Bioturbation by the Invasive Rusty Crayfish (Orconectes rusticus) Affects Turbidity and Nutrients: Implications for Harmful Algal Blooms
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. School of Environment and Natural Resources Honors Theses; 2014
Eutrophication and harmful algal blooms (HABs) are serious anthropogenic stressors impacting water quality and aquatic ecosystems worldwide. Although anthropogenic nutrient loading is a primary factor driving the rise in HABs, aquatic bioturbators may also contribute to the resuspension of nutrients and sediment into the water column and exacerbate HABs. Bioturbators are benthic organisms that rework bottom sediments in aquatic ecosystems through their daily activities, and can contribute to HABS by stirring up and resuspending nutrients and cyanobacteria cells. The rusty crayfish (Orconectes rusticus) is one such freshwater bioturbator that has established itself as an invasive species in central Ohio. The objective of this study was to examine the effect of crayfish density (low, high and no crayfish control) on turbidity and nutrient concentrations in a controlled laboratory experiment. In each of the three treatments, turbidity, nitrogen and phosphorus measurements were taken after a 24 hour acclimation period. Results indicate that the presence of crayfish significantly increased turbidity in the water column relative to the no crayfish control. Additionally, the concentration of nitrogen was significantly higher in the high density crayfish treatment and in the treatments with sediment. Opposite to predictions, phosphorous was higher in treatments without sediment and decreased in the presence of crayfish. Together, this suggests that through its daily activities, O. rusticus is causing a marked resuspension of sediments in the water column. This implies that through its role as a bioturbator, O. rusticus may indeed be exacerbating algae growth by agitating previouslysettled nutrients that can further feed the growth of HABs, although more research would have to be completed on a larger scale to determine if they would indeed have a large enough effect to be biologically significant.
Academic Major: Environmental Science