Ocean Pollution

Link between human activity and red tide confirmed by new study

Written by Oceanographic Staff

A new study has confirmed the long-assumed link between the red tide in Florida and discharges from Lake Okeechobee.

A new study, conducted by the University of Florida Center for Coastal Solutions with help from Sanibel-Captiva Conservation Foundation, has recently confirmed the long-assumed link between human activity at Florida’s largest freshwater lake, Lake Okeechobee, and red tide blooms that are responsible for the widespread death of marine animals. It is the first scientific study to support the link.

The blooms occur on the coastline when K. brevis algae grows out of control, changing the water’s colour, posing a threat to human health and killing off sea life, including manatees and dolphins.

For years, tourism boards, the sugar and agricultural industry, as well as the government have called the event a ‘naturally occurring’ one, despite widespread belief that the blooms are worsened by human activity further up north. While it is true that the red tide does not naturally occur and it is not directly caused by the discharges, the discharges can significantly worsen these blooms.

Florida’s inland is full of widespread sugar farms and agricultural land and much of the industry runoff goes directly into Lake Okeechobee. The lake then feeds rivers that end up in the Gulf of Mexico. As Jack Davis, professor of environmental history at the University of Florida, said: “If a farmer fertilizes a cornfield in Minnesota, it ends up in the Gulf.”

The study, called Nitrogen-enriched discharges from a highly managed watershed intensify red tide (Karenia brevis) blooms in southwest Florida, analysed the relationship between Lake Okeechobee discharges and red tide blooms near Charlotte Harbor and the Caloosahatchee River Estuary between 2012 and 2021 and now has confirmed the link between the two.

It concluded that the nutrient-enriched lake discharges intensify red tide blooms. The red tide algae is a marine dinoflagellate that feeds on nutrients such as nitrogen and absorbs excess nutrients in the water to then multiply.

Many organisations and individuals are currently working on programmes and ideas to tackle the blooms, ranging from calls to re-build mangrove forests, coastal marshes, and seagrass beds to create carbon sinks that protect against this kind of pollution, to encouraging regenerative farming incentives. Furthermore, the Florida Red Tide Mitigation and Technology Development Initiative was founded to research red tide, while some believe in the power of Florida’s natural pine and wetland mosaics as a solution to filter water.

For more from our Ocean Newsroom, click here.
Photography courtesy of Unsplash.

Current issue

Back issues

Enjoy so much more from Oceanographic Magazine by becoming a subscriber.
A range of subscription options are available.