Sargassum Invasion

Near the horizon, an olive green mass more than a mile long floats, drifting languidly from north to south.  A moment later the languidness is put to lie as the south tip of the mass makes landfall on our beach.  The Sargassum has arrived.  This happens periodically every year, but this particular Sargassum landfall is part of an impressive invasion that has the entire coast of Belize mainland and cayes covered with the brown alga.  

The Sargassum is closing in.  All day long a seemingly endless line of Sargassum floated in. 

Some has washed up and much more is headed in.

 The next day there were mounds of it on the beach and floating next to the shore.

Sargassum floating next to the shore.

A thick blanket has mounded up, especially to the south of our dock where it is a couple of feet deep on shore. 

Not quite as much to the north of the dock.

This Sargassum is from the Sargasso Sea in the Atlantic Ocean.  The Sargasso Sea is a very cool thing/place - it is where baby sea turtles spend their growing up years as do European and American eels.  Every now and then the ocean currents change up a little bit and push some of the Sargassum to the south where it is picked up in other currents and pushed through the Anegada, Mona, and Windward Passages of the Caribbean Islands into the Caribbean Sea.  Once in the Caribbean, some of it gets taken up to the Gulf of Mexico and gets deposited on beaches in Mexico, Texas, Mississippi, Alabama, and Florida, while some it heads to Belize and Honduras.  Texas A&M University has an informative website devoted to tracking Sargassum drifts.  I found of lot of this information there in addition to the Wikipedia links below.

Most of the Sargassum that has washed up on our beach seems to be S. fluitans, but there may be some S. natans mixed in with it.

There are several species of Sargassum and the 2 of them from the Sargasso Sea are holopelagic, meaning that they float on ocean waters for their entire life cycle.  Other species of Sargassum that grow attached to rocks and corals are not normally found in the Sargasso Sea.

Besides the olive green-colored Sargassum, there are also greener wide blades of turtle grass (Thalassia testudinum) and some narrower blades of another sea grass in the mix that washed up.  The darker reddish brown stuff is Sargassum that has dried out.  There are also some other seaweeds in there that I haven't identified yet - like the clumps of roundish leaves about halfway down the right side of the photo.

Sea grasses, as opposed to the algal seaweeds, are vascular plants.  There are 3 recorded seagrasses in Belize namely, turtle grass (Thalassia testudinum) manatee seagrass (Syringodium filiforme), duckweed (Halodule spp.).  We have large beds of turtle grass along the very shallow water just off our beach.  And we often see manatees grazing the beds of seagrasses about 100 feet off shore in water that is about 10-15 ft deep.  Almost every day dead seagrass blades wash up on the sand.  We normally get that raked up and composted.  This big invasion of Sargassum will take us longer to deal with, but we are gradually getting it raked up.  Beats shoveling snow!