Environmental drivers of coccolithophore growth in the Pacific sector of the Southern Ocean

The key limiting factors controlling coccolithophore growth supporting this high PIC have not yet been well-characterized in the remote Pacific sector, the lowest PIC but largest area of the GCB. Here, we present in situ physical and biogeochemical measurements along 150 degrees W from January to February 2021, where a coccolithophore bloom occurred.

In both months, PIC was elevated in the Subantarctic Zone (SAZ), where nitrate was >1 mu M and temperatures were similar to 13 degrees C in January and similar to 14 degrees C in February, consistent with conditions previously associated with optimal coccolithophore growth potential. The highest PIC was associated with a relatively narrow temperature range that increased about 1 degrees C between occupations. A fresher water mass had been transported to the 150 degrees W meridian between occupations, and altimetry-informed Lagrangian backtracking estimates show that most of this water was likely transported from the southeast within the SAZ.