Date Approved

4-2016

Graduate Degree Type

Thesis

Degree Name

Biology (M.S.)

Degree Program

Biology

First Advisor

Alan Steinman

Second Advisor

Mark Luttenton

Third Advisor

Rick Rediske

Fourth Advisor

Graham Peaslee

Abstract

Phosphorus (P) is often implicated as a contributing factor to algal blooms. Attention has been focused on P in surface runoff, but agricultural tile drains also can be a source. Lake Macatawa is a hypereutrophic lake located in west Michigan, and the watershed is dominated by row crop agriculture. Further research is needed to understand the influence of bioavailable P originating from tile drains on water quality in Lake Macatawa. The objectives of this study were to 1) conduct a tile drain effluent sampling survey to assess their importance as a source of P in the Macatawa Watershed; 2) investigate the change in tile drain P concentrations spatially and temporally over a one-year period; and 3) use growth chamber algal bioassays and the ratio of soluble reactive phosphorus to total phosphorus (SRP:TP) to assess tile drain P bioavailability. During March 2015 – February 2016, P concentrations varied significantly among sample sites, and the highest P loads occurred during the non-growing season. The SRP:TP ratio measured at the tile drain outlets had a positive correlation with acreage drained by the tile system. Four of six bioassays resulted in a positive relationship between SRP and algal growth, but results from only one bioassay were statistically significant. There was a clear change in the algal community structure when incubated in tile drain water, and dominance was by diatoms, not cyanobacteria as expected. Based on these results, there is a need to quantify the tile drained area in the Macatawa watershed and manage for high P loads during the non-growing season.

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