ACTIVE RESEARCH

CO-RESTORATION OF SEAGRASS AND A NATIVE BIVALVE IN SARASOTA BAY, FLORIDA

Large-scale seagrass declines due to poor water quality and harmful algal blooms (HABs) are a major concern across the State of Florida. However, innovative and cost-effective methods to recover seagrass habitat using hard clams are immediately applicable. This project aims to test whether native bivalves (Mercenaria campechiensis) can facilitate seagrass restoration and evaluate whether additions of hard clams could provide a novel method to speed natural seagrass recovery.

NATIVE CLAMS FOR FLORIDA AQUACULTURE

Florida clam production relies upon the northern hard Clam (Mercenaria mercenaria), but this species is at the southern extent of its range. Its close relative, the southern hard clam (M. campechiensis) is native to the Gulf coast and might be better adapted to summer extreme temperatures. In this NOAA funded study, we are comparing the growth and survival of each species on commercial leases along the Gulf coast to test the hypothesis that differences in performance varies by latitude. Preliminary results indicate similar growth patterns, but M. campechiensis in Tampa Bay survived the Piney Point harmful algal blooms while Mercenaria mercenaria suffered high mortality.

Performance of northern (left) and southern hard clam (right) is currently being compared on commercial leases along on the Gulf coast.

NATIVE CLAM RELEASE OUTCOMES

We are partnering with Sarasota Bay Watch to follow the outcomes of southern hard clam releases in Sarasota Bay. Since 2016, Sarasota Bay Watch has released hundreds of thousands of native clams into local waters, with the goal of releasing over 1 million these filter feeders in 2022. The Gulf Shellfish Institute is assisting with long-term monitoring of release sites, including clam survival, water quality, sediment changes, and nutrient dynamics. Our goal is to not only track the fate of native clam introductions and quantify environmental benefits of large-scale release efforts, but also develop a suitability index for future clam release.

Over 120,000 southern hard clams (Mercenaria campechiensis) heading to Sarasota Bay for release.

 PAST RESEARCH

ECOSYSTEM SERVICES OF NATIVE CLAMS

This 2016-2018 project documented clam growth and mortality by comparing water quality and sediment composition between experimental (with clams) and control (without clams) areas at two sites and recorded any changes in seagrass distribution near the clams. No differences in water quality were detected between different treatments, but organic content in sediment was higher in areas with clams. We feel this could lead to future enhancement of conditions for seagrass growth.

REPRODUCTION AND CONDITIONING OF SUNRAY VENUS

Objectives of this research were to examine the reproductive cycle and main factors controlling reproduction, such as temperature and food availability. We found that in these clams do not have a well-defined reproductive cycle in the wild; instead, they reproduce almost continuously throughout the year. Additionally, food availability is a larger factor controlling reproduction than temperature. This research was published in the Journal of Shellfish Research.

OYSTER SETTLEMENT ON NATURAL VS. FOSSIL SHELL

Oysters require hard substrate for larvae to settle and attach. Oyster reef restoration is often limited by the availability of natural oyster shell. With funding from the Tampa Bay Estuary Program and Solutions to Avoid Red Tide (START), we compared whether fresh shell collected from local restaurants or fossil shell were better substrate for attracting oyster larvae. We found fresh shell attracted significantly more oyster spat than fossil shell, and most spat settled in the fall. Shell recycling programs are therefore key to oyster restoration success.

Restored oyster reefs at Robinson Preserve in Manatee County, Florida.