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Monitoring the Influence of Variations in Remotely-Sensed Values of Sea Surface Temperature Along with the El Niño Phenomenon on the Coral Reefs Bleaching, Case Study: Kish Island, Persian Gulf

Shabani, Fatemeh | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56721 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Raie, Mohammad; Kabiri, Keivan
  7. Abstract:
  8. Coral reefs are one of the most important ecosystems in terms of animal diversity and affect the life of organisms in different ways. This ecosystem is under many stresses today. Among the most important events that threaten corals is the event of coral bleaching, the most important cause of which is the increase in Sea Surface Temperature (SST). Therefore, it is highly important to monitor changes in SST affecting corals. Generally, temperature anomalies are investigated using the Degree Heating Weeks index (DHW) and SST data. DHW index is variable in different coral areas and changes with time. Consequently, in the present study, this index has been investigated due to the lack of sufficient studies about this index in the Persian Gulf, especially in the waters around Kish Island (a rich source of diverse and healthy corals). For this purpose, in the first step, remotely-sensed SST data from 1982 to 2022 were used to draw SST and DHW time history graphs in the target area. Then, the changes in these two parameters were evaluated using the non-parametric Mann-Kendall test and Sen's slope estimator. The result was that the changes of these two parameters in the waters around Kish Island have an upward and significant trend with an incremental annual slope of 0.027 and 0.025 degrees Celsius respectively. In the following, using the time history graph of DHW and the years of bleaching events in this area, a bleaching threshold was obtained, which in this thesis is estimated to be 5.3 degrees Celsius. It should be noted that this threshold was optimized using Pierce's Skill Scores (PSS) test. In addition, the relationship of the El Niño phenomenon as one of the most substantial factors of the increase in temperature anomalies with the DHW index and its influence on coral bleaching was investigated. The result was that there is a direct relationship between this phenomenon and bleaching events. It is worth mentioning that to compare the condition of corals on the northern side of the Persian Gulf with its southern side, a similar process was implemented for the coral areas around the UAE. The result was that the corals located on the south side have higher temperature resistance and adaptation. In the second step, to visualize changes in the spatial distribution of the average SST of the Persian Gulf, Aqua MODIS data and the Google Earth Engine processor were used. The results showed that the SST of the Persian Gulf has warmed by 0.054 degrees Celsius every year during the last two decades, and this annual increment represents a threat to all the coral islands located in the Persian Gulf
  9. Keywords:
  10. Coral Reefs ; Remote Sensing ; Elnino-Southern Oscillation (ENSO) ; Climate Change ; Persian Gulf ; Kish Island ; Degree Heating Week ; Coral Bleaching ; Sea Surface Temperature

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