Marine Microgels

The ocean plays a critical role in global carbon cycling: it handles half of the global primary production, yielding the world's largest stock of reduced organic carbon (ROC) that supports one of the world's largest biomasses. However, the mechanisms whereby ROC becomes mineralized remain unresolved. This review focuses on laboratory and field observations that dissolved organic carbon (DOC) self-assembles, forming self-assembled microgels (SAGs). Self-assembly has similar to 10% yield, generating an estimated global seawater SAG budget of similar to 10(16) g C. Transects at depths of 10-4,000 m reveal concentrations of similar to 10(6) to similar to 3 x 10(12) SAG L-1, respectively, forming an estimated ROC stock larger than the global marine biomass. Because hydrogels have similar to 1% solids (10 g L-1), whereas seawater DOC reaches similar to 10(-3) g L-1, SAGs contain similar to 10(4) more bacterial substrate than seawater. Thus, microgels represent an unsuspected and huge micron-level ocean patchiness that could profoundly influence the passage of DOC through the microbial loop, with ramifications that may scale to global cycles of bioactive elements.