Marvin, C.H. and E.T. Howell, 1996. Contaminant Burdens in Sediments Colonized by Dreissena at Two Nearshore Sites in the Lower Great Lakes, McMaster University, Ontario Ministry of Environment and Energy

Reprinted from "Zebra Mussels and Other Aquatic Nuisance Species." Ed. by Frank D'itri, Ann Arbor Press, 1996.

CONTAMINANT BURDENS IN SEDIMENTS COLONIZED BY DREISSENA AT TWO NEARSHORE SITES IN THE LOWER GREAT LAKES

INTRODUCTION
The exotic mussels Dreissena polymorpha (zebra mussel) and D. bugensis (quagga mussel) have become firmly established in many nearshore areas of the Great Lakes. Impacts associated with the filtration of suspended particulate from the water column by prolific populations of Dreissena include increases in water transparency (Holland, 1993; Leach, 1993; Bunt et al., 1993), decreases in mean chlorophyll a concentrations (Leach, 1993) and declines in phytoplankton densities (Nicholls and Hopkins, 1993; Bunt et al., 1993). Populations of native bivalves in western Lake Erie and Lake St. Clair have exhibited declines in population density and species diversity and depletion of lipid reserves as a result of fouling by Dreissena (Haag et al., 1993; Gillis and Mackie, 1994; Hebert et al., 1991).

Data collected seasonally during the period from late 1988 to 1993 at an Ontario Ministry of Environment and Energy monitoring site near Fort Erie in eastern Lake Erie showed increases with time in water clarity and decreases with time in chlorophyll a concentrations (Howell et al., 1993). These changes coincided with colonization of the site by Dreissena and their subsequent dramatic increases in population density. In addition to changes that occurred within the water column, there was an increase in surficial sediment (top 3 cm) total organic carbon (TOC), an increase in surficial sediment concentrations of polycyclic aromatic hydrocarbons (PAH) and metals, and a transition in particle size distribution of surficial sediment from sand-sized particles to predominately silt-sized particles. Based on these observations, it was concluded that after 1990 there was an increase in the rate of accumulation of fine particulate material, potentially as a result of a shift in the cycling or dispersion of suspended particulate mediated by the recently established Dreissena population.

Suspended particulate, and the associated contaminants, are processed by Dreissena during pseudofecal production (Reeders and Bij de Vaate, 1992). These pseudofecal pellets may be deposited or resuspended into the water column. Studies of Dreissena feeding behaviour in which pseudofecal production rates were measured (Reeders and Bij de Vaate, 1990) provide a basis to predict the magnitude of potential sedimentation. A recent study provides evidence that sedimentation rates in Lake Erie are likely to be higher in areas colonized by Dreissena (Dobson, 1994). The high population densities achieved in some areas suggests that Dreissena may be an important component of contaminant and material exchange pathways in the Great Lakes with implications for increasing rates of integration of particulate material into benthic sediments, altering rates of accumulation of contaminants into sediments, and altering the absolute quantities of contaminants in sediments. Dreissena can impact on the movement of contaminants through the detrital food chain to benthic invertebrates such as amphipods that are important food sources for higher trophic levels (Bruner et al., 1994). Amphipods are commonly abundant in areas of Dreissena colonization, presumably as a result of creation of interstitial habitat and availability of detrital material as food (Griffiths, 1993). The potential effects of Dreissena on the accumulation of contaminants suggests that it is important to understand the effects of colonization on contaminant levels in sediments.

The implications of increased rates of accumulation or retention of material originating in the water column on the concentrations of contaminants in sediments are diverse. If the sediment is characterized by coarse composition and low contaminant concentrations, the contaminant concentrations may increase, particularly in areas of active contaminant loading to the water mass. Conversely, if the sediment is contaminated from past loadings and particulate material in the water mass is relatively less contaminated, the effect of increased sedimentation by Dreissena may be to reduce contaminant concentrations in the surficial sediments. To date there has been little investigation of potential consequences of the Dreissena invasion on accumulation patterns of contaminants in the benthic zone as a result of potentially accelerated sediment accumulation. The objective of this study was to assess the potential effects of Dreissena on the physical and chemical characteristics of nearshore sediments at a site in eastern Lake Erie (Fort Erie) and at a site in western Lake Ontario (Port Dalhousie). The approach was to compare the character and contaminant burdens of sediments in areas colonized by Dreissena with contaminant burdens of sediments in the same areas not colonized by Dreissena, but exposed to similar environmental conditions.

Entire Paper
Contact: C.H. Marvin, Department of Chemistry, McMaster University, 1280 Main Street W., Hamilton, ON L8S 4M1 Canada
Keywords: Zebra_mussel, Quagga_mussels, Ecological_interactions, Environmental_interactions
Product Type: Research, Impact
User Type: General