Location: Great Lakes Environmental Research Laboratory
2205 Commonwealth Blvd.
Ann Arbor, MI 48105-2945
Date: Monday, October 2nd, 2000
Time: 1:00-2:00 pm
Room: 105 (Main Conference Room)
ABSTRACT: In the past 15 years a number of invertebrates have entered the lower Great Lakes ecosystems. Each has the potential to alter trophic relationships and energy flow in these systems. The most dramatic have been the zebra and quagga mussels (Dreissenapolymorpha and D. bugensis). Their impacts have been assessed primarily in Lake Erie, the Bay of Quinte and Saginaw Bay because of the dramatic changes observed in these shallow, nutrient rich systems and in the case of the Bay of Quinte, the presence of a long-term monitoring program. No only has the water cleared, but seasonal areal photosyntheis has declined in the presence of dreissenids translating into less energy flow through the pelagic food-web. Energy flow was tempered by the level of planktivory. Non-dreissenid benthic biomass did not decline and energy flow through the benthos has increased due to the presence of dreissenids. Bythotrephescederstroemi and Cercopagis pengoi are two predatory cladocerans from thePonto-Caspian region. Bythotrephes arrived in the early 1980s and is abundant in Lakes Erie, Michigan and Huron. Cercopagis arrived in Lake Ontario in 1998. These two species may not only compete with the natural predatory cladocerans, Leptodoraand Polyphemus but also may alter the balance of trophic structure and zooplankton production if they are not readily consumed by the native fish. Bythotrephes in Lake Erie can become very abundant even in planktivore dominated situations. The composition and vertical distribution of zooplankton suggests that they may alter the seasonal pattern and extent of zooplankton production, particularly of the cladocerans. Cercopagis is smaller than Bythotrephes. Initial studies suggest that it resides in the epilimnion and metalimnion and likely consumes organisms in the size range of nauplii and Bosmina. The bulk of the zooplankton tend to reside lower in the water column than Cercopagis. Its consumption by fish and effect on energy flow are not yet clear. The net effect of these invertebrate invaders has been to decrease the flow and efficiency of energy flow through the pelagic food web.
For further information, please contact:
Doran Mason
NOAA Great Lakes Environmental Research Laboratory
2205 Commonwealth Blvd.
Ann Arbor, MI 48105-2945
734-741-2148
http://www.glerl.noaa.gov/news/seminars/2000/johannsson.html