According to a research team led by the University of Technology Sydney (UTS), a single-celled marine microbe (Prorocentrum cf. balticum) that is capable of both photosynthesis and hunting and eating prey may turn out to be a valuable secret weapon in the fight against climate change.
This microbe, abundant in the world’s oceans, photosynthesizes and releases a carbon-rich exopolymer which attracts and helps immobilize other marine microbes. After eating some of the entrapped prey, it abandons its exopolymer “mucosphere” which, heavy with entrapped prey, sinks and becomes part of the ocean’s natural biological carbon pump.
While the contribution of phytoplankton to the carbon pump has already been well documented by scientists, the role of mixotrophic protists – microbes that can simultaneously photosynthesize and consume other organisms – is far less understood.
“Most terrestrial plants use nutrients from the soil to grow, but some, like the Venus flytrap, gain additional nutrients by catching and consuming insects. Similarly, marine microbes that photosynthesize, known as phytoplankton, use nutrients dissolved in the surrounding seawater to grow,” said study lead author Michaela Larsson, a marine biologist at UTS.
“However, our study organism, Prorocentrum cf. balticum, is a mixotroph, so is also able to eat other microbes for a concentrated hit of nutrients, like taking a multivitamin. Having the capacity to acquire nutrients in different ways means this microbe can occupy parts of the ocean devoid of dissolved nutrients and therefore unsuitable for most phytoplankton.”
According to a 2019 report of the National Academies of Sciences, Engineering, and Medicine, in order to meet climate change mitigation goals, about 10 gigatons of CO2 should be removed from the atmosphere each year until 2050. Dr. Larsson and her colleagues have estimated that this microbe species has the potential to sink between 0.02 and 0.15 gigatons of carbon annually. Thus, it could be used as a nature-based solution to enhance carbon capture in the world’s oceans.
“The natural production of extra-cellular carbon-rich polymers by ocean microbes under nutrient-deficient conditions, which we’ll see under global warming, suggest these microbes could help maintain the biological carbon pump in the future ocean,” said study senior author Martina Doblin, a professor of Oceanography at UTS.
“The next step before assessing the feasibility of large-scale cultivation is to gauge the proportion of the carbon-rich exopolymers resistant to bacteria breakdown and determine the sinking velocity of discarded mucospheres. This could be a game changer in the way we think about carbon and the way it moves in the marine environment,” she concluded.
The study is published in the journal Nature Communications.