The Continuing Quest for Lophelia
November 17, 2005
Julie Olson, Ph.D.
University of Alabama
View video footage of "marine snow" floating in the water that reduced visibility. (Quicktime, 788 Kb.)
After changing out some of the science crew on Sunday, we encountered rough seas on Monday and Tuesday, which didn't allow us to put the sub in the water (Figure 1). When the seas finally flattened out on Wednesday, we were all very excited to be back in business. Our top priority on our first dive after these days of weather-enforced inactivity was to collect the deep-water coral, Lophelia pertusa.
The Dive: After slowly descending for half an hour, we reach the ocean floor at about 2800 feet and, with directions from the ship's bridge, head towards our first destination. Mapping of the site from bathymetric data has given us a good idea of what the nearby mound looks like and has allowed us to plot a course. As the sub's lights project into the murky water, various life forms begin to emerge from the darkness. Surprised eel-like fish skitter from the light beams and dead coral mounds with just a tip or two of living coral gradually appear at the fringe of our light. Is it our target species? Consultation with the science observer in the back of the sub, Johanna Jarnegren, determined that they were not Lophelia, but rather another deep-water species, Enallopsammia. Encouraged by the sight of the bright white branches, we continue on our traverse across the ocean floor.
Moving upslope, we encounter a series of peaks and valleys, making video documentation difficult. Large amounts of marine snow, or aggregations of particulate material, add to the lack of visibility. Our light beams extend no more than 15 feet from the sub, making the pilot rely upon his sonar to safely navigate the terrain. The amount of coral cover increases as we continue upslope but the vast majority is standing dead Enallopsammia sp. coral. Small snippets of bright white living coral emerge from the gloom with the occasional orange gorgonian or purple octocoral (Figure 2) intertwined among the dead coral. Solitary but elegant glass sponges with intricate basket-weaving patterns beckon from the murky water, guarded by the occasional shark or deep-water fish species (Figures 3 and 4). We continue moving towards the top of the mound, still hoping to find the elusive Lophelia.
After spending two and a half hours and reaching the pinnacle of the mound at 2450 feet, we have to concede defeat. While previous dives on other sites have seen, recorded on video, and collected samples of Lophelia, we have seen no Lophelia at all at this particular site and it's time to return to the ship. Even though we didn't find and document our target species, the dive has otherwise been a success. We've recorded species that inhabit this site and gained a better understanding of the benthic topography. Maybe we'll have more success with finding Lophelia tomorrow. With deep-sea research, there are always more sites to be explored!
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