Nutrient supply in the Southern East China Sea after Typhoon Morakot

Abstract

Recent studies show that typhoons have profound effects on phytoplankton assemblages along their tracks, but it is difficult to quantitatively estimate nutrient supply after a typhoon's passage due to a lack of nutrient information before and after the arrival of a typhoon. During the passage of Typhoon Morakot (July 22 to Aug. 26, 2009), we conducted pre- and post-typhoon field cruises to study nutrient supply in the Southern East China Sea (SECS). The results showed nitrate and phosphate supplies to the water column in the SECS after the typhoon's passage were 5.6 × 1011 g-N/day and 7.8 × 1010 g-P/day which were significantly higher than those before the typhoon occurred (nitrate supply = 1 × 109 g-N/day, phosphate supply = 1.6 × 108 g-P/day). We conclude from this data, and after consulting the available physical data, that the highest nitrate concentration was caused by strong upwelling and/or vertical mixing, and input of nutrient-replete terrestrial waters. The nitrate and phosphate input related to the passage of Typhoon Morakot can account for approximately 86% and 87% of summer nitrate and phosphate supplies to the southern East China Sea.