Sampling and sample processing followed Salk et al., (2018).

Briefly, at each sampling location, water column physical and chemical parameters (pH, conductivity, temperature, dissolved oxygen) were measured using a YSI 600QS sonde (YSI Inc., Yellow Springs, OH, USA). Water samples were collected by Van Dorn bottle at 1m depth for the analysis of NO3, NH4, phosphate, TKN, TP, chl a concentrations, total microcystins and cell identification/biovolume enumeration. Samples for dissolved nutrient analysis were filtered immediately upon collection (0.2 um), kept on ice, and frozen upon return to the lab. Unfiltered sample water was collected for TKN and TP analysis and also frozen. Total and dissolved (<0.2 um) nutrient concentrations were determined following analysis of samples by the National Center for Water Quality Research at Heidelberg University (Tiffin, OH, USA). Samples for chl a analysis were concentrated on GFC filters whereas raw water samples for microcystins were frozen in new polycarbonate bottles with subsequent analysis of both parameters by Ohio EPA. Cell identification and biovolume assessment was conducted on samples preserved with Lugol’s iodine.