Seagrasses and Algae Benefit South Walton Beaches, Ecosystem

Visitors come to South Walton’s beaches for the sugar-white sands and the feeling of those fine quartz crystals squeaking between their toes, but regulars have probably strolled along the beach at some point and came across seagrass or sargassum weed washed up on the shoreline. In warmer months, you might even come across what locals refer to as “June Grass,” which is actually a type of marine algae.

So besides washing up on the beach, or maybe even getting stuck in your hair and bathing suits, what’s the story behind this naturally occurring phenomenon? Well, we reached out the University of West Florida’s Dr. Wayne Bennett, a professor of Marine Biology, to provide some insight.

Types of Seagrass

In our area seagrasses grow in bays and estuaries. The seagrass that we see along the beaches of the Gulf of Mexico are broken or dislodged plants that have been transported by wave and tidal action.  

The types of seagrass commonly found at certain times of the year along the Gulf Coast are:

• Thalassia testudinum: Commonly referred to as turtle grass, this is the most widespread of the seagrasses in our area and makes up the extensive seagrass meadows we see in Florida bays. In fact, 75 percent of all turtle grass found in the Gulf of Mexico is found in Florida.
• Halodule wrightii: Commonly referred to as salt grass, this seagrass is found close to shore and is the most salt and heat tolerant.
• Syringodium filiforme: Referred to as manatee grass, this seagrass can be found, although rarely, scattered among turtle grass growing in deeper waters. Manatee grass, Bennett says, is much more prevalent in Texas than Florida, but bigger strands may be more common in South Florida.

Why are Seagrasses Important to the Ecosystem?

Seagrasses can be unsightly when they wash ashore, but Bennett says that seagrass meadows play an incredibly important role in the overall marine ecosystem.

First, they act as natural nursery areas that provide food and shelter for an array of juvenile fish and crustaceans. In fact, Bennett says many of Florida’s most desired food species spend their first year or more in seagrass ecosystems before they move to deeper waters.

“Seagrasses increase biodiversity,” he says. “Biodiversity is a necessary component to a healthy marine system.”

Healthy seagrass meadows slow water currents and help reduce wave action, allowing sediment to fall out of the water column. As a result, Bennett says, seagrasses prevent erosion and build coastline.

As a food source, seagrasses are very important. Manatees can eat 10-15% of their body weight in seagrass per day, and it’s also a major dietary component for green sea turtles.

Not all seagrass habitats are found in the water, either. When seagrasses become dislodged and wash ashore it can form what’s known as a ‘rack line.’ This thriving marine habitat is dynamic and ever-changing, Bennett says, and is home to a wide variety of crabs and other small crustaceans.

“Some maritime creatures exploit rack lines for shelter, others for food, and many for both,” Bennett notes. “This interesting ecosystem is often overlooked by beachgoers.”

June Grass

If you’ve been to the beach anytime between early June and October, you’ve probably seen what’s commonly referred to as “June Grass” at some point. So what is this bright green phenomenon? Well, it’s actually not grass, but a green marine algae from the Cladophora genus.

Since June Grass is transported via the Gulf’s currents, there’s no real way to predict where it will make an appearance. June Grass may be unsightly, and somewhat foul-smelling, as it makes its way to the shore from the Gulf of Mexico, but it poses no harm to beachgoers. 

Benefits of June Grass

As a marine algae, June Grass plays an important role in the marine ecosystem. According to the University of Florida’s Institute of Food and Agricultural Sciences, marine algae are a primary component of the food web, providing food for all types of animals, from fish and insects to mollusks and zooplankton.

Sargassum Weed

Sargassum weed, which is a brown algae and not a seagrass, grows in the open ocean, and is a common sight along our beaches in the early summer. There are two types of sargassum likely to wash ashore. One is a free-floating form (the most common) which typically originates off the south Atlantic coast, Bennett says. The other can be found growing on rocky jetties, but typically in such small amounts that they don’t wash ashore on our beaches in noticeable amounts.

Large masses of sargassum weed are called ‘rafts’ and serve as a habitat for a variety of animals. While they are mostly beneficial while at sea, Bennett says sargassum “blooms” can cause problems when large amounts wash ashore.

“Rotting sargassum and associated marine animals produce an unpleasant odor,” he says.

Benefits of Sargassum Weed

Much like seagrass, sargassum weed serves as a natural habitat and food source for a variety of marine creatures, such as shrimp, crabs, turtles and whales.

Once it reaches the shore, it becomes a source of food for crabs and a variety of other small creatures, which in turn act as a food source for shorebirds and other coastal animals.

While sargassum can be a nuisance, it poses no health risks to beachgoers, so next time you find yourself at the beach and there’s seagrass or sargassum along the shore, remember that it’s a living habitat for a variety of marine life and part of the natural marine ecosystem.