Application of a Vegetation-Based Index of Biotic Integrity for Lake Erie coastal marshes in Ohio

Abstract

Substantial effort in recent years has been invested in developing monitoring protocols and indicators for assessing the health of coastal wetlands of the Great Lakes. Most efforts have collected data exclusively in Great Lakes coastal wetlands and have not evaluated coastal wetland indicator development in the context of other wetland types in the state, province, or region. “Inland” freshwater wetlands are also subject to multiple hydrologic cycles of differing time scales and in some landscape contexts may be as hydrologically variable as Great Lakes coastal wetlands. The Ohio Environmental Protection Agency developed a Vegetation Index of Biotic Integrity (VIBI) for wetlands based on vascular plants as the indicator taxa group. The extension of the VIBI to Lake Erie coastal marshes was evaluated. Least-impacted Lake Erie marshes did not have significantly lower (or higher) scores (p < 0.001) although the upper 75th percentile of coastal wetland scores was not as high as the upper 75th percentile of inland wetland VIBI scores. Significant correlations (p < 0.01) were observed with two different human disturbance gradients in a combined data set of inland and coastal wetlands. Simultaneous metric evaluation using Principal Components Analysis showed some separation in metric performance between inland and coastal wetlands but also clear overlap, especially between reference-quality inland and coastal systems. Ordination of species presence and abundance data revealed similar patterns with some separation between inland and coastal wetlands but considerable overlap in species composition. Lake Erie coastal marshes represent another type of emergent marsh system. With minor modifications, the VIBI, developed with inland wetland data sets, worked well for assessing Lake Erie coastal wetlands in Ohio. The analysis of data from Ohio coastal wetlands with a larger inland reference data set shows the advantages of treating Great Lakes coastal wetlands as a type of freshwater wetland and working toward indicator development in the context of an overall state or provincial wetland classification and assessment program.