Quantification of new production during a winter Noctiluca scintillans bloom in the Arabian Sea

We present new data on the nitrate (new production), ammonium, urea uptake rates and f‐ratios for the eastern Arabian Sea (10° to 22°N) during the late winter (northeast) monsoon, 2004, including regions of green Noctilucascintillans bloom. A comparison of N‐uptake rates of the Noctiluca dominated northern zone to the southern non‐bloom zone indicates the presence of two biogeochemical regimes during the late winter monsoon: highly productive north and less productive south. The conservative estimates of photic zone‐integrated total N‐uptake and f‐ratio are high in the north (∼19 mmolNm−2d−1 and 0.82, respectively) during the bloom and low (∼5.5 mmolNm−2d−1 and 0.38 respectively) in the south. The present and earlier data imply persistence of high N‐uptake and f‐ratio during blooms year after year. This quantification of the enhanced seasonal sequestration of carbon is an important input to global biogeochemical models.