I explained these currents in detail in one of my most popular blogs on flotsam and jetsam. You can see that one by clicking here. Read more about the weed here in this link and here in this interesting website. This very important sea of floating weed supports a massive habitat and at this time of the year the little turtle hatchlings are usually swimming out into the currents to try to find protection and food within the weeds. What is usually something that helps the turtles is now something that is hurting them. We had months of unusual south currents and many of us who were fishing in May and June complained about these currents. It seems as though they hit the Sargasso Sea at a strange angle possibly pushing some of the weed away from what is normally a current free area within the north Atlantic gyre. Its as if - in a swirl - masses of sargassum broke off and probably went north and east into the currents which now have brought the weeds back across from Africa into the Caribbean. People from Tobago to Hispaniola are complaining about masses of weeds. This photo below taken by a friend shows what is normally a nice little windward bay on the Eastern side of Antigua. As you can see, the dock is now surrounded by sargassum.
Here is photo taken from way above which shows two massive clumps of the weed just east of the islands. I estimate these two patches to be about the size of a football field. There would be so many fish, crabs, shrimp and birds feeding below. It would all come to an end as it washes up on a beach though.
It's important to understand that this only effects the windward beaches of any of these islands.
EDIT Friday 12th. Here is more info that points to the direction that it's coming from and suggesting that we are to see more of it. Click here.