Seagrasses are among the most important cornerstones of the bay ecosystem. An incredible variety of marine creatures - from the stately seahorse to the blue-eyed bay scallop to the portly manatee - find food, shelter or protection from predators within these dense underwater pastures. In fact, studies show that seagrass beds harbor 50 percent more fish and invertebrates than bare sand-bottom areas of the bay.

Seagrasses also anchor shifting sand and filter pollutants from the water, much as grasses help stabilize the soil on dry land.

Seagrasses are a barometer of the health of their environment, signaling changes in long-term water quality trends that alert scientists to potential problems.

For these reasons, bay managers have selected seagrasses as the yardstick by which efforts to protect and improve the bay will be measured.

Since the turn of the century, pollution and dredging have destroyed more than half of the bay's seagrass beds. But surveys have recorded some 2,000 acres of new or expanded seagrass beds in the bay since 1988, some in areas like Hillsborough Bay where they hadn't been seen for decades. This remarkable comeback is largely credited to improvements in sewage treatment that have reduced the amount of nitrogen flowing into the bay, since excess nitrogen causes algae blooms that cloud the water and keep sunlight from reaching the grasses. Advancements in stormwater treatment, and restrictions on dredging and filling activities, also have helped spark the seagrass revival.

Using computer models, scientists working with TBEP calculate that water quality in the bay is now good enough to allow the growth, over time, of as many as 12,000 acres of seagrass. By slightly reducing nitrogen loadings, even more seagrass gains could be achieved.

But seagrass recovery remains threatened by the increasing number of boaters plying Tampa Bay. Many of these boaters unwittingly pilot their boats into water too shallow for them to safely navigate, and their propellers carve damaging trenches through the seagrass meadows.

A recent study by the Florida Marine Research Institute (FMRI) found that almost 30 percent of the bay's seagrass meadows already have been moderately to heavily scarred by propellers - more than any other area in the state except the Florida Keys. On a more optimistic note, additional studies by FMRI have shown that those areas can gradually recover if they are not damaged further.

Since so many animals depend upon seagrasses for safety and sustenance, their loss reverberates throughout the bay system. Declines in spotted sea trout, bay scallops and shrimp are all linked to the loss of seagrasses. The future of the manatee also depends upon the survival of the seagrass beds in which they graze.

In some areas, communities have adopted boating restrictions to protect these vital grass beds. But all these efforts will be wasted unless we maintain the water quality necessary for the grasses to flourish.