Enhanced export of carbon by salps during the northeast monsoon period in the northern Arabian Sea

A drifting sediment trap was deployed and 234Th activity in the water column was measured to calculate export flux of carbon at a time-series station in the northern Arabian Sea (lat. 21°30′ N; long. 64°00′ E) during the winter monsoon, 10–23 February 1997. The sampling period was characterised by an extensive salp swarm, and salp faecal pellets were the dominant contributors to the particulate matter in the sediment traps. Average 234Th flux out of the photic zone was 2300 dpm m−2 d−1 and average POC/234Th ratio in trap-derived particles was 0.14 mg/dpm. Average 234Th-derived export flux of carbon was about 332 mg m−2 d−1, representing 36% of the daily primary production (PP) (925 mg C m−2 d−1). Export of about one-third of the daily PP during the end of the winter monsoon could be due to the episodic nature of salp swarms. Salp swarms are frequently observed in the Arabian Sea and may be a significant pathway for rapid export of carbon from the euphotic zone.