MICROHABITAT MAPPING OF SUBSTRATE, WATER QUALITY, AND FAUNA AT SOUTHERN HYDRATE RIDGE, OREGON CONTINENTAL MARGIN

Southern Hydrate Ridge, an active gas hydrate system, is the local peak of an anticlinal thrust ridge within the Cascadia Accretionary Wedge, positioned approximately 90 km offshore of Newport, Oregon. Due to the extensive authigenic carbonates and chemosynthetic fauna at this methane seep, as well as its thorough documentation by the Regional Cabled Array branch of the Ocean Observatories Initiative (OOI), this site constitutes a prime candidate for habitat mapping. Assessment of this site through habitat mapping provides a deep understanding of its habitat features and biodiversity, which is essential for conservation and management efforts. In 2011 and 2022, ROV ROPOS conducted water quality and image surveys spanning 125m by 110m of the Southern Hydrate Ridge to compile photomosaics informing seafloor cable and instrument placement as part of the University of Washington-NSF-OOI VISIONS cruises. An initial set of 100 of the resulting images was manually annotated for fauna, and these annotations were used to train an object recognition model to assist in annotating the remaining 1327 images. Every tenth image was further analyzed for substrate composition, producing an approximate percent cover of each image by different substrate classes. This work provides fine-scale characterization of habitat across the Southern Hydrate Ridge at two points in time (2011 and 2022). The information generated can now be used to construct a detailed map of Southern Hydrate Ridge microhabitats, which may be employed to identify regions of biological interest. Though focus here is on the Southern Hydrate Ridge, this study aims to extract associations between physical environment and biological assemblage that are applicable to methane seeps across the Cascadia margin or beyond.