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Fingerprints of planktivory: paleolimnological evidence of past fish community structure and dynamics
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Planktivorous fish affect the species composition, size and morphology of their zooplankton prey by size selective predation. Remains of cladocerans are deposited in the lake sediments and this microfossil community hence reflects the historical changes in the planktivore fish community. Most earlier work on quantitatively inferring past planktivory deals with ephippia (resting eggs) of Daphnia, however these remains are very scarce in northern Swedish lakes. In these lakes, often dominated by fish that are not obligate planktivores, such as perch (Perca fluviatilis), the individual size to a large degree determines the type of resource consumed. Therefore, in these lakes, the size distribution as well as the density of the fish community determines the overall planktivoryThis thesis deals with evaluating the use of Bosmina remains in the sediment as indicators of past planktivory. I developed a transfer function based on Bosmina remains to be used in oligotrophic lakes with omnivorous species to reconstruct past planktivory. I test the transfer function in a lake where the history is to a large extent known. Furthermore, in this thesis a novel quantitative measure of planktivore pressure, the PCC (Planktivore Community Capacity) was developed. It was also possible to compare the morphology measurements of carapace length and mucro length of contemporary Bosmina sampled in the lake, with the same measurements on microfossils of Bosmina sedimented during the corresponding time period. By using the resurrection approach this thesis also evaluates the use of Ceriodaphnia clones as indicators of micro-evolutionary responses to past planktivory.From the studies in this thesis I can draw some major conclusions; the morphological measurements carapace length and mucro length of Bosmina can be used to infer past planktivory in northern Swedish lakes. PCC has a higher explanatory power than CPUE in these lakes dominated by omnivorous fish. The morphology of the contemporary Bosmina corresponds well with the remains found in the sediment dating from the same time period. Both the contemporary and microfossil Bosmina changes in body size characteristics was in turn strongly related to PPC. Finally, the hatching of Ceriodaphnia ephippia is promising for studying past planktivory, both because of the high viability of the ephippia and the relationship between eye area and inferred PCC.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2012. , 33 p.
Keyword [en]
planktivory, foraging efficiency, cladoceran remains, Bosmina, planktivore community capacity, PCC, Ceriodaphnia, reserrection
National Category
Ecology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:umu:diva-53561ISBN: 978-91-7459-395-2 (print)OAI: oai:DiVA.org:umu-53561DiVA: diva2:513513
Public defence
2012-04-27, KBC-huset, Lilla Hörsalen, KB3A9, Umeå Universitet, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2012-04-04 Created: 2012-04-02 Last updated: 2012-04-02Bibliographically approved
List of papers
1. Resurrected past-century Ceriodaphnia quadrangula highlight  differences between pheno- and genotypic expressions
Open this publication in new window or tab >>Resurrected past-century Ceriodaphnia quadrangula highlight  differences between pheno- and genotypic expressions
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The hatching of cladoceran ephippia from a 15 cm long sediment core was investigated, and Ceriodaphnia quadrangula -clones were isolated from different sediment layers. Bosmina-microfossil data were also analyzed, and compared with the corresponding data from a Pb210-dated core, which allowed us to infer the age of the sediment-layers. Using changes in Bosmina-microfossil morphologies, we were furthermore able to infer the presence of different regimes of fish-predation. C. quadrangula was found to hatch in layers with an inferred age of approximately a century. Newly hatched individuals had smaller eye-size in sediment layers corresponding to high predation by young-of-the-year perch. Newly hatched individuals also generally had a marked neck-spine. In contrast, morphological characters of C. quadrangula -clones reared in the laboratory over several generations showed no variation in relation to predation regime, indicating the absence of fixed genotype-level changes. Furthermore, the laboratory-grown clones only rarely produced a neck-spine. The results suggest phenotypic variation in response to the regime under which ephippia were produced.

National Category
Natural Sciences
Research subject
Limnology
Identifiers
urn:nbn:se:umu:diva-53560 (URN)
Available from: 2012-04-02 Created: 2012-04-02 Last updated: 2012-04-02Bibliographically approved
2.
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3. Planktivore population dynamics affect body size characteristics of Bosmina: evidence from sediment archive and contemporary lake samples
Open this publication in new window or tab >>Planktivore population dynamics affect body size characteristics of Bosmina: evidence from sediment archive and contemporary lake samples
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Planktivorous fish affect the species composition, morphology and size of their zooplankton prey species by size selective predation. Microfossils of cladocerans are preserved in the lake sediment and hence cladoceran fossil characteristics may be used to reconstruct historical variation of planktivory in lakes. In lakes dominated by fish that are not obligate planktivores (e.g. perch, Perca fluviatilis), the individual size determines to large extent the type of resources consumed. Therefore the size distribution and density of such fish populations determine overall planktivory impact in these lakes.In a Northern Swedish lake over a 9-year period, we compared the carapace length and mucro length of the cladoceran Bosmina spp. from the contemporary samples with the sediment archive. We estimated the temporal variation in overall planktivory pressure on Bosmina by calculating a population planktivore capacity (PPC) measure on zooplankton using the population density and size structure of the perch population together with size dependent attack rate functions on Bosmina.Our results show that temporal changes in body size characteristics of Bosmina in the contemporary and fossil remains were strongly correlated. Contemporary lake samples and fossil remains of Bosmina showed similar responses in body size characteristics to changes in estimated PPC. Initially, when PPC was low in the lake, both size of carapace and mucro were large. As PPC increased due to strong recruitment of perch during the middle of the study period both carapace and mucro size were small, to increase again towards the end of the study when PPC decreased again. Small perch, mainly young-of-the-year (YOY) perch contribution to PPC was high, more than 80% of to the total PPC in most years. This suggests that the contribution of the smallest size classes of fish to PPC can be high and needs to be taken into account when trying to relate changes in zooplankton community characteristics to variation in planktivore densities.The similar response in body size characteristics of Bosmina in contemporary and sediment samples to changes in planktivory pressure strongly suggests the body size characteristics of Bosmina microfossils, i.e. the carapace and mucro length can be used to reconstruct historical changes in planktivory in lakes.

National Category
Natural Sciences
Research subject
Limnology
Identifiers
urn:nbn:se:umu:diva-53556 (URN)
Available from: 2012-04-02 Created: 2012-04-02 Last updated: 2012-04-02Bibliographically approved
4. Remains of Bosmina in sediments reflects historical changes in fish populations in a northern Swedish lake
Open this publication in new window or tab >>Remains of Bosmina in sediments reflects historical changes in fish populations in a northern Swedish lake
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Based on morphological measurements on Bosmina in a sediment core from a boreal lake we estimated 60 years back in time historical changes in Planktivore Community Capacity (PCC), a recent derived approach to estimate past planktivore pressure in lakes. We then validated the PCC approach with available information on changes in the lake fish community based on historical knowledge and more recent fish population studies in the lake. Based on available data on fish density, size structure and size dependent attack rate functions on zooplankton we calculated a measure of planktivore pressure in the lake, the Planktivore Population Capacity (PPC). The reconstructed PCC development over the time from Bosmina remains in the sediment core correlated well with PPC estimates (r2 = 0.89 p<0.05) as well as qualitatively with historical information on the development of fish community in the lake. The results from our study suggest that the derived PCC function based on morphological measurements on Bosmina remains in sediments can successfully be used to track historical changes in planktivore communities in lakes.

National Category
Natural Sciences
Research subject
Limnology
Identifiers
urn:nbn:se:umu:diva-53559 (URN)
Available from: 2012-04-02 Created: 2012-04-02 Last updated: 2012-04-05Bibliographically approved

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