Today the group of NCCOS divers, Mark Monaco, Matt Kendall and Laurie Bauer, accompanied by Greg McFall, deployed additional receivers to record the movements of tagged fish and visited previously established debris sites. The debris sites visited on the morning dive were in low traffic areas and as expected yielded no debris. One interesting observation was made on the way up as the divers were resting at the safety stop. A pod of dolphins swam past, which included two spotted dolphins and eight bottle-nosed dolphins. All four divers remarked that they had never before seen a mixed pod.
In the afternoon, Mark, Matt and Laurie visited a site located on a ledge with heavy boat traffic that had been cleared of debris in October of 2007. Unexpectedly, this site did not have any new debris. The NCCOS divers were also able to establish a new transect for monitoring debris.
One of the divers on the Georgia Southern dive team, graduate student Lauren Divine, described her day as follows:
“After a few days of bad luck with the weather, we finally got a full day of diving in. Keeping with the goal of surveying the benthic invertebrate composition of GRNMS, we made four dives at two sites with our quadrats. (Quadrats, which measure 30 x 30 cm are used to quantify benthic organisms in small areas of the reef.) We found that there was some inconsistency with dominant species in each area; however, one common sponge, Ircinia felix, was abundant at both sites. Working underwater is not as difficult as it may seem. The hardest part may be trying to concentrate on completing our work! The underwater environment is very beautiful with all the different fishes, sponges, starfish, urchins and invertebrates. Now that we are more familiar with GRNMS, we can head back to the Georgia Southern campus to begin working on our theses.”
Scott Noakes, Assistant Research Scientist at UGA’s Center for Applied Isotope Studies and the University System of Georgia Dive Safety Officer, accompanied the divers this week, providing support for both the NCCOS and Georgia Southern dive teams. Today while diving with the Georgia Southern team, Scott made a discovery that is relevant to his own research. In the past he, Greg McFall, and other scientists have observed thick scallop beds on J-Reef, north of Gray’s Reef. These scallops have been carbon dated by Accelerator Mass Spectrometry methods to approximately 32-38,000 years before present. Until today, these scallops have only been observed as imbedded fossils in the Gray’s Reef area, but today’s find identified a cross-sectional view of the scallop bed within Gray’s Reef National Marine Sanctuary. The age of the beds corresponds with a warming period when glaciers were retreating and sea levels were rising along with increased water temperatures offshore Georgia. These scallops, once prevalent offshore Georgia, typically thrived in the deep ocean and required cold water to exist. However, some scientists believe that it is possible that the scallops actually existed in shallow embayments when Gray’s Reef was partially exposed approximately 15-30,000 years ago. There are still many unanswered questions regarding the scallop beds offshore Georgia, and today’s scallop bed discovery within Gray’s Reef gives way to new opportunities for answering these questions. In addition to the scallop beds, Scott also recovered a small fossil rib from a terrestrial mammal estimated to be about 10,000 years old, a time when Gray’s Reef was once dry land.
Grouper Observing Divers at Work.
While the morning dive teams were out, those of us remaining on the Foster released gag and scamp grouper that were tagged yesterday afternoon. We seem to have finally perfected our release technique. The first step is to corral the fish to one side of the circular fish tank. One person reaches into the tank and transfers the fish into a large bucket of water. Two waiting deckhands then carry the bucket to the edge of the deck and using line tied to either side, slowly lower the bucket to sea level. One end of the bucket is then raised and the fish is able to swim free.
Again today, the Ferguson came over for some hook and line sampling. Please see Teacher-at-sea Laurie Brokaw’s separate log on fishing activities.