Thousands of dead rays, shrimp, fish wash up in Florida, drawing memories of 2016 'fish-pocalypse'

BREVARD COUNTY, Fla. – The ecological stage seems set along similar plot lines: Too much errant sewage and fertilizer feeds algae that die, rot, and then the bacterial fallout robs fish of oxygen.

So when thousands of dead fish lined stretches of Florida's Indian River Lagoon this week, many feared a repeat of 2016's "fish-apocalypse" when tons of carcasses of sea life fouled waterways on the Atlantic side of the state, from Titusville to Melbourne.

This week, thousands of dead rays, skates, shrimp, pinfish, trout, whiting, croakers, saltwater catfish and juvenile flounder speckled shorelines from Titusville to Cocoa. 

For months, biologists had been discussing – and fearing – that the lagoon's ongoing algae blooms would eventually kill marine life and seagrass en masse. Ongoing warmer-than-usual temperatures worsened the situation.

But biologists say this latest die-off is nowhere near the levels of dead fish the 156-mile lagoon region saw in 2016. In the short term, they say, this week's cold, windy weather should stir up enough oxygen in the water to bring some temporary relief for fish and the coastal dwellers who must bear the odor of their collective demise.

"The scope of this is not near the scope of the 2016 fish kill, so we're probably looking at thousands of fish," said Duane DeFreese, executive director of the Indian River Lagoon National Estuary Program. "This should sort of shock that bloom a little bit with these colder temperatures."

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Short term relief on the way, but issue remains 'a long-haul situation'

In the long run, an ongoing La Niña climate cycle should ring in a dry winter with less runoff to trigger excess algae. But after that – as an estuary under decades of duress sputters between collapse and recovery – the lagoon's biggest advocates lament each algae onslaught and ensuing fish kill. Each one cuts into years of progress to clean up the estuary before it's too far gone.

"It's almost feels as though we're watching the end of what was a great thing," said Alex Gorichky, a fishing charter captain in Brevard County. "We've kind of lost that 'world-class fishing' moniker."

The St. Johns River Water Management District plans to have results from tests for algae toxins by the end of this week, said Teresa Monson, a spokeswoman with the district. University of Florida biologists also soon will be taking samples to identify specific phytoplankton species involved in the bloom.

The suspected culprit behind the fish kill so far, according to DeFreese, is a type of a marine cyanobacteria, a microscopic algae that is always in the lagoon but not at the levels seen recently.

 "It's not a species we've seen bloom before," DeFreese said, adding that it's not known to be toxic. But the bloom, he noted, is already starting to collapse.

 "I think we've gotten a bit of a short term reprieve with this cold and these winds," DeFreese said.

Gorichky, the charter boat captain, is worried but not willing to write the lagoon's obituary just yet, or relinquish it's unofficial status as a global red fishing mecca. That said, he worries about lagoon-side communities losing focus on the estuary's recovery, as each new fish kill dulls chances and hopes of ecological recovery.

"It's a long-haul situation," Gorichky said. "It's going to be a long road to see any recovery."

While the current kill pales in comparison to 2016, DeFreese says he's still very concerned because the conditions are lining up somewhat similar to 2015 and 2016, with lots of late-season rain pushing polluted runoff into the estuary.

"This season, we are no question wetter than we are supposed to be this time of the year," DeFreese said. 

On Nov. 12, the National Oceanic and Atmospheric Administration's El Niño forecast projected a greater than 95% chance that La Niña conditions will last through the winter, meaning drier months ahead, reducing the runoff that fuels algae growth.

According to NOAA, La Niña winters tend to favor warm and dry conditions in the southern tier of the United States and snowier-than-average conditions across much of the northern U.S. 

The Florida Fish and Wildlife Conservation Commission (FWC) maintains a "fish-kill hotline."

Overall, FWC’s Fish and Wildlife Health staff received 69 calls and online reports "allowing them to document the size and duration of this extensive event, coordinate a response, and disseminate information about the cause of the fish kill," Kelly Richmond, an FWC spokeswoman, said via email.

How fish die-offs happen

Fish die-offs in the lagoon tend to happen more often during warm summer months, when algae blooms are more frequent and more severe.

During daylight, algae produce oxygen through photosynthesis, replenishing oxygen levels in the water. But at night, the algae consume oxygen. This, coupled with the normal demand for oxygen from fish, crabs and other marine life can cause dips in dissolved oxygen in the lagoon, with the lowest levels just before dawn.

When dense clusters of fish die and rot, bacteria increase, further diminishing the available oxygen in the water.

Winds help aerate the water, but stagnant days pose more of a threat.

Two phytoplankton blooms devastated the lagoon's seagrass in 2011, followed by two years of brown algae blooms, ultimately killing 47,000 acres of seagrass.

A major "superbloom" of green and blue-green algae was first seen in Banana River Lagoon in March 2011. Within a month or two, the bloom spread westward through the Barge Canal and into the northern lagoon near Cocoa, then northward through Haulover Canal and into southern Mosquito Lagoon. Ultimately, the bloom covered 132,500 acres.

The superbloom was preceded and accompanied by a less intense bloom that began in late 2010 and eventually covered 47,500 acres (74 square miles) from southern Banana River Lagoon to just north of Fort Pierce Inlet.

Follow reporter Jim Waymer on Twitter: @JWayEnviro

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