Seasonal phosphorus retention in the Lake Erie western basin

Session: 41b. - Great Lakes Harmful Algal Blooms Research from Watershed Influence to Ecosystem Effects

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

Abstract

In the western basin of Lake Erie, late summer cyanoHABs are believed to be fueled by spring nutrient loading, however the time between spring loading and peak biomass is frequently longer than the average water retention time of the western basin.  Five years of time series data indicate that total nitrogen decreases over the summer as expected based on a spring nutrient loading pulse and summer washout.  However, total phosphorus in most years shows a late-summer increase in concentration that is not explained by riverine loading.  We explore four hypotheses to explain the retention and summer increase in phosphorus: (1) sediment uptake and release, (2) Dreissenid mussels and the near shore shunt, (3) uptake and release from coastal wetlands, and (4) summer fish mortality. These hypothesized mechanisms are likely to respond differently to environmental drivers, thus, determining the dominant mechanism(s) will improve predictions of long-term lake response to nutrient management, changing weather patterns, and changing food webs.

1. Keyword
ecosystems

2. Keyword
harmful algal blooms

3. Keyword
nutrients