After days spent on land refining a model for where millions of gallons of wastewater pumped from Piney Point to Tampa Bay could flow, Bob Weisberg wanted to see it for himself.
With a couple members from his lab last Thursday he set out on his sailboat, tacking across the bay to Port Manatee. The port is where, according to the Florida Department of Environmental Protection, about 215 million gallons of polluted water from Piney Point, high in nutrients like nitrogen, have been discharged to date.
“All of a sudden the water turned a really nasty brown,” Weisberg said, recalling his approach, about level with Bishop Harbor, just off the coast. “And it stayed that way all the way to the port. ... What we’re observing is quite consistent with what we’ve modeled.”
Weisberg’s Ocean Circulation Group at the University of South Florida, including graduate students and PhD associates, is forecasting where the waste could go each day. The model shows pollution slowly dissipating, with the highest nutrient load concentrated along lower Tampa Bay’s east coast.
The brown water near Port Manatee, Weisberg said, is evidence the discharge has already spurred plant growth.
“What those plants are, I don’t know,” he said. Other researchers from the university’s College of Marine Science are studying water quality and trying to understand the impact on the bay’s ecology.
“It’s a slow process. It’s going to be with us for a while,” said Weisberg, a physical oceanography professor.
The big fear for many is a bloom of Red Tide, which Weisberg has also studied. It is still too soon to say exactly what’s growing in the bay, he said, and whether the added nutrients will fuel a Red Tide. “The question is: How much Red Tide organism is already around and how quickly can that organism grow relative to everything else that is growing?” Weisberg said.
Harmful algal blooms can cause fish kills, scientists say. When algae dies and decays, oxygen levels in the water might drop. A dark plume of algae could also block sunshine before it reaches seagrass beds, which need light to grow and which serve as a food source for marine life such as manatees.
Ed Sherwood, director of the Tampa Bay Estuary Program, said very early evidence suggests what’s growing already could be a form of phytoplankton, or a microscopic marine organism, “which is considered a non-harmful algal bloom at this point.” The phytoplankton may still shade seagrasses if it lingers or lower oxygen when it decays if it drifts into backwater areas, he said.
The Department of Environmental Protection is monitoring water quality near the port; it has reported elevated levels of phosphorus near the discharge point. Sherwood said the Estuary Program’s main concern is forms of nitrogen, including ammonia. Some data, he said, have suggested higher ammonia concentrations immediately around Port Manatee.
Releases from the former Piney Point fertilizer plant property began after the site’s owner, HRK Holdings, reported a leak in a reservoir containing more than 450 million gallons of wastewater. State regulators allowed discharges to Tampa Bay through the port, fearing pressure from the leak would break apart a phosphogypsum stack around the pond and cause a devastating flood.
Phosphogypsum is a radioactive byproduct of the fertilizer industry. Manatee County officials temporarily ordered evacuations from more than 300 homes.
The Department of Environmental Protection said a dive team using a remote vehicle with a camera identified a separation in a seam in the reservoir’s plastic liner, which may have caused the leak. Over the weekend, the state said, the dive crew helped position a steel plate over the break.
Meanwhile, storms dumped heavy rain, the agency said, which added several million gallons to what is left in the pond. It held approximately 221 million gallons of water as of Sunday, according to the state. Discharges to the bay were halted late last week, and regulators say they want to treat the water to lower nutrient levels before releasing more.
The University of South Florida model has followed shifts in the Piney Point response, Weisberg said. It considers tides, winds, freshwater river flows and factors like momentum and salinity.
Weisberg’s lab publishes forecast graphics online that show a nutrient-rich plume of water swaying across the lower bay like a bassinet. Weisberg said the movement is in part reflective of tides, which “alone do very little flushing” but combine with winds and river flows to move water around the bay.
Eventually, he said, remnants of the wastewater will reach the Gulf of Mexico, diluting into even greater volumes of water. The bay is large, Weisberg said, but even a single release like the one from Piney Point can tweak a delicate chemical balance.
Charter captains worry about damage to valuable areas like Bishop Harbor and a snook spawning ground off the port. Weisberg said the model shows nutrients have likely already reached the harbor and Terra Ceia Bay, in at least low concentrations.
Capt. Chasten Whitfield, 21, who fishes out of Anna Maria Island, said she knows of a good spot to land snook and redfish near the port. She said the area has shallow grass flats where she remembers seeing plenty of birds diving and jumping fish, with boats predictably idling nearby.
“With the polluted water, that would change all of that,” Whitfield said. “This is our livelihood. This is what we do.”
Brian Rosegger, co-founder of Lost Coast Oyster Company, which farms oysters in Joe Bay a few miles south of Port Manatee, said he worries a Red Tide would close his harvest or news of the pollution alone could turn people off of eating shellfish from the region.
“With the amount of nutrient loading that has occurred, it’s almost impossible not to have a harmful algae bloom on the mind,” he said. “We’ve invested a lot of time and resources into making this work, and now this thing is entirely out of our hands. It’s something that we just kind of have to sit back and watch play out.”
Times staff writer Ashley Dye contributed to this report.