Long-term shifts in phenology of nearshore zooplankton in Lake Ontario

Seasonal succession of nearshore zooplankton reflects the physical environment and biological competition and predation.  Nearshore habitats are important spawning areas for fish, and thus recruitment success is largely determined by the alignment in the timing of zooplankton peaks with the larval fish emergence and growth at early life stages.  We use a thirty-year (1995-2025) biweekly time series from May-October of seven nearshore (10 m depth) sites in Lake Ontario to track shifts in zooplankton community phenology.  The seven sites are distributed along the US southern shore tracking a well-known west to east gradient in thermal structure.  Copepod populations are first to peak in May with cyclopoid followed by calanoid species peaks.  As the nearshore habitat warms we see bosminid and then daphniid grazers dominate. In late summer and fall, predatory cladocerans are a small component of overall biomass but have a major impact on zooplankton community structure.  Sites were grouped by similarity in phenology that reflected geographic patterns.  We evaluate whether zooplankton phenology has changed over this critical time period marked by climate change and the expansion of invasive species.  This timing is then put in context of the life history of fish species known to utilize nearshore habitat.                       

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: James Watkins, Cornell University (jmw237@cornell.edu)

Authors:

James Watkins, Cornell University  (jmw237@cornell.edu)

Lars Rudstam, Cornell University  (lgr1@cornell.edu)