A review on utilizing Bosmina size structure archived in lake sediments to infer historic shifts in predation regimes

Zooplankton are considered excellent indicators of aquatic food web structure, due to their role as grazers on primary producers and their sensitivity to predation by both planktivorous fish and invertebrates. Several key zooplankton taxa also leave identifiable remains that are often well-preserved in lake sediments, providing an opportunity to track changes in predation pressure over timescales of decades to thousands of years. For example, the small-bodied cladoceran zooplankter Bosmina (Branchiopoda, Crustacea) is often highly abundant in lake sediments, and because Bosmina often undergoes cyclomorphosis in response to fish and invertebrate predation, measurements of subfossil Bosmina features can be indicative of predation regime shifts. This review focuses on Bosmina cyclomorphic responses to varying predation regimes and the application of these principles to Bosmina subfossil remains to better understand long-term ecological changes occurring in lakes. We conclude that subfossil Bosmina size structure is a promising indicator of historic changes in predation pressure in response to fish introductions/extirpations/population dynamics and other anthropogenic disturbances. Size measurements of Bosmina subfossils can often complement traditional zooplankton community assessments and provide critical insight into how predatorprey dynamics change as a result of environmental stressors, as well as the timescale of response to historic predation regime shifts.