Jim Waymer

FLORIDA TODAY

Thousands of fish have died in the Indian River Lagoon in recent days in one of the area's most massive fish kills in recent memory. Here is what we know – and don't know – about what has happened.

Q: What happened?

A: Since Friday, thousands of fish encompassing 30 or more species have died in the Indian River Lagoon leaving fish carcasses from Titusville to Melbourne.

Q: What do biologists think caused it?

A: Several species of algae have been blooming in the lagoon since January, predominately a species called Aureoumbra lagunensis, also known as "brown tide." It's shown up in lagoon samples in 2005, but not at bloom levels until 2012. The algae cells are so tiny that it would take 200 of them to stretch across the period at the end of this sentence. The algae produce a mucus that clogs up oysters, clams and other shellfish, eventually killing them.

Volunteers scoop up Indian River Lagoon's rotting fish

Q: How does algae kill fish and other marine life?

A: 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.

As dense clusters of fish rot, bacteria increase, further consuming oxygen in the water.

The kinds of algae blooming now are not known to be toxic. But some kinds of algae can kill fish by releasing toxins into the water. Or the shape and amount of algae particles in the water can clog up fish gills.

Q: Why is the lagoon so unhealthy?

A:The problem has been brewing for years. Decades of pollution from septic tanks, fertilizers, stormwater runoff and other sources, coupled with a "perfect storm" of drought, followed by record cold in 2010, set the stage for harsh algae blooms in 2011.

A "superbloom" of green algae that year and subsequent brown algae blooms killed some 60 percent of the lagoon's seagrass, the barometer of the estuary's ecological health. Hundreds of manatees, dolphins and pelicans also died in the wake of the blooms.

Q: Did the large water releases from Lake Okeechobee cause the current bloom?

A: No. While those water releases cause blooms in the St. Lucie River and the southern Indian River Lagoon, most of that water exits inlets before it reaches Brevard's portion of the lagoon.

"It's not Lake Okeechobee, that's pretty much certain," said Ed Phlips, professor of algal physiology and ecology at the University of Florida. "Lake Okeechobee discharges more for the St. Lucie (River). That's a whole different ballgame down there."

Q: Will it get better or worse?

A: Usually algae blooms worsen in warming months, but the prognosis is uncertain and depends upon temperature, winds, rain and other weather factors. Cooler water holds more oxygen. Winds can aerate the water. But recent sampling of this brown tide show it may have already peaked in February and is gradually on the wane.

Phlips said: "As the water warms up and the bloom continues, we could see some more problems." Out in the more open water, even a small amount of wind can keep the water mixed and aerated, he added. But in isolated pockets, there is very little mixing. The concentrations of algae cells have been waning in recent samples, he said, but sometimes when a bloom crashes, "that's when you can have the most problems," he said, as bacteria decomposes the dead fish.

Local government to ramp up fish kill cleanup

Q: What's being done now?

A: The Legislature has allocated more than $72 million to Brevard County over the past three years, most of it for large-scale muck removal projects. There are two major muck-dredging projects going on right now to remove the nutrient-laden soils that have built up in the lagoon over decades.

The dredging is intended to remove nitrogen and phosphorus in the muck that fuels harmful algae blooms. The muck also stirs up, clouding the sunlight seagrass needs to grow.

County officials and the Brevard Zoo have been growing and placing oysters in the lagoon to filter-feed on algae and remove excess nitrogen from the water.

Q: What's muck?

A: Muck is rotted plant matter, clays and soils from construction sites. It has been likened to "black mayonnaise." It blocks sunlight to seagrass and contributes to bacterial decay, which consumes oxygen in the water, causing fish kills.

Q: Why not just open up Canaveral Lock?

A: It's been tried, and it didn't do much other than causing expensive dredging and repairs.

When Tropical Storm Fay caused severe flooding along the Banana River Lagoon in August 2008, the U.S. Army Corps of Engineers left the lock open and used it as a spillway to drain the lagoon. The lock was opened for at least a week, Corps officials said, which prevented millions of dollars’ worth of flooding damage to properties.

But when operators tried to close the lock gates after the storm, two sector gate couplings broke, because silt had built up in the gates recesses.

Recent research by the Florida Institute of Technology showed that simply keeping the lock open wouldn’t do much to improve the lagoon, but there may be other ways to improve the exchange of lagoon and ocean water near the port, or elsewhere. Specifically, small inlets or culverts along the most narrow strips of barrier island, coupled with a pumping station, could provide significant benefits, the FIT study found.

Local government to ramp up fish kill cleanup

In simulations, either a narrow tidal inlet or pumping station in the southern Mosquito Lagoon produced complete flushing of the Mosquito Lagoon and the northern Indian River Lagoon within about 70 days or less, the study found. A tidal inlet just north of Patrick Air Force Base also substantially improved flushing of the Banana River. But doubling Sebastian Inlet’s width did not noticeably improve flushing rates or extent.

Q: What else is government doing?

A: Several projects have been completed in recent months to reduce nitrogen and phosphorus flowing into the lagoon, according to the St. Johns River Water Management District, including the Wheeler Stormwater Park, C-1 flow restoration and Fellsmere Water Management Area. Future projects to help the lagoon include a C-10 Reservoir flow restoration from C-10 to Three Forks; repair and maintenance of U.S. Army Corps of Engineers structures, levees, and culverts; wetland restoration projects; and the dredging of Eau Gallie River.

Q: Is it safe to swim and for other recreation?

A: Yes, but don't touch the fish or enter the water with scratches or other open wounds. Your local health department can give advice about human health issues associated with algal blooms.

Q: Where can I learn more about health risks posed by algae blooms?

Q: Where can I learn more about the lagoon?

A: Visit http://floridaswater.com/indianriverlagoon/.

Q: How do I report a fish kill?

A: Report a fish kill to FWC's Fish Kill Hotline: 800-636-0511

Or report the fish kill online: http://myfwc.com/FishKill

Q: What can I do?

A: Beyond maintaining your septic tanks and reducing fertilizer use, here's just a few of the things what the city of Cocoa Beach suggests: