Great Lakes Sites Research Articles

The Ratio of DDE to PCB Concentrations in Great Lakes Herring Gull Eggs and its Use in Interpreting Contaminants Data

The ratio of DDE to PCB (DDE.PCB) concentrations was examined in herring gull ( Larus argentatus) eggs collected from thirteen sites on the Great Lakes from 1979 to 1996. This ratio has been shown to have had a number of biological interpretations in the past and the data in this study have been used to test the validity of these interpretations. The findings suggest that the consistency of DDE:PCB over many years reflects the relative availability of DDT and PCB in different geographical areas and provides an indication of a bird's general foraging ecology. The ratio can also be used as a reflection of the relative rates of increase or decrease of DDE and PCBs in food over time. A significant increase was found in the ratio in eggs sampled from sites on the upper Great Lakes and Lake Ontario during the study period. This is attributed to PCB levels decreasing faster than DDE levels at these sites. At Lake Erie and its two connecting channels, a significant increase was detected in the ratio but at a rate 56% or less than that found at other Great Lakes sites. This lower rate is attributed to DDE and PCB levels decreasing at high and equal rates. Similarities/differences in the fates of these contaminants among the Great Lakes would never have been realized upon an examination of individual contaminant levels alone. The ratio is valuable as a measure of the relative exposure of the two contaminants in non-migratory birds such as herring gulls. The use of the ratio as an indication of contamination movement through the food chain could not be assessed; the ratio cannot be used as a reflection of the interspecific differences in the accumulation and metabolism of the two contaminants. Similarities in the patterns of these ratios shown by eggs collected from sites in close proximity or within the same lake reinforce the fact that herring gulls are important as monitors of regional contaminant conditions.

Invertebrate abundance at occupied and potential piping plover nesting beaches: Great Plains alkali wetlands vs. the Great Lakes

We assessed the potential for reestablishment of endangered piping plovers (Charadrius melodus) at selected Great Lakes beaches by comparing invertebrate biomass and abundance with that at alkali wetland beaches occupied by breeding plovers in the Great Plains. We measured invertebrate occurrence using sticky traps secured to beach foraging substrates. Diptera (especially Chironomidae and Ephydridae) comprised from 45 to 99% of invertebrate abundance and 24 to 53% of the biomass at six separate sites in the Great Lakes. Coleoptera (<1–17% abundance; 28–54% biomass) and Hymenoptera (<1–10% abundance; <1–9% biomass) also were frequently detected on beaches at the Great Lakes sites. At alkali wetland beaches in North Dakota, Diptera (Ephydridae and Chironomidae) comprised 95% of the invertebrate fauna numerically and made up more than 80% of the biomass. The mean invertebrate biomass at two Great Lakes beaches (Plate Bay, MI=0.16 g/m2/hr, Long Island, WI=0.11 g/m2/hr) was similar (P<0.05) to that at North Dakota alkali beaches (0.09 g/m2/1hr) occupied by breeding piping plovers. However, at four other Great Lakes beaches, we measured 3 to 6 times less (0.01–0.02 g/m2/hr; P<0.01) invertebrate biomass than at the alkali wetland beaches. Mean invertebrate abundance showed similar patterns among the sites. Food availability may limit the reestablishment of piping plovers at some Great Lakes beaches. We recommend that invertebrate abundance and biomass be measured at currently occupied piping plover nesting areas in the Great Lakes and be assessed at any sites proposed for reintroduction of piping plovers.

Controls on Formation and Form of Barred Nearshore Profiles

Linear regression is used to examine effects of maximum fetch length and nearshore slope in controlling characteristics of barred nearshore profiles. Data came from twelve sites in the Great Lakes and two in the Gulf of St. Lawrence. Fetch length is a good predictor of height of the outer bar, depth to the crest, and offshore distance; bar number correlates significantly with decreased nearshore slope. Incident waves are the dominant control on nearshore bar formation and maintenance during storms. THE purpose of this article is to examine the extent to which the variation in several morphological parameters of barred profiles can be explained by fetch length and nearshore slope. The approach is empirical, with data from sites in the Great Lakes and the Gulf of St. Lawrence, and the strength of the explanation is tested by linear regression. Barred profiles exist year-round at the two locations. This condition allows definition of a characteristic profile for each site and avoids complication induced by the seasonal change from a barred to a nonbarred profile that occurs on some oceanic coasts. Data for the analysis came from twelve sites in the lower Great Lakes and two in the Gulf of St. Lawrence (Fig. 1). Thirteen of the sites have one or more nearshore bars year-round, but the other site has a nonbarred profile throughout the year. My research was the source of data for ten sites; data for three other sites were taken from published studies (Hands 1976; Owens 1977; Gillie 1980), and John Coakley of the Canada Centre for Inland Waters provided data for one site. Typical profiles for each site appear in Figure 2, and selected characteristics of each site and profile are contained in Table I. The sites were chosen to encompass a wide range of fetch lengths, nearshore slopes, and nearshore-profile characteristics. However, short, steep storm waves dominate at all sites, swell waves having limited importance. During a period of years, the wind climate at all the Great Lakes sites should be very similar, and conditions at the two gulf sites are probably comparable. The actual wave climate at each site varies with orientation and fetch, but the magnitude of the dominant storm waves is controlled largely by fetch length and is generally independent of orientation. The Great Lakes sites are virtually tideless, although water level fluctuates seasonally by 0.3 to 0.4 m. Both sites in the gulf are microtidal, with a mean tidal range of less than 1 m. * Grants from the Natural Sciences and Engineering Research Council of Canada since 1977 supported the fieldwork on which this article is based. * Department of Geography, University of Guelph, Guelph, Ontario, Canada N1G 2W1. This content downloaded from 207.46.13.101 on Sat, 08 Oct 2016 05:42:06 UTC All use subject to http://about.jstor.org/terms 186 THE GEOGRAPHICAL REVIEW

Organic and Inorganic Contaminants in the St. Lawrence River: Some Preliminary Results on Their Distribution

Abstract Volatile hydrocarbons (VHC’s) have been measured at many locations in the St. Lawrence River, Several concentrations of VHC’s were higher than those measured at other polluted Great Lakes sites, e.g. the St. Clair River. Tributaries to the St. Lawrence River were found to be significant sources of VHC’s. Cadmium in the St. Lawrence River is mostly found in dissolved (bioavailable) forms as compared to the Mississippi River where dissolved cadmium accounts for about 10% of the total cadmium. The major sources of cadmium appear to be in the Montreal area. Although the analytical results show local impairment in water quality, intensive sampling is required to pinpoint sources and/or quantify loadings, However, none of the VHC or cadmium concentrations exceed water quality guidelines or objectives. In fact there are no guidelines for most VHC’s. Nevertheless, the concentrations of VHC’s and cadmium found should have no toxic effect on aquatic organisms. The results of this study indicate that there are major sources of VHC’s and cadmium in Quebec. For example, inputs on the southwestern portion of Lac St.Louis may be a major source of perchloroethylene, and effluents in the vicinity of the Montreal STP may be a major source of cadmium. U.S. tributaries, e.g. the Grassy River, may also be a significant source of VHC’s.