Effect of sea surface temperature (SST) changes on coral ecosystems in Kish Island

Background and Theoretical Foundations: Coral reefs are one of the world's most attractive ecosystems. They have been covering large parts of the world in the tropic areas. Coral reefs in the Iranian waters of the Persian Gulf are largely limited to the Islands. Many factors, including natural and anthropogenic activities cause stress to the reef communities affecting reef development. Coral bleaching events due to raised temperatures are increasing in both frequency and magnitude worldwide. Coral bleaching is considered a major threat to coral reefs worldwide, especially because large-scale bleaching events have been linked to global warming. The most intense global coral bleaching events reported have occurred worldwide in the last three decades. The Persian Gulf is considered the warmest coral sea in the world. Temperature conditions associated with coral bleaching in the Persian Gulf are higher than in any other area in the world. Therefore, the coral reefs in the Persian Gulf are also at assailable to temperature anomalies and their long-term effects. Sea surface temperature is one of the most important physical factors that affects the life of coral reef communities. Coral bleaching occurs in the Persian Gulf in the recent years due to the global warming and increased sea surface temperature (SST) resulting in high mortality in the coral. Thus, in this research the effects of coral bleaching and its threats in Kish Island have studied. The study area includes coral reefs in the around Kish Island in the Persian Gulf and the effects of stresses. Methodology: In this research, sea surface temperature (SST) daily values from 1985 to 2017 (in 1°×1° spatial resolution) prepared by the National Oceanic and Atmospheric Administration (NOAA). The degree heating week index (DHW) was examined to check the cumulative effect of heat stress, which indicate the severity of the whitening threshold based on a long-term period for each site. For trend analysis of sea surface temperature (SST) changes in studying regional, the Mann-Kendall non-parametric test has been used. Findings: The results indicated that the maximum of sea surface temperature is 35.17 ˚C (August, 11th, 2017). Analysis of sea surface temperature trend indicates that SST has increased trend. The DHW threshold for the study region is 5.3 which is warning for whitening of coral communities on Kish Island. The results illustrate the ability of the DHW index to predict bleaching events in the coral reef communities of Kish Island, and can be an effective tool in managing this ecosystem. Conclusion: The thermal analysis showed that there is an overlap between the recorded bleaching events in different years and the years of the El Niño occurrence. Therefore, these results help in years when there are no reports of bleaching or the data isn’t recorded properly, using overlap, the reconstructed this lack of information.