Paleo-environmental evidence of ecosystem change in Lake St. Clair region of Laurentian Great Lakes basin: contrasting responses to land-use change and invasive mussels

Abstract

The Laurentian Great Lakes have been subject to substantial modification from diverse anthropogenic stressors, including nutrient enrichment, climate change, chemical and biological pollutants, and invasive species, yet little is known of the relative historical influence of these factors. Here we analyze diverse fossil metrics from vibracores at two sites, a bay area (Anchor Bay) and a tributary (Clinton River) in the Lake St. Clair ecosystem to determine the ecological responses from land-use practices and invasive mussel invasions. Sediment cores spanning over 100 years indicated that the expansion of nonnative Dreissena polymorpha and Dreissena rostriformis (dreissenid mussels) into Anchor Bay site after the mid-1990s was associated with * 60 to 95% reduction in algal and cyanobacterial abundances and twofold increase in sedimentary organic matter (SOM) and bioavailable phosphorus. These increases in SOM and bioavailable phosphorus are relatively similar to increases inferred from the late nineteenth century when large portions of the watershed were cleared and drained for agriculture. In contrast, the Clinton River site experienced a continuous increase in the influx of nutrients, organic matter, and elevated sedimentary phototrophic pigments during the twentieth century and into the twenty-first century. Site comparisons suggest different mechanisms inducing changes in primary production varied, where Anchor Bay was mainly affected by the comparatively recent (since ca. mid-1990s) endogenous influence of invasive species, while the Clinton River site was primarily influenced by the input of exogenous anthropogenic nutrients over the past 100 years. These new findings illustrate that watershed management and policies within large Electronic supplementary material The online version of this article (

First data on water mite (Acari, Hydrachnidia) assemblages of Point Rosa Marsh, Harrison Township, Michigan, USA,and their use as environmental bioindicators of aquatic health

“…The changes of water mite diversity could also be the result of benthic changes that Lake St. Clair has undergone due to the invasion of Dreissenid mussels back in the late 80s and early 90s (Baustian et al 2020). Recent studies on the phytoplankton of the Detroit River, which receives most of its water from Lake St Clair, has shown that historical phytoplankton assemblages has shifted when present day data was compared to pre-1980s data which suggests changes in the trophic structure of the lake that would affect predatory invertebrates like water mites (Vasquez et al 2021a).…”

“…It contains Point Rosa Marsh, one of the last marsh habitats on the shore of Lake St. Clair in the US state of Michigan. Lake St. Clair is a shallow basin which connects the upper and lower Laurentian Great Lakes of North America (Baustian et al 2020). Water mites were sampled during the end of Summer and Fall (August to October) during the years 2017-2019 in up to four locations (sites 1-4) within Point Rosa Marsh and abundance and diversity of water mites was investigated (see Figure 1 and 2).…”