Diatoms account for roughly 40% of global ocean primary production and are an important component of the biological carbon pump that sequesters carbon. They are characterized by a silica shell, which provides partial protection against grazers. However, the defense has only been studied in so called “black-box” incubation experiments, where the defense mechanism cannot be observed. We use direct observations of copepods and three species of differently sized diatoms with differing silica content in an attempt to reveal that mechanism. We find that cells that have been manipulated to increase their silica-shell thickness are much more frequently rejected by the copepods than thin-shelled cells of the same species. In addition, we find that the thick-shelled cells are handled for so long that copepods waste time for feeding and that grazing on not only the diatoms, but also other phytoplankton, is reduced. This has major implications to phytoplankton bloom dynamics and consequent carbon sequestration.
Read the paper here: https://aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lol2.10243
Ryderheim, F., J. Grønning, and T. Kiørboe. 2022. Thicker shells reduce copepod grazing on diatoms. Limnology and Oceanography Letters. https://doi.org/10.1002/lol2.10243