2022 Early Hearing Detection & Intervention Virtual Conference

March 13 - 15, 2022

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5/20/2019 | 2:15 PM - 2:30 PM | LONG-TERM RESPONSE OF LAKE PHYTOPLANKTON TO CHANGES IN NUTRIENT AND DETRITUS SUBSIDIES FROM ITS WATERSHED AND NUTRIENT CYCLING BY FISH | 253 AB

LONG-TERM RESPONSE OF LAKE PHYTOPLANKTON TO CHANGES IN NUTRIENT AND DETRITUS SUBSIDIES FROM ITS WATERSHED AND NUTRIENT CYCLING BY FISH

We examined the response of phytoplankton in eutrophic Acton Lake to changes in subsidies of nutrients and detritus (sediments) over 24 years, driven by a pronounced increase in conservation tillage in this agricultural watershed. In streams draining the watershed, flow-weighted mean concentrations (FWMC) of suspended sediment, all forms of nitrogen (N), and particulate phosphorus (P) declined over the entire period. In contrast, FWMC of soluble phosphorus declined over the first decade, then increased. Acton Lake phytoplankton biomass increased over the first decade, despite decreasing stream concentrations of P, which was then the limiting nutrient. The phytoplankton increase was driven by increased light (due to decreased suspended sediments) in the water column, and by an increase in biomass, and hence nutrient excretion by, sediment feeding fish (gizzard shad). Over roughly the second decade, phytoplankton biomass remained relatively constant; however, phytoplankton have become increasingly limited by N, relative to P. The increase in relative N limitation appears driven by decreased N:P from stream inputs, and increased nutrient cycling by fish, which excrete at low N:P. Our results illustrate how phytoplankton dynamics are regulated by watershed inputs as well as animal-mediated nutrient cycling.

Watershed
Nutrients
Fish

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Presenters/Authors

Michael Vanni (), Miami University, vannimj@miamioh.edu;