The Ocean Blog

A World Adrift: Life in the Sargassum

Wed, 05/30/2012 - 12:38pm
Seabird McKeon is a postdoctoral fellow with the Smithsonian Marine Science Network . His work focuses on the role of interspecies interactions in the formation and maintenance of...

Shrimp hides in the sargassum

The shrimp Latreutes fucorum is perfectly colored to hide on the leaf-like blades of the sargassum. That could be why they are popular members of the seaweed community. Dive in to see more creatures hidden in this drifting habitat.

Floating Sargassum Seaweed

Sargassum fluitans, a.k.a. “Gulfweed,” forms dense clumps up to the size of a beach ball that slowly rotate as they drift. The fronds are quite dense, but if you look carefully, sometimes you can see hints of the rich community that hides in the floating sargassum.

 

Tiny crab in the sargassum

The sargassum is coated with encrusting organisms, such as bryozoans and hydroids, that use it as a perch to filter feed in the oceanic waters, as well as crustaceans such as the swimming crab Portunus sayi.

Adult Swimming Crab

When they get larger, Portunus sayi are formidable predators- quick to consume any smaller animal that comes within reach. Fish, other crustaceans, and even smaller members of their own species are not safe from this hungry sargassum swimming crab.

Juvenile plane-head filefish

Relatively slow moving, juvenile plane-head filefish Monacanthus hispidus (Monacanthidae) travel along with the algae. They pick off and eat small animals as they move around in the rotating sargassum ball. Adult filefish only grow to be about 11 inches long.

Seaslug Camouflages in Seaweed

Winner of the ‘best camoflauge’ contest, the nudibranch Scyllaea pelagica is usually betrayed only by its motion. Along it’s back, the sea slug has growths called papillae that help its masterful disguise. The papillae resemble the sargassum's own hydroids that these sea slugs love to graze.

Brown Grass Shrimp

Another common species of sargassum shrimp, Leander tenuicornis (Palaemonidae), can be spotted by its long transparent claws or "chelae". Very similar shrimp are found in near shore habitats all around the world. Using genetic tests we may determine if they are the same species, or two different species that look the same.

Sargassum Frogfish

The sargassum frogfish Histrio histrio is a small but voracious predator - it can ingest animals up to it’s own size! The fins of the frogfish are perfect for creeping around in the algae and stalking unsuspecting prey.

Frogfish Histrio histrio

The Sargassum frogfish Histrio histrio is a small but voracious predator - it can ingest animals up to it’s own size! The fins of the frogfish are perfect for creeping around in the algae and stalking unsuspecting prey.

The open ocean is surprisingly barren to the naked eye. Every now and again you will encounter a school of fish and their attendant predators, but most of the life that you find is gathered around some sort of sheltering structure like a coral reef.  In the Atlantic, the pelagic macro-algae, or sargassum seaweeds (Sargassum fluitans and Sargassum natans) serve as shelter, drawing in a tremendous variety of marine life and forming a nearly unique structural habitat in the open ocean. Without roots, a top, or a bottom, the sargassum is in constant motion until it is cast up on a beach, or sinks out of the range of light and into the depths of the ocean. The algae is buoyed in the water column by small floats called pneumatocysts, which are full of gas.

In collaboration with the Smithsonian Marine Station and Chris Meyer of the Smithsonian National Museum of Natural History, we work on the ecology, genetics, and connectivity of this community.The photos in this series illustrate the group of organisms that live in intimate association with the algae. They are camouflaged to look just like their home. Unlike the mahi-mahi and other predatory fish that come to sargassum to feed, most of these organisms are rarely found living anywhere else. In the summer and fall, when sargassum is washed ashore along Atlantic beaches, many of these creatures will still be hiding within. As with many ocean habitats, there is much more than meets the eye. Take a look and see what is hidden in the world adrift. 

For more information on these species check out the full slideshow

Editor's Note: Seabird McKeon is a postdoctoral fellow at the Smithsonian Marine Science Network and Dan Barshis is a postdoctoral scholar at the Hopkins Marine Station of Stanford University. All photos were taken by Seabird McKeon and carry a Creative Commons Attribution-NonCommercial-ShareAlike license. 

Comments

Submitted by Anonymous (not verified) on

I would really like to see a Smithsonian program (PBS tv, etc) on the ocean life found in the floating islands of the seas and oceans... both the natural, like the sargassum, and the un-natural: Like how the floating islands of garbage are affecting the environment... the animals who are using it for shelter as well as the ones who suffer from it's presence.