November 8, 2017
Algal blooms return to Florida Bay
By Chuck Wickenhofer
FLORIDA BAY — Algal blooms,
which kill fish, suffocate seagrass and make life harder for those who rely on
the Everglades estuary for their livelihoods, have surfaced again this year.
Bob Johnson, director of the National Park Service’s South Florida
Natural Resources Center, says that large areas of Florida Bay are beset by
blooms, which is not surprising after Hurricane Irma and more recent weather
events churned up the nutrient-rich bay bottom, one of many likely contributors
to the problem.
Pete Frezza, a local fishing guide and research manager for
Audubon’s Everglades Science Center, says he’s noticed algal blooms in
different areas of the bay.
“It’s gotten pretty bad,” Frezza said. “There is very little water
in the bay now that doesn’t have some type of bloom. The only place that looks
fine is the areas where there are strong Atlantic tides near the Keys.”
Frezza points to dead seagrass as one possible culprit, as it
releases nutrients that feed algae when it decays. About 22,000 acres of
seagrass meadows died after a drought in 2015, which likely helped feed algal
blooms that appeared shortly thereafter.
“We had a massive amount of floating seagrass come into Florida
Bay from the Gulf of Mexico during Irma,” Frezza said. “A lot of that grass
most likely sunk into the bay, and when that plant matter breaks down, that’s
another release of nutrients.”
Another potential source of nutrients is freshwater flow from the
Everglades via central Florida, namely Lake Okeechobee. Frezza says that while
Florida Bay relies on freshwater flow, much of what comes into the bay now is
nutrient-laden and carries pollutants.
“More freshwater flow is something we want, but this water is
moving through agricultural areas (and) urbanized areas where there are high
concentrations of nutrients,” Frezza said. “We have a lot of water moving into
the bay with elevated nitrogen and phosphorus levels, which can spur the growth
of these blooms.”
A reservoir to be built south of Lake Okeechobee, which would
store and filter water before it flows south, is in the works, and Frezza says
the reservoir could be a significant factor in preventing future algal blooms.
“I imagine (the reservoir) would have helped the situation,
absolutely,” Frezza said. “That reservoir will allow for a timely distribution
of water, as well. That certainly could help.”
Steve Davis, an Everglades Foundation ecologist, is less sure that
runoff is contributing to the algal bloom this year. He points to dead seagrass
and an intense rainy season as likely factors in the most recent algae threat.
“It’s not any upland source of pollutants,” Davis said. “It’s not
freshwater inflow that’s a bad thing, it’s just that we’ve got all this dead
grass out there. Once the (nutrients) are released into the water, algae is
much faster growing and more adept at taking up nutrients than seagrass, which
has to grow roots and become stable and needs lots of light.”
Drought, which killed off so much seagrass in 2015, is not an
issue this year, as rain has reduced salinity levels in Florida Bay
significantly, according to Davis. Though the threat of drought killing off
seagrass is not currently an issue, past die-offs still potentially haunt the
bay when it comes to the formation of algae.
Another factor is that while many believe that Irma actually
flushed out the bay, it also blew seagrass and other nutrient-rich plant
material into it, which has created conditions which can allow algae to
“We saw this type of phenomenon with Wilma and in previous storms.
Lots of grass and mangrove leaves get moved around and deposited,” Davis said.
“We can’t discount the contribution of that (seagrass die-off) to what we’re
seeing today in terms of having a compromised Florida Bay.”
National Park Service testing of chlorophyll-A levels, which
indicate the presence of algae and cyanobacteria, are sky-high in some parts of
Florida Bay, according to Johnson.
“Our last measurement post-Irma (indicates) that we have very high
levels of chlorophyll-A in the water column,” Johnson said. “The (Florida
Department of Environmental Protection) standard for central Florida Bay is
about 2.2 micrograms per liter. We’re up to about 30 to 40 in that part of the
Other areas of the bay measure at as much as 200 micrograms per
liter, according to Johnson, meaning that it’s all but certain that a major
algal bloom event is not only happening now, but is likely to persist for some
“Some of this is expected, but the problem is that it’s happening
right after the prior seagrass die-off and algal bloom. That’s why it’s likely
going to persist longer than we’d normally see,” Johnson said, adding that the
current bloom could last “for six months or so.”
Davis says it’s tough to pin down one factor that may be causing
the current bloom among sediment disruption, the release of nutrients from dead
seagrass and other foliage, and other possible contributors.
“If the seagrass beds were healthy and intact, it may not have
been so bad,” Davis said. “I can’t say that without a controlled experiment,
and when you’re working with Mother Nature it’s hard to have a controlled
experiment of this scale.”
Paul Tejera, a local fishing guide who recently ran a backcountry
tournament to benefit guides, told the Free Press that the fishing in that
tournament and in his experience so far this year has been “very good,”
indicating that the nascent bloom may not yet be affecting fish and other
That’s welcome news for the many industries that rely on a healthy
fish stock to survive, though if an algal bloom is indeed taking hold in
Florida Bay, those conditions could rapidly change.
As scientists and others continue to monitor the situation, Frezza
says those who haven’t ventured out into Florida Bay much past the coastline
may not have noticed much change yet, though he says some in Key Largo are
already complaining about the quality of the water.
“It’s all in their backyards in Key Largo, but it’s not as bad
there as it is in the central bay,” Frezza said. “I don’t think people realize
how much worse it looks.”
For him and everyone else who is concerned with the health of
Florida Bay, another widespread bloom would hardly be a surprise, as Frezza
says they happen now with disturbing regularity.
“It’s large in extent. This is not unprecedented, though,” Frezza
said. “To have a (bloom) this big is a little odd, but algal blooms are common