Although seagrass recovery baywide is still on pace to achieve goals adopted by the Tampa Bay Estuary Program, slowdowns or declines in seagrass growth in some parts of the bay deserve further study.

The most recent monitoring data collected by the Southwest Florida Water Management District, for the years 1994-1996, indicates that seagrass recovery baywide continues at about 350-500 acres a year. But the regrowth is not consistent in all segments of the bay. For example, Middle Tampa Bay actually lost about 240 acres of seagrasses during that 2-year period, while Lower Tampa Bay gained an additional 240 acres of seagrasses. Old Tampa Bay also lost about 150 acres of seagrasses from 1994-1996.

While the overall gains still offset the losses, bay scientists are concerned about the disparity in seagrass recovery among bay segments -- especially given the fact that water quality is believed to be sufficient to allow seagrasses to recover in all areas of the bay. They will investigate other factors that may contributing to seagrass slowdowns or declines -- such as boat propeller scarring, changes in circulation patterns in the bay, and seagrass diseases -- in a special 3-day workshop slated for August (see related article).

Recommendations expected from that workshop may allow bay managers to modify a recently approved seagrass "early warning system" to take into account factors other than water quality which may impair seagrass growth, and adjust management strategies accordingly.

Members of the TBEP's Technical Advisory Committee (TAC) developed the “early warning system” as a way to determine when seagrass or water quality declines warrant additional management actions.

The system suggested by the TAC -- and adopted by TBEP's Management Board in February -- presents a graduated response to seagrass management based on changes in the relationships between three major variables: chlorophyll, light levels and seagrass acreage.

Chlorophyll is an indicator of the amount of algae in the water. Too much algae turns the water pea-green, preventing sunlight from penetrating to the bottom. Too little light restricts the growth of underwater seagrasses, just as it does for plants growing on land. TBEP has set numerical targets for both chlorophyll and light penetration based on scientific understanding of water quality conditions necessary to restore the amount of seagrasses that were present in the bay around 1950 -- some 12,000 acres more than currently exists.

Restoring seagrasses is a key goal of Charting The Course, the Comprehensive Conservation and Management Plan for Tampa Bay. Seagrass beds provide vital habitat for both juvenile and adult fish and invertebrates, filter pollutants from the water, and stabilize bottom sediments. From 1950 to 1984, more than 40 percent of the bay's seagrasses disappeared, although improvements in water quality since then have allowed about 5,000 acres to return.

The approach developed by the TAC establishes a "green, yellow and red" matrix to guide bay managers in ensuring that this comeback continues. For example, if the chlorophyll and light penetration targets are being met and seagrass acreage is expanding, the matrix is considered "green" and current management strategies are assumed to be adequate for achieving the 12,000-acre restoration goal.

If one of the targets is not being met (such as chlorophyll levels rising or light levels declining), a "yellow" caution warning is warranted, and bay managers may wish to conduct further research to determine the nature of the problem, or consider additional management strategies.

If two or all three targets aren’t being met, then a “red alert" is declared, calling for additional management actions to reverse the negative trend.