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Scharnweber, KristinORCID iD iconorcid.org/0000-0003-2858-5947
Publications (10 of 30) Show all publications
Scharnweber, K., Chaguaceda, F. & Eklöv, P. (2020). Fatty acid accumulation in feeding types of a natural freshwater fish population.
Open this publication in new window or tab >>Fatty acid accumulation in feeding types of a natural freshwater fish population
2020 (English)In: Article in journal (Refereed) Submitted
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-404188 (URN)
Available from: 2020-02-14 Created: 2020-02-14 Last updated: 2020-02-17
Chaguaceda, F., Eklöv, P. & Scharnweber, K. (2020). Regulation of fatty acid composition related to ontogenetic changes and niche differentiation of a common aquatic consumer.
Open this publication in new window or tab >>Regulation of fatty acid composition related to ontogenetic changes and niche differentiation of a common aquatic consumer
2020 (English)In: Article in journal (Refereed) Submitted
National Category
Ecology
Research subject
Biology with specialization in Limnology
Identifiers
urn:nbn:se:uu:diva-404183 (URN)
Available from: 2020-02-14 Created: 2020-02-14 Last updated: 2020-02-17
Chaguaceda, F., Scharnweber, K., Tranvik, L. & Eklöv, P. (2020). Short-term apparent mutualism drives responses of aquatic prey at increasing productivity.
Open this publication in new window or tab >>Short-term apparent mutualism drives responses of aquatic prey at increasing productivity
2020 (English)In: Article in journal (Refereed) Submitted
Abstract [en]

According to apparent competition theory, sharing a predator should cause indirect interactions among prey that can substantially influence food-web responses to environmental drivers. However, empirical evidence of apparent competition under ongoing environmental change is still scarce. In an 8-week mesocosm experiment, we found that short-term responses of aquatic food webs to increasing productivity were strongly regulated by apparent mutualism between benthic and pelagic prey in the presence of a generalist fish. Following trends in natural systems, increasing productivity in our mesocosms favored the relative abundance of benthic prey. This elicited a shift in fish selectivity from pelagic to benthic prey driven by fish switching behavior which resulted in lower and delayed top-down control on pelagic prey. Our results highlight that apparent competition theory may explain food-web responses across environmental gradients, whereby resulting prey dynamics and stability may highly depend on the foraging behavior exhibited by generalist predators.

Keywords
Apparent competition, top-down control, trophic cascade, food web, resource coupling, eutrophication, indirect interactions, crucian carp, mesocosm
National Category
Ecology
Research subject
Biology with specialization in Limnology; Biology with specialization in Animal Ecology
Identifiers
urn:nbn:se:uu:diva-404054 (URN)
Funder
Knut and Alice Wallenberg Foundation, KAW 2013.0091
Available from: 2020-02-08 Created: 2020-02-08 Last updated: 2020-02-17
Marklund, M. H. K., Svanbäck, R., Faulks, L., Breed, M. F., Scharnweber, K., Zha, Y. & Eklöv, P. (2019). Asymmetrical habitat coupling of an aquatic predator: The importance of individual specialization. Ecology and Evolution, 9(6), 3405-3415
Open this publication in new window or tab >>Asymmetrical habitat coupling of an aquatic predator: The importance of individual specialization
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2019 (English)In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 9, no 6, p. 3405-3415Article in journal (Refereed) Published
Abstract [en]

Predators should stabilize food webs because they can move between spatially separate habitats. However, predators adapted to forage on local resources may have a reduced ability to couple habitats. Here, we show clear asymmetry in the ability to couple habitats by Eurasian perch—a common polymorphic predator in European lakes. We sampled perch from two spatially separate habitats—pelagic and littoral zones—in Lake Erken, Sweden. Littoral perch showed stronger individual specialization, but they also used resources from the pelagic zone, indicating their ability to couple habitats. In contrast, pelagic perch showed weaker individual specialization but near complete reliance on pelagic resources, indicating their preference to one habitat. This asymmetry in the habitat coupling ability of perch challenges the expectation that, in general, predators should stabilize spatially separated food webs. Our results suggest that habitat coupling might be constrained by morphological adaptations, which in this case were not related to genetic differentiation but were more likely related to differences in individual specialization.

Keywords
diet specialization, food web, landscape genetics, morphological specialization, Perca fluviatilis
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-315719 (URN)10.1002/ece3.4973 (DOI)000462384800024 ()30962901 (PubMedID)
Funder
Swedish Research Council
Note

Title in thesis list of papers: Asymmetrical habitat coupling of a top predator

Available from: 2017-02-20 Created: 2017-02-20 Last updated: 2019-11-25Bibliographically approved
Scharnweber, K. (2019). Chironomidae fatty acid proportions.
Open this publication in new window or tab >>Chironomidae fatty acid proportions
2019 (English)Data set, Primary data
National Category
Natural Sciences
Research subject
Biology with specialization in Limnology
Identifiers
urn:nbn:se:uu:diva-389470 (URN)
Available from: 2019-07-15 Created: 2019-07-15 Last updated: 2019-08-01Bibliographically approved
Nydahl, A., Wallin, M., Tranvik, L., Hiller, C., Attermeyer, K., Garrison, J. A., . . . Weyhenmeyer, G. A. (2019). Colored organic matter increases CO2 in meso-eutrophic lake water through altered light climate and acidity. Limnology and Oceanography, 64(2), 744-756
Open this publication in new window or tab >>Colored organic matter increases CO2 in meso-eutrophic lake water through altered light climate and acidity
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2019 (English)In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 64, no 2, p. 744-756Article in journal (Refereed) Published
Abstract [en]

Many surface waters across the boreal region are browning due to increased concentrations of colored allochthonous dissolved organic carbon (DOC). Browning may stimulate heterotrophic metabolism, may have a shading effect constraining primary production, and may acidify the water leading to decreased pH with a subsequent shift in the carbonate system. All these effects are expected to result in increased lake water carbon dioxide (CO2) concentrations. We tested here these expectations by assessing the effects of both altered allochthonous DOC input and light conditions through shading on lake water CO2 concentrations. We used two mesocosm experiments with water from the meso‐eutrophic Lake Erken, Sweden, to determine the relative importance of bacterial activities, primary production, and shifts in the carbonate system on CO2 concentrations. We found that DOC addition and shading resulted in a significant increase in partial pressure of CO2 (pCO2) in all mesocosms. Surprisingly, there was no relationship between bacterial activities and pCO2. Instead the experimental reduction of light by DOC and/or shading decreased the photosynthesis to respiration ratio leading to increased pCO2. Another driving force behind the observed pCO2 increase was a significant decrease in pH, caused by a decline in photosynthesis and the input of acidic DOC. Considering that colored allochthonous DOC may increase in a warmer and wetter climate, our results could also apply for whole lake ecosystems and pCO2 may increase in many lakes through a reduction in the rate of photosynthesis and decreased pH.

National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:uu:diva-366220 (URN)10.1002/lno.11072 (DOI)000461865500022 ()
Available from: 2018-11-18 Created: 2018-11-18 Last updated: 2019-08-15Bibliographically approved
Scharnweber, K. (2019). Data of morphological and trophic divergence of lake and stream minnows (Phoxinus phoxinus).
Open this publication in new window or tab >>Data of morphological and trophic divergence of lake and stream minnows (Phoxinus phoxinus)
2019 (English)Data set
National Category
Natural Sciences
Research subject
Animal Ecology
Identifiers
urn:nbn:se:uu:diva-389472 (URN)
Available from: 2019-07-15 Created: 2019-07-15 Last updated: 2019-08-01Bibliographically approved
Mehner, T., Lischke, B., Scharnweber, K., Attermeyer, K., Brothers, S., Gaedke, U., . . . Brucet, S. (2018). Empirical correspondence between trophic transfer efficiency in freshwater food webs and the slope of their size spectra. Ecology, 99(6), 1463-1472
Open this publication in new window or tab >>Empirical correspondence between trophic transfer efficiency in freshwater food webs and the slope of their size spectra
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2018 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 99, no 6, p. 1463-1472Article in journal (Refereed) Published
Abstract [en]

The density of organisms declines with size, because larger organisms need more energy than smaller ones and energetic losses occur when larger organisms feed on smaller ones. A potential expression of density-size distributions are Normalized Biomass Size Spectra (NBSS), which plot the logarithm of biomass independent of taxonomy within bins of logarithmic organismal size, divided by the bin width. Theoretically, the NBSS slope of multi-trophic communities is exactly - 1.0 if the trophic transfer efficiency (TTE, ratio of production rates between adjacent trophic levels) is 10% and the predator-prey mass ratio (PPMR) is fixed at 10(4). Here we provide evidence from four multi-trophic lake food webs that empirically estimated TTEs correspond to empirically estimated slopes of the respective community NBSS. Each of the NBSS considered pelagic and benthic organisms spanning size ranges from bacteria to fish, all sampled over three seasons in 1 yr. The four NBSS slopes were significantly steeper than -1.0 (range -1.14 to -1.19, with 95% CIs excluding -1). The corresponding average TTEs were substantially lower than 10% in each of the four food webs (range 1.0% to 3.6%, mean 1.85%). The overall slope merging all biomass-size data pairs from the four systems (-1.17) was almost identical to the slope predicted from the arithmetic mean TTE of the four food webs (-1.18) assuming a constant PPMR of 10(4). Accordingly, our empirical data confirm the theoretically predicted quantitative relationship between TTE and the slope of the biomass-size distribution. Furthermore, we show that benthic and pelagic organisms can be merged into a community NBSS, but future studies have yet to explore potential differences in habitat-specific TTEs and PPMRs. We suggest that community NBSS may provide valuable information on the structure of food webs and their energetic pathways, and can result in improved accuracy of TTE-estimates.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-347754 (URN)10.1002/ecy.2347 (DOI)000434094400021 ()29856494 (PubMedID)
Funder
German Research Foundation (DFG), Me 1686/7-1
Available from: 2018-04-06 Created: 2018-04-06 Last updated: 2018-08-31Bibliographically approved
Marklund, M. H. K., Svanbäck, R., Zha, Y., Scharnweber, K. & Eklöv, P. (2018). The influence of habitat accessibility on the dietary and morphological specialisation of an aquatic predator. Oikos, 127(1), 160-169
Open this publication in new window or tab >>The influence of habitat accessibility on the dietary and morphological specialisation of an aquatic predator
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2018 (English)In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 127, no 1, p. 160-169Article in journal (Refereed) Published
Abstract [en]

Individual diet and habitat specialisation are widespread in animal taxa and often related to levels of predation and competition. Mobile consumers such as predatory fish can stabilise lake food webs by ranging over a larger area than their prey, thereby switching between habitats. Although, this switching assumes that the predator has equal preference for the available prey, individual diet specialisation and morphological adaptations to different habitats could potentially prevent individuals from switching between habitats. In this study, we assessed the niche width and individual specialisation in Eurasian perch Perca fluviatilis in response to a shift in habitat use by manipulating the ability for this top predator to couple habitats. We ran an eight weeks pond experiment, to test the effect of habitat switching on diet and morphological specialisations. We show that habitat coupling influenced individual diet specialisation and niche use in expected directions where specialisation increased with decreasing habitat switching. In contrast to expectations, the morphological variation decreased with increasing diet specialisation. Our results expand on previous work and suggest that individual specialisation and niche width can impact the ability of mobile predators to couple habitats. Furthermore, it shows the importance of individual specialisations in relation to habitat coupling.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-315718 (URN)10.1111/oik.04094 (DOI)000419102100015 ()
Funder
Swedish Research CouncilSwedish Research Council Formas
Available from: 2017-02-20 Created: 2017-02-20 Last updated: 2018-12-11Bibliographically approved
Lischke, B., Mehner, T., Hilt, S., Attermeyer, K., Brauns, M., Brothers, S., . . . Gaedke, U. (2017). Benthic carbon is inefficiently transferred in the food webs of two eutrophic shallow lakes. Freshwater Biology, 62(10), 1693-1706
Open this publication in new window or tab >>Benthic carbon is inefficiently transferred in the food webs of two eutrophic shallow lakes
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2017 (English)In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 62, no 10, p. 1693-1706Article in journal (Refereed) Published
Abstract [en]

1. The sum of benthic autotrophic and bacterial production often exceeds the sum of pelagic autotrophic and bacterial production, and hence may contribute sub- stantially to whole-lake carbon fluxes, especially in shallow lakes. Furthermore, both benthic and pelagic autotrophic and bacterial production are highly edible and of sufficient nutritional quality for animal consumers. We thus hypothesised that pelagic and benthic transfer efficiencies (ratios of production at adjacent trophic levels) in shallow lakes should be similar. 2. We performed whole ecosystem studies in two shallow lakes (3.5 ha, mean depth 2 m), one with and one without submerged macrophytes, and quantified pelagic and benthic biomass, production and transfer efficiencies for bacteria, phytoplank- ton, epipelon, epiphyton, macrophytes, zooplankton, macrozoobenthos and fish. We expected higher transfer efficiencies in the lake with macrophytes, because these provide shelter and food for macrozoobenthos and may thus enable a more efficient conversion of basal production to consumer production. 3. In both lakes, the majority of the whole-lake autotrophic and bacterial produc- tion was provided by benthic organisms, but whole-lake primary consumer pro- duction mostly relied on pelagic autotrophic and bacterial production. Consequently, transfer efficiency of benthic autotrophic and bacterial production to macrozoobenthos production was an order of magnitude lower than the transfer efficiency of pelagic autotrophic and bacterial production to rotifer and crustacean production. Between-lake differences in transfer efficiencies were minor. 4. We discuss several aspects potentially causing the unexpectedly low benthic transfer efficiencies, such as the food quality of producers, pelagic–benthic links, oxygen concentrations in the deeper lake areas and additional unaccounted con- sumer production by pelagic and benthic protozoa and meiobenthos at interme- diate or top trophic levels. None of these processes convincingly explain the large differences between benthic and pelagic transfer efficiencies. 5. Our data indicate that shallow eutrophic lakes, even with a major share of auto- trophic and bacterial production in the benthic zone, can function as pelagic sys- tems with respect to primary consumer production. We suggest that the benthic autotrophic production was mostly transferred to benthic bacterial production, which remained in the sediments, potentially cycling internally in a similar way to what has previously been described for the microbial loop in pelagic habitats. Understanding the energetics of whole-lake food webs, including the fate of the substantial benthic bacterial production, which is either mineralised at the sedi- ment surface or permanently buried, has important implications for regional and global carbon cycling

Keywords
bacterial production, benthic food chain, pelagic food chain, quantitative food webs, trophic transfer efficiency
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-334883 (URN)10.1111/fwb.12979 (DOI)000410094000003 ()
Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2018-05-17Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-2858-5947

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