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A new study shows the Piney Point spill likely made red tide worse

Dead fish and eels killed by a red tide happening in the Tampa Bay area collect in St. Petersburg.
Eric Higgs
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Tampa Bay Estuary Program
Dead fish and eels killed by a red tide happening in the Tampa Bay area collect in St. Petersburg.

A new study shows that the wastewater dumped into Tampa Bay last year from the Piney Point phosphate plant likely made the subsequent outbreak of red tide much worse. It says a year's worth of nutrients flowed into the bay in 10 days.

The study published in the journal Marine Pollution Bulletin shows that about 180 metric tons of nitrogen poured into the bay from a leak at the phosphate plant. Those nutrients fueled the growth of algae called cyanobacteria. It essentially "fed" red tide when it entered Tampa Bay from the Gulf several weeks later — killing millions of fish and marine life.

 Marcus Beck
LinkedIn profile
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Marcus Beck

"What we think happened is because the nutrients were around, it was available for the red tide," said Marcus Beck of the Tampa Bay Estuary Program, , the study's lead author. "It just created this set of conditions that prompted the growth of the red tide to levels that we hadn't really seen in the bay — in that part of the bay, specifically — since 1971."

Since Tampa Bay is considered a "closed system" with only one outlet into the Gulf of Mexico, he said that meant putting that much nitrogen into the system, it would fuel algae blooms.

"The level of red tide that we saw, the concentrations that we saw this year, that was very abnormal," Beck said, "and with Piney Point, it wasn't too much of a stretch to suggest that that was the causative factor that was likely stimulating the growth in the bay in July."

The state has approved a plan for the remaining water at Piney Point to be injected deep underground. But some fear a heavy hurricane season could cause the stack to overflow once again.

Highlights of the study:

  • 186 metric tons of total nitrogen from wastewater were added to Tampa Bay
  • An initial diatom bloom was observed near the release site
  • Filamentous cyanobacteria were observed at high biomass
  • Karenia brevis (red tide) was at high concentrations, co-occurring with fish kills
  • Seagrasses were unimpacted during the six-month study period
 Timeline of Piney Point spill aftermath
Courtesy Marine Pollution Bulletin
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Timeline of Piney Point spill aftermath

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