Submerged marine habitat mapping, Cape Cod National Seashore: a post-Hurricane Sandy study

Abstract

Coastal storms are the primary drivers of coastal change, but submerged areas historically have been difficult to map and consequently to document change. Hurricane Sandy had a dramatic impact along coastal areas in proximity to landfall in late October 2012 and those impacts have been well-documented in terrestrial coastal settings, however, due to the lack of data on submerged marine habitats similar studies have been limited. One of the motivations for this study was to provide park managers with a baseline inventory of submerged marine habitats to measure change during future storm events. A three-year study to map submerged habitats in Cape Cod National Seashore was recently completed. This was one of four contemporaneous studies that developed maps of submerged shallow water marine habitat in and around coastal national parks along the east coast of the United States. These four projects used similar methods of data collection, processing and analysis for the production of benthic habitat maps. Data from a phase-measuring sidescan sonar, bottom grab samples, seismic reflection profiling, and sediment coring we all used to develop submerged marine habitat maps using the Coastal and Marine Ecological Classification Standards (CMECS) in Cape Cod National Seashore. Over 76 vessel-based acoustic surveys were conducted in extreme shallow water, across four embayments from 2014-2016. Sidescan sonar imagery totaling 83.1 km2 were collected and within that area 61.3 square kilometres of collocated bathymetric data were collected with a mean depth of 4.6 m. Bottom grab samples (n = 476) and ancillary data were collected, macroinvertebrates were identified and used within the CMECS framework along with the geophysical and coring data to develop final habitat maps.