PC-1704: August 28-September 8, 2017   Chief Scientist: Martha Nizinski

1. Survey canyon area and inter-canyon slope habitats using the AUV Sentry; with concurrent sampling of environmental factors (i.e. depth, salinity, turbidity and hydrography) to characterize benthic habitats and identify areas of coral presence;

2. Conduct mapping operations in areas where multibeam data were missing or incomplete;

3. Assess geological features and characterize canyon morphology;

4. Collect CTD data, as well as sediment and water samples;

5. Assemble a database of seafloor photographs to identify benthic species and assess faunal diversity, abundance and distributions; and

6. Assemble maps of geo-referenced coral locations and associated data.

Most canyons are poorly known, but based on data collected during previous investigations, many scientists and managers believe submarine canyons provide refuge for a variety of fauna, including deep-sea corals, fishes, and other animals. Federal and state agencies are tasked with resource management responsibilities, particularly those related to deep-sea corals. The focus of this project is to collect contemporary scientific information needed by managers to protect and conserve deep-sea coral ecosystems.

Surveys of canyon walls and seafloor were conducted using AUV Sentry operated by Woods Hole Oceanographic Institution (WHOI). During each survey, the AUV descended to the seafloor and then transited at a mean altitude of 11-16 m off bottom at a speed over ground of approximately 0.4-0.8 knots. The AUV was equipped with the following equipment that continuously collected data throughout each dive: (1) a 1Kx1K, 12-bit color still camera with strobe that collected photographs every three seconds, (2) parallel lasers projected 10 cm apart, which were used to scale images collected by the still camera, (3) a Seabird SBE49 CTD sensor, (4) a Seapoint optical backscatter (turbidity) sensor, (5) an Anderaa Optode oxygen sensor, (6) a Reson 7125 multibeam mapping sonar, (7) an Edgetech 120kHz/410kHz sidescan sonar, (8) a NOAA Pacific Marine Environmental Laboratory oxidation reduction potential (ORP) sensor, and (9) a Doppler velocity logger and ultra-short baseline (USBL) navigation system, which was used to calculate the AUV’s real-time position once per second.

CTD data and water samples were collected using the Niskin-bottle rosette with attached SeaBird 43 CTD sensor supplied by NOAA Ship Pisces. A monocore sampler was attached by ¼ inch line to the CTD rosette. During each cast, 1.5 L water samples were collected at predetermined depths ranging from 288 to 1756 m depth. Once water samples were brought back to the surface, they were filtered and prepared for future stable isotope analyses that will be conducted at the United States Geological Survey (USGS) facility in Gainesville, Florida. Monocore samples were taken during preselected CTD casts. Once on deck, the resulting sediment core was first photographed. Next, the sediment core was sliced from top to bottom at 1 cm intervals. Each slice was subsampled for several analyses, including infaunal community analysis, grain size, organic carbon, nitrogen, CaCO3, and radiocarbon. Foraminifera were also be picked from the sediment and sorted. These organisms will subsequently be analyzed for radiocarbon to determine the date of the different layers of the sediments. Analyses of the sediments will be conducted at USGS facilities in Gainesville, Florida and in Woods Hole, Massachusetts.