Small cells matter: The Tiniest Phytoplankton and their Role in the Biological Carbon Pump

by Prof. Susanne Neuer (Arizona State University)

Thursday Nov 14, 2024, 10:00 AM → 11:30 AM Europe/Berlin

8A-002 - Hörsaal Ostufer / Lecture Hall East (GEOMAR - Standort Ostufer / GEOMAR - East Shore)

Prof. Dr. Susanne Neuer, School of Ocean Futures, Arizona State University:

'Small cells matter: The Tiniest Phytoplankton and their Role in the Biological Carbon Pump'

Abstract

Phytoplankton aggregation contributes to particulate organic carbon export, a key process in the Biological Carbon Pump. Despite their abundance in all ocean regions, small-celled phytoplankton (<5 nm) were long considered minor contributors to export production due to their size. However, DNA-based studies of sinking particles from the Bermuda Atlantic Time-series Study (BATS) in the Sargasso Sea paint a different picture. Small phytoplankton, including the cyanobacteria Prochlorococcus (0.7 nm) and Synechococcus (1 nm), the diatom Minutocellus polymorphus (4 nm) and prasinophyte Ostreococcus lucimarinus (0.6 nm), are significant components of sinking particle communities. Laboratory experiments show that these taxa can form microaggregates (5-60 nm) and produce transparent exopolymer particles (TEP), which enhance aggregation. This behavior likely increases their incorporation into larger sinking particles and makes them more susceptible to grazing by copepods and euphausiids, which further accelerates their sinking through fecal pellet excretion and active transport.