Science Results : Daily Update

Daily Update | Current SEA Research

July 8, 2010

By Skye Morét-Ferguson

When I first heard about the Sargasso Sea, I conjured images of a single giant floating raft of Sargassum in the middle of the ocean. Sargassum that floats by the ship typically gathers in clumps about the size of a grapefruit. Though these clusters can form grand rafts extending to the horizon, sometimes along windrows, I have observed that small clusters are much more common out here. We have actually not seen any rafts during this trip. Sargassum is a type of gold to brown macroalgae that lives in the open ocean. It forms the only (natural) floating ecosystem in the world.

We have been collecting and examining Sargassum throughout our summer on the Sargasso Sea. Luckily for us, while completing more than one hundred neuston tows to collect plastic and plankton on this trip, clumps of Sargassum randomly flow into the net. We record the dry weight (and, as a result, concentration) of the two primary species in the North Atlantic: S. fluitans and S. natans. We delight in the various Sargassum-colored fauna that live amidst their floats and blades. Sargassum fish, shrimp, crabs, and nudibranchs have made great additions to our temporary observation aquarium.

Why do we record amounts of Sargassum? Well, like most aspects of the ocean, scientists know very little about it. We do not have a firm grasp on exactly how long it lives, where it originates, how and where it distributes itself, or much about its tolerance to physical conditions (e.g., temperature, salinity). Sea Education Association students and crew have been recording Sargassum concentrations for 35 years and we are just beginning to compile this data.

What scientific questions can we answer with these data besides those regarding distribution? Concentration values of Sargassum may be useful in determining the fate of anthropogenic debris such as tar and plastic, though it is still unclear whether they wind up in the same place. Comparing Sargassum values and climate variations (e.g., El Niño) may also give us a better grasp on how this floating ecosystem may fare in a future warmer world.

The many willing volunteers out here weighing Sargassum and recording quantities of Sargassum critters in the wee hours are continually inspired by the fact that we just don't know much about it. A great scientist and teacher once told me that "science is about passion, exploration, and discovery", and the discoveries that are made at sea every time a net tow comes out of the water have been nothing but astonishing to me.

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For more from sea, listen to an interview with Chief Scientist Giora Proskurowski on the July 2, 2010 Science Update podcast, produced by AAAS.