Geographic, anthropogenic, and habitat influences on Great Lakes coastal wetland fish assemblages

Abstract

We analyzed data from coastal wetlands across the Laurentian Great Lakes to identify fish assemblage patterns and relationships to habitat, watershed condition, and regional setting. Nonmetric multidimensional scaling (NMDS) ordination of electrofishing catch-per-effort data revealed an overriding geographic and anthropogenic stressor gradient that appeared to structure fish composition via impacts on water clarity and vegetation structure. Wetlands in Lakes Erie and Michigan with agricultural watersheds, turbid water, little submerged vegetation, and a preponderance of generalist, tolerant fishes occupied one end of this gradient, while wetlands in Lake Superior with largely natural watersheds, clear water, abundant submerged vegetation, and diverse fishes occupied the other. Fish composition was also related to wetland morphology, hydrology, exposure, and substrate, but this was only evident within low-disturbance wetlands. Anthropogenic stress appears to homogenize fish composition among wetlands and mask other fish-habitat associations. Because land use is strongly spatially patterned across the Great Lakes and aquatic vegetation is a key habitat element that responds to both biogeography and disturbance, it is difficult to disentangle natural from anthropogenic drivers of coastal wetland fish composition.Résumé : Nous analysons des données provenant de terres humides riveraines réparties sur l'ensemble des Grands Lacs laurentiens afin d'identifier les patrons d'associations de poissons et leurs relations avec les habitats, les conditions du bassin versant et l'environnement régional. Une ordination de cadrage non métrique multidimensionnel (NMDS) de données de captures par unité d'effort de pêche électrique révèle l'existence d'un gradient prédominant de facteurs de stress géo-graphiques et anthropiques qui semble structurer la composition des peuplements de poissons par son impact sur la clarté de l'eau et la structure de la végétation. Les terres humides aux lacs É rié et Michigan avec des bassins versants agricoles, de l'eau turbide, une végétation submergée rare et une prépondérance de poissons généralistes et tolérants, occupent une extrémité de ce gradient; en revanche, les terres humides du lac Supérieur avec des bassins versants en grande partie naturels, de l'eau claire, une végétation submergée abondante et une diversité de poissons, occupent l'autre extrémité. La composition des peuplements de poissons est aussi en relation avec la morphologie des terres humides, l'hydrologie, l'exposition et le substrat, mais la relation n'est évidente que dans les terres humides peu perturbées. Le stress anthropique semble homogénéiser la composition des peuplements de poissons dans les différentes terres humides et masquer les autres associations poissons-habitats. Parce que l'utilisation des terres dans la région des Grands Lacs forme un patron spatial bien marqué et que la végétation est un élément essentiel de l'habitat qui réagit à la fois à la biogéographie et aux perturbations, il est difficile de démêler...

Relative importance of macrophyte community versus water quality variables for predicting fish assemblages in coastal wetlands of the Laurentian Great Lakes

“…This evidence implies that a change in fish community should be a synergistic consequence of the effect of changes in water quality, and the effect of water quality on plants and the subsequent impact on fish. While recent studies have shown the importance of both water quality (described in terms of water clarity) and aquatic vegetation assemblages to the Great Lakes fish community (Trebitz et al, 2009), no studies to our knowledge have directly investigated which of these two factors, water quality or macrophyte community, has a more prominent influence on fish composition. Ultimately, such investigations could refocus research efforts to improve wetland sampling and monitoring programs and provide enhancement of wetland restoration projects.…”

“…(Janecek, 1990;Randall et al, 1996). Given that empirical studies evaluating the co-occurrence of fish and macrophyte taxa are scarce (see Janecek, 1990;McNair, 2006), there is a demand for papers that advance this branch of fish habitat research in order to gain a more detailed understanding of the complex connections between macrophyte and fish communities (Randall et al, 1996;Brazner and Beals, 1997;Trebitz et al, 2009).…”

Spatial and temporal dynamics of phytoplankton communities in a Great Lakes drowned river-mouth lake (Mona Lake, USA)

“…The geological history of drowned river-mouth lakes dates back ~10,000 years when the last glaciers retreated to the north and the rising Great Lakes water levels flooded the eroded river mouths. Their complex hydrodynamics can influence material transport and processing, with associated implications for biological structure and function (Trebitz et al, 2009;Larson et al, 2013). For example, fish composition within coastal wetlands differs depending on their Great Lake connectivity (i.e., lacustrine-protected vs barrier-beach lagoons, Trebitz et al, 2009).…”

“…Their complex hydrodynamics can influence material transport and processing, with associated implications for biological structure and function (Trebitz et al, 2009;Larson et al, 2013). For example, fish composition within coastal wetlands differs depending on their Great Lake connectivity (i.e., lacustrine-protected vs barrier-beach lagoons, Trebitz et al, 2009). Due to their locations near areas of development and human population centers, many of these drowned river-mouth lakes are heavily utilized by humans, which can result in ecological impairment and loss of ecosystem services (cf.…”

Impacts of Riprap on Wetland Shorelines, Upper Winnebago Pool Lakes, Wisconsin

“…Other studies have focused on specific habitat components, such as aquatic macrophytes (Radomski and Goeman 2001), nearshore cover (Christensen et al 1996), substrate (Jennings et al 1999), and fish (Hook et al 2001), and variations in assessment methodologies and scale present uncertainty in integrating these to characterize ecosystem response. Although these studies generally indicate that shoreline protection projects can cause changes in the nearshore environment, including the lake bottom, the water column, and the biota (Brazner and Magnuson 1994;Goforth and Carman 2005;Trebitz et al 2009), the challenge is to understand the potential magnitude and the complexity of interactions among these factors.…”