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Indian River Lagoon saw 'fairly extensive' fish kills this year

This image from 2011 shows discolored water from algae blooms that contributed to fish kills in the Indian River Lagoon.
Florida Fish and Wildlife Conservation Commission (FWC)
This image from 2011 shows discolored water from algae blooms that contributed to fish kills in the Indian River Lagoon.

The Indian River Lagoon’s algae bloom this year extended farther south into the lagoon than normal, coinciding with fairly extensive fish kills, according to the state’s Harmful Algal Blooms Task Force.

Harmful algal blooms, or HABs, form in waterways when large, highly-concentrated amounts of algae grow rapidly and release toxins, according to the National Ocean Service. An algae species called karenia brevis — also known as “red tide” — is usually responsible for forming HABs in Florida’s saltwater habitats, according to the state’s Fish and Wildlife Conservation Commission (FWC).

FWC’s Fish and Wildlife Research Institute appoints members of the HAB Task Force, which meets periodically throughout the year to determine strategies to research, monitor and mitigate HABs like red tide.

Director of FWC’s Center for Red Tide Research Kate Hubbard heads up the task force. At Tuesday’s meeting, she identified the Indian River Lagoon as one area of concern this year.

“We do have a bloom there [in the Indian River Lagoon] every year,” Hubbard said. “But this year, the bloom extended further south, into the central lagoon, and it co-occurred with fish kills, fairly extensive fish kills.”

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This year’s fish kills were linked to the lagoon’s low levels of dissolved oxygen, Hubbard said.

Dissolved oxygen in the water is what fish rely on to “breathe,” and without enough, they suffocate, according to FWC.

Excess nutrients like nitrogen and phosphate can exacerbate the problem by spawning more algae to rapidly grow. As that algae decomposes, it can reduce the water’s oxygen levels enough to suffocate fish, according to Florida’s Department of Environmental Protection.

The warmer water becomes, the less dissolved oxygen it’s able to hold, according to the U.S. Environmental Protection Agency (EPA). This summer, NOAA said high ocean temperatures created “unprecedented heat stress conditions” in the Caribbean Basin, including in the waters surrounding Florida.

For Brevard Indian River Lagoon Coalition chairman Craig Wallace, that tracks.

“This year? It was hotter than hell,” Wallace said. “The canal in my backyard is a major canal; it’s like, 12 feet deep. And I was getting readings of 90 degrees, in the water, for at least a month period of time this summer. I have not seen that before.”

There was no observable "red tide" in any of the most recent samples collected by FWC's Fish and Wildlife Research Institute, which tracks concentrations of the organism formally defined as <i>Karenia brevis.</i>
Florida Fish and Wildlife Conservation Commission
There was no observable "red tide" in any of the most recent samples collected by FWC's Fish and Wildlife Research Institute, which tracks concentrations of the organism formally defined as Karenia brevis.

Wallace says his coalition formed in response to Brevard County’s massive fish kill in 2016, the same year county residents voted to pass a half-cent sales tax to fund water quality enhancement projects for the Indian River Lagoon.

Today, the county’s Save Our Indian River Lagoon program oversees those projects, sharing progress at monthly Citizen Oversight Committee meetings, which Wallace and other coalition members also participate in. The county's algae bloom mapping tool uses satellite imaging to track blooms in the Indian River Lagoon.

Wallace said he encourages Floridians and especially Florida newcomers to be conservative when using lawn fertilizer, because it often contains nitrogen and other nutrients that can reduce water quality.

“The amount of fertilizer that gets applied to lawns in Florida is just ridiculous,” Wallace said. “That’s what kills. That’s the source of a lot of the algae.”

UF/IFAS Extension’s Florida-Friendly Landscaping Program provides some resources for state residents, including tips for how to fertilize responsibly, reduce stormwater runoff and select plants native to their area.

Copyright 2023 WMFE.

Molly Duerig
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