Fall/Winter 1995
Marine Bulletins

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Shrinking Wetlands
and Sea Level Rise

Understanding how coastal marshes grow or shrink in response to changes in sea level and climate fluctuations over time is important for wetlands management. Detailed records of relative sea level rise exist only for the past 200 years or so in the United States. That's not long enough to put current trends into perspective, because coastal marshes undergo episodes of submergence or emergence lasting as long as a century. So, researchers must literally dig into the past to uncover more information.

Geologist Johan Varekamp and paleozoologist Ellen Thomas at Wesleyan University have teamed up to investigate marsh response to changes in sea level rise over the past 2,000 years and how these changes relate to climate. Using radiocarbon dating to establish the time frame, Varekamp and Thomas examined sediment cores from marshes in Clinton and Guilford, Conn., analyzing chemistry, vegetation, and fossilized animal assemblages. The appearance of fine-grained deposits, such as iron and zinc, indicates when the marsh was flooded, and the positions of certain species of fossilized animals in the sediment suggest what the marsh's elevation was.

What can we learn from this information? We know that sea level has been rising, at different rates, for the past 10,000 years. For most of the past 1,000 years, the rate remained fairly steady, but about 300 years ago it increased and continues to rise rapidly at about 3 millimeters per year.

The Connecticut marshes can no longer grow fast enough to keep up with the rate of sea level rise. If current trends continue, present middle - to high - marsh areas may become low marsh within a few centuries, and today's low marsh may be submerged.

Can we blame this rapid sea level rise on global warming from greenhouse gases? Surprisingly, this accelerated rise began around 1650, a period still considered to be within the Little Ice Age. The rise preceded the rapid accumulation of greenhouse gases from anthropogenic sources, which most researchers say began around 1900. Varekamp and Thomas believe that the rapid sea level rise may be a result of the thermal expansion of ocean waters or the dynamics of the ocean surface.

Predicting Future
Lobster Harvests

Although lobster harvests in the Northeast have been at all-time highs in recent years, fishery scientists have warned that stocks are overfished and a collapse is possible. If lobster landings can be predicted and techniques developed to help regulate the lobster industry, a stock collapse could be averted.

According to Robert Steneck, lobster ecologist at the University of Maine's Darling Marine Center, the multi-institutional Sea Grant research team is focusing on inch-long planktonic lobsters that swim in coastal waters and eventually settle to the sea floor.

Steneck is working in collaboration with Richard Wahle, marine biologist with the Bigelow Laboratory for Ocean Sciences in West Boothbay Harbor; Win Watson, UNH zoology professor; Hunt Howell, UNH zoology associate professor; J. Stanley Cobb, URI biological sciences professor; and Michael Fogarty, acting chief, population biology branch, National Marine Fisheries Service.

Over the next three years, the research team will track landings and monitor environmental conditions, such as temperature and food availability. The team will also use sampling techniques to estimate the numbers of lobsters settling on the sea floor. These numbers will be compared to the number of lobsters that settle into artificial collectors Steneck recently developed. In addition, participant lobstermen are keeping logbooks in which they record how many sublegal lobsters and legal sized lobsters they catch in their traps.

Researchers Seek to Save Urchin Fishery

Gulf of Maine urchin landings declined last year. Larry Harris, UNH zoology professor, attributes the decline to overfishing and thinks the future of the fishery lies in managed and controlled aquaculture operations.

Exported to Japan where their roe is a delicacy, high quality urchins bring fishermen $2 to $3 per pound. Over the past 20 years, urchin fisheries in Japan, Great Britian, and Chile, as well as along the WestCoast, have been decimated to meet the demand.

Currently in the second year of a four-year Sea Grant- supported research project, Harris has been working to develop the expertise and techniques needed to sustain the urchin fishery. In this effort, he is working with Jay Gingrich, a former urchin fisherman, and Robert Bryant, a lobsterman.

"From everything we know and are learning about urchins," Harris explains, "the fishery will be a great aquaculture opportunity. When the conditions are right, urchins stay at home and eat. Their growth can be enhanced with commercial feeds so that they reach the 2-inch, 5- to 6-ounce marketable size in two to three years." Harris and his colleagues plan to produce a guide book as part of their project.

 

Odyssey IIB Explores
Marine Habitats

MIT Sea Grant's Autonomous Underwater Vehicles (AUV) Laboratory sent its latest vehicle to study marine habitats in Massachusetts Bay's Stellwagen Bank. Video and acoustic data collected are being used to measure depths and roughness of the sea floor, as well as to assess fishery stocks. Odyssey IIB also collected measurements of water temperature and salinity, which provide information about where nutrients and animals congregate. The research was a collaboration with the National Undersea Research Center at the University of Connecticut, with support from the Stellwagen Bank National Marine Sanctuary.

Five new Odyssey IIBs were constructed by MIT Sea Grant through an Office of Naval Research five-year, multi-university research initiative. Collaborators include WHOI and the Naval Research and Development Center.

The AUV Lab will launch four AUVs in Buzzards Bay (Woods Hole, Mass.) this spring to test acoustic communication between researchers on a ship and their vehicles. In summer, in the Haro Strait off the coast of British Columbia, the lab will study how tidal fronts form and dissipate while controlling the AUVs from a shore station via the Internet. A site on the World Wide Web will report on the researchers' progress.

Underwater Fluorescence

Under ultraviolet light, many otherwise drab corals, anemones, shrimps, and other organisms mysteriously fluoresce in brilliant colors. To study this phenomenon, Charles Mazel, MIT ocean engineering research engineer, and undergraduates Lydia Chan and Quoc Tran developed a prototype instrument to measure the spectral distributions of underwater fluorescence.

Small enough to strap to a diver's wrist or chest, the contraption uses fiber optics to excite fluorescence and a low-cost spectrometer to measure incoming light.

"The light that comes into the ocean affects what grows and what pigmentation it has, and that affects light coming off the bottom," explains Mazel. By recording measurements of fluorescence from different sources, Mazel expects to learn about the biological processes that affect fluorescence and to aid researchers who study how light interacts with the sea floor and organisms that live there.

The MIT Sea Grant-funded project has resulted in four related research projects, including efforts supported by the Office of Naval Research's Environmental Optics Program.

 

Studies Reveal Atmosphere
as Source of Contaminants

Pollution management programs in the metropolitan area should consider the atmosphere a major source of contaminants to nearshore environments, according to investigators at the Marine Science Research Center at SUNY at Stony Brook. With funding from New York Sea Grant, researchers Kirk Cochran, Bruce Brownawell, and David Hirschberg measured atmospheric inputs of contaminants, such as metals, PCBs, petroleum derivatives, and pesticides, in tidal marshes in the western Long Island Sound area and compared them to those measured in less urban areas. Organic contaminants near urban areas were significantly higher than those at remote locations elsewhere in North America - more than 250 times higher for polychlorinated biphenyls (PCBs) and more than 100 times higher for polynuclear aromatic hydrocarbons (PAHs). These findings could have implications for policy makers who have focused on controlling other contaminant sources, such as sewage effluent from wastewater treatment plants, excessive fertilizer used on lawns or agricultural crops, and discharges from septic systems.

Release Coatings Show
Promise Against
Fouling Organisms

Sea Grant researchers are developing new nonpolluting coatings that should help in the battle against zebra mussels and other fouling organisms. Concern about exposure of marine organisms to toxic non-fouling paint, as well as potential human health implications of application, maintenance, and disposal of toxic coatings, has sparked interest in new types of defense against fouling.

The research of Robert Baier, Industry/University Center for Biosurfaces director, has shown that most biological adhesion follows surprisingly similar modes of action. Protein is the glue that binds one surface to another, whether tube worms like those found on the propellers of navy ships in Pearl Harbor or tomato ketchup found in a food processing plant. Therefore, a properly designed surface should perform equally well against most fouling organisms or substances. Several industry collaborators have begun to manufacture coatings based on this work.

Return of the Grass
to Narragansett Bay

Eelgrass beds that once flourished throughout Narragansett Bay have disappeared through the years. Many theories account for this. Most often mentioned are disease, pollution, and dredging. But now, under the direction of Scott Nixon, R.I. Sea Grant director; Steve Granger, URI marine research associate; and graduate student Blaine Kopp are working to return the grasses to Narragansett Bay.

The researchers are trying two different approaches. Kopp, with funding from Rhode Island Aquafund and active participation from Save The Bay, is working to transplant healthy eelgrass plants into areas of the Bay where they were known to thrive in the past. Granger, funded by NOAA's National Estuarine Research Reserve Program and supported by the R.I. Department of Environmental Management, is working to reseed the Bay.

Granger decided to investigate the use of seeds because of the difficult, labor-intensive task of transplanting whole plants. "With seeds, you can do very large areas," he says. "It is a low-cost, large-scale way of restoration."

In all, Granger is trying four reseeding techniques: 1) pelletizing the seed; 2) impregnating the seed onto a biodegradable mesh; 3) sowing naked seed; and 4) planting untreated seed into mechanically prepared furrows in the sediments.

The different methods are being tried because direct seeding of nature's seeds doesn't seem to work well. The reason: naked seed has trouble sinking to the bottom, where it needs to go to germinate. And even when it does sink to the bottom, it isn't heavy enough to sink into the sediments. Instead, it rolls around at the surface and may be eaten by marine organisms or carried away by strong currents. The other methods - pelletizing the seed by encasing it in a protective coat, embedding it in mesh, or planting it into prepared furrows - should overcome those problems.

During this growing season, the researchers will evaluate the success of each of these methods. Next year, they will focus on the two most successful methods.

The benefit of all this? "We have experienced a decline in our inshore fisheries of finfish and shellfish over recent years. Some would say that it has resulted in part from the loss of nursery habitat," Granger says. "Sea grasses provided this habitat. This project is just one effort to expand sea grass habitat in our nearshore waters."

 

Mapping the Shrimp Genome:
A New Approach to Animal Health

Acacia Alcivar-Warren, Tufts University School of Veterinary Medicine assistant professor, and her colleagues have developed a size-selected DNA library from adult-specific, pathogen-free (SPF) shrimp, Penaeus vannamei, in an effort to improve knowledge of the genetics of this commercially important species. The penaeid shrimp fishery is this country's most valuable fishery. However, over 70 percent of the shrimp consumed in the United States is imported, creating an annual net trade deficit of $2 billion in shrimp.

In 1984, the U.S. Marine Shrimp Farming Program (MSFP) was formed by Congressional initiative to improve the domestic shrimp farming industry and reduce this trade deficit. Tufts University, a member of the MSFP, is performing genetic diversity studies in wild and SPF shrimp developed by the MSFP. Alcivar-Warren's work, supported in part by WHOI Sea Grant program development funds, could provide clues about the productivity and susceptibility to disease of this shrimp species.

In the last year, a disease known as Taura Syndrome devastated this country's P. vannamei aquaculture industry and, along with it, millions of dollars in projected revenues. Some shrimp stocks developed by the U.S. MSFP were used at the time this virus wiped out the population, suggesting that these stocks are susceptible to the viral agent that causes Taura Syndrome. If disease susceptibility is genetically determined, genetic markers must be developed that could differentiate between susceptible and resistant populations.

To obtain these markers, however, the shrimp genome map has to be developed. Working toward this goal, Alcivar- Warren and her colleagues have cloned a genomic DNA (nuclear chromosomal DNA) library obtained from one population of SPF shrimp developed by the U.S. MSFP. Their efforts are now focused on identifying and sequencing potential microsatellite-containing clones, which could be used to map the shrimp genome. The Sea Grant- sponsored portion of this work involves the beginning stages of mapping the shrimp genome, using microsatellite technology to examine the loci (locations of genes on a chromosome) involved in disease resistance and productivity in P. vannamei. This information could provide the industry with biological tools for developing healthy, fast-growing seed stocks, thereby increasing U.S. shrimp farming production.

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