Page 16 - AlertDiver_Spring2013

Far from being hazardous, sargassum plays a significant
role in the marine ecosystem, providing a variety of habitats
that include resting, feeding and breeding areas for many
species. The young of four types of sea turtles — loggerhead,
hawksbill, Kemp’s ridley and green — hide from predators in
the mats and eat both the algae and creatures that live in it.
(They and other creatures also eat plastic bits that collect in
the mats, sometimes with deadly consequences.)
More than 100 species of fish spawn in the Sargasso Sea,
including white marlin, porbeagle shark, dolphinfish and eels,
and the mats shelter larval forms of billfish, flying fish and many
other species. More than 150 invertebrates are associated with
sargassum. Ten species endemic to the environment (which
include fish, mollusks and crustaceans) are camouflaged to
match the surroundings. The sargassumfish even has modified
fins that allow it to crawl through the seaweed.
McKinney likens sargassum to a huge, moving nursery
for open-water megafauna. “Inshore, these organisms hide
and grow in wetlands, bays and estuaries, and sargassum
plays that role out in the open ocean,” he said. “You have
transients — the juveniles that hide there to grow and then
move into the open ocean. You have resident populations,
which have evolved together with the algae over millions of
years. And hanging around the edges of these mats are the
predators, waiting to pounce on anything that comes out.”
Humpback whales pass through the Sargasso Sea on their
annual migrations, as do birds and commercially valuable fish
such as tuna, all depending on it for food. Particulate rains from
sargassum mats to nourish creatures in the ocean’s depths;
depending on when and where mats sink, they may represent
the bulk of that marine snow. “The open sea is like a desert, and
sargassum is an oasis in that desert,” said Blair Witherington,
a research scientist with the Florida Fish and Wildlife
Conservation Commission’s Fish and Wildlife Research Institute.
DIVE SLATE
14 | SPRING 2013
The Sargasso Sea, a 1.5-million-square-mile circle of ocean filled with vast rafts of free-floating algae,
occupies the North Atlantic Subtropical Gyre, a large system of rotating currents within the Atlantic.
The Sargasso Sea is bounded by the Gulf Stream, the North Atlantic current, the Canary Current and the
North Atlantic Equatorial Current, and it has inspired ancient poets, mariners’ tales, 20th-century science
fiction and even music videos. “Sailing ships were afraid of becoming trapped in it,” said Larry McKinney, executive
director of the Harte Research institute for Gulf of Mexico Studies at Texas A&M University-Corpus Christi. “I’ve
been in sargassum mats so thick … the size of 10 football fields, I could almost imagine that happening.”
Significant Sargassum
The golden floating rainforest