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Using MBES Backscatter and Bathymetry to Assess the Distribution of Benthic Communities for Piston Coring Operations

Abstract

Recent advances in multibeam echosounder (MBES) and seismic technologies have prompted focused piston coring campaigns to target cold seeps on the seafloor to obtain samples to test for hydrocarbon charge. However, the presence of benthic mollusk and tubeworm colonies, as well as naturally derived authigenic carbonates, can complicate coring operations. These carbonate-producing benthic communities limit penetration depth of cores and can lead to damaged coring equipment. These communities frequently limit penetration of cores, which is not ideal geochemical sampling. Recently, a method using MBES has been developed for predicting the presence of these benthic assemblages around cold seeps (Sen et al., 2016). This methodology differentiates types of hard-ground created by mollusk and tubeworms, as well as predicting authigenic carbonate using Autonomous Underwater Vehicle (AUV) MBES data (instrument flying 30-40 m above seafloor), which were verified using AUV photography. This study examined data from hull-mounted MBES systems from several seephunter surveys to determine if this methodology can be applied to hull-mounted MBES (thousands of meters above seafloor) backscatter and bathymetry derivatives, verified with piston core descriptions to differentiate mollusks, tubeworms, and authigenic carbonate. These results will optimize planning of seephunter piston coring campaigns which will provide better coring penetration for hydrocarbon sampling, as well as minimize impact to these communities, which may be protected by local regulations.