Patterns in the Potamoplankton of the Saginaw River and Shiawassee National Wildlife Refuge, Michigan

Abstract

As part of ongoing research evaluating the baseline conditions of the Shiawassee National Wildlife Refuge (SNWR), Michigan, prior to a large scale floodplain wetland restoration, this project focused the variation in phytoplankton and water chemistry; spatially, seasonally, and hydrologically. During the growing season of 2014, phytoplankton and water chemistry parameters were surveyed throughout the SNWR and Saginaw River. These samples were synthesized and data were compared for patterns by season, sample location, and longitudinal position on the Saginaw River. Phytoplankton and water chemistry were also compared to hydrologic data including river slope (which served as an indicator of hydraulic residence time) as well as the occurrence of reverse or stalled flow in the Saginaw River. Results indicated that phytoplankton communities in floodplain wetlands, tributaries, and the main river channel varied significantly by taxonomic composition and abundance, as did key water chemistry parameters (Total Phosphorus, Nitrate, Total Dissolved Solids). Additionally, potamoplankton communities in the Saginaw River varied longitudinally, becoming more abundant, taxonomically rich, and diverse from upstream to downstream. Prolonged residence times due to low slopes also showed more diverse and abundant potamoplankton communities with fewer diatoms than times of high slopes. The occurrence of reverse flow was found to be associated with a homogenizing effect along the course of the Saginaw River both in terms of biology and water chemistry.