A large proportion of the contaminants that enter Long Point Bay do so directly through Big Creek. As the Big Creek watershed is primarily rural, wastes washed into Big Creek Marsh and Long Point Bay are primarily agricultural in nature. Consequently, the amount and type of contaminants entering the system are directly related to agricultural practices in the catchment. Elevated mercury, arsenic, lead, and manganese concentrations in the Big Creek Marsh are presumably associated with pesticide application in the catchment, the residues of which enter nearby tributaries and eventually, Big Creek and the Inner Bay (Miles 1976; Miles et al. 1976). For example, atrazine is a chemical widely used to control weeds in corn fields and between 0.3 and 1.9% of the amount applied enters adjacent streams. Therefore, practices far from Long Point Bay, implemented by people who likely have little vested interest in the health of that aquatic system, are directly responsible for the bulk of its contamination.
Groundwater also transports agrochemicals, road salts, and sewage wastes to lakes and rivers (Stenson 1993). During high Lake Erie water levels, higher groundwater tables result in seepage of private septic systems and increased bacterial contamination of water, particularly at Long Point and Turkey Point (Murdoch 1981). Heavy metals and organic chemicals also enter aquatic environments through household and industrial sewer systems such as those at the Nanticoke industrial complex (Downey et al. 1994). This is problematic because most sewage treatment facilities are not capable of removing toxic substances, with the result that chemicals and metals are being deposited directly into streams and lakes (Downey et al. 1994). Urbanization also contributes to decreased water quality as stormwater carries pollution, petroleum products and salts into the Bay (Environment Canada 1993). For example, Long Point Bay receives seasonal surges of chloride from road salts suspended in storm run-off and sewage discharge (Ongley 1976). This causes receiving waters to become more alkaline which can have negative impacts on certain components of the aquatic ecosystem.
The Nanticoke industrial complex has caused nutrient enrichment as well as increased levels of residue particulate, phenols, cyanide, and heavy metals in its adjacent waters (Haymes and Dunstall 1989). However, while influencing adjacent waters, contaminant discharges are at present having limited effects on the rest of Long Point Bay (Haymes and Dunstall 1989). Nevertheless, the presence of the industrial complex and resource development on the Bay has increased the potential for toxic waste spills, oil spills and gas line ruptures (Francis et al. 1985). An oil spill on the Bay in 1976 killed about 3,900 ducks, primarily Oldsquaw. Luckily the spill was in December, after most waterfowl had left the Bay for southern wintering areas. Unfortunately, the shallow depth and reduced circulation of the Bay make it particularly susceptible to the long and short term effects of industrial accidents.
Once in the system, contaminants start to be transferred through trophic levels, ultimately becoming concentrated at often unhealthy levels in the fat and tissue of tertiary consumers such as birds. The cycling of contaminants and accumulation and concentration at higher trophic levels is known as bioaccumulation. The introduction of zebra mussels with their prolific filtering capacities has drastically accelerated this process. Contaminants readily fuse to abiotic and biotic particles, which are subsequently filtered by zebra mussels. The result is that mussels readily assimilate contaminants into their tissues, which in turn become readily available to higher level consumers such as waterfowl. This may be problematic for Lesser Scaup, Greater Scaup, and Buffleheads at Long Point, as they consume large quantities of zebra mussels (see Chapter 8). For instance, Tufted Ducks that were fed quantities of contaminated zebra mussels experienced reproductive abnormalities (Scholten et al. 1989). Therefore, the assimilation of contaminants into zebra mussel tissue may cause substantial, yet to be recognized, ecological problems for at least a few of the species of waterfowl using Long Point. This is supported by the fact that Lake Erie's aquatic contaminants have already adversely affected Herring Gull and eagle eggs (Struger et al. 1987; Metro Toronto Remedial Action Plan Office) as well as several species of fish (Ontario Ministry of Environment 1993).
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