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Sewage dump may lead to algae blooms, fish kill, lost seagrass, experts say

Expect algae blooms. Seagrass die-off. Fish kills. Dead birds.

Those are some of the environmental consequences that could result from the tens of millions of gallons of sewage that has flowed into Tampa Bay over the past year, according to bay experts.

"The long-term effects, we will not know for several months," warned Holly Greening, executive director of the Tampa Bay Estuary Program, which has spent years leading the cleanup of the bay. "We are watching this very carefully."

Peter Clark of Tampa Bay Watch said he hasn't seen any effects yet, and long term the extent will depend on how the bay flushes itself into the Gulf.

The region's ongoing sewage crisis struck just as the waters of Tampa Bay had recovered after decades of waste had been dumped into it. As of last year, there were signs that the bay was the cleanest it had been in 60 years.

That's critical in a tourist-dominated economy. A healthy bay is estimated to generate $22 billion worth of economic activity and is linked to one in every five jobs.

But over the past year — particularly in the aftermath of Hurricane Hermine — the bay area's rain-soaked utilities spilled, leaked and dumped an estimated 253 million gallons of sewage into streets and waterways. Much of that ended up in Tampa Bay.

So much sewage can fuel the bloom of toxic algae in the bay — not necessarily Red Tide, Greening said, but perhaps another kind. Leaking septic tank waste has been partially blamed for fueling the toxic algae bloom off the state's Atlantic coast that laid atop the waves like a thick layer of guacamole. Such a bloom could lead to the death of seagrass beds and fish kills.

An El Niño-fueled cycle of storms in 1998 led to a similar problem with sewer discharges to the bay, she said. It happened in January and February, not in the depth of summer.

"We did see an impact on the bay," Greening said. "The water became a very, very dark color."

Because sunlight could not get through, 2,000 acres of seagrass were wiped out "and it took us four years to get it back," she said.

So far the most obvious potential impact of the current sewage spill is the die-off on St. Pete Beach of nearly 50 juvenile black skimmers, a type of sea bird. Those deaths have not yet been conclusively tied to the sewage being dumped into Boca Ciega Bay. State wildlife officials have sent samples to a Georgia laboratory for testing.

Other than that, the Florida Fish and Wildlife Research Institute in St. Petersburg "has not had any reports of fish kills and has not confirmed any impacts on wildlife," said state Fish and Wildlife Conservation Commission spokeswoman Susan Smith.

Hundreds of manatees live in Tampa Bay. But manatees tend to be pretty adaptable to poor conditions such as polluted water, said Pat Rose of the Save the Manatee Club. However, a loss of seagrass would rob them of their main source of food.

Elizabeth Forys, the Eckerd College biology professor who has spent years monitoring the skimmer population in Pinellas County, says the skimmers appeared to have died from salmonella spread by the fish they ate from Boca Ciega Bay.

"The way the chicks have died with convulsions and diarrhea and weight loss is also consistent with" that cause, she said.

Seabirds commonly contract salmonella-related illness when they feed on fish swimming amid untreated or partially treated sewage, she said.

The skimmer die-off may be only the start. She said the same illness may affect other types of birds, such as least terns, that feed exclusively on fish, "so the impact of these spills may go well beyond this one population and may have a broader impact in years to come."

Seeing young seabirds go into convulsions and keel over is the most dramatic effect the sewage is having on the natural environment. It's unlikely to be the only one.

The waste that's been pouring into the bay carries with it a steep increase in nitrogen, one of the main pollutants that the Tampa Bay Estuary Program has been working hard to eliminate since Congress created it in 1991. Nitrogen can spur the growth of algae blooms.

Tampa Bay is Florida's largest open-water estuary, covering about 398 square miles at high tide. It's important both for the bay area's environment and for its economy.

But in the 1950s and '60s, dredging created land for development around the bay but wiped out much of its seagrass, hurting commercial and recreational fishing. Polluted runoff and sewer plants that dumped untreated waste directly into the bay killed even more seagrass.

By the early '90s, the bay had lost 80 percent of its seagrass, more than anywhere else in Florida. But shutting down the routine flow of sewage into the bay and making other changes spearheaded by Greening's group turned that around.

By last year, Tampa Bay was supporting 40,295 acres of seagrass beds, the largest amount of seagrass measured since the 1950s. In other words, the bay's water was the cleanest it had been in six decades.

If not for that, Greening said, the sewage spills of this summer would be a greater disaster: "The bay may be quite a bit more resilient than it used to be."

Times staff writer Charlie Frago contributed to this report. Contact Craig Pittman at Follow @craigtimes.