Space based Coral Bleaching Monitoring over Indian Reef Region: Need for High-Resolution SST Data

This presentation was held at the 24^th International SST Users’ Symposium and GHRSST Science Team Meeting (GHRSST24) held in Ahmedabad, India/Online from 16 – 20 October 2023.

Explore the full program at GHRSST24 on the GHRSST Website here.

Abstract

Space based monitoring and forewarning of Mass Coral Bleaching (MCB) events require a synergy of climate quality, long-term Sea Surface Temperature (SST) data record and high-resolution, real-time, diurnal SST observations. Zooxanthellate corals and other marine invertebrates in reef ecosystem are generally adapted to their local, seasonal temperature ranges that define their tolerance limits. In case of above-normal SSTs beyond the local summer maxima for a prolonged period, these marine invertebrates are exposed to thermal stress. This stress leads to expulsion of their photosynthesizing endo-symbiont, loss of tissue colour and eventual mortality. Coral Bleaching Monitoring System developed at Space Applications Centre (SAC), ISRO, for Indian coral reef regions based on NOAA’s Optimum Interpolated Sea Surface Temperature (OISST) data detected an unusual warming of the Lakshadweep reef region and forecasted likelihood of mass coral bleaching in summer of 2020. Co-incident ground observations from Lakshadweep islands confirmed in situ coral bleaching. Six out of the sixteen coral reefs of Lakshadweep showed close overlap of average summer SST anomalies when compared with the SST anomalies of summer 2016, an El Niño impacted MCB year. Comparison of Degree Heating Week (DHW) index revealed pronounced thermal stress for a northern and six central islands of Lakshadweep in 2020 as compared to 2016. Improvisation on the current continuous series of accurate OISST will be a welcome step towards real-time coral bleaching monitoring. The availability of high-resolution SST products from a host of advanced multi-thermal sensor satellites has the potential to augment this effort.