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School of Environment and Natural Resources


Chloe Welch's Honors Defense

Apr 18, 2014, 3:30pm - 4:30pm


Chloe Welch will present Bioturbation by the Invasive Rusty Crayfish (Orconectes rusticus) Affects Turbidity and Nutrients: Implications for Harmful Algal Blooms on Friday, April 18, at 3:30 p.m. in Kottman 245.

Eutrophication and harmful algal blooms (HABs) are serious anthropogenic stressors impacting water quality and aquatic ecosystems worldwide. Aquatic 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. 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 previously-settled 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.