umu.sePublications
Change search
Refine search result
1 - 15 of 15
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Andersson, A
    et al.
    Wallberg, P
    Nordback, J
    Bergqvist, P A
    Selstam, Eva
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Effect of nutrient enrichment on the distribution and sedimentation of polychlorinated biphenyls (PCBs) in seawater1998In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 377, p. 45-56Article in journal (Refereed)
    Abstract [en]

    The effect of nutrient enrichment on the distribution of polychlorinated biphenyl's (PCBs) in the microbial food web and the residence time of PCBs in seawater was studied in an experimental mesocosm system. Two 5 m high temperature and light controlled mesocosm tubes (empty set = 0.5 m) were filled with seawater from the northern Baltic Sea. Inorganic phosphorus and nitrogen were added daily to one mesocosm, while the other served as a control. Experiments were conducted at 5, 10 and 20 degrees C. Three C-14-labelled PCBs of different degree of chlorination were added to subsamples of the mesocosms: 4-chlorobiphenyl (MCB), IUPAC # 3, 2,2',5,5'-tetrachlorobiphenyl (TCB), IUPAC # 52 and 2,2',4,4',5,5'-hexachlorobiphenyl (HCB) IUPAC # 153. The biomasses and growth rates of the microorganisms as well as the sedimentation rate of particulate organic material increased with nutrient enrichment. The size distribution of the microorganisms changed with nutrient status, from dominance of picoplankton (< 2 mu m) in the control towards increased importance of micro (> 10 mu m) and nanoplankton (2-10 mu m) in nutrient enrichment. The specific growth rate of the bacterial community was found to be more temperature dependent than that of the phytoplankton community. The relative proportion of PCBs in the > 2 mu m fraction was observed to be in the order MCB < TCB < HCB, while the opposite distribution prevailed in the < 2 mu m fraction. We hypothesize that this is due to the combined effect of the different K-ow values of the PCBs and a different composition of the particulate organic carbon in the > 2 mu m and < 2 mu m fractions (e.g. different lipid composition). The residence time of the PCBs in the mesocosm generally decreased with nutrient enrichment, but was dependent on the degree of chlorination of the PCB. Our results indicate that the transport of organic pollutants up through the food web is more important in nutrient poor than in nutrient rich waters and that the importance of sedimentation is higher in eutrophic ecosystems.

  • 2. Bakker, Elisabeth S.
    et al.
    Sarneel, Judith
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gulati, Ramesh D.
    Liu, Zhengwen
    van Donk, Ellen
    Restoring macrophyte diversity in shallow temperate lakes: biotic versus abiotic constraints2013In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 710, no 1, p. 23-37Article in journal (Refereed)
    Abstract [en]

    Although many lake restoration projects have led to decreased nutrient loads and increased water transparency, the establishment or expansion of macrophytes does not immediately follow the improved abiotic conditions and it is often unclear whether vegetation with high macrophyte diversity will return. We provide an overview of the potential bottlenecks for restoration of submerged macrophyte vegetation with a high biodiversity and focus on the biotic factors, including the availability of propagules, herbivory, plant competition and the role of remnant populations. We found that the potential for restoration in many lakes is large when clear water conditions are met, even though the macrophyte community composition of the early 1900s, the start of human-induced large-scale eutrophication in Northwestern Europe, could not be restored. However, emerging charophytes and species rich vegetation are often lost due to competition with eutrophic species. Disturbances such as herbivory can limit dominance by eutrophic species and improve macrophyte diversity. We conclude that it is imperative to study the role of propagule availability more closely as well as the biotic interactions including herbivory and plant competition. After abiotic conditions are met, these will further determine macrophyte diversity and define what exactly can be restored and what not.

  • 3.
    Båmstedt, Ulf
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Comparing static and dynamic incubations in primary production measurements under different euphotic and mixing depths2019In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 827, no 1, p. 155-169Article in journal (Refereed)
    Abstract [en]

    Since phytoplankton production is usually estimated from static incubations (fixed depths or light levels), a mesocosm study was performed to evaluate the significance of mixing depth, mixing intensity and load of humus of natural phytoplankton assemblages. Vertically rotated (dynamic) incubations usually gave higher results than static incubations in humus-rich water. Mixing intensity was of significant importance in one of 2years tested, but strong interaction effects with humus complicated the explanation. Differences in primary production between dynamic incubations did not fully reflect the received PAR dose, and increased humus and increased mixing depth increased the photo-assimilation efficiency. Different single-depth incubations did not provide a shortcut method to measure water-column primary production with high accuracy. Results diverged from theoretical estimates based on recent combined photo-biological and physical environmental models. The large variability in responses to mixing is supposed to reflect species-specific adaptations and pre-history regarding quantity (photons) and quality (spectral distribution) of the optical environment in an assemblage of different species. The proportional abundance of each species with its specific characters will therefore strongly influence bulk primary production. Due to such variable responses, clear guidelines for a best practice in primary production measurements cannot be given, based on the present results.

  • 4.
    Båmstedt, Ulf
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Productivity related to ambient photon flux for phytoplankton communities under different turbid conditions2019In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 837, no 1, p. 109-115Article in journal (Refereed)
    Abstract [en]

    Phytoplankton productivity standardized to chlorophyll a and photon flux (mg C mg chl. a(-1) mol photons(-1)) of natural communities from northern Bothnian Sea under dynamic (vertically rotating) incubations and different optical conditions was studied during four mesocosm experiments between April 2013 and April 2016. The standardized productivity showed a positive exponential relationship with calculated optical depth (P<0.001 in all four cases) although a considerably weaker one for one of the series where the community was pre-adapted to the same optical condition as used in the measurements. This series also showed a lower regression slope than the three non-adapted series, which in turn showed identical regression slopes, thus indicating a similar response on the standardized productivity to short-term changes in average ambient photon flux and mixing depth. These results indicate that phytoplankton communities in environments with episodic inflow and mixing of humus-rich water can partly compensate for the reduced photon flux by increased production efficiency.

  • 5.
    Båmstedt, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    Martinussen, Monica B.
    Institute of Marine Research, Bergen, Norway .
    Ecology and behavior of Bolinopsis infundibulum (Ctenophora; Lobata) in the Northeast Atlantic2015In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 759, no 1, p. 3-14Article in journal (Refereed)
    Abstract [en]

    Results from field surveys with net sampling and video profiling, combined with laboratory experiments on feeding and growth, revealed the ecological function of Bolinopsis infundibulum in northern temperate coastal waters. B. infundibulum reaching a peak abundance of around 250 ctenophores m(-2), in mid-May, followed by a dramatic reduction over the next few weeks, presumably explained by predation from the ctenophore Beroe cucumis. The field data on maximum individual body height in the population indicated an instantaneous growth rate of 0.129 d(-1). Newly hatched cydippid larvae showed an average instantaneous growth rate of 0.240 d(-1) over 4 weeks, whereas ctenophores in the size range of 4.4-9.8 mm height gave instantaneous growth rates between 0.10 and 0.20 d(-1). B. infundibulum disappeared from surface water in mid-June, but big individuals were found in deeper water, where they preyed on copepods. The results indicate that the new generation of the year was recruited from February onwards. Laboratory predation and digestion experiments showed a continuous increase in predation rate with increased prey abundance, throughout the tested range of 5-400 copepods l(-1), and a digestion time increasing from 39 min with a single copepod ingested to 73 min with 8 copepods ingested.

  • 6.
    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).

  • 7. Elmberg, Johan
    et al.
    Dessborn, Lisa
    Englund, Göran
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Presence of fish affects lake use and breeding success in ducks2010In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 641, no 1, p. 215-223Article in journal (Refereed)
    Abstract [en]

    Several previous studies indicate that presence of fish has negative effects on waterbirds breeding on lakes, owing either to competition for common invertebrate prey or fish predation on ducklings/chicks. However, others have reported results to the contrary and it remains unresolved what factors trigger, inhibit, and modulate fish-waterbird interactions. The present study was designed to test the effect of fish presence per se, with a minimum of variation in possibly confounding environmental variables. Thus, after stratifying for area, depth, altitude, pH, and total phosphorus we compared 13 lakes with and 12 without fish (mainly pike Esox lucius and perch Perca fluviatilis) with respect to (i) general species richness of waterbirds, (ii) species-specific utilization and breeding success of two dabbling ducks (mallard Anas platyrhynchos and teal Anas crecca) and a diving duck (goldeneye Bucephala clangula). General species richness of waterbirds was higher on fishless lakes. Overall use (bird days) and brood number of teal and goldeneye were higher on fishless lakes. The latter also had more benthic and free-swimming prey invertebrates compared to lakes with fish. Mallard use, mallard brood number, and abundance of emerging insects did not differ between lake groups. Generalized linear models including fish presence as factor and considering seven environmental variables as covariates, confirmed that all waterbird variables except mallard days and broods were negatively correlated to fish presence. There was also a residual positive relationship of lake area on general species richness, teal days, and teal broods. Our data demonstrate a stronger effect of fish presence on diving ducks and small surface feeding ducks than on large surface-feeding ducks. We argue that observed patterns were caused by fish predation on ducks rather than by fish-duck competition for common prey.

  • 8.
    Jonsson, Micael
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Polvi, Lina E.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sponseller, Ryan A.
    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.
    Catchment properties predict autochthony in stream filter feeders2018In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 815, no 1, p. 83-95Article in journal (Refereed)
    Abstract [en]

    Stream ecological theory predicts that the use of allochthonous resources declines with increasing channel width, while at the same time primary production and autochthonous carbon use by consumers increase. Although these expectations have found support in several studies, it is not well known how terrestrial runoff and/or inputs of primary production from lakes alter these longitudinal patterns. To investigate this, we analyzed the diet of filter-feeding black fly and caddisfly larvae from 23 boreal streams, encompassing gradients in drainage area, land cover and land use, and distance to nearest upstream lake outlet. In five of these streams, we also sampled repeatedly during autumn to test if allochthony of filter feeders increases over time as new litter inputs are processed. Across sites, filter-feeder autochthony was 21.1-75.1%, did not differ between black fly and caddisfly larvae, was not positively related to drainage area, and did not decrease with distance from lakes. Instead, lake and wetland cover promoted filter-feeder autochthony independently of stream size, whereas catchment-scale forest cover and forestry reduced autochthony. Further, we found no seasonal increase in allochthony, indicating low assimilation of particles derived from autumn litter fall. Hence, catchment properties, rather than local conditions, can influence levels of autochthony in boreal streams.

  • 9.
    Liess, Antonia
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Faithfull, Carolyn
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Reichstein, Birte
    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.
    Guo, Junwen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Pete, R.
    Thomsson, Gustaf
    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.
    Francoeur, S. N.
    Terrestrial runoff may reduce microbenthic net community productivity by increasing turbidity: a Mediterranean coastal lagoon mesocosm experiment2015In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 753, no 1, p. 205-218Article in journal (Refereed)
    Abstract [en]

    Terrestrial runoff into aquatic ecosystems may have both stimulatory and inhibitory effects, due to nutrient subsidies and increased light attenuation. To disentangle the effects of runoff on microbenthos, we added soil to coastal mesocosms and manipulated substrate depth. To test if fish interacted with runoff effects, we manipulated fish presence. Soil decreased microphytobenthic chlorophyll-a per area and per carbon (C) unit, increased microbenthic phosphorous (P), and reduced microbenthic nitrogen (N) content. Depth had a strong effect on the microbenthos, with shallow substrates exhibiting greater microbenthic net ecosystem production, gross primary production, and community respiration than deep substrates. Over time, micobenthic algae compensated for deeper substrate depth through increased chlorophyll-a synthesis, but despite algal shade compensation, the soil treatment still appeared to reduce the depth where microbenthos switched from net autotrophy to net heterotrophy. Fish interacted with soil in affecting microbenthic nutrient composition. Fish presence reduced microbenthic C/P ratios only in the no soil treatment, probably since soil nutrients masked the positive effects of fish excreta on microbenthos. Soil reduced microbenthic N/P ratios only in the absence of fish. Our study demonstrates the importance of light for the composition and productivity of microbenthos but finds little evidence for positive runoff subsidy effects.

  • 10.
    Liess, Antonia
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Laboratoire Ecosystémes Marins Côtiers, UMR5119 CNRS, Université Montpellier2, IRD, IFREMER, Paris, France.
    Rowe, Owen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Francoeur, S. N.
    Guo, Junwen
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lange, K.
    Schroeder, A.
    Reichstein, Birte
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lefèbure, Robert
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Deininger, Anne
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Mathisen, Peter
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Faithfull, Carolyn L.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Terrestrial runoff boosts phytoplankton in a Mediterranean coastal lagoon, but these effects do not propagate to higher trophic levels2016In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 766, no 1, p. 275-291Article in journal (Refereed)
    Abstract [en]

    Heavy rainfall events causing significant terrestrial runoff into coastal marine ecosystems are predicted to become more frequent with climate change in the Mediterranean. To simulate the effects of soil runoff on the pelagic food web of an oligotrophic Mediterranean coastal lagoon, we crossed soil extract addition (increasing nutrient availability and turbidity) and fish presence in a full factorial design to coastal mesocosms containing a natural pelagic community. Soil extract addition increased both bacteria and phytoplankton biomass. Diatoms however profited most from soil extract addition, especially in the absence of fish. In contrast zooplankton and fish did not profit from soil extract addition. Furthermore, our data indicate that nutrients (instead of light or carbon) limited basal production. Presumed changes in carbon availability are relatively unimportant to primary and secondary production in strongly nutrient limited systems like the Thau Lagoon. We conclude that in shallow Mediterranean coastal ecosystems, heavy rainfall events causing soil runoff will (1) increase the relative abundance of phytoplankton in relation to bacteria and zooplankton, especially in the absence of fish (2) not lead to higher biomass of zooplankton and fish, possibly due to the brevity of the phytoplankton bloom and the slow biomass response of higher trophic levels.

  • 11. Manfrin, Alessandro
    et al.
    Traversetti, Lorenzo
    Pilotto, Francesca
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Larsen, Stefano
    Scalici, Massimiliano
    Effect of spatial scale on macroinvertebrate assemblages along a Mediterranean river2016In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 765, no 1, p. 185-196Article in journal (Refereed)
    Abstract [en]

    Although the assembly of stream macroinvertebrates is regulated by environmental heterogeneity at multiple spatial scales, field bioassessment studies that explicitly considered such scale-dependency are rare. Here, we investigated how large scale longitudinal gradients and local microhabitat structure jointly regulate the assembly of macroinvertebrate communities along a Mediterranean river. We compared community composition, metrics and functional feeding traits among three microhabitat categories (grain-size > 20 cm; grain-size < 20 cm; organic substrata) along three river sectors (up-, middle-, downstream), which reflected a gradient of anthropogenic modification. Macroinvertebrate assemblages varied mostly over the large-scale longitudinal gradient, but the influence of local micro-habitat features was evident at the within-sector scale. The effects of micro-habitats appeared stronger for feeding traits compared to simple taxonomic metrics, supporting the hypothesis that feeding traits are sensitive to river substratum character. Beta-diversity among micro-habitat types was smaller in the modified downstream sector, which supported more homogeneous communities. An explicit consideration of spatial scales is recommended when interpreting results from environmental assessment studies. In the Aniene River, the influence of local-scale substratum character on macroinvertebrates depended on the longitudinal gradient in anthropogenic pressure. Also, the findings suggest that taxonomic and functional metrics reflect processes operating at different spatial scales.

  • 12.
    Persson, Jan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hansson, Hans
    Renberg, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    The stone brusher, a new sampler for submerged epilithic material in shallow streams and lakes2006In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 560, no 1, p. 385-392Article in journal (Refereed)
    Abstract [en]

    The Stone Brusher is designed to take qualitative or semi-quantitative samples of material attached tostones at 7–50 cm depth in running or stagnant waters. The epilithic material is dislodged from the stonesurface with a rotating brush enclosed in a chamber and the material is drawn up directly into the samplebottle with an air-cylinder. The operator takes a sample quickly and without putting hands into the water.The sampling area is about 28 cm2. The sampler is made of plastic, stainless steel and aluminium andweighs 3.1 kg. The equipment is robust and easily handled and it is constructed to meet the demand forstandardized sampling for research and environmental monitoring and to improve working conditions forsampling personnel. The equipment allows sampling from bedrock and large stones that cannot be liftedfrom the bottom and it can be used for reliable sampling also in fast-flowing streams where the dislodgedmaterial is easily flushed away. Using Near-Infrared Spectroscopy and diatom analyses, this new sampler isevaluated in comparison to the recognized toothbrush method, which indicates that the Stone Brusherreduces sampling variability compared with the toothbrush method.

  • 13.
    Sarneel, Judith
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    The dispersal capacity of vegetative propagules of riparian fen species2013In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 710, no 1, p. 219-225Article in journal (Refereed)
    Abstract [en]

    Flowing water can disperse a high number of seeds and vegetative propagules over long distances and is therefore a very important dispersal vector in wetland habitats. Although the dispersal of seeds is relatively well studied, the dispersal of vegetative propagules has received less attention. However, in riparian and aquatic systems where many species have clonal growth forms, it can be very important. The relative importance of vegetative propagules in the dispersal of fen species was assessed first by determining their relative abundance in the field and second, by determining the buoyancy of plant fragments of ten fen species experimentally. On average, vegetative propagules made up 3.2-58.9% of the total propagule number (mainly Elodea nutallii). Buoyancy of the tested species ranged from 25 days to over 6 months. Surprisingly, the propagules of Stratiotes aloides and Hydrocharis morsus-ranae increased buoyancy when spring started (after ca. 100 days). The results demonstrate that vegetative propagules of riparian and aquatic fen species have a high capacity to disperse over long distances via water and are therefore likely to play an important role in the colonisation of new habitats. Especially because in nine out of the ten species tested, over 50% of the propagules were still viable after 6 months of floating.

  • 14. SHELDON, RW
    et al.
    Rassoulzadegan, Fereidoun
    Azam, Farooq
    Berman, Tom
    Bezanson, DS
    Bianchi, M
    BONIN, D
    Hagström, Åke
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    LAVALPEUTO, M
    NEVEUX, J
    RAIMBAULT, P
    RIVIER, A
    Sherr, Barry
    Sherr, Evelyn
    VANWAMBEKE, F
    Wikner, Johan
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
    WOOD, AM
    YENTSCH, CM
    NANOPLANKTON AND PICOPLANKTON GROWTH AND PRODUCTION IN THE BAY OF VILLEFRANCHE-SUR-MER (NW MEDITERRANEAN)1992In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 241, no 2, p. 91-106Article in journal (Refereed)
    Abstract [en]

    Plankton production in the Bay of Villefranche was relatively constant during March and April 1986 but the particle size at which the production occurred was more variable. At the beginning of the study, production was dominated by the larger (ca. 6 mum) flagellates but towards the end it was more or less equally divided between the nano- and picoplankton. There were considerable differences in the estimates of population growth rates, depending on the methods used, but on average the population doubling times were close to 12 hours for autotrophs and 24 hours for heterotrophs. As autotrophs do not grow during the night, each population was therefore doubling once per day. It seemed that each of the nano- or picoplankton populations could adversely affect the growth of the others. This could be either by simple predation or by some form of inhibition. Although nutrient levels in the bay were uniformly low, the addition of nutrients did not always stimulate algal growth. The plankton populations seemed to be both in a state of equilibrium and intense ecological competition.

  • 15.
    Vasconcelos, Rivera Francisco
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Departamento de Ecologia, Universidade Federal do Rio Grande do Norte, Natal, Brazil.
    Menezes, Rosemberg Fernandes
    Attayde, José Luiz
    Effects of the Nile tilapia (Oreochromis niloticus L.) on the plankton community of a tropical reservoir during and after an algal bloom2018In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 817, no 1, p. 393-401Article in journal (Refereed)
    Abstract [en]

    The invasive species Nile tilapia is a filter-feeding omnivorous fish that can have a negative effect on zooplankton and phytoplankton resources. However, the strength of its effects on plankton communities should decrease with increasing plankton biomass, e.g., during an algal bloom. We tested this hypothesis by performing two experiments in a tropical reservoir, where we randomly allocated two treatments (with and without tilapia) to 20 mesocosms. The first experiment was conducted during an algal bloom (biovolume = 1038.34 mm(3) l(-1)), while the second experiment was conducted after the bloom (biovolume = 1.05 mm(3) l(-1)). The negative effects of fish on mesozooplankton (mean size of 480 mu m in both experiments) and large algae (GALD < 50 mu m) were stronger in the second than in the first experiment. On the other hand, the negative effects of fish on microzooplankton (experiment 1: mean size 180 mu m; experiment 2: mean size 128 mu m) and small algae (GALD < 50 mu m) were stronger in the first than in the second experiment. We conclude that the Nile tilapia can suppress phytoplankton and zooplankton biomass in tropical lakes and reservoirs, but the magnitude of this effect depends on plankton biomass and size-structure.

1 - 15 of 15
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf