Ecosystems

, Volume 2, Issue 4, pp 338-350

First online:

Filtering Impacts of an Introduced Bivalve (Dreissena polymorpha) in a Shallow Lake: Application of a Hydrodynamic Model

  • Hugh J.  MacIsaacAffiliated withGreat Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario N9B 3P4
  • , Ora E.  JohannssonAffiliated withGreat Lakes Laboratory for Fisheries and Aquatic Sciences, Department of Fisheries and Oceans, Burlington, Ontario L7R 4A6
  • , Jian  YeAffiliated withGreat Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario N9B 3P4
  • , W. Gary  SprulesAffiliated withDepartment of Zoology, University of Toronto at Mississauga, Mississauga, Ontario L5L 1C6
  • , J. H.  LeachAffiliated withOntario Ministry of Natural Resources, Lake Erie Fisheries Station, R.R. #2, Wheatley, Ontario N0P 2P0, Canada
  • , J. A.  McCorquodaleAffiliated withGreat Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario N9B 3P4
  • , Igor A.  GrigorovichAffiliated withGreat Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario N9B 3P4

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ABSTRACT

Nonindigenous species may exert strong effects on ecosystem structure and function. The zebra mussel (Dreissena polymorpha) has been attributed with profound changes in invaded ecosystems across eastern North America. We explored vertical profiles of water flow velocity and chlorophyll a concentration in western Lake Erie, over rocky substrates encrusted with Dreissena, to assess the extent to which mussels influence coupling between benthic and pelagic regions of the lake. Flow velocity was always low at surveyed sites (less than or equal to 2.9 cm s-1) and declined in direct proximity to the lakebed. Mean chlorophyll a concentration was also low (less than 5μg L-1) at all sites and depths. Chlorophyll a concentration was positively correlated with distance above lakebed and was lowest (0.3μg L-1) directly adjacent to the lakebed. Spatial patterns of zooplankton grazers could not explain observed vertical gradients in chlorophyll concentration. Hydrodynamic modeling revealed that filtering effects of Dreissena in a nonstratified, shallow basin depend mainly on upstream chlorophyll concentration, intensity of turbulent diffusion, feeding efficiency of the mussel colony, and the distance downstream from the leading edge of the mussel colony. In contrast to widespread perceptions that molluscs reduce phytoplankton concentration only adjacent to the lakebed, modeling scenarios indicated that depletion occurs throughout the water column. Depletion was, however, inversely proportional to distance above the lakebed. Simulation results are consistent with field-based observations made in shallow water habitats populated by large Dreissena populations in the Great Lakes and elsewhere. Results from this study indicate that zebra mussels strongly enhance coupling between pelagic and benthic regions in shallow lakes. Enhanced coupling between these regions explains, in part, high population densities of Dreissena and of many benthic invertebrates in ecosystems invaded by zebra mussels.

Key words: zebra mussel; benthic–pelagic coupling; Great Lakes; hydrodynamics; exotic species.