Algae causes fish kill in Manatee River

Algae causes fish kill in Manatee River
Algae clogged up waterways in Robinson Preserve last week; Manatee County crews helped remove some of it. - Kristin Swain | Sun

BRADENTON – Blue-green algae persists in Robinson and Perico Preserves, and has caused its first fish kill.

“Blue-green algae and brown algae have become pervasive in the Lower Manatee River, Perico Bayou and Perico Preserve, resulting in a modest fish kill, primarily mullet, as a result of heavy algae bloom concentrations,” according to the latest report from the Manatee County Environmental Protection Department.

Manatee County crews skimmed and contained floating blue-green algae mats near Robinson Preserve’s waterway connection to the Manatee River and directed it back into the river on an outgoing tide, according to a recent email update to county commissioners from Charlie Hunsicker, director of the Manatee County Parks and Natural Resources department.

Algae causes fish kill in Manatee River
From left, Will Robinson, for whose family Robinson Preserve is named, Manatee County Commissioner Carol Whitmore and Congressional Rep. Vern Buchanan were among several officials at Robinson Preserve on Monday to see the algae bloom up close. Carol Whitmore | Submitted

“A floating turbidity boom, normally set in place to protect surface waters from turbidity and sedimentation, was deployed under the footbridge at that tidal connection to keep additional floating algae mats from coming back into the preserve on the incoming tides. This will not prevent all algae mats from entering the preserves from other Manatee River or Perico Bayou connection points, however, this will reduce the algae coverage in what the media has photographed to be the worst places where algae build-up has occurred,” according to Hunsicker.

“These efforts will have a positive effect on reducing the build-up of additional algae in the preserve and reduce, but not prevent, the accumulation of additional marine detritus which will continue to degrade at the bottom of many of Robinson’s internal waterways linked by tides to the outside bays and Manatee River,” according to Hunsicker.

Non-toxic algae blooms were detected in 18 water samples along the Manatee River in June, according to a Friday, June 28 Florida Department of Environmental Protection (DEP) report.

Parts of the river, and Robinson Preserve, which borders it to the south, are “experiencing a large bloom of the cyanobacteria species Aphanizomenon flos-aquae,” which so far has tested non-toxic, according to the report. No samples were taken off Anna Maria Island this week.

Red tide did not show up in any water samples in Manatee County last week, according to the Friday, June 28 Florida Fish and Wildlife Conservation Commission (FWC) report.

Filamentous cyanobacteria (Lyngbya-like) was first detected in Holmes Beach waters on Thursday, May 9 in Anna Maria Sound at Key Royale and in the Intracoastal Waterway south of Grassy Point, and in Palma Sola Bay near San Remo Shores.

The algae found in Manatee County waters are not the same species that has plagued Lake Okeechobee, the toxic Microcystis aeruginosa, according to DEP.

Blue-green algae can be blue, green, brown or red and emit a foul, rotten egg odor caused by the production of hydrogen sulfide gas, according to DEP, which advises staying out of water where algae are visible as specks, mats or water is discolored pea-green, blue-green or brownish-red. Additionally, pets or livestock should not come into contact with the algal bloom-impacted water, or the algal bloom material or fish on the shoreline.

Even non-toxic blooms can harm the environment by depleting oxygen levels in the water column and reducing the amount of light that reaches submerged plants, according to DEP.

The growth of blue-green algae typically increases in the spring and summer months when water temperatures and daylight hours increase.

To help keep algae growth at bay, Florida law bans the use of phosphorus and nitrogen fertilizers during the rainy season, June 1 through Sept. 30.

Report algae blooms to DEP at 855-305-3903. Report fish kills to FWC at 800-636-0511.