The influence of Daphnia spp. on resuspended sediments in shallow prairie lakes

Abstract

Low water transparency in shallow lakes, which may limit macrophyte growth, is usually attributed to excessive phytoplankton biomass. However, abundant resuspended sediments also contribute substantially to reductions in water clarity. The ability of the large-bodied zooplankter, Daphnia to increase water clarity by reducing phytoplankton is well studied, but less is known about Daphnia’s effect on resuspended sediments. To evaluate Daphnia’s ability to reduce suspended detritus and inorganic particles and the resulting effect on late summer macrophyte biomass, I combined field observations with a field enclosure experiment. My field results suggest that abundant Daphnia can reduce detritus concentrations and that this effect is most pronounced in the spring. I also demonstrate that summer macrophyte biomass and plant species richness increases with lower spring turbidity. My field enclosure experiment confirms that Daphnia are capable of clearing resuspended sediments during both low and high turbidity conditions in spring.