Salps, the Carbon Cycle, and Climate Change

As a curious person interested in biology, I follow a series of blogs run by various expeditions and research groups run through the Alfred Wegner Institute. Their work in polar and arctic research is really exciting and important in this time of climate change, and knowledge of Antarctica and its surrounding waters is something humans have been trying to gather for decades. I've always been fascinated by the stories of the Shackleton expeditions and others like it, where people spent long periods of time traveling across Antarctica to reach the South Pole, or were stranded while exploring the oceans around Antarctica, like the Weddell Sea, in the 1900s. The blogs run by the members of the current research expeditions give me a small glimpse of the awe-inspiring climates and geographical features of Antarctica, while being able to learn about the current research that is being done there.

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This Spring, fifty international researchers spent close to eight weeks on a research vessel near Antarctica. Off the coast of Chile's southernmost point, they conducted research on a variety of organisms like krill, fish, and whales. Their focus, however, was directed on salps. Salps are gelatinous marine organisms, related to tunicates and, while not well known or researched, play a potentially huge role in the marine ecosystem, as well as the carbon cycle. Their involvement in the carbon cycle also indicates that salps may also be affecting climate change.

Germany's largest research vessel, the Polarstern, used mainly for arctic and antarctic research expeditions. 

The AWI (Alfred Wegner Institut, named after the German polar researcher, meteorologist, and geophysicist) is a marine and arctic research institute, and this expedition was one like many others they have done in the past. The AWI has a number of permanent and seasonal research stations in Antarctica, as well as a field station in the Siberian permafrost.

The fifty-man crew of researchers, PhD students, engineers, mechanics, pilots, camera people, and technicians came from all over the world, from a dozen different institutions and organizations, from Europe to Canada to South Africa to Australia, and one scientist from the US. While a few of those on board were filming fin whale aggregations for a BBC documentary, others focused on oceanography, or research on Antarctica's food web.

One of the most interesting, timely, and marine ecology focused research foci on board was that of the salps. Salps are related to tunicates, and are gelatinous sea creatures that live (among other places), in antarctic waters. They reproduce incredibly quickly, in long chains, and in some places become a nuisance by coating beaches in their slimy bodies. They feed on phytoplankton, creating massive booms in population in response to large phytoplankton populations. They move by contracting their bodies, forcing water through themselves, and are among the most efficient animals to do so. They vary greatly in size based on their stage in their lifecycle, from 1 to 10 cm, and are found both in long chains (when budding off and shortly thereafter as offspring grow in size) and alone.

Salps in the red sea. Salps reproduce asexually and sexually, forming long chains before budding off.

Salps are very efficient and grow quickly, but they also play a vital role in the carbon cycle in the oceans, since they produce very carbon-rich feces, which sink to the bottom of the ocean and the carbon enclosed in the fecal pellets doesn't enter the atmosphere again for a very long time.

A diagram of how carbon moves through the ocean and the atmosphere

The researchers aboard the Polarstern hoped to collect more detailed data on the lifecycle of salps, their eating habits, the carbon in their fecal matter, and how they interact with competing organisms like krill.

This is a graphic from the expedition outline handbook, which shows a number of different aspects of krill and salp interaction and behavior that researchers hoped to conduct research on.

As the expedition ended on May 6, we can now eagerly await the peer-reviewed articles with the results of the research done aboard the Polarstern.