Sargassum Identification Guide

Two species of sargassum are found in the Carribean: Sargassum natans and Sargassum fluitans. The photos and drawings below provide assistance in differentiating between the two.

Click on any photo to open a larger version.

Identification guide - Sargassum natans and Sargassum fluitans
Sargassum natans, left, and Sargassum fluitans, right
photo by GCRL

Sargassum natans Sargassum fluitans
Sargassum natans
Common Gulfweed

photo by Phillipe Rouja
Sargassum fluitans
Broad-toothed Gulfweed
photo by GCRL

The characteristics described below are useful in differentiating between the two species. However, characteristics vary and identification of a particular sample may not be straightforward.

Sargassum natans Sargassum fluitans
Sargassum natans Sargassum fluitans
  • Pods - usually tipped with spikes or small leaves
  • Leaves - ┬álong-stalked, narrow
  • Pods - usually not tipped with spikes or small leaves
  • Leaves - short-stalked, broad

Illustrations by Julia S. Child (Schneider and Searles, 1991)