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Seafloor Characterization of the U.S. Caribbean |
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February 29, 2004
Nancy Foster Mission Cruise Update #9
The seas on Sunday morning were flat calm, and the scientific divers prepared themselves for a set of deep dives on portions of the Mid-shelf reef (MSR) that are known to be in pristine condition. The US National Park Service (NPS) and NOAA's NCCOS have been collaborating on a coral reef ecosystem monitoring effort on these reefs for several years now, and the team was excited to get back to one of their favorite dive sites. As usual, the relatively pristine reefs did not let them down. Various species of Star coral (Montastraea spp.) are the most common reef building corals in the US Caribbean, and usually take on a mounded shape in shallow waters; however, due to the depths at which these dives took place (approximately 115 feet), these corals take on a more plate-like form (see top picture).
While at depth, divers encountered many species of fishes that make their home among the healthy deep-water reefs of the MSR. Pictured below, a lone Atlantic spadefish (Cheatodipterus faber) swimming high above the reef, with a juvenile sharksucker (Echeneis naucrates) attached to its side (note long, slender attachment on fish's nape). Also high above the reef, divers were greeted by a pair of very curious ocean triggerfish (Canthidermis sufflamen). These two seemed to be attracted to our bubbles, and stayed with the scientists for much of the dive. Lower on the reef, NPS scientist Rob Waara and NCCOS scientist Alan Friedlander scared up this very large tiger grouper (Mycteroperca tigris). Tigers are rarely seen on reefs in the region due to over-exploitation. Our divers counted a total of 8 tigers on the reef this morning, a phenomenal number for a single dive.
After the morning dive, it was again time to set fish traps so that we can compare catches of fishery species from both inside and outside of the NPS's Virgin Islands Coral Reef National Monument (VICRNM). Mission Chief Biologist John Christensen (NCCOS) and his colleague Rob Waara (NPS) can be seen here on the fantail of the Foster preparing traps for deployment. Once the traps had been deployed at their pre-selected sites, the Foster steamed to the locations where traps were set the evening before. These traps were the first of a series to be set outside of VICRNM boundaries. The trap catch was once again diverse, and was dominated by the French grunt (Haemulon flavolineatum). Other fish species that were seen in the traps included princess parrotfishes (Scarus taeniopterus), red hind (Epinephelus guttatus), coney (Cephalopholis fulvus), yellowtail snapper (Ocyurus chrysurus), and this queen triggerfish (Balistes vetula) (below).
While the trapping crew worked up the remainder of the fish, and returned them to the reef below, weather began to descend on the Foster from the north. A large low pressure system swept in while the MiniBat crew (see update #7, 2.27.2004 for info on the MiniBat) attempted to acquire video of the substrate below. Low visibility due to the squalls, coupled with the many traps that were being fished in the area made "Batting" a difficult task. Twice the Foster had to be stopped because the Bat was caught up in "ghost trap" lines (traps that have no surface floats). The picture below shows chief scientist Mark Monaco (NCCOS), Chris Caldow (NCCOS), Russell Callender (NCCOS), Jason Vasques (USVI Division of Fish & Wildlife), Tim Battista (NCCOS), and the Foster's chief Bosun Jeff Brawley hand pulling the Bat back aboard during a rainstorm.
The day is now gone, and our mapping crew has once again taken over for the night and early morning hours. We've decided to leave you with a composite image of the bathymetry collected to date along the MSR. Warm tones indicate shallower areas, while blues and green indicate deeper water. The MSR is now becoming clearly visible from the sonar data. Dive sites that we have visited during the past 7 days are also shown on the map (squares), while trapped sites are shown as open circles. As we head into the remaining few days of the cruise, we will dive, trap, and map more of the western side of the MSR. Please come back again tomorrow to see what's going on aboard the NOAA Ship Nancy Foster.
