Integrated, quantitative expressions of anthropogenic stress over large geographic regions can be valuable tools in environmental research and management. Despite the fundamental appeal of a regional approach, development of regional stress measures remains one of the most important current challenges in environmental science. Using publicly available, pre-existing spatial datasets, we developed a geographic information system database of 86 variables related to five classes of anthropogenic stress in the U.S. Great Lakes basin: agriculture, atmospheric deposition, human population, land cover, and point source pollution. The original variables were quantified by a variety of data types over a broad range of spatial and classification resolutions. We summarized the original data for 762 watershed-based units that comprise the U.S. portion of the basin and then used principal components analysis to develop overall stress measures within each stress category. We developed a cumulative stress index by combining the first principal component from each of the five stress categories. Maps of the stress measures illustrate strong spatial patterns across the basin, with the greatest amount of stress occurring on the western shore of Lake Michigan, southwest Lake Erie, and southeastern Lake Ontario. We found strong relationships between the stress measures and characteristics of bird communities, fish communities, and water chemistry measurements from the coastal region. The stress measures are taken to represent the major threats to coastal ecosystems in the U.S. Great Lakes. Such regional-scale efforts are critical for understanding relationships between human disturbance and ecosystem response, and can be used to guide environmental decision-making at both regional and local scales.

Assessing the ecological importance of coastal habitats to Great Lakes ecosystems requires an understanding of the ecological linkages between coastal and offshore waters. Elemental analysis of fish otoliths has emerged as a powerful technique that can provide a natural tag for determining nursery area affiliation, population structure, and movement of individual fish. Since the elemental composition of fish otoliths reflects some of the environmental conditions under which a fish was reared, otolith chemistry can record differences in ambient water conditions specific to habitats used during a fish's life history. Although few studies have been conducted in freshwaters, trace element analysis of marine fish otoliths has proven useful in identifying the chemical signatures unique to particular spawning and nursery habitats. To examine the utility of this method in freshwater, sagittae were removed from 275 young‐of‐the‐year yellow perch Perca flavescens captured from eight wetlands in western Lake Superior during August 2001. They were analyzed for Ca and 13 minor and trace elements using inductively coupled plasma mass spectrometry (ICPMS) and inductively coupled atomic emission mass spectrometry (ICPAES). Otolith concentrations of Ba, K, Mg, Mn, Na, and Sr differed significantly among wetlands (ANOVA, P < 0.001). Interwetland differences were also pronounced when analyzed as a multivariate fingerprint (MANOVA, P < 0.001). Discriminant function analysis revealed relatively distinct chemical fingerprints associated with each wetland. Wetland classification accuracy based on a five‐element model (Sr, Mn, K, Ba, and Mg) ranged from 62% to 100% and averaged 76%. Differences in fingerprints between wetland types (river‐influenced versus lagoon) were also distinct (MANOVA, P < 0.001). Classification accuracy for wetland type was 81% based on a five‐element model that included Ba, Mg, Mn, Na, and Sr. Our results suggest that otolith elemental fingerprints may be useful for quantifying the relative contributions of different wetland nursery areas to recruitment in adjacent lake populations.

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From May to September in 1990 and 1991, 24 coastal wetland and beach sites in Green Bay, Lake Michigan, were sampled to investigate abiotic and biotic factors influencing fish assemblages; half the sites were modified by human developments, and half were relatively undeveloped. The greatest assemblage differences were observed among regions, but there also were strong differences among assemblages from different habitats. Degree of development had less of an effect on site differences, although assemblages at undeveloped wetlands were unique, and those from developed and undeveloped sites in the upper bay were relatively distinct. The most influential abiotic factors were turbidity, reflecting the trophic gradient in the bay, and a suite of variables associated with macrophyte coverage and diversity, which were critical components of nursery habitats for the primarily immature fishes we captured. The volatile and unpredictable nature of shoreline habitats in the Great Lakes apparently precluded competition and predation from having a strong organizing role. This study demonstrates that undeveloped wetlands are a valuable and intensely utilized fish habitat, particulartly as nursery areas, that should receive special consideration in ecosystem management plans for the Great Lakes.