Leptodora kindtii Population Dynamics in the Island Region of Western Lake Erie Before and After the Invasion of the Predacious Cladoceran Bythotrephes LongimanusOHSU-RS-1556 ABSTRACT:
Competition among native and non-native species can cause decreases in population size and production of both species. The native predaceous crustacean zooplankter Leptodora kindtii shares a similar niche with the invasive Bythotrephes longimanus in Lake Erie. This niche overlap may contribute to the decline in abundance, and production of L. kindtii in the Western Basin of Lake Erie. Historical (1946) and recent (2006) data were used to determine if the decline in L. kindtii abundance and production was associated with the effects of B. longimanus, which invaded Lake Erie in the mid-1980’s. Pre-invasion abundances and lengths of L. kindtii were compared with current data (2006). A change in prey community abundance, composition and dynamics were observed, relative to pre-invasion, with a marked decline in abundance and size of L. kindtii after the invasion of B. longimanus. Competition for food and direct predation are two explanations, among others, for the declines observed in L. kindtii size, abundance and production that have occurred since B. longimanus invasion.
VOLUME: 116 ISSUE: 2 LENGTH: 7 pages
12 July 2012 Stone Laboratory Guest Lecture Series: USGS Science- Partner Driven Research: Huron Erie Corridor, Asian Carps and Harmful Algal BloomsOHSU-CAST-410
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Expansion of Tubenose Gobies Proterorhinus semilunaris into Western Lake Erie and Potential Effects on Native SpeciesOHSU-RS-1539 ABSTRACT:
The Eurasian freshwater tubenose goby Proterorhinus semilunaris (formerly Proterorhinus marmoratus) invaded the Laurentian Great Lakes in the 1990s, presumably via ballast water from transoceanic cargo ships. Tubenose gobies spread throughout Lake St. Clair, its tributaries, and the Detroit River system, and also are present in the Duluth-Superior harbor of Lake Superior. Using seines and bottom trawls, we collected 113 tubenose gobies between July 2007 and August 2009 at several locations in western Lake Erie. The number and range of sizes of specimens collected suggest that that tubenose gobies have become established and self-sustaining in the western basin of Lake Erie. Tubenose gobies reached maximum densities in sheltered areas with abundant macrophyte growth, which also is their common habitat in native northern Black Sea populations. The diet of tubenose gobies was almost exclusively invertebrates, suggesting dietary overlap with other benthic fishes, such as darters (Etheostoma spp. and Percina sp.), madtoms (Noturus spp.), and sculpins (Cottus spp.). A single mitochondrial DNA haplotype was identified, which is the most common haplotype found in the original colonization area in the Lake St. Clair region, suggesting a founder effect. Tubenose gobies, like round gobies Neogobius melanostomus, have early life stages that drift owing to vertical migration, which probably allowed them to spread from areas of colonization. The Lake St. Clair-Lake Erie corridor appears to have served as an avenue for them to spread to the western basin of Lake Erie, and abundance of shallow macrophyte-rich habitats may be a key factor facilitating their further expansion within Lake Erie and the remainder of the Laurentian Great Lakes.
DOI: 10.1007/s10530-011-9962-5 VOLUME: 13 ISSUE: 12 LENGTH: 9 pages
The Effects of Dreissenid Mussels on the Survival and Condition of Burrowing Mayflies (Hexagenia spp.) in Western Lake ErieOHSU-RS-1542 ABSTRACT:
Burrowing mayflies (Hexagenia limbata and H. rigida) are once again prominent members of the benthic community in western Lake Erie. However, this community is now dominated by dreissenid mussels. We conducted a laboratory experiment and field sampling to investigate whether survival and condition of Hexagenia were affected by the presence, density, and quality of dreissenid mussels. In a laboratory experiment, Hexagenia survival was higher in microcosms without dreissenid mussels. We also found Hexagenia density to be higher at field sites with low dreissenid density, suggesting that Hexagenia survival is higher in these areas as well. In microcosm treatments with low dreissenid density, Hexagenia survival was higher in treatments with live dreissenids than in treatments containing only dreissenid shells. These findings suggest that while dreissenid shells degrade the quality of soft sediments for Hexagenia, some of the negative effect is offset by the presence of live dreissenids. The positive effect of live dreissenids is likely due to additional food resources made available to Hexagenia by the filtering activity of dreissenids. Neither dreissenid density nor shell “type” (shells alone or live dreissenids in shells) had an effect on Hexagenia condition. Thus, the interactions between these dominant benthic invertebrates are complex. Recovery of Hexagenia populations in western Lake Erie is likely affected by both changing environmental conditions due to anthropogenic activities and the introduction of exotic species into the benthic community. The results are likely to be continued instability of the benthic food web and unpredictable consequences for human utilization of this ecosystem.
DOI: doi:10.1016/j.jglr.2011.04.006 VOLUME: 37 ISSUE: 3 LENGTH: 5 pages
Transient Social–Ecological Stability: the Effects of Invasive Species and Ecosystem Restoration on Nutrient Management Compromise in Lake ErieOHSU-RS-1546 ABSTRACT:
Together, lake ecosystems and local human activity form complex social–ecological systems (SESs) characterized by feedback loops and discontinuous change. Researchers in diverse fields have suggested that complex systems do not have single stable equilibria in the long term because of inevitable perturbation. During this study, we sought to address the general question of whether or not stable social–ecological equilibria exist in highly stressed and managed lacustrine systems. Using an integrated human–biophysical model, we investigated the impacts of a species invasion and ecosystem restoration on SES equilibrium, defined here as a compromise in phosphorus management among opposing stakeholders, in western Lake Erie. Our integrated model is composed of a calibrated ecological submodel representing Sandusky Bay, and a phosphorus management submodel that reflects the societal benefits and costs of phosphorus regulation. These two submodels together form a dynamic feedback loop that includes freshwater ecology, ecosystem services, and phosphorus management. We found that the invasion of dreissenid mussels decreased ecosystem resistance to eutrophication, necessitating increased phosphorus management to preserve ecosystem services and thus creating the potential for a shift in social–ecological equilibrium. Additionally, our results suggest that net benefits in the region following the invasion of dreissenids may never again reach the pre-invasion level if on-site phosphorus control is the sole management lever. Further demonstrating transient system stability, large-scale wetland restoration shifted points of management compromise to states characterized by less on-site phosphorus management and higher environmental quality, resulting in a significant increase in net benefits in the region. We conclude that lacustrine SESs are open and dynamic, and we recommend that future models of these systems emphasize site-specific perturbation over equilibrium, thereby aiding the development of management plans for building system resistance to undesirable change that are both flexible and sustainable in an unknowable future.
VOLUME: 15 ISSUE: 1 LENGTH: 28 pages