Scyphozoan jellyfish blooms and their relationship with environmental factors along the South-eastern Arabian Sea

Abstract

his study correlated the abundance of five jellyfish species in the south-west coast of India, South-eastern Arabian Sea, Crambionella orsini, Lychnorhiza malayensis, Chrysaora caliparea, Netrostoma coerulescens and Cyanea nozakii, with hydrographic parameters. Partial least square (PLS) analysis suggested strong correlations between jellyfish abundance and phosphate, silicate and chlorophyll-a content in water and showed a significant positive relationship with the first PLS component, while pH and sea surface temperature showed a significant negative correlation with the first PLS component, indicating that the abundance of four species, C. caliparea, C. nozakii, L. malayensis and N. coerulescens, increases with phosphate, silicate and chlorophyll-a content and decreases with pH and sea surface temperature. In contrast, the abundance of C. orsini increased with an increase in sea surface salinity and decreased with an increase in dissolved oxygen; except for this species, the abundance of jellyfish in the South-eastern Arabian Sea was positively affected by phosphate content of the water. The continuous decline in abundance of jellyfish from 2016 to 2019 in the south-west coast of India could be due to the influence of regional environmental changes or due to the specific ecological strategies of the jellyfish species in the upwelling zone subjected to high fishing pressure.