Tiny single-celled algae have begun to cast a huge pea-soup green shadow over the Indian River Lagoon, setting the stage for a repeat of the massive fish kill four years ago, when dead sea life fouled canals and choked the lagoon during a smelly summer of environmental chaos.
So far, the current green algae bloom covers parts of the northern lagoon and Banana River. What happens in coming weeks with temperature and rains will dictate whether the lagoon region relives the severe fish kills of 2016. Excess algae consume oxygen dissolved in the water, killing fish and other marine life.
The water management district is tracking the algae bloom and dissolved oxygen levels via sensors deployed throughout the lagoon, targeted samples of the algae, and ongoing sampling. Scientists also try to determine the extent of the bloom from satellite imagery when there are gaps in cloud cover and no glint from the water's surface.
"I'm really worried about where we're setting up right now," said Duane DeFreese, executive director of the Indian River Lagoon National Estuary Program. "It's like bowling balls coming at us ... There have been a few reported fish kills, but they've been small in size. We have been in a watch and wait."
The algae can block sunlight from seagrass — the most important plant habitat for fish. The cumulative nitrogen and phosphorus we contribute via leaky septic tanks, sewage spills, fertilizers and from tailpipes triggers the algae fallout. But wet weather can make it worse.
Biologists like DeFreese blame the current bloom on the dog days of summer, excess nitrogen from fertilizer, sewage and other sources, as well as a thick drift seaweed clumping up in the lagoon. The seaweed, called Caulerpa prolifera, dies and rots in the heat, unleashing massive amounts of nutrients for microscopic algae to feast upon.
"The bloom was likely (started) once the water was warm and rains were consistent, i.e., once summer came," said Chuck Jacoby, a scientist with the St. Johns River WaterManagement District.
The dominant algae in the current bloom is thought to be what's called "a green nanoplankter," Jacoby said. The algae cells are small (between 0.00008 and 0.0008 inches across), Jacoby added.
"There also are some cells of brown tide in the mix, but they are not dominant currently," he said. "We had been having patchy blooms dominated by diatoms and dinoflagellates up until about mid-August.”
Diatoms are common single-celled marine algae typically in the shape of fans, stars, ribbons, or zigzags. Dinoflagellates are an algae that uses a whip-like tail, called a flagellum, to propel through the water. One potentially toxic red-tide-like dinoflagellate has been thriving lately in the lagoon and causes the bright glowing bioluminescence when the water is stirred at night.
There were small fish kills in the region, but before the nanoplankton became dominant, Jacoby said. "Given their location, most fish kills were attributed to low dissolved oxygen concentrations in shallow water and canals."
= The Caulerpa seaweed, or drift algae, dies back after it reproduces and when the water is warm, Jacoby explained. "Along with persistent winds from one direction, both events could have led to macroalgae collecting in the shallows where bacterial decomposition would use up dissolved oxygen," he said. That's when fish and other marine life die.
"It's mainly the drift algae that causes a lot of the smell problems," DeFreese said. It's impractical to remove drift algae to eliminate excess nutrients from the lagoon, he added. "The problem is you can't get enough of it to make a difference." Brown tide has been known to become dominant following blooms of other species, so it will be tracked via sampling, water management district officials said.
Brown tide has devastated the lagoon ecosystem in the past several years, first blooming here in 2012 and then almost every year since then. The algae is so small that it would take 200 to stretch across the period at the end of this sentence. The same brown tide species hit Laguna Madre and Baffin Bay along Texas' Gulf Coast in the early 1990s, killing off seagrass for years. The bloom lasted almost eight years, making it the longest continuous harmful algae bloom ever recorded.
A similar brown tide species emerged in coastal waters off New England and New York in the mid-1980s, devastating scallops, clams and seagrass in Long Island's southern bays. Biologists aren't sure how brown tide got here, whether the species always resided in the lagoon or was introduced from the ballast water of a boat. But scientists at Stony Brook University linked brown tide blooms in the Long Island area to nutrients from septic tanks polluting the groundwater, then oozing up in the bays.
Although not toxic to humans, in some ways brown tide can be worse than toxic algae blooms, at least economically. It put countless scallop fishermen and clammers out of work in Long Island in the 1980s and has bloomed there almost every year since.
In March 2016, thousands of dead fish floated up throughout the lagoon after brown tide bloomed. Neither brown-tide algae nor the current bloom is considered toxic, and no fish consumption advisories or recreational advisories have been issued as a result of the current bloom.
DeFreese fears a repeat of 2016 is coming. "What we're seeing is that instability of the system in stress," DeFreese said.
While many point to septic tanks and sewage leaks as the catalyst of all the brown tide algae, those alone don’t completely explain the frequency and duration of the blooms, said Ed Phlips, a professor of algal physiology and ecology at University of Florida.
"There really isn't enough evidence to say septic tanks are the major driver of this," Phlips said. "It's no doubt contributing. I think people tend to focus on that. I think it's more complex than that. It's very hard to quantify septic tank inputs."
Brevard's not alone with its recent algae onset. According to a weekly Florida Department of Environmental Protection report for the week of Aug. 28 to Sept. 3, algae bloom conditions were seen by the samplers at six sites in Florida. Satellite imagery for Lake Okeechobee and the Caloosahatchee and St. Lucie estuaries from Sept. 2 showed about 65% coverage of low- to high-algae bloom potential on the lake. No bloom potential was observed on the visible portions of either estuary.
The lagoon's plight accelerated in 2009 and 2010, and the same drift algae was at play. While runoff often delivers the nitrogen and phosphorus that trigger algae blooms, drought preceded the massive lagoon microalgae blooms that began in late 2010 and a "superbloom" of algae that covered much of the lagoon in 2011. So the two nutrients may have originated from rotting muck on the bottom, the report says, possibly the product of drift algae killed by extreme cold in 2009 and 2010, biologists concluded.
Then 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, more than half the grass on the bottom in 2009.
In 2015, St. Johns River Water Management District scientist said drought, then extreme cold, set the stage for severe algae blooms that killed off 60 percent of the Indian River Lagoon's seagrass, according to a consortium of 26 scientists.
"I'm very concerned about where we are right now," DeFreese said. "But it's impossible to predict where we're going to go."
Article by Jim Waymer, environment reporter at FLORIDA TODAY.