Water column properties associated with massive algal bloom of green Noctiluca scintillans in the Arabian Sea

An algal bloom of Noctiluca scintillans (NS) was monitored for 20 days in the Arabian Sea during February 2017. The stations under the influence of NS had low temperature and high salinity compared to outside indicating influence of convective mixing. The microscopic cell count of NS reached a value of 52,600 cells l^-1. The surface variability in oxygen and pCO₂ measured alongside showed a strong disconnect. Modest supersaturation of surface waters (ΔpCO₂ = 3-75 μatm) was observed around the NS bloom compared to outside. However, as these stations were under the influence of convective mixing, the observed change in pCO₂ due to subsurface ventilation cannot be ruled out. From the viewpoint of climate change and its influence on oceanic processes, constant monitoring of this bloom becomes essential due to its survival strategy in nutrient-depleted conditions and light of the present observations.