Islamorada’s shoreline is being inundated with a “tsunami” of sargassum seaweed that keeps relentlessly piling up. It represents more than just an eyesore: After about 48 hours on the beach, sargassum starts to decay and can produce hydrogen sulfide and ammonia gases. Hydrogen sulfide smells like rotten eggs and ammonia gives off notes of urine, sweat or dead fish.

Even more weed is expected - possible record-breaking levels of sargassum piling up this summer. 

Why are sargassum blooms getting so large?

Scientists began noticing major changes in sargassum growth around 2011. That's when the floating mats began expanding dramatically, reaching sizes large enough to be tracked by satellites.

The blooms peak during summer months, fueled by longer daylight hours, warmer ocean water, and favorable growing conditions.