First account of an exotic freshwater diatom (Discostella asterocostata) in Lakes of Ohio, USA

Surface sediment analysis offers a cost-effective way to document the spread of exotic micro-organisms, potentially presaging the spread of other exotic and invasive species. An analysis of surface sediment samples from 11 inland lakes in Ohio revealed the presence of an exotic diatom species, Discostella asterocostata, in seven lakes. While the presence of D. asterocostata has been documented in the waterways of surrounding states, this is the first documentation of the species in the lakes of Ohio. Previous research suggests the exotic diatom may have crossed the Pacific in the digestive tracts of the invasive bighead (Hypophthalmichthys nobilis) and silver carp (Hypophthalmichthys molitrix), planktivorous fish that were originally imported from Asia to North America for aquaculture. However, these carp species have not been reported in the Ohio lakes in which the exotic diatom was found, making it likely that D. asterocostata has spread throughout the state’s inland waterways via a different vector, potentially stocked fish. All seven lakes containing D. asterocostata are in the Ohio River Watershed, while the remaining four without D. asterocostata are in the Lake Erie Watershed. Ordination of the diatom assemblage data from each lake revealed that the diatom communities form two distinct groups, separated by watershed, which were significantly different from each other. Exotic and invasive diatoms can outcompete native diatoms and can potentially affect the environmental availability of nutrients and silica in a lake, leading to the restructuring of algal communities; however, it is currently unclear whether the presence of D. asterocostata is causing a restructuring of the assemblages in this case. Future work should focus on retrieval and analysis of sediment cores to shed light on the timing and ecological consequences of D. asterocostata’s introduction into Ohio’s inland lakes. This research documents the presence of the exotic diatom Discostella asterocostata in the Ohio River Watershed of the state of Ohio, USA.The spread of Discostella asterocostata is independent of the Asian carp, its hypothesized original vector, suggesting that the diatom may have a variety of vectors, including other wildlife, making management of its spread into other waterways intractable. It is, therefore, important to monitor the lakes where Discostella asterocostata has been found to determine if this introduced species has negative ecological impacts on the ecosystem.Although diatoms are small, they can have a large effect on the health of a lake ecosystem, potentially impacting water quality/water purification (especially important in reservoirs used for drinking water) and food webs and biodiversity (especially important for lakes used primarily for fishing). Because of these potential impacts on the larger ecosystem, introductions of exotic diatoms species should be carefully monitored.Analysis of lacustrine surface sediments is a cost-effective method for (1) documenting the spread of exotic and invasive diatoms in a watershed, (2) monitoring the impact of introduced species on the overall diatom assemblage, and (3) providing information on the overall health of the lake ecosystem after the introduction of an exotic species. This research documents the presence of the exotic diatom Discostella asterocostata in the Ohio River Watershed of the state of Ohio, USA. The spread of Discostella asterocostata is independent of the Asian carp, its hypothesized original vector, suggesting that the diatom may have a variety of vectors, including other wildlife, making management of its spread into other waterways intractable. It is, therefore, important to monitor the lakes where Discostella asterocostata has been found to determine if this introduced species has negative ecological impacts on the ecosystem. Although diatoms are small, they can have a large effect on the health of a lake ecosystem, potentially impacting water quality/water purification (especially important in reservoirs used for drinking water) and food webs and biodiversity (especially important for lakes used primarily for fishing). Because of these potential impacts on the larger ecosystem, introductions of exotic diatoms species should be carefully monitored. Analysis of lacustrine surface sediments is a cost-effective method for (1) documenting the spread of exotic and invasive diatoms in a watershed, (2) monitoring the impact of introduced species on the overall diatom assemblage, and (3) providing information on the overall health of the lake ecosystem after the introduction of an exotic species.