Vadim A. Karatayev

Limnoperna fortunei Versus Dreissena polymorpha: Population Densities and Benthic Community Impacts of Two Invasive Freshwater Bivalves

ABSTRACT In this study, for the first time, using similar methods, we compared the population density and distribution across different substrate types of Limnoperna fortunei and Dreissena polymorpha, as well as their impacts on the composition of benthic communities. Data on L. fortunei were obtained in Rio Tercero Reservoir, Argentina, whereas studies on D. polymorpha were conducted in North America and Europe. We found that, similar to the zebra mussel, L. fortunei creates high densities on hard substrates in the littoral zone, and avoids soft substrates in the profundal zone; however, the overall population density of L. fortunei in a water body seems to be higher than that of zebra mussels. Additional studies on Limnoperna are needed to confirm this hypothesis. The effect of L. fortunei on macrobenthos is very similar to the effect of D. polymorpha and is associated with an increase in the overall diversity, density, and biomass of native macroinvertebrates in druses compared with bare sediments. The presence of L. fortunei druses in the littoral zones of Río Tercero has increased the average species richness of native benthic invertebrates per sample by almost 70% and their density and biomass by threefold, positively affecting epifaunal organisms and negatively burrowing invertebrates and unionids. In the near future, the freshwaters of North America may be colonized by L. fortunei, resulting in strong impacts on entire invaded ecosystems and devastating impacts on native unionids, especially in the southern regions of the United States, which are not colonized with dreissenids.

Exotic Molluscs in the Great Lakes Host Epizootically Important Trematodes

ABSTRACT One of the most significant ecological and economic impacts of exotic species is associated with their role as vectors for the introduction of parasites into invaded areas. Exotic parasites may have devastating impacts on invaded ecosystems; moreover, invaders may also become hosts for aboriginal parasites, promoting native diseases that otherwise would not have emerged. During 2009 and 2010, exotic molluscs were collected from 27 sites in the Lower Great Lakes and their tributaries, the Finger Lakes, and Lake Oneida. Seven species of exotic molluscs were examined for the presence of trematodes, including the zebra mussel (Dreissena polymorpha), quagga mussel (Dreissena rostriformis bugensis), faucet snail (Bithynla tentaculata), European stream valvata (Valvata piscinalis), Asian clam (Corbicula fluminea), Chinese mystery snail (Cipangopaludina chinensis), and the New Zealand mudsnail (Potamopyrgus antipodarum). Most of the examined molluscs were infected with trematode larvae that may be harmful to their subsequent vertebrate hosts, including fish, birds, and mammals. These included Sphaeridiotrema sp. cercariae and Cyathocotyle bushiensis metacercariae from B. tentaculata, Echinostoma sp. cercariae from V. piscinalis, and echinostomatid metacercariae from Dreissena spp. and C. fluminea. Many exotic molluscs that were believed to be free of parasites have already acquired trematodes native to North America. Hotspots of trematode infections were recorded in the western basin of Lake Erie and in Lake Oneida, where several species of exotic molluscs had a high prevalence of trematodes, and thus potentially pose risk of transmission to definitive hosts.

Eutrophication and Dreissena invasion as drivers of biodiversity: a century of change in the mollusc community of Oneida Lake.

Changes in nutrient loading and invasive species are among the strongest human-driven disturbances in freshwater ecosystems, but our knowledge on how they affect the biodiversity of lakes is still limited. We conducted a detailed historical analysis of the mollusc community of Oneida Lake based on our comprehensive lakewide study in 2012 and previous surveys dating back to 1915. In the early 20th century, the lake had a high water clarity, with abundant macrophytes and benthic algae, and hosted the most diverse molluscan community in New York State, including 32 gastropod and 9 unionid species. By the 1960s, lake turbidity increased during a period of anthropogenic eutrophication, resulting in a 38% decline in species richness and a 95% reduction in abundance of native gastropods grazing on benthic algae. Following the invasion of Dreissena spp. in 1991 and subsequent increases in water clarity, native gastropod species richness expanded by 37% and abundance increased 20-fold by 2012. In contrast, filter-feeding unionids were unaffected by increased turbidity during the period of eutrophication but were extirpated by dreissenids. Through contrasting effects on turbidity, eutrophication and Dreissena spp. have likely driven the observed changes in native grazing gastropods by affecting the abundance of light-limited benthic algae. Given the high species richness and ecological importance of benthic grazers, monitoring and managing turbidity is important in preserving molluscan diversity.