DISCOVRE 2008

Cruise Log: 10/07/2008    Seastate: 3-4'

Descending to the Deep Oasis

Amanda W.J. Demopoulos

Today was the first day of our ROV dive operations. ROVs, or Remotely Operated Vehicles, are robots used to explore difficult to reach areas of the deep. They are more than just windows into the deep sea; they allow us to observe, collect, and document organisms in their environment. I was very excited to participate in this ROV dive because it was my first time using an ROV for my research. Today's blog will be Part 1 of our ROV dive blogs and in it I will describe the overall highlights from the dive, including some images of organisms that we took while examining the deep coral habitat. Future ROV blogs will include more details regarding the ROV used, the ROV team from SEAVISION (Jeff Snyder, Matthew Cook, and Geoff Cook), and the associated equipment. For this ROV dive, we set out to locate and document the benthic landers that were launched on Monday, and to collect sediments and other animal samples. I was particularly interested in the sediment collections because I specialize in the ecology of animals that live in the substrate, whether that is sand, mud, or rock. Before the ROV launched this morning, I made sure that my sediment sampling gear was ready. In addition, the ROV had 4 boxes that would be used to collect additional animals. After the ROV launched, it took about 35 minutes to reach the bottom, at 447 m. We immediately saw thickets of coral, specifically Lophelia pertusa. Within the branches of the coral were many of the same animals that we typically see in shallow water corals, including crabs, sea urchins, and anemones. In addition, the sediments were covered with small tubes containing worms. There were several of these tubes blanketing the sediment surface, with the plumage of the filter feeder worms only obvious close up. Every now and then we would see different fish, lying close to the seafloor or tucked away, hidden within the live coral branches.

After exploring a bit and verifying our position on the bottom, we started searching for the landers. We had a target GPS location and used scanning sonar to try to pin point where they might have landed on the bottom. After searching for a while, we decided to collect some animal samples, including coring for sediment fauna and grabbing pieces of coral from the thickets. Sediment coring proved difficult, because the substrate was composed of hard carbonate rock covered by only a thin layer of fine sediment. While coring was not possible, we were able to grab some samples of Lophelia, sea urchins, and cup corals. These samples will be identified and analyzed for genetics, and stable isotopes for food web studies. After our dive was complete, we returned to the surface to collect and process our data. The ROV team retrieved their data and put the ROV to bed for the night. Tomorrow, our next ROV dive will include locating the benthic landers, collecting specimens, and conducting video transects to document the animals that live in these deep coral ecosystems.

The sea urchin, Echinus tylodes, rests in amongst the branches of the Lophelia bush. - (photo credit: USGS DISCOVRE Expedition) - click to enlarge

Several fish species, such as this roughy relative, Hoplostethus, stay in close contact with the deep coral environment. - (photo credit: USGS DISCOVRE Expedition) - click to enlarge