“Sea Snot” Explosions Feed Deep-Sea Creatures.
By Carrie Arnold 22nd November 2013.
It’s a feast of epic proportions. Storms of “sea snot”—a mix of dead plankton and gelatinous sea creatures, and their feces—drift to the ocean floor, where deep-sea organisms gobble up the sudden windfall.
But these snotty blizzards aren’t just an occasional bonus to life at the bottom of the ocean—new research shows they depend on it to stay alive.
“Sea snot” seen in the Gulf of Mexico in 2010. Image courtesy Arne Diercks
The scientists found that not long after sea snot blooms drift to the seafloor, the activity of these deep-sea critters accelerated. (See “Giant, Mucus-Like Sea Blobs on the Rise, Pose Danger.”)
Global warming and ocean acidification, however, may be increasing the frequency of these sea snot storms, which could have unforeseen effects on marine life by altering how nutrients move around the oceans.
“In the 24 years of this study, the past 2 years have been the biggest amounts of this detritus by far,” said study leader Christine Huffard, a marine biologist at the Monterey Bay Aquarium Research Institute in California.
With lead author Ken Smith, Huffard and colleagues were interested in learning how deep-sea marine life uses carbon and other elements, so they turned to Station M, which is located 145 miles (220 kilometers) west of the coast of California (map) between Santa Barbara and Monterey.
Although it sounds more like a secret CIA hideout than an ocean-research area, Station M has been giving scientists data on ocean productivity for two decades.
The ocean is most productive at the surface, where algae and phytoplankton use the sun’s energy to photosynthesize, creating a large portion of our atmosphere’s oxygen. Other animals, like slimy sea salps—barrel-shaped, jellyfish-like organisms—feed on the phytoplankton. (Related: “Huge Swarm of Gelatinous Sea Creatures Imaged in 3-D.”)
Somewhat regularly, large blooms of phytoplankton cover large areas of the ocean’s surface, which in turn boosts populations of sea salps that gorge on the giant marine banquet.
Eventually, however, all good things come to an end. The phytoplankton eventually dies off, and so do the hordes of sea salps.
“Anything that was once living or breathing or had been eaten at the surface makes its way to the bottom of the ocean,” Huffard said. “The sea salps sink pretty quickly because they’re very dense, but even fecal pellets from zooplankton fall to the seafloor.” (See pictures of deep-sea creatures.)
All of this feasting—and the digesting that follows—requires significant amounts of oxygen. So, using a special deep-sea robot, Huffard and colleagues measured the oxygen used by this deep sea life and the subsequent carbon it produces (as proteins and cells) to determine its activity level.
Their data revealed small seasonal increases in the activity of deep-sea organisms after spring and fall phytoplankton blooms.
Huffard points out that the use of oxygen and carbon levels to measure deep-sea productivity does have limitations.
Perhaps the biggest one is that the method can’t tell whether the number of deep-sea organisms has increased, or if they’re just more active and thus producing more carbon.
Global warming may also be influencing the rhythm of sea snot explosions. For instance, warmer oceans may encourage the growth of more phytoplankton. The scientists observed the largest spikes in deep-sea productivity in 2011 and 2012, corresponding with massive phytoplankton blooms. (Also see “‘Sea Snot’ Explosion Caused by Gulf Oil Spill?”)
In March 2012, less than one percent of the seafloor beneath Station M was covered in dead sea salps. By July 1, more than 98 percent of it was covered in the decomposing organisms, according to the study, published this week in the Proceedings of the National Academy of Sciences.
The major increase in activity of deep-sea life in 2011 and 2012 weren’t limited to Station M, though: Other ocean-research stations reported similar data.
Although climate change is a leading contender for explaining the major increases in 2011 and 2012, Huffard says that these spikes could be part of a longer-term trend that scientists haven’t yet observed.
She hopes to continue gathering data from Station M to try and figure it out.