Effects of growing season flow regime on stream periphyton growth in a coastal plain stream

Increasing water extractions for irrigation coupled with climate shifts in the lower Flint River Basin in southwestern Georgia can decrease water flows in local stream systems. We conducted controlled experiments to examine the relationships between low flow stream discharges, associated environmental factors and periphyton growth, biomass, and composition in Ichawaynochaway Creek (IC), a major Flint River tributary during the summer of 2014. We used an artificial stream facility to manipulate discharge, nutrients, and grazers in a series of experiments. Our study indicated that there is rapid periphyton accumulation potential during the summer growing season. Nutrient enrichment effects were greatest at higher discharge and grazers exerted limited control over periphyton growth. All flow treatments were dominated by diatoms but lower flow treatments had higher relative abundance of green algae. Flow alterations can potentially affect periphyton accumulation rates and shift algal composition with impacts on in-stream habitats and food web dynamics.