Water quality in Tampa Bay is meeting all targets for the second year in a row, according to data just released by the Tampa Bay Estuary Program (TBEP).

The 2007 results indicate that water quality in all four major bay segments -- Hillsborough Bay, Middle Tampa Bay, Old Tampa Bay and Lower Tampa Bay -- continues to be good enough to promote the natural recovery of underwater seagrasses that are critical to the bay ecosystem. Although water clarity dipped a bit in five sampling stations in Old Tampa Bay, the declines were not considered serious enough by area scientists to downgrade water quality in that entire segment. Seagrasses, which generally grow in waters less than 6 feet deep, are an important barometer of the bay’s health because they require relatively clear water to flourish. With improvements in wastewater and stormwater treatment, and checks on dredging and filling activities, Tampa Bay has regained 6,000 acres of seagrasses since 1982. The bay now supports 28,299 acres of seagrass – far less than the Estuary Program’s goal of 38,000 acres, but the highest recorded total since the 1950s.

To help track seagrass recovery, TBEP annually compares water quality to established targets in the bay and reports the results in a form called the “Decision Matrix.” This simple chart uses a red, green and yellow color system (similar to a stoplight) to assess overall water quality in the bay. The rating system considers both the amount of microscopic algae (as indicated by chlorophyll a, a plant pigment) in the water, as well as the amount of visible sunlight penetrating the water column.

"Green" means a section of the bay is meeting both water quality measurements, while “red” means a bay segment failed to reach either target. “Yellow” indicates an area did not meet one of the targets and bears watching, as is the case in Old Tampa Bay. In 2006, for the first time since scientists began documenting water quality in Tampa Bay 30 years ago, all four major bay segments met all the water quality targets. In 2007, all bay segments met the targets again.

But though Old Tampa Bay slipped a bit last year, with 5 stations slightly below the “green” threshold, scientists aren’t too worried yet. For now, they will be keeping an eye on the area to see if seagrasses are negatively affected by the small dip in water quality.

“There still appear to be isolated areas within Old Tampa Bay that aren’t meeting the chlorophyll target. These areas deserve closer investigation in the future,” said TBEP Program Scientist Ed Sherwood.

Data on water clarity is collected by the Environmental Protection Commission of Hillsborough County from more than 45 sampling stations scattered throughout the bay. The water quality targets used for the Decision Matrix were developed by TBEP’s Technical Advisory Committee, composed of area scientists and environmental managers.

The targets are specific to each bay segment because water quality naturally varies throughout the bay. For example, the water in the upper part of the bay is generally less clear than the water in the lower bay nearest the Gulf of Mexico, so the water quality targets for the upper bay are less stringent.

For more information on water quality and seagrasses in Tampa Bay, call Nanette O’Hara at (727) 893-2765 or e-mail nanette@tbep.org.