Coral Degradation Analysis of the Great Barrier Reef

The coral reef ecosystems are delicate and extremely susceptible to environmental fluctuations; such as changes in, water temperatures, pH levels, salinity levels, light levels, and nutrient levels, that often result in mass die­offs. The environmental phenomenon known as El Niño is one of these fluctuations that has been observed to negatively affect coral reefs. El Niño occurs on irregular intervals and is classified by warmer oceanic waters within the Pacific Ocean. Corals have a symbiotic relationship with zooxanthellae, which is a type of algae that through photosynthesis provide corals with a majority of their energy requirements. One problem is that the zooxanthellae are vulnerable to heat­stress. When these algae are stressed they produce toxins which in turn cause the coral to expel them leaving the coral without the means necessary to produce the energy levels needed to survive. This process is known as coral bleaching, and is characterized by the corals bright white skeleton being exposed. The objective of this project is to determine trends of coral bleaching during El Niño events in the area of the Swain Reefs in the Great Barrier Reef.

 

Various remote sensing systems are able to determine the extents of coral reefs and the environmental factors that affect these ecosystems. Data was obtained from various time frames starting in 1998 to the later part of 2015. This temporal range enables analysis of multiple El Niño events which then can be used to determine trends and the growth of El Niño. LandSat data from multiple systems was obtained. LandSat is a multispectral sensor that has the ability to distinguish differences spectral signatures. Hyperspectral data from the Hyperion instrument allows for a more detailed analysis over the study area due to its greater spatial and spectral resolutions. The discrete spectral signatures obtained from these sensors permits the classification of live coral versus bleached coral. The variations of extents of coral reefs will be determined through interpretation of change detections within the timeframe. SeaWifs data collected over the study area further facilitates the assessment of coral health by measuring biological parameters that are produced by the zooxanthellae algaes present in thriving coral populations. Once this analysis is complete it will be compared to oceanic water temperatures collected from AMSR in order to correlate variations of temperature to the health of coral populations.

 

The worst El Niño effect was recorded between 1997 and 1998. A lot of ecosystems around the globe experienced a significant loss of coral reef. Even though the causes of El Niño phenomenon are not fully understood, by analysing the historic deterioration of the Great Barrier Reefs, we can better predict the effects of the current El Niño event on the marine ecosystems. Major advances in captive coral cultivation allows endangered species located in areas of risk the chance to be saved from extinction. According to recent global studies, the temperature of the ocean is rising and is expected to surpass the 1997 event; therefore, the focus of our research will be on the extent of El Niño and the possibility of coral bleaching.