Impact of geographical variability on the bleaching stresses in the Atlantic, Indian and South Pacific Ocean

Abstract

This dissertation examines the relationship between the geographical location and the degree of coral bleaching. Corals within different ocean regions are subjected to fluctuations in temperature causing variations in thermal thresholds which affects how the reef fauna adapts to the changing environment. Quadrats were obtained from XL Catlin Global Reef Record and analysed to determine the state of the coral at three locations: East Bermuda (Atlantic Ocean), Egmont (Indian Ocean) and Agincourt (South Pacific Ocean). The mean monthly and weekly sea surface temperature (SST) data was extracted from Giovanni between 2002-2020 for all three reefs. ANOVA: single factor tests (analysis of variance) were carried out to test for differences between reefs on each of three factors: if there was a difference between bleaching, long term heating and number of degree heating weeks (DHW) between the sites. The analysis of the quadrats showed that the condition of the coral deteriorated with the increase of SST and bleaching was worse at Egmont and Agincourt. The DHW results at the three reef sites were consistent with previous findings that long term heating events above °C lasting for a minimum of two weeks can cause DHW’s which push the coral past their thermal threshold causing bleaching. Although there were limitations to the scale of the research results indicated that the geographical location of the reef has an impact on the severity of bleaching. This knowledge is important when deciding mitigation and conservation strategies.