Southern Florida’s wildlife in the Indian River Lagoon has faced hardship over the last four years. Harmful algal blooms (HABs) may be responsible for the death of manatees, dolphins, and pelicans in the cherished estuary of southern Florida. HABs result when algae colonies grow out of control, producing toxic and damaging effects on humans and the surrounding ecosystem (NOAA). Recently, the Indian River Lagoon is suffering from these nitrogen-fed algal blooms. The blooms are causing massive fish die-offs, depletion of sea grass populations, and the water to be too toxic for swimmers to handle.
The Indian River Lagoon
The most recent HAB in Florida takes place in the Indian River Lagoon (IRL). The IRL is a 156-mile estuary stretching along Florida’s eastern coast. Three water bodies make up the lagoon system: Mosquito Lagoon, Banana River, and the Indian River. Like all estuaries and lagoons, the IRL is a semi-confined body of water made up of both saline oceanic water and freshwater. Wind drives the water circulation within the lagoon.
Biodiversity in the Indian River Lagoon
The IRL is one of the most biologically diverse estuaries in North America. The combination of a warm-temperate climate to the north and a subtropical climate to the south is one factor that fosters such incredible biodiversity. Additionally, the presence of distinct and thriving habitats in the lagoon contributes to high levels of biodiversity. The most prominent habitats in the IRL are seagrass meadows, mangrove forests, and salt marshes.
The numbers of different species in the IRL is staggering. The IRL houses more than 2,100 unique species of plants and more than 2,200 species of animals, including 700 species of fish and 310 species of bird. Among these plant and animal species, 50 are threatened or endangered, including 12 plant species and 36 animal species.
Algal Blooms Effect on Manatees, Dolphins, and Pelicans
According to the Orlando Sentinel report, to date, as of May, eight manatee bodies have been recovered from the IRL. The cause of these deaths has yet to be determined, but the most plausible hypothesis is that the manatees are eating the new vegetation growing as a result of the algal blooms, according to a Dr. Martine de Wit, a veterinarian with the Florida Fish and Wildlife Conservation Commission. Consuming this vegetation makes their guts more susceptible to complications.
These recent deaths come years after a series of manatee deaths between 2012 and 2015. More than 150 manatee carcasses were found in the lagoon whose waters had been turned dark brown as a result of an algal bloom, killing off the population of sea grass. When a large algae bloom takes over a body of water, it blocks the sunlight from getting to the sea grass. It also depletes the levels of dissolved oxygen, leaving the plants with little oxygen to survive on. Without the manatees’ typical sea grass diet, they turned to the red seaweed, known as gracilaria, and complications further ensued. After further inspection, the guts of the manatee carcasses (both recently and between the years of 2012 and 2015) were found full of seaweed, with little sea grass. Typically, the stomach contents of a dead manatee will be fairly dry, but the stomachs of these carcasses connected with the algae bloom deaths was “like a Slurpee,” according to de Wit.
Algal blooms are also being held responsible for the unexpected deaths of dolphins and pelicans in the lagoon between 2012 and 2015. Luckily, the deaths of more dolphins and pelicans have not resumed during recent times.
So What Is Being Done?
There are numerous small groups and larger organizations that are working to try to decrease the number and size of algal blooms in southern Florida. One of the groups, the Ocean River Institute, is working to educate people across the country about safe land practices in order to protect our oceans. One specific action they are moving forward with is working with municipal workers to pass lawn-fertilizing regulations in the hope of reducing nitrogen pollution into the ocean. This is especially important when the water is warmest and algae are extremely hungry for nutrients to flourish. Reducing this nitrogen runoff could dramatically reduce the algae blooms in the ocean.
Aerial shot of the IRL: https://en.wikipedia.org/wiki/Indian_River_Lagoon