Distribution, abundance and grazing impact of <i>Salpa fusiformis</i>, with response to environmental conditions and their effects on other zooplankton species in Korean waters

Abstract The highly abundant pelagic tunicate Salpa fusiformis blooms in the Korean Peninsula. In this study, we examined the composition of mesozooplankton species and the environmental parameters in the S. fusiformis bloom areas in the East China Sea, the East Sea and the South Sea to understand the possible reasons behind this bloom. Salps abundance ranged from 0 to 547 ind. m−3 in the East China Sea, 0 to 161 ind. m−3 in the East Sea and 0 to 124 ind. m−3 in the South Sea. High salp abundance was associated with elevated chlorophyll a concentration and a shallow thermocline, particularly in regions where chlorophyll a concentrations did not exceed 1.5 μgL−1. Other mesozooplankton abundance was negatively correlated to salp abundance. Salp clearance rate estimated from Chl a concentration of the water ranged from 0.74 to 2.1 L ind.−1 h−1, and the grazing impact of salps was as high as 68.7% of the primary production at station J3 with moderate to high salp abundance in the South Sea. Salp ingestion rate positively correlated with both salp length and volume. The results suggest that episodic blooms of the salps can play a significant role in shaping the distribution of the plankton community and potentially carbon flux in this region.