This data product was created as part of the Northwest Atlantic Marine Ecoregional Assessment. The Nature Conservancy developed this science-based ecoregional assessment for the Northwest Atlantic Marine region (Bay of Fundy to Cape Hatteras, North Carolina). This assessment synthesizes information on oceanography, chemistry, geology, biology, and social science to inform decisions about coastal and marine ecosystems. By integrating this information at a regional level, the Conservancy is able to provide both a greater understanding of the interrelated biological diversity of the marine ecoregion, and a clearer picture of the current condition of its natural areas and the challenges to their continued persistence. The ten categories of targets identified as the primary structure for the marine ecoregional assessment are: coastal and estuarine habitats, benthic habitats, diadromous fish, demersal fish, pelagic fish, forage fish, nearshore shellfish, shorebirds and seabirds, marine mammals, and sea turtles. For more information and a detailed report, please visit http://nature.org/namera/.

Ecological Marine Units (EMUs) represent all three-way combination of depth, sediment grain size and seabed forms based on the ecological thresholds revealed by the organism relationships. The source data includes National Geographic Data Center's Coastal Relief Model (CRM), augmented the data with insets from the NOS Bathymetric & Fishing Maps (BFM). The BFM contours were drawn by hand, by cartographers interpreting topography from soundings. The BFM contour maps provide a more credible topography in some of the problematic sections of the CRM. The Canadian portion of the ecoregion, including the Bay of Fundy, was covered by USGS' Gulf of Maine 15' Bathymetry. Because the spatial resolution of this layer (~350 meter cell size) is coarser than the CRM (~82 m cell size), it was used only to fill in areas north of the Hague line and in a section of eastern Georges Bank. We removed a fringe from the CRM where data had been inferred up to 9 km beyond actual soundings.