Tuesday, September 30, 2014

Coral bleaching as a marine issue in Indonesia

The marine ecosystem would be balance depends on every element involved in it. If there is damage occurs to one element, then it would impact the other elements of that ecosystem. Coral reefs are one of the elements of marine ecosystem. It plays some important role not only for most of ocean creatures but also for the coastal environment and human being.

Marine Ecosystem, Source: www.sciencelearn.org.nz
The beauty of coral reefs becomes the backbone for local economies, especially through tourism. Beyond this phenomenon, coral reefs have some importance. It could protect coastline from erosion due to storms and sea waves, stabilize mangroves and seagrass beds, be the food and habitat for wide range plants and animals, give numerous nutrition for marine creature’s food, be the drugs ingredient for many diseases, increase coastal water quality, preservation biodiversity, etc.

Coral reefs in Gili Kedis Lombok
Coral reefs, as known as “rainforests of the sea”, generally live at shallow depths in tropical waters. These marine invertebrate from class Anthozoa live only in small numbers in deep water and cold water. Coral’s growth rate is vary depends on the species. Some research stated that its growth rates are about 8 millimeters per year depends on the amount of dissolved calcium carbonate that it could deposit and bind from the sea water. Some particular coral species in tropical water could grow 10-20 cm per year. It indicates that coral should be conserved due to its slow growth beside its advantages for other creatures.

Unfortunately, a number of coral reefs in the world include Indonesia have a significant degradation due to coral bleaching. Coral bleaching is a phenomenon about coral algal symbionts (zooxanthellae) that separates from its host coral (Navalgund, R.R. & Singh, R.P., 2011). It lead the coral to turn white and to mortality. The increasing of ocean temperature is the major factor of coral bleaching. This issue has been described nearly 80 years ago but became a highlight in 55 years later. It might generate overfishing, pollution, anthropogenic stressors, and damage for coastal environment in the future.

To prevent the mortality of coral reefs and to reduce coral bleaching impact, the maps of coral bleaching distribution area is necessary. The required data to get a good analysis are (Hendey, et al., 2012):
  • Bathymetry data
  • Basic geomorphological mapping of reef extent that consist of reef fauna area versus sand
  • Coral reef health to detect coral mortality or shifts to macroalgal domination
  • Coral bleaching to detect various levels of bleaching in areas of high coral cover.

To create a map of coral bleaching distribution area in Indonesia, we could utilize remote sensing technology (SPOT, Landsat ETM+, or IKONOS). It is also utilized for bathymetry mapping and benthic composition, and for detecting coral bleaching. Maps of benthos could inform management decisions about the placement of marine protected areas and to predict ecosystem dynamics (Hendley et.al., 2012; Dunstan & Johnson, 2006; Mumbly et al., 2006). The example of coral bleaching mapping is shown in this figure.

A map resulted from spatial correlation between sea surface temperature (SST) and bleaching on the Great Barrier Reef, in northeastern of Australia. Source: Berkelmans, R. et al., 2004
Elvidge (2004) stated that quantification of coral bleaching requires heavy bleaching and extensive coral coverage. It is concluded after he did studies using both small and high resolution of satellite images or high accuracy aerial photography. Based on the spatial information about coral bleaching, I think government should conduct a management, monitoring, and conservation of the coral reefs area that potentially be damaged due to coral bleaching. This action could be supported by using GIS-based tools for decision makers.

References

Berkelmans, R., et al. (2004). A comparison of the 1998 and 2002 coral bleaching events on the Great Barrier Reef: spatial correlation, patterns, and predictions. Springer-Verlag, Coral Reefs (2004) 23: 74-83.

Elvidge, C.D., et al. (2004). Satellite observation of Keppel Islands (Great Barrier Reef) 2002 coral bleaching using IKONOS data. Springer-Verlag, Coral Reefs (2004) 23: 123-132.

Hedley, J., et al. (2012). Capability of The Sentinel 2 Mission for Tropical Coral Reef Mapping and Coral Bleaching Detection. Remote Sensing of Environment 120 (2012) 145-155.

Navalgund, R.R. & Singh, R.P. (2011). Climate Change Studies Using Space Based Observation. Indian Society of Remote Sensing (September 2011) 39(3):281-295.

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