Planktivore population dynamics affect body size characteristics of Bosmina: evidence from sediment archive and contemporary lake samples
(English)Manuscript (preprint) (Other academic)
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.
Research subject Limnology
IdentifiersURN: urn:nbn:se:umu:diva-53556OAI: oai:DiVA.org:umu-53556DiVA: diva2:513441