Now the mold is in the ocean

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6/25/99

Dangerous mold on the march in seagrass beds alarms researchers

By JAN HOLLINGSWORTH of The Tampa Tribune

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ST. PETERSBURG - Marine scientists go on alert when an unexpected - and

unwelcome - visitor turns up in local waters.

The seagrass beds off Fort DeSoto Park have caught a mold, and no one knows

quite what to make of it.

Scientists discovered the infectious disease - a slime mold suspected of

decimating seagrass beds near the Florida Keys - while testing a new

environmental monitoring program.

``We had never looked for it here before. It was really a surprise,'' said

Holly Greening, a senior scientist for the Tampa Bay Estuary Program.

The slime mold also turned up near the mouths of the Anclote and Homosassa

rivers.

But the area sampled in Tampa Bay east of Fort DeSoto had the highest rate

of infection on the Gulf Coast.

``So far we have very limited information. But what we have is telling us we

need to find out more,'' said Greening.

Biologists for the Florida Marine Research Institute in St. sburg have

spent the past four years studying the Labyrinthula organism in Florida Bay,

where it is a prime suspect in a massive seagrass die-off.

``It is transmitted by contact, one plant to another,'' said Bruce Ackerman,

a member of the institute's research team.

The Florida Bay die-offs began in 1987 when a lack of rain and the diversion

of fresh water from the Everglades raised salt levels in the bay.

Not everyone agrees on what caused the seagrass to die. But most believe the

high salt levels play some role, perhaps stressing the grass and making it

susceptible to disease.

Labyrinthula thrives in salty water, said Ackerman.

Much of Tampa Bay also has a high salt content, said Greening.

While 30 percent to 40 percent of Florida Bay's seagrass beds are infected,

the limited sampling in Tampa Bay revealed a startling infection rate of 80

percent to 90 percent.

``The question is, is that indicative of the rest of the bay?'' Greening

said.

Some strains of Labyrinthula are more aggressive than others, said Ackerman.

Its presence alone does not necessarily signal an imminent die-off.

The estuary program is expanding its monitoring to see how widespread the

infection is.

Then researchers will have to figure out what it means to the health of

Tampa Bay, which has been rebounding in recent years from decades of

pollution that killed off its seagrass.

The lush underwater meadows are vital nurseries for juvenile fish and

shellfish. They also filter out contaminants.

The seagrass in Tampa Bay has been expanding by an average of 350 acres a

year since 1982. The continued expansion would seem to suggest the slime

mold is not having an obvious effect, said Greening. But it is too early to

tell.

``This is an early warning for us and something we definitely need to follow

up on and are doing so,'' she said.

Read about environmental issues at www.tampatrib.com/news/enviro.htm