Credit: St. Johns River Water Management District
The Indian River Lagoon is under attack on northern and southern fronts.
Most Treasure Coast residents are aware billions of gallons of contaminated Lake Okeechobee water are being discharged into the St. Lucie River and the southern lagoon. The influx of freshwater into those estuaries from the lake and local runoff is killing oysters, and high levels of nitrogen and phosphorus in the water threaten to spur the growth of algae blooms that could kill sea grass.
In the northern lagoon, algae blooms are no threat: they’re a reality.
An algae bloom known as “brown tide” started showing up about six months ago in Brevard County’s Mosquito Lagoon, which is considered part of the 156-mile Indian River Lagoon system.
The bloom began as a mixture of several algae types, including brown tide. As it spread into the northern Indian River Lagoon about three months ago, the brown tide took over, said Charles Jacoby, supervising environmental scientist for the St. Johns River Water Management District, which includes Brevard and Indian River counties.
“In January, the brown tide started really taking off hot and heavy,” Jacoby said. It now can be found throughout the Banana River and in the northern Indian River Lagoon as far south as Melbourne.
Interestingly, the algae is starting to break up in the Mosquito Lagoon where it started.
“From Melbourne up to Cocoa, the lagoon water is horrendous,” said Jerry Pope, a commercial fisherman based in Indialantic. “It’s got a yellow-green look to it, and it smells. I grew up here, and I know the lagoon sometimes smells; but this is not a natural smell.”
The Treasure Coast section of the lagoon is less susceptible to brown tide, Barker said, “probably because the northern lagoon has no inlets and far less flushing with ocean water. I don’t think the brown tide will spread much farther south because the Sebastian Inlet is there to flush out the lagoon water.”
Dirty déjà vu
Brown tide is not new to the northern lagoon.
In 2011 and 2012, massive blooms covered the lagoon from Titusville to just north of Fort Pierce.
“We believe we’re seeing the same type of algae as in 2012: Aureoumbra lagunensis,” said Virginia Barker, Brevard County natural resources director.
The previous brown tides shaded and killed about 47,000 acres of sea grass. It’s hard to tell what effect the brown tide has had on sea grass in the lagoon.
“Sea grass naturally sheds leaves and recedes back to its roots in the winter,” Jacoby said.
The current bloom is not as dense as in 2012 but thick enough to block light and kill sea grass, Barker said.
“This should have been a big recovery year for sea grass in the northern lagoon,” Barker said, adding that about 10 percent of the grass lost in 2011 has grown back. “Now, that’s not going to happen. There probably will be further losses.”
The loss of sea grass can be devastating to the lagoon ecosystem. Lots of animals, including manatees, eat it. Lots of fish — including bonefish, snook, sea trout and red fish — spawn or live in sea grass beds.
Brown tide also kills shellfish such as oysters and scallops. Pope suspects it’s killing, or at least harming, fish as well.
Baitfish he’s caught in the Melbourne area since late January are missing scales or “look like they’ve been hit with a ball-peen hammer,” Pope said. “I’ve come across pods where, if I caught 200 to 300 in a cast net, there’d be so many messed up that I’d have to throw them all back. It wasn’t worth picking through them all to find the healthy ones.”
Some sea trout and redfish he’s caught “were really skinny. Their stomachs were caved in like they were starving, but there was plenty of baitfish around for them to eat.”
Small, scattered fish kills have been reported in the areas affected by the brown tide, Jacoby said, but mostly because of low oxygen levels in the tributaries emptying into the lagoon.
“It’s mostly small fish like anchovies and sardines and bottom-feeders that are dying,” Jacoby said. “It’s not like we’re losing large numbers of sea trout or other game fish.”
STEM THE TIDE
Scientists don’t know if the algae in brown tide always has been in the lagoon and only recently has started having massive blooms, or if it was recently introduced to the lagoon. It’s common on the Texas Gulf Coast, so it could have been brought in and released from the holds of boats that came to the lagoon from Texas.
Brown tide was first reported in the lagoon in 2005, Jacoby said.
“That doesn’t mean it wasn’t here before that,” he added. “It just means it’s not in our archives.”
Uncommonly heavy winter rains brought by the El Niño weather pattern are partly to blame for flushing excess nutrients into the lagoon for the brown tide to feed on. So is the release of so-called “legacy nutrients” from the muck at the bottom of the lagoon.
“What we need now is some cold, dry weather with no more rain,” Jacoby said. A lack of rain would keep the nutrients that feed the bloom from washing into the lagoon. Cold weather probably wouldn’t kill the bloom, but would keep the bloom from spreading.
But with the water temperature right now, Barker said, “the water should be gin-clear. But it’s not. You can’t see half an inch in that water. Whatever it is in the lagoon, the cold hasn’t killed it yet.”