Seaweed Is Choking Caribbean Beaches

Aug 29, 2022
 by Seven Seas News Team

Sargassum clogs the water and piles up on the beach in Punta Cana, a resort town in Dominican Republic.

Nutrient runoff is implicated in the unprecedented sargassum overgrowth, which is disrupting navigation and harming wildlife

One ferry captain in the Caribbean said that in 47 years, he’d never seen anything like it when sargassum seaweed made it impossible for him to sail. The brown macroalgae had filled the bay of Cul-de-Sac near Pinel Island, piling up in smelly mounds on the shore, making navigation impossible and effectively closing the island.

Pinel is far from unique in the Caribbean. From Puerto Rico to Barbados, the overgrowth of sargassum is clogging beaches, off-gassing hydrogen sulfide, choking navigation, killing wildlife, and decimating the tourist industry that is vital to the region. Even Miami has been affected, and in the Gulf, Tulum, in the Mexican state of Quintana Roo, is constructing barriers to keep the seaweed from shore.

Reasons for Seaweed Overgrowth

In 2011, a belt of the seaweed longer than the coastline of Brazil appeared in the Atlantic Ocean, surprising scientists. In 2018, the Great Atlantic Sargassum Belt had grown by 1,000%. This year, the bloom is 20% larger than the 2018 record. The belt stretches for almost 9,000 kilometers, nearly 5,600 miles. Why did it appear, and how can it be controlled?

A team of researchers from the United States has pinpointed nitrogen overloads from domestic sewage and farm runoff as the most likely cause, finding that nitrogen content in the sargassum is up 35% since the 1980s.

Other scientists suspect a more complex matrix that includes climate change, destruction of the Amazon rainforest, and wind-borne dust from the Sahara. With storm intensity increasing, floods might be carrying more nitrogen into the ocean, particularly from the Amazon basin. Stronger, more frequent hurricanes also might be stirring up nutrients from the ocean floor.

Wastewater Treatment Is One Solution

Although individuals can do little to shrink the enormous Sargassum Belt, larger-scale solutions can help as well as provide bottom-line benefits.

For instance, Caribbean resorts can treat and safely reuse their wastewater for nonpotable applications like landscape irrigation, topping up water features, pressure washing, and toilet flushing. Resorts can dramatically lower water cost this way while also keeping nitrogen from entering the sea.

In one example, a Seven Seas Water Group plant at the Sandals resort on Great Exuma in the Bahamas reuses wastewater for golf course irrigation, saving money while caring for its ecology. While an estimated 85% of wastewater in the Caribbean is discharged untreated, harming the reefs, aquatic ecosystems, and beaches that draw tourism, wastewater treatment and reuse can protect the long-term health of island economies.

Because the nitrogen overloads that nourish sargassum are problems across watersheds, decentralized treatment is a possible solution. Smaller treatment plants placed strategically can handle the same capacity as large, centralized plants, but without the astronomical expense of long pipelines and construction delays.

Smaller plants dotted across a watershed would allow a more surgical approach to nutrient reduction. Although farm runoff has been unregulated under the Clean Water Act in the U.S., the Environmental Protection Agency has signaled that regulation is in the works. Agricultural areas that channel their runoff into drainage tiles or ditches can treat runoff to avoid a possible regulatory crunch and reuse effluent for irrigation.

With Water-as-a-Service® from Seven Seas Water Group, water reuse and desalination infrastructure are bundled with long-term operations and maintenance, and capital can be optimized with unprecedented flexibility. Contact Seven Seas to maximize your resources and become a part of the solution.
Image Credit: sborisov/123RF