What are mucospheres? A new ally in carbon capture in the oceans
Mucospheres, complex mucous structures, are gaining attention in science for their crucial role in the carbon cycle in the oceans. Secreted by mixotrophic protists such as Prorocentrum cf. balticum, these spheres act as ingenious traps for microscopic prey and can significantly contribute to the export of carbon from surface waters to the ocean depths.
According to recent studies, these protists produce mucospheres in response to light and prey availability. During the day, the cells photosynthesize and form a spherical structure up to 100 µm in diameter, filled with seawater. At night, they use chemical cues to attract prey, which become trapped in the mucosphere and are subsequently consumed. After ingestion, the protist discards the mucosphere, which sinks, carrying organic carbon to the ocean floor.
These mucous traps not only aid in the protist's feeding but also play an essential biogeochemical role. Estimates suggest that the carbon flux associated with mucospheres can reach up to 0.29 mg C m−2 per day under normal conditions, increasing significantly during bloom events. This process is comparable to the impact of gelatinous structures produced by larger zooplankton, traditionally seen as primary vectors of carbon transport to the deep ocean.
The discovery that mucospheres are fundamental to carbon export reveals an underestimated mechanism in the role of mixotrophic protists in the biological carbon pump. In addition to being a fascinating foraging tool, mucospheres represent an important pathway for CO₂ sequestration, contributing to global climate regulation.
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