Have you ever wondered how the global warming caused by humans is dampened? A new study has revealed that a distant human relative is playing a major role in this process. In this blog post, we’ll explore the findings of the study and talk about the potential of this distant relative to help in mitigating the effects of global warming.
The study, led by Dr. Deborah Steinberg of William & Mary’s Virginia Institute of Marine Science, was published in the latest issue of Global Biogeochemical Cycles. It reveals that a species of gelatinous zooplankton called Salpa aspera plays an outsize role in damping the impacts of greenhouse gases.
These tiny drifting animals, also known as “jelly barrels,” begin life with a notochord and as adults drift through the world’s oceans like tiny transparent whales, filtering microscopic plants afloat in the water. Salpa aspera can reproduce asexually and rapidly clone into immense blooms under the right conditions. They are also bigger and filter more water than most other zooplankton, thus producing larger, heavier fecal pellets. On top of that, they migrate up and down through the water each day, rising to feed on phytoplankton during the cover of night and jetting to the perpetual darkness of the deep sea during sunlit hours to avoid their own predators.
This combination of features has led researchers to suspect that salps might play an important role in the biological pump, as large blooms of these relatively bulky zooplankton could effectively transport carbon to depth through their heavy, fast-sinking fecal pellets; vertical migrations that give those pellets a head start on their journey to depth; and the sinking of countless salp carcasses during a bloom.
The proof is in the pudding, and the ephemeral life cycle and uneven distribution of salps has long challenged efforts to study their role in carbon export and deep-sea food webs. During the 2018 EXPORTS expedition to the Pacific, Steinberg and colleagues were able to overcome these challenges by deploying a wide range of ocean-observation tools. The results of the team’s unprecedented field campaign were clear: high salp abundances, combined with unique features of their ecology and physiology, lead to an outsized role in the biological pump.
To put things in perspective, the observed salp bloom covered more than 4,000 square miles (~11,000 km2), about the size of Connecticut. With onboard experiments showing salps capable of exporting a daily average of 9 milligrams of carbon through each square meter at 100 meters below the bloom, the amount of carbon exported to the deep sea was about 100 metric tons per day. For comparison, a typical passenger car emits 4.6 metric tons per year. Comparing these values shows the carbon removed from the climate system each day of the bloom is equal to taking 7,500 cars off the road.
The team calls for increased recognition of the key role that salps play in global carbon export. Incorporation of salp dynamics into a recent carbon-cycle model illustrates the potential of salp-mediated export. In this global model, salps and other tunicates exported 700 million metric tons of carbon to the deep sea each year, equal to emissions from more than 150 million cars.
In conclusion, the study reveals that a distant human relative plays an outsize role in damping the impacts of greenhouse gases by pumping large amounts of carbon from the ocean surface to the deep sea. This distant relative has the potential to help in mitigating the effects of global warming, and further research into its role in the biological pump is needed.