A novel focus on the diatom phycospere and the ocean´s biological carbon pump

Diatoms contribute approximately 20% to the Earth’s primary production.

Diatom biomass is projected to decrease in the global ocean due to warming and decreased nutrient supply from the deep water column through the thermocline during climate change.

However, warming can also produce increased turbulence and/or increased associations and interactions between diatoms and microbiota in the phycosphere, i.e., the boundary layer with steep concentrations gradients of gases, nutrients and solutes between the diatom surface and the ambient water.

These processes can both alleviate nutrient limitation and lead to increased CO2 assimilation and transport by diatoms in the ocean.

Our recent research employing stable isotope tracers, secondary ion mass spectrometry, and mass transfer theory has demonstrated that chain forming diatoms can contribute substantially to overall CO2 fixation in plankton communities despite relatively low biomass in warm coastal waters.

Here, I propose to directly measure metabolic activities, C and nutrient exchange between diatoms, bacteria, and protozoa in the phycosphere and compare these with physical/chemical processes as turbulence and diffusion of nutrients from the ambient water to untangle the physical/chemical/biological constraints of CO2 assimilation and transport by diatoms in the ocean.