Phytoplankton community composition: comparisons between contrasting embayments and across time prov

Session: Poster Session

Mary Anne Evans, USGS, Great Lakes Science Center, [email protected]

Abstract

Phytoplankton community composition integrates numerous environmental drivers, some responsive to human management and others currently unmanaged, and in turn is of interest because it influences food quality for fisheries and productions of fish, wildlife, and human toxins. We compare historical (1971) to recent (2015) phytoplankton community data for Grand Traverse Bay to assess continued recovery from the direct disposal of fruit pulp into the bay. Historical species composition data from shortly after reductions in fruit pulp disposal show a sharp contrast to recent community composition indicative of oligotrophication.  For example, in 1971, a Microcystis aeruginosa synonym was noted as exceeding 5% of phytoplankton cell counts in September but this harmful algal bloom species was not detected in 2015.  Abiotic conditions and phytoplankton community composition are also compared among Grand Traverse Bay, Saginaw Bay, and western Lake Erie.  Both phytoplankton biovolume and community composition varied with average nutrient concentrations among bays.  Finally, among year community variability in western Lake Erie is assessed relative to the influence of nutrient and weather variability and the potential for nutrient management to shift community composition, the community varied in response to both nutrient loading and the timing of that loading.