Outline of a new approach to evaluate ecological integrity of salt marshes

The integrity of coastal salt marshes can be determined from the extent to which they provide key ecosystem services: food and habitat for fish and wi ldlife, good water quality, erosion and flood control, and recreation and c ultural use. An outline of a new approach for linking ecosystem services wi th metrics of structure and function to evaluate the ecological integrity o f salt marshes is described. One main objective of the approach is to deter mine whether differences in structure and function can be detected among sa lt marshes with similar geomorphology and hydrology but different degrees o f anthropogenic stress. The approach is currently being applied to salt mar shes of Narragansett Bay, RI, USA. Stable nitrogen isotopic ratios of the m arsh biota reflected the nitrogen sources from the adjacent watersheds and were significantly correlated with percent residential land use. Results sh ow that plant zonation significantly (r = -0.82; p<0.05) relates with perce nt residential land use and is potentially a sensitive indicator of anthrop ogenic disturbance of New England salt marshes. We are currently examining species diversity, denitrification rates, and susceptibility to erosion amo ng the sites for additional indicators of salt marsh condition. Our results to date suggest that this approach will provide the methods needed for man agers to systematically monitor and evaluate the integrity of salt marshes.