Bioturbation by the Invasive Rusty Crayfish (Orconectes rusticus) Affects Turbidity and Nutrients: Implications for Harmful Algal Blooms
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Date
2014-05
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The Ohio State University
Abstract
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.
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Keywords
bioturbation, harmful algal blooms, crayfish, Orconectes rusticus, nutrients, eutrophication