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  • 1.
    Liess, Antonia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Hillebrand, Helmut
    Role of nutrient supply in grazer-periphyton interactions: Reciprocal influences of periphyton and grazer nutrient stoichiometry2006In: Journal of The North American Benthological Society, ISSN 0887-3593, E-ISSN 1937-237X, Vol. 25, no 3, p. 632-642Article in journal (Refereed)
    Abstract [en]

    Grazer-periphyton interactions are shaped, in part, by indirect effects of nutrient regeneration. They are an important model system with which to test predictions of ecological stoichiometry and the Growth Rate Hypothesis. We conducted a laboratory experiment to test how nutrient enrichment and grazer identity interact to regulate the nutrient content and stoichiometry of both periphyton and consumers. We considered a situation in which P concentration in the water column was high, in contrast to previous experiments in which P was the limiting nutrient. We added N and P, alone and in combination, to the water in experimental aquaria that contained periphyton communities on clay tiles and grazers (1 of 3 snail species) or no grazers (ungrazed control). Benthic algae incorporated nutrients in close proportion to their availability in each nutrient treatment. Algal biomass increased significantly with +N+P enrichment, but not with +N or +P enrichment alone. Grazers had no effect on periphyton C:N ratios and positive effects on periphyton C:P and N:P ratios. P content of grazers (% dry mass) increased and C:P and N:P molar ratios of grazers decreased in response to N enrichment of the water. Grazer P content increased in response to N enrichment, probably because of increased grazer growth rates. We hypothesize that the addition of N under N-limiting conditions led to increased P uptake or retention by grazers because of high growth rates and RNA production, consistent with the Growth Rate Hypothesis.

  • 2.
    Liess, Antonia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
    Hillebrand, Helmut
    Stoichiometric variation in C:N, C:P and N:P ratios of littoral benthic invertebrates2005In: Journal of The North American Benthological Society, ISSN 0887-3593, E-ISSN 1937-237X, Vol. 24, p. 256-269Article in journal (Refereed)
    Abstract [en]

    Nutritional constraints on herbivores are important factors structuring food webs. Our study presents field data on the nutrient content of benthic invertebrates from Lake Erken (Sweden). The most abundant benthic invertebrates of the littoral community were sampled in 3 seasons at 5 sites to examine the influence of spatial and temporal variation of abiotic conditions on invertebrate C:N:P stoichiometry. The relationships between nutrient ratios and dry mass (DM) of invertebrates were evaluated using regression analysis. Nutrient ratios of periphyton, sampled in an earlier study, were compared to those of benthic invertebrates. C:N, C:P, and N:P ratios differed among invertebrate taxa. Coleoptera had relatively high C:N, C:P, and N:P ratios, whereas Isopoda had low C:N, C:P, and N:P ratios. Nutrient ratios differed with respect to season and location. C:P and N:P ratios were significantly lower and C:N ratios were significantly higher in autumn than in spring and summer. C:P and N:P ratios increased as a functions of invertebrate DM when all taxa were analyzed together. C:N and C:P ratios of periphyton were higher than those of benthic invertebrates, but N:P ratios were similar. Our results suggested that benthic invertebrates have taxon-specific C:N and C:P ratios, but the seasonal variability in ratios indicated that littoral invertebrates were rheostatic rather than homeostatic with respect to nutrient stoichiometry. The temporal and spatial variation in grazer nutrient content must be taken into account when applying stoichiometric theory to benthic food webs.

  • 3.
    Naddafi, Rahmat
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Pettersson, Kurt
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Eklöv, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Predation and physical environment structure the density and population size structure of zebra mussels2010In: Journal of The North American Benthological Society, ISSN 0887-3593, E-ISSN 1937-237X, Vol. 29, no 2, p. 444-453Article in journal (Refereed)
    Abstract [en]

    The zebra mussel (Dreissena polymorpha) provides one example of successful invaders in novel environments. However, little attention has been devoted to exploring the factors regulating zebra mussel density and population size structure at the local scale. We tested effects of physicochemical factors and fish predation on the density of zebra mussels at several sites and between years in a natural lake. Water depth and roach (Rutilus rutilus) density were the most important variables affecting local zebra mussel density. Substrate was also an important factor but affected Dreissena density only at the shallowest depth examined (2 m), which also supported a large population of the mussels. Mean shell length of Dreissena increased with water depth. Our results indicate that predation pressure, intraspecific competition, and food limitation might be responsible for variation in zebra mussel density and population size structure in space and time and that fish predation might have strong top-down effects on zebra mussel populations.

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  • 4.
    Premke, Katrin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Karlsson, Jan
    Steger, Kristin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Gudasz, Cristian
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    von Wachenfeldt, Eddie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Tranvik, Lars J.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    Stable isotope analysis of benthic fauna and their food sources in boreal lakes2010In: Journal of The North American Benthological Society, ISSN 0887-3593, E-ISSN 1937-237X, Vol. 29, no 4, p. 1339-1348Article in journal (Refereed)
    Abstract [en]

    The origin of organic C supporting zoobenthic communities in 8 boreal lakes with different concentrations of dissolved organic C (DOC) was assessed by stable-isotope analysis. Profundal zoobenthos was depleted in C-13 compared to littoral zoobenthos, and this difference increased with decreasing DOC concentration. The delta C-13 of littoral zoobenthos suggested reliance on benthic algae, whereas depleted C-13 of profundal zoobenthos could be explained by contributions from allochthonous and autochthonous C sources. In deeper lakes, profundal zoobenthos diets also included C processed by methanotrophic bacteria. Littoral zoobenthos delta C-13 decreased with increasing DOC concentration in the lake water. Our results suggest that littoral benthic fauna are mainly supported by benthic algae in low-DOC lakes and by phytoplankton and allochthonous organic C in high-DOC lakes and that this difference is a result of light absorbance and energy supply by allochthonous organic C. Increasing allochthonous DOC inputs, as expected in a warmer and wetter climate, might reduce benthic algal production and alter the organic C base for benthic food webs in lake ecosystems.

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