Survey of deep-water coral and sponge habitats along the West Coast of the US using a remotely operated vehicle
- Kevin Stierhoff
- John Butler
NOAA Fisheries, Southwest Fisheries Science Center
- Peter Etnoyer
National Centers for Coastal Ocean Science
- David Murfin
NOAA Fisheries, Southwest Fisheries Science Center
End Date: November 05, 2010
Remotely operated vehicle (ROV) surveys were conducted from NOAA’s state‐of-the‐art Fisheries Survey Vessel (FSV) Bell M. Shimada during a six‐day transit November 1‐ 5, 2010 between San Diego, CA and Seattle, WA. The objective of this survey was to locate and characterize deep‐sea coral and sponge ecosystems at several recommended sites in support of NOAA’s Coral Reef Conservation Program. Deep‐sea corals and sponges were photographed and collected whenever possible using the Southwest Fisheries Science Center’s (SWFSC) Phantom ROV.
The surveyed sites were recommended by National Marine Sanctuary (NMS) scientists at Monterey Bay NMS, Gulf of the Farallones NMS, and Olympic Coast NMS. The specific sites were: Sur Canyon, The Football, Coquille Bank, and Olympic Coast NMS. During each dive, the ROV collected digital still images, video, navigation, and along-track conductivity‐temperature‐depth (CTD) and optode data. Video and high‐resolution photographs were used to quantify abundance of corals, sponges, and associated fishes and invertebrates to the lowest practicable taxonomic level, and also to classify the seabed by substrate type. A reference laser system was used to quantify area searched and estimate the density of benthic fauna.
Summary to DateSur Canyon (Dive 10‐306A) – 11/02/2010
The Sur Canyon is an unexplored area of MBNMS and needs to be characterized. Surveys of deep coral and sponges are necessary to inform sanctuary resource management. Moreover, a north/south deep‐sea cable route was planned to cross this area in the past, and the proposal may be resubmitted in the future. A characterization of canyon fauna is important for assessing environmental impacts from potential cables (pers. comm., A. DeVogelaeare, MBNMS). The canyon site is located ~6 km offshore of the Big Sur Coast, south of Monterey Bay.
The ROV was deployed in challenging conditions: the wind speed was ~10 knots and the seas were 3‐4 m. This 4‐hour dive targeted the steep eastern wall of Sur Canyon, covering approximately 1 km of seafloor at an average depth of 400 m. The steepest part of the canyon wall was near the transect line, but this particular part of the canyon was avoided to minimize the risk of damage to the ROV. The slope was moderate to steep, composed primarily of hard (low‐ and high‐relief reef, 59% total area) and soft substrate (mostly mud, 34% total area), and punctuated by intermittent boulders.
Corals and anemones
The predominant corals were the soft coral Anthomastus ritteri and the large cup coral Desmophyllum sp.. Swiftia beringi and Euplexaura marki were present, but relatively uncommon. Several unidentified sea pens (Pennatulacea) were also observed. Almost all observations occurred on hard substrate. Coral density across all habitat types was estimated to be ~36 colonies per km2.
The sponge assemblage was fairly diverse. Fan‐shaped, vase‐shaped, plate‐shaped (bracket sponges), barrel‐shaped and whip‐like colonies were observed. Large boot sponges (~30 cm height) and yellow vase sponges (~20 cm diameter) were the predominant habitat forming benthic invertebrates. Numerous whip‐like colonies of Asbestopluma sp. (identified by Lonny Lundsten, Monterey Bay Aquarium Research Institute) were observed. Sponge density across all habitat types was estimated to be ~80 colonies per km2. Almost all observations occurred on hard substrate, where sponges were attached to boulders.
Shortspine thornyheads (Sebastolobus alascanus) were the most common fishes observed (~32 per km2) and were mostly observed over soft substrate. Other notable Scorpaenid fishes included bank rockfish (Sebastes rufus), aurora rockfish (S. aurora), and blackgill rockfish (S. melanostomus). Dover sole (Microstomus pacificus), California rays (Raja inornata) and several sablefish (Anoplopoma fimbria) were also observed. Echinoderms, arthropods and mollusks and numerous Humboldt squid (Dosidicus gigas) were observed feeding amidst a midwater aggregation of Diaphus sp. (likely Diaphus theta, California headlightfish) near 400 m depth during the descent. Deep‐sea sun stars (Rathbunaster californicus) were highly abundant over the hard substrate. Several other unidentified sea stars, feather stars (crinoids), and suspension‐feeding sea cucumbers were also observed. Two brittle stars were collected inadvertently in the sample basket.
DiscussionFor further information, and to see details on the other sites surveyed, please download the PDF located in the Documents tab. All information on this project page was extracted from that report.
- Substrate characterization
- Habitat association
Study MethodsFive ROV transect surveys were conducted between San Diego, CA and Seattle, WA. The total submerged time of 9 hours 45 minutes. The total seafloor distance surveyed was ~5.1 kilometers (km). The depth range of observations was from 110‐400 meters (m). Many deep‐sea octocorals, cup corals, and sponges were observed throughout the survey. The ROV’s single function manipulator was used to collect four deep‐sea coral specimens for molecular and morphological taxonomy plus three serendipitous samples of invertebrates associated with those corals. Samples consisted of: (1) Dendrophyllia sp., (2) brittle stars, (2) Euplexaura markii, (~20) amphipods associated with E. markii, and (1) Swiftia pacifica.
The ROV (Deep Ocean Engineering, Inc. Phantom DS4) was equipped with a CTD sensor (Citadel CTD, Teledyne RDI), an oxygen optode, a Doppler velocity log (DVL, for precisely measuring speed and distance, Workhorse Navigator, Teledyne RDI), a scanning sonar, a single‐function manipulator, a digital still camera (Insite Pacific, Inc. Scorpio with Nikon Coolpix 995), a video camera (Sony FCB‐IX47C with 468x720 lines of resolution and an 18x optical zoom), a reference laser system, and an ultra‐short baseline (USBL) tracking system (LinkQuest). The ROV’s down weight was equipped with collection baskets for holding coral specimens. The FSV Shimada was equipped with an azimuthal bow thruster and dynamic‐positioning (DP) system that provided precise control over the ship’s course, heading, and speed. These tools allowed the ROV to survey and navigate to precise coordinates and change course while underway. A live‐feed of the ROV’s real‐time tracking system to the bridge aided communications among the helm, deck crew and ROV operations. Navigation data from the ship and ROV were logged at 2‐second intervals using the WinFrog integrated navigation system software (Fugro‐Pelagos, Inc.).
During each dive, the ROV collected digital still images, video, navigation data (e.g. latitude/longitude, speed, and depth), and along‐track CTD‐optode (CTD‐O) data. Video and high‐resolution photographs were reviewed post‐cruise to quantify the abundance of all observed organisms to the lowest practicable taxonomic level. Distance was calculated every 2‐seconds using the speed of the ROV. Video and the reference laser system were used to quantify total area searched at 2‐second intervals using the 3Beam© Quantitative Measurement System (QMS) software (Pinkard et al. 2005, Stierhoff et al. In prep.). Habitat types were classified following the classification system of Greene et al. (1999), but were subsequently summarized into broader habitat classes (hard, soft, mixed) for ease of comparison. The total area searched within each broad habitat type was also calculated to estimate habitat‐specific densities of each organism at each dive site.
Figures and Images
- Stierhoff et al. (2011)A survey of deep‐water coral and sponge habitats along the West Coast of the US using a remotely operated vehicle
2.1 MB PDF