Sargasso Weed,Sargassum natans gathers in large mats in the middle of the Atlantic Ocean. Storms breaks up these mats and they then drift via currents all over the Atlantic. Little gas floats allow this brown algae (Phaeophyta) to ride atop the waves in the open ocean.You REALLY need to see this one at full-resolution: www.flickr.com/photos/nashworld/7068343447/sizes/o/in/pho... ...to appreciate the hydroids covering almost the entire surface of this algae.
This is a female reproductive frond of the kelp floating on the surface and phot.ographed in August. It shows the meiotically produced developing eggs. When these are released and fuse with sperm from a male plant another diploid thallus results. The alga's holdfast is anchored to the sea floor. This life cycle contrasts with that of most kelps in which the diploid thallus alternates with a microscopic haploid sexual phase.
The thallus of this perennial brown alga is being swept horizontally by the ocean's surge. The holdfast anchors the kelp at a depth of 15 m. A short, tough stipe bears flattened blades. From the tips of the blades each year the alga will send slender reproductive fronds to the sea surface where eggs or sperm will be released. Fertilization will lead directly to another thallus.
