Sargassum Weed Biocube
The area...
The patch of Sargassum Weed used for this data set was found at the coordinates 24˚ 57’ 15” N and 80˚ 11’ 5” W. This location was approximately nineteen miles northeast of the island of Key Largo, Florida. The sampled patch was roughly ten feet long, four feet wide, and six inches thick. These patches of Sargassum are home to juvenile offshore pelagic fish; such as the Acenthocybium solandri (Wahoo), the Coryphaena hippurus (Mahi-Mahi), and the Thunnus atlanticus (Blackfin Tuna). Without the Sargassum, the juvenile fish would be vulnerable to the many predators of the ocean and the populations as a whole would most likely decline. With this in mind, the seemingly unimportant Sargassum is actually vital for populations that are already being threatened from the booming commercial fishing business.
Impacts...
Like all ecosystems, Sargassum Weed faces many problems caused by the environment and humans. In major storms or hurricanes the Sargassum can be pushed ashore, leaving the organisms beached and the weeds dried out. Sargassum is also negatively affected by the growing boat traffic in the area. As the boats pass through these large colonies, the weeds get stuck in the props of the boat, breaking up the Sargassum and propelling the organisms out into open waters. Sargassum also faces the problem of pollution. Oil or other runoff coats the Sargassum, thus interfering with its ability to photosynthesize and killing the organisms with its harmful toxins. Finally, the Sargassum is sometimes harvested because of its believed medicinal use for clearing phlegm.
Biodiversity...
Overall, the biodiversity of this one cubic foot of Sargassum was fairly low in comparison to the other surveyed areas. Nearly half of the diversity was found in different species of flora, including various algae, and even a sprout from a mangrove tree. Together the flora provides a basic structure for Sargassum colonies that allow for the many other creatures to find their niche. The rest of the biodiversity was found in the decapods, crabs and shrimp, and the various fishes. Due to the significantly less biodiversity, the Sargassum communities are ecosystems that are fragile and susceptible to a potential collapse. This Biocube had twenty species in one cubic foot.
Key species...
The two pivotal components of the Sargassum ecosystem are the two species of weeds, Sargassum fluitans and Sargassum natans. The differences between these two species is that the pods on S. fluitans are smooth, while the pods on S. natans are tipped with small spikes or leaves. These pods are gas-filled sacs that enable the Sargassum weed to float on the surface of the water to promote photosynthesis. Also, the leaves on S. fluitans are short-stalked and broad, while the leaves on S. natans are long-stalked and narrow. These two species of Sargassum allow for organisms to raise their young and provide a long-term protected environment for several species adapted specifically for Sargassum Weed, such as the Portunus sayi (Sargassum Swimming Crab) and the Latreutes parvulus (Sargassum Shrimp).
Interesting finds...
The Histrio histrio (Sargassum Fish) is part of the anglerfish family, categorized by its illicium. This illicium on the fish’s forehead acts as a lure to attract prey such as shrimp or other small fish. The Sargassum Fish is also a quintessential example of evolution. In order to blend into its surroundings, the fish has a brown and tan camouflage that makes it nearly impossible to spot. Also, for movement the Sargassum Fish has adapted fins that are used to grasp onto the Sargassum and crawl through it. The Sargassum Fish is only around six inches in length, but is the main predator in Sargassum colonies. When another predator enters the area, threatening the Sargassum Fish, it will leap out of the water and land on top of the weed and stay there for up to half an hour at times.
Species list...
Portunus sayi
Spirorbis spirorbis
Family Nereididae
Eurythoe complanata
Leander tenuicornis
Latreutes parvulus
Order Decapoda
Tricolia sp.
Latreutes fucorum
Histrio histrio
Latreutes sp.
Brown Algae
Sargassum fluitans
Rhizophora mangle
Bryopsis sp.
Monacanthus hispidus
Balistes capriscus
Seriola dumerili
Caranx crysos
Cheilopogon melanurus
