Benthic Mapping for Habitat Classification in the Peconic Estuary: Phase I Groundtruth Studies

Benthic habitat maps of the estuary seafloor will increase our knowledge of range and variability in benthic habitats, will assist managers in their efforts to protect and/or restore commercially and recreationally important finfish and shellfish, will link land usage (e.g. developed vs. undeveloped areas) and water quality data to benthic habitat quality, and will make it possible to utilize faunal data as a long-term indicator of the overall “health” of the estuary. We are developing benthic habitat maps by combining high-resolution remote sensing techniques with detailed study of the physical and faunal characteristics at point locations in different seafloor environments. In Phase I, six critical natural resource areas (CNRA: Robins Island, Shelter Island, Flanders Bay, Orient Bay, Northwest Harbor, and Gardiners Island) were acoustically mapped and sampled. Acoustic mapping used side-scan sonar and multibeam swath bathymetry and backscatter to generate bathymetric and backscatter images that provide high resolution detail about bottom morphology, sediment processes, and geophysical habitat, and that allow classification of the sea bed into regions. Samples for macrofauna and sediment properties were collected within each bottom region to provide ground truth for the acoustic maps. Robins Island and Shelter Island areas were sampled at 30 and 35 locations, respectively, with two replicate samples at each location. The other four CNRA areas were sampled at 7-15 locations each, with no replication. Results suggest that the acoustic provinces identified do indeed represent areas of similar faunal and sedimentary characteristics, and that this approach can provide new insights into benthic community structure. Phase II benthic habitat studies will extend mapping from nearly shore to shore (north-south) across four different reaches of the Peconic Estuary