"Oceanic Rainforest" - Why and How we need to save them?

 Saving the Rainforest of the Ocean

-- Arindam Biswas

A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most reefs grow best in warm, shallow, clear, sunny and agitated water. Sometimes called rainforests of the sea, shallow coral reefs form some of Earth's most diverse ecosystems. They are fragile, partly because they are sensitive to water conditions. There are uplifted reefs also and they form a kind of marine terrace found in intertropical regions as a result of biological activity, shoreline advance and accumulation of reef materials. The formation of these platforms is controlled by changes in environmental conditions and by tectonic activity during recent geological times. Changes in climatic conditions have led to eustatic sea-level oscillations and isostatic movements of the Earth's crust, especially with the changes between glacial and interglacial periods.

Source: Hello Travel

Topographic and hydrographic information are basic elements in studies of nearshore geomorphology, hydrology, and sedimentary processes. This information includes both longterm and short-term changes taking place along the coast; which includes beach profiles, and changes due to erosion (Klemas, 2009). Remote sensing from satellites is an efficient and cost-effective approach to carry out the study. While remote sensing cannot provide the level of detail and accuracy at a single point than a field survey, the statistical power for inferring large scale patterns benefits in having complete areal coverage. Remote sensing imagery in the visible wavelengths is commonly used to perform mapping on coral reefs, utilising multispectral and hyperspectral data, acquired by airborne or satellite-based sensors. Both spatial and spectral resolutions help discriminate various mapping objective, from geomorphic zones (e.g., fore reef, reef crest) to benthic community cover (e.g., coral on reef matrix, algae and coral on rubble). 

Remote sensing covers many technologies, from satellites to airborne sensors, unmanned aerial systems, boat-based systems, and autonomous underwater vehicles. Using available remote sensing technologies for coral reef mapping, the extent of the reef can be studied routinely. Apart from mapping only, the rugosity, macroalgal matters, and bleached corals present in the colony can also be studied.  

A fire coral before (left) and after (right) bleaching. (Source: Mongabay)

 

Remote sensing techniques are also used to identify the proxy for various environmental parameters, such as estimation of water attenuation as a proxy for water depth, turbidity for sedimentation, algal bloom for pollution, and sea surface temperature for thermal stress.  

It is particularly very important to preserve coral reefs because they constitute the first line of defence against erosion and flooding through wave attenuation. They dissipate wave energy and thereby protecting the shoreline and the production and retention of sand. Apart from offering more than just protection from extreme weather events; they also help create ecosystems. Live coral provides the reef with shallower geometrical complexity and more surface roughness that dissipate wave energy through friction and wave breaking, thus they need both protection and care. By the above-integrated approach, factors affecting coral growth and coral degradation can be understood. By modelling wave energy for the past bathymetry, the erosional process can be compared with the change in climate and historical sea-level change. Also, well-developed coral platforms, which record the former sea-level position can be used to explain different uplift histories (Ota, 1992).  

Presently coral reefs (platforms) are under threat from excess nutrients (nitrogen and phosphorus), rising temperatures, oceanic acidification, overfishing, and harmful land-use practices. So, few necessary steps in protecting these coral platforms are:

1. Prevention of coastal erosion is necessary as corals can not grow properly if there is an influx of clastic sediments.
2. Artificial coral plantation and use of coral fusion technology to help them grow at a faster rate.
3. Regular monitoring of sea surface temperature is required as corals are very sensitive to temperature.
4. Monitoring of ocean water acidity should be given top priority as acidic ocean water can cause bleaching of coral colonies.
5. Safe and responsible practice should be adopted while diving and snorkelling. 

Reference:  

1. Reguero, B.G., Beck, M.W., Agostini, V.N., Kramer, P. and Hancock, B., 2018. Coral reefs for coastal protection: A new methodological approach and engineering case study in Grenada. Journal of environmental management, 210, pp.146-161. 
2. Klemas, V., 2011. Remote sensing techniques for studying coastal ecosystems: An overview. Journal of Coastal Research, 27(1), pp.2-17.