Sargassum Seaweed is Back on Tybee

May 30, 2018

Joseph Richardson, Ph.D

Tybee’s Sargassum Event 2018

There is something happening on Tybee’s beach right now that only occurs occasionally every few years. The last time it happened on Tybee was in 2012. As you walk the beach, you might be noticing bunches of the brown seaweed Sargassum washed up. I’ve been getting a few calls, emails and messages asking, “where did all this seaweed come from?” Here’s probably more than you really want to know (but those who know me, know that I’m not good at giving short answers)!

1. Sargassum seaweed clumps drifted up on Tybee Island beach.

This species of Sargassum is unlike most seaweeds, that have to grow attached to a hard bottom or structure in shallow water where they get enough light to do photosynthesis. This Sargassum actually grows unattached, floating in open water, generally well out in the Atlantic Ocean. In fact some charts refer to the middle of the Atlantic Ocean as the “Sargasso Sea” because there is lots of it floating around out there. The small berry-looking structures on the Sargassum are actually air floats that keep it floating near the surface. Clumps of Sargassum in the open ocean serve as places to hide for some animals and as structure for others to attach on to.

2. A clump of Sargassum seaweed washed up along the high tide line

So for a phycologist (someone who studies algae and seaweeds) like myself, the Sargassum washing ashore is exciting enough, but it’s all those small animals associated with it that makes it really interesting.

3. The berry-like structures on the Sargassum are actually air floats that keep the seaweed floating at the sun-lit surface.

During my Tybee Beach Ecology Trips, we are already finding lots of those small animals hiding in and clinging onto clumps of Sargassum washing up on Tybee. These animals include Sargassum shrimp, Sargassum Swimming crabs, small file fish, and baby flying fish. All these animals are yellow-orange in order to camouflage or blend in with the seaweed. So the Sargassum has brought with it lots of interesting animals from far offshore, that we normally don’t see on our beach.

4. Sargassum shrimp (this one carrying eggs under her abdomen) were abundant in some of the clumps of seaweed.

The floating clumps of Sargassum in the open ocean also serve as places to hide for small young animals that will eventually become larger as they age and grow. When the baby Loggerhead Sea Turtles hatch on Tybee’s beach later this summer, they will head out to sea, and many will hide among clumps of floating Sargassum far offshore. Many years ago, while on a research cruise offshore, we anchored overnight and found ourselves among a large area of floating Sargassum. Being curious scientists, we used some long dip nets to catch some clumps of the floating seaweed to see what sort of animals were among it. This was how I caught the only Sailfish I’ve ever caught!

5. Sargassum Swimming Crabs hide and cling onto clumps of the floating seaweed.

So, if the Sargassum normally lives far out in the Atlantic, why did it wash ashore here? My guess is that it is related to the consistent south and southeast winds that we have had over the past weeks. This will move floating things like Sargassum clumps, Portugese Man-of-War, logs and planks toward the coast. In fact, there were some recent reports of a few Portugese Man-of-War sighted on Tybee, and I’ve seen old logs and planks covered with Goose-neck Barnacles washed up as well. These Goose-neck Barnacles don’t grow along the shore, but grow only on floating objects far out at sea. So it will be interesting to see if we also start seeing other types of tropical and offshore, open-water type animals showing up as well.

6. Small filefish with camouflage colors matching the seaweed can be found among many of the Sargassum clumps.

As you are walking along Tybee’s beach, it might be worth checking through some of those clumps of Sargassum. You might get a chance to see some small animals that normally live far offshore in the open ocean.

7. Although only about an inch long, what appears to be a baby flying fish was another type of fish found among the drifting seaweed.

Dr. Joe Richardson is a marine biologist who conducts research through Coastal Environmental Analysis, and conducts beach ecology trips on Tybee Island through Tybee Beach Ecology Trips www.TybeeBeachEcology.com (facebook: Tybee Beach Ecology Trips).