Sargassum seaweed is the unwelcome visitor that began washing up on beaches in parts of the Caribbean and Mexico's Yucatan peninsula in late spring and shows no signs of leaving anytime soon. Senior editor Gay Nagle Myers talked with Brian Lapointe, a research professor and oceanographer with Florida Atlantic University's Harbor Branch Oceanographic Institute in Fort Pierce, about the reasons behind the seaweed increase this year and why no short-term solution is on the horizon.
Q: What's the origin of sargassum?
A: We know that sargassum is an important part of the ecosystem, and it's been around for hundreds of years. It generally "blooms" in the Sargasso Sea, a 2-million-square-mile body of warm water in the North Atlantic that serves as a major habitat for numerous marine species. The floating masses are carried by currents, winds and tides south through the Yucatan Strait into the Gulf of Mexico. Once there, sargassum can head toward Texas, the islands of the Caribbean and Yucatan or get caught by the Gulf Stream and travel up onto Florida beaches.
Q: Why is it such a problem this year?
A: Sargassum masses have been around for years, and their appearance is a cyclical event, and until 2011, a manageable one. Sargassum needs nutrients to grow. Our research has found that nitrogen and phosphorus from land-based runoff and pollutants, including nitrogen-heavy fertilizers and sewage waste, are washing into rivers such as the Mississippi and the Amazon. This fuels sargassum growth. Satellite imagery shows high biomasses of sargassum in the northern Gulf of Mexico and near the mouth of the Amazon River. Nutrients are increasing and that feeds sargassum growth. We saw increases beginning in 2011. Some theories hold that dispersants used to break down the oil in the Gulf following the BP oil spill in 2010 produced nitrogen, which fertilized the sargassum. Climate change, too, has resulted in higher sea temperatures and increased amounts of carbon dioxide that enhance its growth.
Q: Is sargassum dangerous to humans?
A: It's unsightly, and it smells like rotten eggs when it drys out on shorelines and begins to rot. The masses are heavy, hard to remove and can stand in piles as much as 10 feet high. When layers of sargassum are trapped in coves, the air can become very toxic. No one wants to walk on a beach or swim in water that's choked by this seaweed. It can kill sea turtles as they try to come ashore to lay eggs and it's causing problems for the juveniles as they try to make their way from the beaches to the shore.
Q: Will it go away before the winter high season?
A: No one has the answer to that. This year is the worst we've ever seen, and I've been studying sargassum growth rates since the 1980s. We don't know if or when these masses of sargassum will dissipate or be carried to other shores.
Q: What advice do you have for destinations on dealing with sargassum?
A: Keep visitors informed so they know what to expect when they arrive at a beach that's not pristine. Tell them what action plans are in place to deal with it. Educate them on the ecological occurrences taking place. Offer volunteer programs so they can be part of the cleanup if they so choose. Don't pretend this problem does not exist.