Organic Enrichment of the Seafloor; Impact Assessment Using a Geographic Information System

Two state-of-the-art techniques involving computer analysis are used in the study of pollution impact assessment. A synoptic survey of Narragansett Bay (USA), conducted in 1988, is presented as an example. A REMOTS® camera, an optical instrument that photographs vertical in-situ profiles of the upper 20 cm of the sediment, was deployed at 56 stations throughout the Bay. REMOTS® sediment-profile images were analyzed with SAIC Image Analysis Software that allows systematic measurement of up to 21 seafloor variables (e.g. modal grain-size, apparent RPD depth). Gradient maps of REMOTS® parameters, as well as bathymetry and traditional measurements of dissolved oxygen, vertical salinity differences, and sediment densities of Clostridium perfringens (a microbial indicator of fecal pollution) were digitized and transferred to a Geographic Information System (GRASS). Diverse overlay analysis tools within GRASS allowed us to identify severely degraded sites in the upper Bay. Areas at risk could also be defined in the mid Bay. Advantages of such a protocol are discussed.