Determining thermal stress using indices: sea surface temperature anomalies, degrees heating days and heating rate to allow for-casting of coral bleaching risk

Abstract

Sea temperatures in many tropical regions have increased by almost 1°C over the past 100 years and are currently increasing at 1 ~ 2°C per century. Satellite and compiled in situ observations of sea surface temperatures have greatly increased the ability to detect anomalous and persistent warm water and are being widely used to predict climate change, coral bleaching and mortality. In my study I attempted to measure in situ sea surface temperature using vemco water prob loggers. I used three indices: sea surface anomalies, degree heating days and heating rate to determine thermal stress 011 a reef flat. I identified the indices sea surface temperature anomalies provide significant data to determine heating is accruing on a reef and just mean monthly temperature data of a reef is not sufficient enough to indicate that the reef is heating and result in bleaching. Accumulated heat stress represented by exposure time and temperature (DHD) allows for-casting of bleaching severity. The cumulative thermal stress graph in my study indicates that after 120 degree heating days the thermal stress kept increasing on the reef for at least 3 more weeks in cooler month hence its vital to note temperature even after summer months.