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Multibeam echosounder, video observation, and derived benthic habitat data offshore of south-central California in support of the Bureau of Ocean Energy Management Cal DIG I, offshore alternative energy project

January 7, 2022

Coastal and Marine Ecological Classification Standard (CMECS) geoform, substrate, and biotic component (also known as "biotope") GIS products were developed for the U.S. Exclusive Economic Zone of south-central California motivated by interest in development of offshore wind energy capacity and infrastructure. The lead agency responsible for planning and leasing in the Exclusive Economic Zone, the U.S. Bureau of Ocean Energy Management (BOEM), funded the acquisition of these data to assess baseline conditions of the seafloor environment. Raw data from which these GIS products were developed include 8,234 km2 of bathymetry and backscatter data acquired using a multibeam echosounder (MBES) system during four surveys from 2016 to 2019, and underwater video acquired in 2019 using a Remotely Operated Vehicle (ROV). Nearly 120,000 annotations of organisms and their habitat were made from 25 video transects comprising 185 hours of underwater video. Derivatives of the MBES data (for example, induration, rugosity, and slope), and observations from the underwater video, were used to supervise the classification of the MBES data into 22 geoforms, 6 substrate types, 28 modifier groups, and 16 biotopes following the Coastal and Marine Ecological Classification Standard (CMECS). In total, 2,714 km2 of seafloor were successfully assigned to biotopes. Some biotopes were assigned to separate areas spatially distant from the transects that define the biotope. Expected relationships between physical habitat and biota such as the number of species and the substrate induration and rugosity were verified. Slope is typically a predictive variable and was used in the classification of habitat, but the ground-truth used for biotic component analysis included very little steeply sloping area. Ground-truth ROV operations were reduced by the sea state; additional ground-truth would improve the biotic results and increase confidence in the spatial distribution of classifications reported here.