The Indian River Lagoon at Melbourne: the 2011 blooms and after

The Indian River at Melbourne is part of a 156-mile estuary that Florida Atlantic University’s Harbor Branch Oceanographic Institute notes has been cited as among the most biologically diverse in North America. In 2011 it had the worst algal blooms on record, and the dividing line between the two that year ran through Eau Gallie, at Melbourne’s northern edge.

Two blooms, split at Eau Gallie

The St. Johns River Water Management District, which investigated the 2011 event, found two blooms running at the same time from early spring to late fall.

North of Eau Gallie was the one its scientists called the superbloom. It covered about 53,000 hectares of the northern Indian River (from Eau Gallie up to the Turnbull and Scottsmoor area), the Banana River Lagoon and the southern Mosquito Lagoon. Its chlorophyll readings, the standard measure of how much algae is in the water, often went above 100 micrograms per liter, more than any bloom documented before. It was dominated by tiny cyanobacteria and a flagellate alga of the class Pedinophyceae that, when the district wrote its plan in 2012, had not yet been identified.

South of Eau Gallie, the district recorded a lesser bloom covering about 19,000 hectares of the central lagoon, from Eau Gallie to around Vero Beach and Fort Pierce. It was moderately intense, with chlorophyll often between 20 and 30 micrograms per liter. In the Melbourne reach it was dominated by cyanobacteria, followed by diatoms and dinoflagellates; farther south, in the Sebastian and Vero reaches, diatoms and dinoflagellates shared dominance.

The seagrass

The blooms blocked the light the seagrass needed. By the end of June 2011, the district found, grassbeds in the Banana River Lagoon and the northern and central Indian River together had shrunk about 45 percent from the summer before, roughly 31,600 acres of the 70,230 acres mapped in 2009. Because the superbloom went on for seven months, it warned, the full loss for the year may have been greater. Seatrout and other fish that depend on seagrass were the economic worry.

After 2011

The lagoon did not recover quickly. Brevard County’s records list brown tides in 2012, 2013 and 2015 and unusual mortality events for dolphins, manatees and pelicans. From January through March 2016, county residents “endured the most extensive and intensive algal bloom ever recorded in the Indian River system during winter to spring months,” and its collapse in March caused “one of the most extensive fish kills ever recorded in the county.”

The seagrass losses eventually starved the manatees. The Florida Fish and Wildlife Conservation Commission recorded an Unusual Mortality Event on the Atlantic coast from December 1, 2020, to April 30, 2022, with 1,255 manatee carcasses documented, and found the cause to be starvation from a lack of forage in the Indian River Lagoon. The event was administratively closed on March 14, 2025.

The lagoon tax

In 2016 Brevard County adopted the Save Our Indian River Lagoon plan, and on November 8 of that year county voters approved a half-cent sales tax to pay for it, for ten years starting January 1, 2017. According to the county, every city and town in Brevard, Melbourne among them, signed the agreement on how the money would be used.

The lagoon as a whole is covered on Old Space Coast’s lagoon page, and the Palm Bay reach on Old Palm Bay.

Further Reading

• Florida’s Fabulous Natural Places by Tim Ohr