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Benthic macroinvertebrate assemblages in the US nearshore zone of Lake Erie, 2009: Status and linkages to landscape-derived stressors
Citation:
Scharold, J., T. Corry, P. Yurista, AND J. Kelly. Benthic macroinvertebrate assemblages in the US nearshore zone of Lake Erie, 2009: Status and linkages to landscape-derived stressors. JOURNAL OF GREAT LAKES RESEARCH. International Association for Great Lakes Research, Ann Arbor, MI, 41(2):338-347, (2015).
Impact/Purpose:
The survey design employed in this study provided both an efficient means to make a comprehensive report on densities and metrics of benthic invertebrate assemblages for the entire U.S. nearshore zone of Lake Erie, and to examine spatial aspects of their distributions and link these measures to potential stressors in the watershed. Our contribution beyond region-wide estimates of measures of the benthic assemblage and their local environment was a demonstration that land use/stressors in adjacent watersheds was additionally correlated with the benthic community structure and metrics leading toward a method for monitoring the effectiveness of best management practices of the landscape. The survey was an efficient and unbiased monitoring strategy providing a spatial context and connection with the landscape and anthropogenic stress.
Description:
Benthic macroinvertebrate assemblages have been used as indicators of ecological condition because their responses integrate localized environmental conditions of the sediments and overlying water. Assemblages of benthic invertebrates in the near coastal region are of particular interest, because they are expected to be the first impacted by certain, land-derived anthropogenic stressors, and effects are expected to be greatest in the coastal receiving region. As a pilot for the National Coastal Condition Assessment, we conducted a survey of benthic invertebrates in the US shallow near shore zone of Lake Erie during August-September 2009. Forty five sites were selected in the region 0-5 km from the shoreline using a probability-based survey design. Benthic macroinvertebrates were collected using a standard ponar grab. The dominant taxonomic group was dreissenid mussels, with a mean density of 8415 + 1826 (SE) m-2. Other major taxa included oligochaetes (2736 + 442 m-2) and chironomids (794 + 139 m-2). Mean density of the burrowing mayfly Hexagenia was 114 + 39 m-2. Multivariate stepwise regressions across sites revealed significant correlations of several benthic invertebrate assemblage metrics with landscape measures of anthropogenic stress in adjacent coastal watersheds. The Shannon diversity index, the oligochaete trophic index, taxa richness, and densities of chironomids and Hexagenia were significantly related to agricultural activity in basin watersheds. Other significant landscape-level explanatory variables included population density, shoreline modification, atmospheric deposition, and land cover. Study results provide evidence that benthic macroinvertebrate assemblages in the nearshore zone of Lake Erie are responsive to landscape-derived stressors emanating from the adjacent watersheds, and ancillary regression analyses reinforce the concept that responses in benthic metrics appear to be mediated through site-level trophic enrichment effects in the open nearshore.
