Tampa Bay algae blooms could be fed by Piney Point wastewater

Even though recent water quality tests have not been detecting nutrients of the Piney Point wastewater spill, researchers believe current red tide and cyanobacteria blooms across Tampa Bay are likely being exacerbated by the nutrients which still exist in the bay's ecosystems.

Tampa Bay is experiencing multiple algae blooms. Toxic red tide has made its way north to the Pinellas County coast from Collier County and around Port Manatee. But there are also Lyngbya-like cyanobacteria blooms, which are stringy green mats floating in Joe Bay, Anna Maria Sound, and just north of Port Manatee — near where more than 200 million gallons of nutrient-rich wastewater was dumped from the Piney Point phosphate plant back in March.

Scientists think nutrients, such as nitrogen, from that spill are feeding both types of algae blooms, although results are pending to scientifically confirm this.

When water quality tests stopped measuring nutrients in the water, people began assuming they had just dissipated and were gone. But that’s not the case, said Maya Burke, with the Tampa Bay Estuary Program.

“Helping people understand this issue of nutrient cycling and how the nitrogen gets transferred from organism to organism and kind of stays within the system is something that I think is really important for the public to understand,” she said.

The Tampa Bay Estuary Program is part of a large effort to monitor the bay's water quality, including multiple government entities, private sector partners, and universities.

WUSF's Jessica Meszaros spoke to Burke about the current state of nutrients and algae in Tampa Bay:

Based on the status reports, it looks like concentrations of the red tide organism Karenia brevis appear to be higher around Port Manatee. Could that be caused by lingering nutrients from the Piney Point discharges?

That's what we think is going on for certain. I mean, I don't think it's a coincidence that you're seeing these algae blooms in the vicinity of the place where we discharged more than 200 tons of nitrogen over the period of 10 days.

That's not to say it's the only thing that's going on, though. I mean, we know Karenia brevis was in the Gulf of Mexico beforehand, and it had been systematically making its way northward, so it's about sort of how that species was interacting with the nutrients. Once it did get in here through these larger oceanographic phenomena, like currents, wind, tides, those sorts of things.

And same with the Lyngbya-like blooms that we're seeing. Those were documented in Manatee County a month before the spill, so they were there already. But are they worse now? Maybe. that's why we're monitoring.

Red tide seemed to flow into the mouth of Tampa Bay along the same lines as the Piney Point discharges flowed out. Could that just be a coincidence, or is there a connection?

That makes sense that that's where we're seeing things because we wouldn't necessarily otherwise be measuring up in the bay like that until you started to get things like a fish kill.

Some of the spatial distribution of the monitoring is an artifact of the monitoring that we're doing for Piney Point. So, there is that kind of thing that is perhaps coincidental, but we don't always see Karenia make its way up into the bay. Sometimes it stays more along the barrier islands in the intercoastal waterways, and sometimes it makes its way up there.

Like I said, there's a few things that are going on: the fact that the bay was really salty because it was so dry made it more hospitable. And so, Karenia is more likely to come inward in those kinds of instances. But once we saw it come inward, it didn't come in at medium concentrations, right? It came in, and we were getting those low to very low hits. Once it's interacting with the nutrients that are in that vicinity of the spill, that's when we started to see the intensification towards those medium levels, which is a bloom threshold. And that's when you start to get things like the fish kills that we're reporting now.