Development of an IBI-based assessment of depressional wetlands in Maryland and Delaware

Abstract

The hydrogeomorphic approach (HGM) of wetland assessment emphasizes functional components of wetlands such as water storage, transformation and cycling of elements, accumulation of sediments, and preservation of habitats. Many of the elements measured in HGM are physical rather than ecological or biological. The HGM approach, therefore, provides information on certain aspects of wetlands and omits other aspects. In contrast, the Index of Biological Integrity (IBI) approach focuses on biological components of wetlands such as species richness, the presence or proportion of certain 'indicator' species, representation of different trophic levels, and measures of wildlife or fish health. Here too, some aspects of a wetland are omitted and others not covered by HGM are included. We contend that these differences in focus add strengths and weaknesses to each method. This paper reviews progress on the development of IBIs for restored depressional wetlands in the Mid-Atlantic States, especially Maryland and Delaware. During our first field season we identified 25 wetlands ranging from 1-10 acres, most of which were restored with federal, state, and private landowner cooperation over hydric soils. Separate IBIs are being created for macrophytes, macroinvertebrates, amphibians, and data on mammal and avian populations are being collected. Simultaneously, chemical and physical data are being collected on water DO, turbidity, temperature, conductivity, nitrates, ammonia, chlorophyll, pH; soil metal levels and texture; and wetland size, configuration, hydrology, drainage area, and surrounding land use.