This is a two part project in which the viability of Landsat 8 as a tool to evaluate and monitor coral reefs was assessed, as well as the effects of the chemical oxybenzone on Porites fucatas’s reflectance signature. Data from the satellite Landsat 8 was downloaded from the USGS Earth Explorer, and processed using the GRASS GIS application. A k-means unsupervised classification was performed on the coral reefs surrounding Heron Island, Australia, with the corals being classified by information pertaining to their reflectance. Recent research by Downs et al. 2015, demonstrated that the chemical oxybenzone, which is commonly found in sunscreens, can actually lead to increased rates of coral bleaching in planulae. Building off their research, a controlled laboratory based experiment was performed using the Caribbean coral species Porites furcata. The experimental group was subjected to stress from a 200 ppm solution containing the chemical oxybenzone. The experiment was conducted for 5 days, and the reflectance measurements of the corals were taken each day around 1:30 p.m.
This research can help to establish whether or not Landsat 8 can be an adept tool for remote sensing of coral reefs. The results from the experiment demonstrated that as the corals bleached, the reflectance signatures decreased. The reason for this is that as the coral’s health deteriorated, algae built up on the coral’s surface, thus causing the reflectance signature to decrease. Therefore, the experiment showed that coral health and reflectance signatures may have an inverse relationship. Because satellites can be used to monitor reflectance signatures, then it is possible that they could be used to monitor coral reefs. However, Landsat 8’s 30 meter pixel size and small number of bands proved to be insufficient in classifying corals around Heron Island, which shows that a relative miniscule pixel size and a greater number of bands would be required to effectively monitor coral reef health and bleaching.
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