evolution of the consumer stoichiometric trait can cause complex dynamics where rapid evolution destabilizes population dynamics and rescues the consumer population from extinction (evolutionary rescue). The model results also show that rapid evolution may influence the level of nutrients available in the environment and the flux of nutrients across trophic levels. Our study represents an important step for theoretical integration of rapid evolution and ecological stoichiometry.

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