Ocean's 'Poop Machines' Could Help Fight Climate Change

salp photo

Image from WHOI

Believe it or not, there actually has been a good deal of research done on whether salps, a group of tubular, free-floating tunicates (which one of my former professor affectionately to as nature's "poop machines"), could help slow climate change. (And, if you don't, try typing "salp carbon," or some variant, into Google Scholar and see what you find.) How, you wonder? By living up to their nickname, of course: producing copious amounts of carbon-replete waste, or particulate organic matter (POC), that are exported to the deep ocean.The secret's in the fecal pellets
They do this by constantly eating -- a lot (think "vacuuming up" large quantities of phytoplankton and you'll get the idea). Lacking natural predators, salps can often be found clustering in huge swarms, sometimes numbering in the billions, and eating every microscopic organism in their path -- producing huge quantities of waste, in the form of large, fast-sinking fecal "pellets," which are transported (and sequestered) to the deep sea.

These swarms often last for months and are capable of sequestering several thousand tons of carbon a day. Salps are also some of the fastest reproducing multi-celled organisms on the planet; they can more than double their numbers in one day. When they die, they sink quickly and, because they often form long chains (by budding off through asexual reproduction), take large amounts of carbon with them.

One of the best overviews of the research can be found in Oceanus, a magazine published by the Woods Hole Oceanographic Institution. This passage, in particular, caught my eye:

One swarm covered 38,600 square miles (100,000 square kilometers) of the sea surface, containing perhaps trillions of thumb-sized salps. The scientists estimated that the swarm consumed up to 74 percent of microscopic carbon-containing plants from the surface water per day, and their sinking fecal pellets transported up to 4,000 tons of carbon a day to deep water.

Huge, rapidly-reproducing swarms could provide natural alternative to CCS
Though breeding enormous swarms of salps could hardly be considered a practical mitigation strategy, it seems as though Mother Nature may be taking matters into her own hands -- at least in Australia, as reported by The Sydney Morning Herald's Geoff Strong: "Vast numbers of marine "jelly balls" now appearing off the Australian east coast could be part of the planet's mechanism for combating global warming."

According to Mark Baird, a researcher at CSIRO, the number of salps in the waters off of Sydney are almost 10 - 15 times what they were when their population was first surveyed 70 years ago. (You can read more about CSIRO's recent survey in this recent ABC interview.) While no one seriously believes that these swarms will be able to stop climate change, many scientists believe they could have an important role to play by providing a potent, but natural, alternative to carbon capture and sequestration (CCS).

More "creative" ways to slow climate change in the ocean
Giving Geo-Engineering Another Go: Dumping Limestone into the Oceans to Fight Acidification
Wallace Broecker vs. Greenpeace: Climate Scientist Argues in Favor of Ocean CO2 Storage

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