Response of macrobenthic communities to restoration efforts in a New England estuary

Changes in macrobenthic communities were studied over a 3.5 yr period follo wing restoration activities in Alewife Cove, a small estuary located in sou theastern Connecticut, U.S. Development around this estuary had resulted in reduced freshwater and tidal inflows, loss of critical habitats such as sa lt marshes, and eutrophication. Early in 1988, the lower reach of the estua ry was dredged to increase tidal flushing and enhance environmental quality . Following dredging, tidal range within the Cove increased from 52 to 83 c m. Due to erosion within the Cove's lower channel and sediment migration in to the Cove, tidal flows and ranges approached pre-dredge levels by 1991. D espite these changes, the percentage of silt/clay in the surface sediments in the middle and upper basins of the Cove declined by 30-45% over the stud y period. Changes in infaunal community structure in the lower reach follow ing dredging were not great, primarily comprising shifts in the relative ab undances of species typical of sandier versus muddier sediments. Directiona l changes in community structure were most evident in the middle and upper basins, away from the dredged area. Infaunal species richness increased sig nificantly, with many species previously found only in the sand habitats of the lower reach establishing populations in the middle and upper basins. T here was a significant decrease in the summer abundances of the pollution i ndicator polychaete Capitella capitata throughout much of the middle and up per basins. Restoration efforts in Alewife Cove centering on altered hydrol ogy resulted in selected positive changes, increases in tidal flow altered environmental conditions in the middle and upper basins where shifts in inf aunal community structure indicated decreases in organic loading of sedimen ts over 2-3 yr. Continued changes in the physical dynamics of the lower rea ch reduced tidal flow, arresting the positive ecological changes that were beginning to occur. This type of restoration approach of small estuaries ca n have positive results, but there may be a lag in the ecological response of the system. Macrobenthic communities, in particular summer abundance pat terns of selected species, provided an integrated assessment of ecological changes in the Cove.