Taxon‐specific differences in C/P and N/P drawdown for phytoplankton in the Ross Sea, Antarctica

Data from 11 cruises to the Ross Sea, Antarctica show that non‐Redfield N/P and C/P drawdown ratios for diatoms and Phaeocystis antarctica were a consistent feature of the phytoplankton communities between 1990 and 1998. Ratios of N/P drawdown for waters dominated by P. antarctica ranged from 17.2–19.5, consistently exceeding the Redfield ratio of 16. Similarly, the C/P drawdown ratio for P. antarctica‐dominated waters ranged from 120–154, 13–45% greater than the Redfield ratio of 106. Waters dominated by diatoms exhibited much lower ratios than Redfield for N/P (mean = 11.9) and C/P (mean = 76.2) drawdown. There was no seasonal trend to the drawdown ratios by either taxa. Sediment trap data exhibited C/P ratios for P. antarctica‐dominated samples that were twice that for diatoms, suggesting that the large taxonomic difference in C/P drawdown ratio is expressed as a difference in particulate C/P ratio which is subsequently exported to depth.