Tampa Bay has gained nearly 1,300 acres of seagrass since 2004, and now supports more seagrass than at any time measured since the 1950s, according to newly released data presented to the Tampa Bay Estuary Program (TBEP).

Additionally, water clarity in the bay is also the best it has been since record-keeping began, with all major bay segments meeting targets.

Overall, the amount of seagrasses in Tampa Bay increased by 4.7 % percent from 2004-2006, according to surveys conducted by scientists with the Southwest Florida Water Management District’s Surface Water Improvement and Management (SWIM) Program. Seagrasses – which generally grow in waters less than 6 feet deep – are an important barometer of the bay’s health because they require relatively clean water to flourish.

SWIM scientists assess seagrass coverage in the bay every two years, using a combination of maps produced from aerial photographs followed by ground-truthing to verify accuracy. The results are used to track trends in seagrass extent in estuaries throughout Southwest Florida.

Digital photography was used for the first time this year to collect the aerial images, said Kris Kaufman, the project coordinator. The use of digital imagery, combined with good water clarity in February 2006 -- when the surveys were conducted -- allowed scientists to reliably map deeper-water seagrass beds for the first time. Field verification also eliminated some areas that had previously been mapped as seagrass but were actually thick mats of algae or some other anomaly.

The results indicate that Tampa Bay has about 28,299 acres of seagrass – far less than the Estuary Program’s goal of 38,000 acres, but the highest recorded total since the benchmark 1950s period adopted by the Program. Water clarity also is meeting Estuary Program goals for all bay segments for the first time since scientists began tracking water quality in the 1970s. Data on water clarity is collected by the Environmental Protection Commission of Hillsborough County from more than 60 sampling stations scattered throughout the bay.

Although the overall “report card” on the bay’s health is positive, not all bay segments experienced seagrass expansion. Significant declines were noted in Middle Tampa Bay – which lost 1,180 acres of seagrass from 2004-2006 -- and in Hillsborough Bay, with a loss of 151 acres of seagrass during that time frame.

Conversely, the area generally north of the Gandy Bridge, known as Old Tampa Bay, experienced a 16% increase in seagrasses from 2004-2006 – good news for an area that had been steadily losing seagrasses for a decade.

Seagrasses are the nurseries of the bay, sheltering and supporting an amazing variety of juvenile fish and other marine creatures. The Tampa Bay Estuary Program has set a goal of restoring seagrasses baywide to the levels at which they were present in the 1950s, roughly 38,000 acres.

Results of the 2004-2006 surveys show that the bay is regaining seagrasses overall at a rate of 2-3% every year. These new statistics are surprising to some scientists because they came in spite of the active hurricane seasons of 2004 and 2005, indicating that seagrasses may be more resilient to hurricane impacts than previously thought.