How to Check and Report Algae Blooms and Fish Kills near Sebastian

Around Sebastian, fish kills go to the FWC Fish Kill Hotline, algal blooms go to the Florida Department of Environmental Protection, and red tide conditions are posted by FWC on Friday afternoons.

Each agency covers one piece of the problem, so the right call depends on what is seen on the Indian River Lagoon or the beach at Sebastian Inlet. The state's Protecting Florida Together site, a partnership of FWC, the Florida Department of Environmental Protection and the Florida Department of Health, lists the contacts that apply in Sebastian, and the county health office comes from the Florida Department of Health in Indian River County.

Last verified: October 14, 2026, on the FWC, Florida DEP and City of Sebastian websites.

A fish kill near Sebastian is reported to the FWC Fish Kill Hotline by calling 1-800-636-0511 or by filing the online fish kill report.

The FWC Fish Kill Hotline page asks for three things: the location of the event, ideally the nearest street address or GPS coordinates; the number of fish involved and their species if they can be identified; and a phone number or email address so biologists can follow up or send an update on the report. The same line takes reports of diseased fish, fish with other abnormalities and discolored water, so a strange patch of water off the Sebastian riverfront can be reported before any fish die.

The hotline is a citizen science project that started in 1995 and has received over 40,000 reports, and about 2,000 people submit reports of fish kills and disease each year. Reports from Sebastian, like those from anywhere in the state, go to biologists in FWC's Fish and Wildlife Health lab, who use them to spot fish disease outbreaks and harmful algal blooms such as red tide, learn the causes and patterns of kills, and coordinate a response with partner agencies across Florida.

Reporting and cleanup are separate jobs. The Indian River Lagoon National Estuary Program's One Lagoon fish kill page states that the hotline is for reporting only and that local municipalities remove dead fish, so dead fish piling up on a Sebastian shoreline are a matter for local government. Injured or dead manatees and sea turtles in the lagoon go to FWC's Wildlife Alert Hotline at 888-404-3922 instead.

An algal bloom in the Indian River Lagoon near Sebastian is reported to the Florida Department of Environmental Protection online at ReportAlgalBloom.com or toll free at 855-305-3903.

The state's blue-green algae page says DEP staff review submitted reports daily and then prioritize site visits to sample the reported blooms, and that DEP, the water management districts and FWC also collect samples when they find blooms during routine monitoring. DEP responds to algal blooms in public lakes, rivers, streams and estuaries, the categories that cover the lagoon and the St. Sebastian River. In public fresh waterbodies the site visits and sampling can be done by DEP, a water management district or trained county and city staff.

Sampling teams enter each site visit in real time, recording the location, the bloom conditions seen and whether toxins were detected, and the results appear on the statewide water quality map. The Florida Department of Health is the lead agency for public health notices: based on the results, it may advise a county health department, here the Florida Department of Health in Indian River County, to issue either a caution notice or a health alert.

A practical tip for Sebastian households: the Protecting Florida Together notification system lets subscribers sign up for customizable email and text alerts about blue-green algae, red tide and other water quality updates, so a new notice for the Indian River Lagoon arrives without checking the map each day. The online report form is open around the clock, while the phone line is listed for weekdays from 8 a.m. to 5 p.m.

FWC posts the statewide red tide status on Friday afternoons, and its October 9, 2026 update found that Karenia brevis was not observed along the Florida East Coast, the stretch that includes Sebastian Inlet.

The FWC red tide current status page also carries a daily sample map with the last eight days of sampling, updated each day at 5 p.m., and FWC adds information on Wednesday afternoons when it has any. The October 9 report listed no fish kills suspected to be related to red tide and no respiratory irritation suspected to be related to red tide over the past week, and set the next report for Friday, October 16. A recording of statewide conditions is available at any time at 866-300-9399, and email notices of each update are offered through FWC's subscription area. For Sebastian Inlet State Park and Wabasso Beach Park, the East Coast paragraph of the Friday report is the one to read.

FWC grades every sample against a fixed key, so a level named in a report for the Sebastian Inlet area translates directly into possible effects:

Red tide reaches the Sebastian coast less often than the Gulf coast. FWC says Karenia brevis is found year round at background concentrations of 1,000 cells per liter or less, that its blooms are most common off the central and southwestern coasts of Florida between Clearwater and Sanibel Island, and that blooms are less common but do occur along the southeastern Atlantic coast as far north as North Carolina. Most blooms last three to five months.

The state advises that people and animals not drink or swim in any water with a blue-green algae bloom, the lagoon at Sebastian included, and the Department of Health advises not touching, collecting or eating dead or dying fish.

For anyone on the Indian River Lagoon at Sebastian, the state blue-green algae guidance explains that there are no visual signs that show when blue-green algae are producing toxins, that most problems occur when water with high toxin levels is swallowed, and that direct contact or breathing airborne droplets while swimming or showering can irritate the skin, eyes, nose and throat. Children, the elderly and people who are immunocompromised may still be at risk at low concentrations and should avoid any exposure. The state's educational sign also warns that the toxins can be harmful to humans and pets.

Red tide works differently. FWC says Karenia brevis produces brevetoxins capable of killing fish, birds and other marine animals; in people they can cause respiratory irritation when wave action breaks open cells and the toxins become airborne, and people who eat contaminated shellfish can suffer Neurotoxic Shellfish Poisoning. That is why the Friday report tracks respiratory irritation as well as fish kills, a line worth reading before a beach day at Sebastian Inlet State Park.

Brown tide in the Indian River Lagoon is a third case: FWC says brown tide organisms are nontoxic with no known human health concerns, though shellfish and fish kills can occur during blooms, and it relays Department of Health advice that fish or wildlife found dead or dying not be touched, collected or eaten. Anyone in Sebastian who feels ill after contact with bloom water should contact a healthcare provider or Florida Poison Control Centers at 800-222-1222, and call 911 in a medical emergency (Protecting Florida Together).

FWC records a long Pedinophyceae bloom that clouded the Indian River Lagoon from March 2011 to as late as March 2012 and a 2012 brown tide in the northern Indian River Lagoon, and the Sebastian Inlet District tracks the seagrass recovery since.

On its brown tide history page, FWC says FWC, the St. Johns River Water Management District and the University of Florida analyzed water samples from the northern Indian River Lagoon and identified a bloom of the brown tide alga Aureoumbra lagunensis, the first time FWC had documented a bloom of that alga in state waters. Brown tides can cut water transparency to less than a foot, limiting the light that reaches seagrass, and in parts of the Indian River Lagoon the brown tide occurred alongside a bloom of Pyrodinium bahamense, which can also discolor water and reduce visibility.

The Sebastian Inlet District 2024 seagrass report puts pre-2011 seagrass coverage on the inlet's monitored shoals at about 110 to 115 acres and notes that the west side of the Zone A shoal suffered significant erosion and was largely barren after 2011. In 2024 the six monitored shoals held 115.38 acres, about 1.4 percent or 1.64 acres less than the 117.02 acres mapped in 2022, and the biologist who leads the monitoring describes a general upward trend at Sebastian Inlet since the 2011 bloom.

Two cautions apply to those numbers. They describe conditions as of the 2024 survey, so they say nothing about the lagoon at Sebastian today. And there is no 2023 figure at all: persistent poor water clarity and unsuitable weather kept GPI Geospatial, Inc. from capturing aerial images good enough for an acreage estimate, which means cloudy water near Sebastian Inlet can block the very survey that tracks seagrass recovery.

Large algal blooms are the most common trigger of Indian River Lagoon fish kills, because the decay of a dying bloom uses up the dissolved oxygen that fish need.

The One Lagoon fish kill page puts the line at about 5 milligrams of oxygen per liter for normal function, with organisms under stress between 3 and 5 and many species unable to survive below that; crabs, shrimp and shellfish die in the same conditions. Warm water holds less oxygen than cool water, calm weather limits the mixing that puts oxygen back, and decaying muck draws oxygen down near the bottom. Most kills in the Indian River Lagoon are small and local, but when a bloom collapses across miles of lagoon, low oxygen water spreads faster than fish can escape, and in northern stretches far from an inlet the water can linger as long as a year.

Nutrients set the stage. One Lagoon explains that algae feed on nitrogen and phosphorus in the Indian River Lagoon much as landscape plants take up fertilizer, and that harmful algal blooms bring seagrass loss, low oxygen and deaths of fish and wildlife. The One Lagoon fish kill page gives a short prevention list for lagoon households: fertilize according to local ordinances or skip fertilizer, keep grass clippings and leaves out of storm drains, and maintain a septic system or connect to a sewer where one is available.

In Sebastian the local rule is a summer blackout. A City of Sebastian fertilizer guide states that fertilizer use is banned between June 1 and September 30 under Ordinance O-14-02. During those months the ban covers fertilizer products containing nitrogen or phosphorus, synthetic or organic, along with high nitrogen liquids such as fish emulsion and manure based teas, and applying fertilizer within 10 feet of a waterbody is banned year round. The blackout applies to turf and in-ground landscapes in Sebastian, not to potted plants, container gardens or houseplants, which may be fertilized during the blackout as long as runoff is prevented.