Working Together to Achieve a Common Goal: Exploring the New England Seamounts

Download 13.77 Kb.
Size13.77 Kb.

Working Together to Achieve a Common Goal: Exploring the New England Seamounts

Mercer R. Brugler

Grice Marine Laboratory

College of Charleston, Charleston, SC

Dr. Jon Moore

Florida Atlantic University

Wilkes Honors College, Jupiter, FL

Even before this cruise, the many scientists looking to study the New England (NE) seamounts knew it would take more than a single effort to accurately characterize even a small piece of this seamount chain. The first investigation of the organisms on these seamounts was a series of trawls conducted by the National Marine Fisheries Service (NMFS) in December 2000 at the closest seamount to the United States, Bear Seamount. That cruise provided the first glimpse of the animals on only one of the more than 30 seamounts in this chain. The faunal list was compiled from identifications made by several scientific experts after the cruise and is currently in press.

Bearinverts.15july.jpg : Miscellaneous invertebrates collected during the 2000 cruise to Bear seamount. Photo by Michael Vecchione.
In September of 2001, a team of deep-sea scientists set out on the Deep East expedition to study two of the NE seamounts (Bear and Physalia), but due to bad weather (Hurricane Erin), were confined to working in two areas on the continental slope of George’s Bank, Oceanographer and Hydrographer canyons. Close in proximity to the northernmost seamount in the NE seamount chain (Bear Seamount), the canyons, which are often characterized by swift currents and similar fauna, afforded the scientific crew an opportunity to achieve several of their goals.
Coralscape.15july.jpg: A coral landscape in Oceanographer Canyon. Photo WHOI.
Deep_sea_corals.15july: Unique species of deep sea corals collected from Oceanographer Canyon.
The Deep East expedition had several objectives. The primary objective was to characterize the various types of coral and fishes associated with the NE seamounts using the manned submersible Alvin. Other goals included describing coral distribution, invertebrates associated with the corals, fish diversity, and the reproductive biology of corals. Unfortunately, only one task was accomplished with regard to the NE seamounts. Both Bear and Physalia seamounts were topographically mapped using a multibeam sonar system, which provided a very detailed map of the various features of each seamount. All other objectives were modified and accomplished within the canyons. Some of the research results were written up and are currently in press. Such results include a description of the pattern of slope-fish diversity with relation to the landscape (Peter Auster), describing a new method of swimming in a deep-sea shrimp, which may be physiologically mediated (Les Watling), a description of a likely new species of coral from the genus Thourella (Les Watling), and an interactive CD-ROM that includes data, history and the underwater landscape of Oceanographer canyon (which was recently made available to the public). Dr. Scott France’s lab (College of Charleston, S.C.) has DNA-sequenced mitochondrial genes for all of the corals collected. The France lab awaits additional samples from the seamounts to learn about patterns of gene flow in the world’s oceans.
Sortedmix.15july.jpg: A partially sorted mix of fishes, shrimps, and salps from one of the trawls over Bear Seamount. Photo by Jon Moore.
Bearshrimp.15july.jpg: The shrimp trawl coming up onto the deck of the R/V Delaware II at Bear Seamount. Photo by Jon Moore.
Another NMFS cruise to Bear Seamount was sponsored by NOAA Ocean Exploration in July 2002. Again, the fauna was sampled using both midwater and bottom trawls. This added considerably to the faunal list of organisms associated with the New England seamounts, including new records of a number of very unusual fish species. This work provided greater information on the geographic distribution of particular groups, especially deep-sea fishes. This data was also incorporated into an international initiative, the Census of Marine Life, which includes Bear Seamount within the Gulf of Maine pilot project.
Deepangler.15july.jpg: A deep-sea anglerfish collected during the 2002 Bear Seamount cruise. Photo by Jon Moore.
Deep-sea research can be quite expensive, especially when both manned and autonomous deep submergence vehicles (e.g., Alvin and ABE) are implemented (~$35,000/day). Thus, even when the weather is at its worst, it is of utmost importance to achieve the objectives set forth, even if it is accomplished in a very different manner. This was the situation presented to the scientific crew of the Dive & Discover cruise led by Dr. Jess Adkins in May-June 2003. While this cruise had a somewhat different primary objective, the secondary objectives were similar to what the Deep East cruise set forth (to characterize where deep-water corals live on seamounts). The primary goal was to collect both living and fossil deep sea stony corals (e.g., Desmophylluym cristagalli), and to use radioactive decay dating (Uranium-thorium or C14) on the coral skeletons to better understand water masses and deep ocean currents (each of which has a chemical ‘signature’) that a particular coral grew in at a particular time. Corals absorb compounds from seawater in order to secrete their calcium carbonate skeleton, and it is the ratio of these compounds that radioactive decay focuses upon. It is thought that abrupt changes in the Earth’s climate are caused by changes in the circulation of the deep ocean, and if one can trace the track of water masses in the past, it is conceivable that we can predict changes in the future.

DiveandDisc.15july.jpg: Corals and other invertebrates seen from the Dive & Discover cruise. From left to right, a sponge, two gorgonian corals, clumps of dead and live Lophelia stony coral, and a sea whip gorgonian. Photo by Rhian Waller.
Besides several Alvin dives on the Dive & Discover cruise, other methods of viewing the seafloor were implemented, such as using a towed camera sled. Ironically, the second camera tow got caught on the seafloor, and after dislodging and bringing it back to the surface, we discovered on top of the camera the largest number of intact D. cristagalli corals collected to date. The ten Alvin dives that actually occurred brought up numerous coral (gorgonian and antipatharian) and non-coral invertebrates. ABE (the Autonomous Benthic Explorer, a robot submarine), for the first time ever, was outfitted with a down-looking camera. These images from ABE, together with the Alvin and camera tow images comprised almost 48,000 digital photos. With the plethora of organisms and data collected, the scientists of the Dive & Discover cruise were able to leave the ship with the appropriate material to answer their individual questions.
Alvinsponge.15july.jpg: A large sponge in the basket of the submersible Alvin, collected during the Dive & Discover cruise. Photo by Jon Moore.
Exactly what types of questions were the scientists aboard the Dive & Discover cruise looking to answer? They included growth, age structure, and dispersal of gorgonian corals (Lauren Mullineaux and Susan Mills), biodiversity and biogeography of faunal inhabitants (Jon Moore), molecular systematics and population connectivity of seamount faunal populations (Tim Shank and Kate Buckman), reproductive biology and ecology of scleractinian corals (Rhian Waller), and population genetic (and systematic) relationships of gorgonian and antipatharian corals (Scott France and Mercer Brugler). Other scientists were particularly interested in the rocks collected from the various seamounts, which were all coated in a thick manganese oxide layer. Even others were interested in putting together photo mosaics from the large number of images.
Beartrawl.15july.jpg: Sorting animals from the trawl catch at Bear Seamount in 2002. From left to right: Dr Tracey Sutton, Dr Jon Moore, Edward McChain, Chris Kenaly, Dr Michael Vecchione. Photo by Ruth Gibbons.
Ocean Explorer’s ‘Mountains in the Sea’ cruise continues the effort to characterize the New England seamounts. The current cruise looks to sample Manning, Kelvin, and Bear seamount, using information obtained from the NMFS, Deep East and Dive & Discover cruises (such as multibeam sonar data, and the various maps produced by ABE). Combining the previous cruises, only 3 out of 30 NE seamounts (Bear, Manning, and Gregg) have been sampled, along with another isolated seamount (Muir) that was also sampled. Two seamounts will be resampled on this cruise, Bear and Manning. Because we now know that a large number of corals exist on the NE seamounts, we can attempt to accurately map the distribution of the octocorals and assess the overall diversity of organisms living on and among the coral communities. Other scientists are hoping to determine the reproductive state and potential larval strategies of seamount octocorals, and are also looking to investigate the colonization dynamics of dense coral aggregations using basaltic recruitment blocks. Another important question that will be addressed looks at the physical impact of bottom trawling on octocoral communities and seamount biodiversity, which is of utmost importance as the trawling industry is pushed to deeper waters (as the shallow water sources are becoming more and more depleted).
Manningstar.15july.jpg: A large brisingid sea star collected from Manning Seamount. Photo by Jon Moore.
After the current cruise, a total of 5 northwestern Atlantic seamounts will have been partially explored. That is only 17 percent of New England seamount chain. Thus, it is imperative that the scientists of past NE seamount expeditions work with the scientists of future endeavors in order to pass along methods of collecting that both worked and failed, and to collaborate on what was found, and what still needs to be characterized. We are finding the New England seamounts to be very diverse, and it is going to be very exciting to see the results of both this cruise and future cruises that explore this general area.

Download 13.77 Kb.

Share with your friends:

The database is protected by copyright © 2024
send message

    Main page