Scalable mapping of photopigments in coral reefs using spectral images.
Supervisor: Arjun Chennu (Leibniz Centre Tropical Mar Res)
Coral bleaching is a phenomenon for corals reefs to release captive zooxanthellae and decrease chlorophyll content. Chlorophyll is a biomarker in all photosynthetic algae and conducting biomarker mapping is one of the focuses of monitoring coral reefs since it is one of the most important marine ecosystems. Photopigment chlorophyll-a has ecological significance, such as its role in light harvesting for photosynthesis and energy conversion. We use the HyperDiver, a diver-operable hyperspectral imaging system, to quantify photopigment concentration and generate chlorophyll-a proximation abundance maps. We combined the chlorophyll-a maps with habitat maps from a previous study, to perform masking for determining each species’ approximate value of chlorophyll-a (chlorophyll-p). We also analysed the habitat maps, discovers that sediment, turf algae, and macroalgae dominated eight sites in our study area, with coral ranking fourth. Madracis auretenra was the most common species found along our 23 transects. A depth wise analysis of the chlorophyll-p maps showed that their chlorophyll-p values increased with depth. The findings of our study indicate that coral reefs at a depth of 9 meters perform photoadaptation and photo acclimation to maximize light interception in greater depth if compared to chlorophyll-p at 3 meters. We believe that our chlorophyll-p value is a viable approximation for chlorophyll-a concentration. It is supported by the fact that our results follow the previously reported pattern of chlorophyll a, which increases with depth. Future research based on the correlation of chlorophyll-p and chlorophyll-a field sampling concentration values could reveal more about the relationship between the taxonomic environmental setting with actual chlorophyll-a concentration values. Keywords: coral reef, photopigment, chlorophyll-a, hyperspectral technology, habitat map.