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Fieldwork

Seagrass Restoration in Tampa Bay


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A turtlegrass (Thalassia testudium) bed in Tampa Bay, FL
Seagrass: A turtlegrass (Thalassia testudium) bed in Tampa Bay, FL
Seagrasses form one of the world's most productive marine plant communities; some of the most extensive beds occur in Florida's estuaries and nearshore coastal waters (more than 2.5 million acres). The communities provide food and habitat for commercial and sportfishing species, such as spotted sea trout, tarpon, pink shrimp, and spiny lobster, as well as for many types of wading birds and endangered species, such as manatees and sea turtles.

Seagrass meadows, however, are declining worldwide, primarily owing to human-induced disturbances. Declines in seagrass coverage in Florida, particularly in Tampa Bay, have been linked to pollution, worsening water quality, coastal development, loss of tidal marshes, and mechanical damage from dredge filling and scarring by boat propellors. About 35 percent of the seagrass beds have been lost in Florida, where turtlegrass (Thalassia testudinum) is the most heavily affected. The greatest impacts occur in such estuaries as Tampa Bay, which has undergone a greater-than-70-percent decrease in seagrass. The slow recovery of turtlegrass after various human impacts, the continued growth of Florida's population, and the subsequent increase in the numbers of shallow-draft boats all suggest that damage to seagrass beds will continue.

Seagrass recovery and restoration, which are a high priority in the Tampa Bay area, are one focus of the U.S. Geological Survey (USGS)'s Gulf of Mexico Integrated Science-Tampa Bay Pilot Study. This project, conducted in collaboration with the University of South Florida (USF), combines experiments in seagrass ecology, biogeochemistry, microbiology, and analysis of chemical contaminants at two sites in the Tampa Bay estuary: Little Cockroach Bay in the Terra Ceia area and Feather Sound in Old Tampa Bay. Little Cockroach Bay, which is adjacent to an aquatic preserve, has healthy seagrass beds near the test site. Feather Sound has been heavily affected by humans, and very little native seagrass remains.

Clinton Dawes and students lead the way to the seagrass-transplantation site
Clinton Dawes and students lead the way to the seagrass- transplantation site.
USF professor Clinton Dawes and his graduate student Mike Meads have constructed a series of seagrass plots, each containing a single plant. These plots are set up to test whether different types of sediment can improve transplantation. The idea is to experiment with sediment of varying coarseness to see whether keeping the roots of the transplants better oxygenated will allow them to "take" more effectively. The trials are comparing oyster shell, limestone gravel, coarse sand, fine sand, and natural bottom sediment (which varies in texture from plot to plot).

Additional plots are being treated with various slow-release fertilizers, to see whether adding nutrients will give the transplants an advantage. The third part of their study seeks to determine whether planting the seagrass in degradable containers will improve survival during the critical first 3 to 6 months after transplantation. They are comparing cardboard, peat pots, pressed-paper pots, and commercial containers.

In coordination with the USF group, several scientists from the USGS St. Petersburg Science Center in St. Petersburg, FL, have been linking the transplantation study to their integrated science.

  • The SHARQ chamber, 16 feet long by 8 feet wide by 4 feet high, is designed to isolate several cubic meters of water and underlying sea floor from the surrounding environment
    SHARQ: The SHARQ chamber, 16 ft long by 8 ft wide by 4 ft high, is designed to isolate several cubic meters of water and underlying sea floor from the surrounding environment.
    Kimberly Yates and her team have mobilized their Submersible Habitat for Analyzing Reef Quality (SHARQ). This underwater "tent" is set up on a native seagrass bed near the transplant plots to gather such data as salinity, pH, dissolved oxygen, fluorescence, and temperature, allowing calculations of metabolism and growth rates for the benthic community.

  • Christina Kellogg sampled each of the sediment test plots and fertilizer test plots just after they were set up, to count total bacteria and aerobic versus anaerobic viable bacteria. (Viable bacteria are those that will grow on the culture medium, typically just 1 or 2 percent of the total bacteria.) She resampled the same plots later in October, after the plants had completed several growth cycles, to determine whether the treatments have altered the microbial community and whether a correlation exists between healthy plants and any particular microbial group.

  • Mario Fernandez collected sediment samples from the transplant plots for chemical-contaminant analysis, to test for concentrations of pesticides, such as chlordane or DDT, that might be inhibiting growth of the transplanted seagrass.

A petri dish showing viable aerobic bacteria, grown overnight from a sediment sample collected in the seagrass bed
Viable bacteria: A petri dish showing viable aerobic bacteria, grown overnight from a sediment sample collected in the seagrass bed.
Currently, replanting of damaged turtlegrass beds requires damaging a donor bed to obtain transplants, owing to a lack of nurseries. The development of both nursery stock to supply transplants to damaged areas and techniques to increase growth and survival of damaged beds is needed. Our long-term goal is to formulate procedures for enhancing the growth of turtlegrass and to set up land-based nurseries so that plants will no longer need to be removed from donor beds.

A poster describing this research was presented at the Second Gulf of Mexico Integrated Science-Tampa Bay Pilot Study Annual Science Conference (St. Petersburg, FL, Sept. 19, 2002) and will soon be available on the USGS Gulf of Mexico Integrated Science Web site.


Related Web Sites
Gulf of Mexico Integrated Science
U.S. Geological Survey (USGS)

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in this issue: Fieldwork cover story:
Seagrass Restoration in Tampa Bay

Tracking Pintail-Duck Population Decline

Remote Sensing of Coral Reefs at Biscayne National Park

Exploring the Puerto Rico Trench

Research Assateague Island Restoration

Outreach Dedication of New Lake Mead Research Vessel

Meetings Sea-Level Change Workshop

The Need for Better Scientific Understanding of Sea-Level Change

Remote-Sensing at Cape Cod National Seashore

Familiar Faces at Fall Meetings

Giving Interns a View of Science Career Paths

Staff & Center News Visiting Engineer Brings Modeling Expertise

Parsons Succeeds Lee as Acting Chief Scientist for WRCMG Team

Publications November Publications List


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