Carbon export of the smallest phytoplankton

Marine phytoplankton fix carbon dioxide and drive the biological pump, the sequestration of carbon into the deep oceans.

The smallest phytoplankton, picophytoplankton, are significant carbon fixers but because of their small size, their biomass has been assumed to be regenerated in the upper ocean.

Recent discoveries, in oligotrophic oceans, suggest that picophytoplankton cells may stick together and form aggregates and that their contribution to carbon export is substantial.

Picophytoplankton are abundant also in coastal ecosystems, but their role in carbon export is currently unknown an understanding of how and when aggregation occurs is lacking.

The aim of this project is to determine carbon export of picophytoplankton and gain insights into mechanisms that induce aggregation.

The project will sample sinking aggregates in a coastal gradient over three productive seasons and use controlled laboratory experiments with well characterized model strains, to identify stressors that induce aggregation.

Molecular mechanisms that are cues for aggregate formation will be identified providing microbial functional links to carbon cycling in the global oceans.

The project will use high-resolution microbial and molecular methods that allow for detailed identification and quantification of previously overlooked small phytoplankton.

The results will be important for re-evaluating the role of picophytoplankton in carbon export and make it possible to integrate them in carbon budgets.