For decades marine biologists have been studying a barrel-shaped organism that resembles a kind of streamlined jellyfish—the salp.
These mid-ocean dwellers are known to rapidly increase their numbers by budding off hundreds of clones in long chains without the need of a partner. Fortunately, for scientists, their abundance has yielded significant findings that could help the environment.
In a recent report by the Woods Hole Oceanographic Institution (WHOI), researchers believe that the salp’s waste material may actually help remove carbon dioxide (CO2) from the upper ocean and atmosphere. “We had long thought that salps were about the most efficient filter feeders in the ocean,” said Laurence P. Madin, WHOI director of research and one of the investigators. These creatures consume particles spanning four orders of magnitude in size. “This is like eating everything from a mouse to horse.”
Salps capture food particles, mostly phytoplankton, with an internal mucous filter net. Until now, it was thought that only particles as large as or larger than the 1.5-micron-wide holes in the mesh could be captured. However, a mathematical model suggests that they might be capturing smaller particles. So why is this important? According to the researchers it enhances the importance of the salps’ role in carbon cycling. As they eat these particles, “they consume the entire ‘microbial loop’ and pack it into large, dense fecal pellets,” explained Madin.
The larger and denser the carbon-containing pellets, the sooner they sink to the ocean bottom. “This removes carbon from the surface waters,” revealed researcher Kelly R. Sutherland, “and brings it to a depth where you won’t see it again for years to centuries.” And the more carbon that sinks to the bottom, the more space there is for the upper ocean to accommodate carbon, hence limiting the amount that rises into the atmosphere as CO2.
As much as they are impressed with the practical implications involving the salp’s carbon exchange, the scientists are captivated by the unique, almost magical performance of this natural undersea engine.
“The work does imply that salps are more efficient vacuum cleaners than we thought,” concluded Roman Stocker, a contributor to the study from MIT’s Department of Civil and Environmental Engineering. “Their amazing performance relies on a feat of bioengineering—the production of a nanometer-scale mucus net—the biomechanics of which still remain a mystery, adding to the fascination for, and the interest, in these animals.”
