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Anchor Watch Seminar Series
December 12, 2018 @ 5:00 pm - 6:30 pm
Dr. Hunter Carrick from Central Michigan University brings the microbial food web to YOU, freshwater biologists!
Evaluating Recent Changes in Lake Michigan’s Lower Food Web
by Hunter Carrick, PhD
Unprecedented and rapid changes have been observed in the open water region of southern Lake Michigan (e.g., decline in spring diatom bloom), while comparatively little is known about the impact mussels and other associated changes have had on components of the lower food web. We evaluated plankton abundance, and population dynamics (growth, loss rates) along a near to offshore gradient in Lake Michigan from 2013-18. Our findings showed that current chlorophyll levels in Lake Michigan ~ 1.0 ug/L, with bloom-like conditions now relegated to the nearshore region during the spring run-off events. The spring diatom assemblages appears to be dominated by small centric diatoms, compared with larger-celled, colonial diatoms prior to 2005. Despite significant declines in Ppico abundance, the group now makes up the majority of phytoplankton chlorophyll in both northern and southern Lake Michigan (>50%), while heterotrophic bacteria numbers appear to be stable since 1990. Microplankton (ciliated protists, diatoms) have declined by >2-fold since 1990; however, their abundance appeared to be augmented by near-shore subsidies. Nanoplankton (flagellated protists) populations have remained stable and may now play a larger role in supporting the crustacean zooplankton assemblage in the lake.