Annual POC export is 1.7 times higher in the naturally-fertilized area (P3 site).

POC export remains low at both sites (<50 mmol m⁻² yr⁻¹).

Diatom resting spore drives 42% of annual POC export at P3.

BSi:POC is higher at P2 (low productivity) with higher proportion of empty cells.

Resting spores relative abundance increases from the surface ocean to the sediments.