The last few days have brought large clumps of Sargassum seaweed to our beaches.
We had a turtle crawl on Thursday morning, and I was so surprised to see the big piles of seaweed that it slowed us down in processing the turtle crawl. I have never seen this much on our beach~ I usually love to sort through the clumps for tiny creatures that make their home in Sargassum. On this morning, I couldn’t even figure out where to start!
Free Floating Habitat
This form of brown algae is doesn’t have roots or stems that fix it in one place. The bladders, about the size of BBs, are filled with tiny air bubbles that keep the masses of Sargassum at the surface of the water. The mats of seaweed can be 3-4 feet deep, can create shade underneath where lots of developing creatures, like sea turtles and juvenile eels can develop, shelter, and feed. It’s so productive it’s even been called a “golden rainforest.”
Habitat for all sorts of other things
We spent some time looking through the seaweed for creatures: the most common is the encrusting bryozoan (sargassum sea mat) that gives this textured lace crust. There are also tiny snails, small arthropods, and we even found an isopod sometimes called a sea roach. I’ll confess, I have been wishing that there would be a seahorse in one, but I have yet to find one of those. I think the textures and those little air sacs are really pretty!
Here are some super-magnified pics of encrusting bryozoan and the tiny snails, using a microscope.
Where is the Sargasso Sea, anyway?
If you went looking for the Sargasso Sea on a map, it might be hard to find. That’s because it’s not necessarily a fixed location~ it’s a spot defined by the boundaries of the four major Atlantic ocean currents: the Gulf Stream, the North Atlantic Current (Drift) the Canary Current, and the North Atlantic Equatorial Current. These currents swirl around in a pattern called a gyre, and free-floating flotsam and jetsam within that gyre tends to circle around.
Sargassum generally tends to stay in there (as does ocean plastic) unless something happens and it jumps the boundaries. Storm systems might push big clumps ashore with strong winds (which is probably the case now in South Carolina) or there is some sort of expansive bloom which sends Sargassum to beaches in greater quantities than normal.
Decomposing Sargassum Has Nutrients for Other Organisma
When the sargassum begins to decompose, it will turn a darker brown, and some of the insects along the beach will visit. Small crabs and other invertebrates that were living in the sargassum will provide food for land scavengers like ghost crabs and gulls.
Sargassum Pile-up can be a Problem
Apparently, not everyone was as excited to find some sargassum along the beaches. Christopher Columbus complained that his ships got stuck in the relatively wind-free tangles of seaweed. In the Caribbean, there have been problems with large rafts creating a noxious mess since 2011. Warmer waters and nutrient-rich runoff have combined to create optimum conditions for a “bloom,” a sort of out-of-control overgrowth of sargassum that can affect the quality of life of everyone from tourists to snorkelers to nesting turtles. Climate change seems to be a culprit here, and deforestation may play a part. And when the LARGE piles of Sargassum begin to decompose, they emit hydrogen sulphide gas. This is not only smelly, but can attract insects and be quite interruptive to vacationers. So while normal amounts of sargassum enrich the dunes and help stabilize the shoreline, truckloads of it are definitely problematic. Some people in the Caribbean are experimenting with ways to turn it into treasure. I found a number of articles that cautioned against letting pets eat it or play in it, and warnings that people might not want to handle sargassum because it could harbor larval jellyfish, which could create a reaction.
We’ll approach it carefully, and hope that it’s just some storm-strewn treasure that has washed up with a reminder that there’s a vast ocean of mystery out there, sheltering some of our turtle babies to adolescence.