4. CHROMOPHORIC DISSOLVED ORGANIC MATTER (GELBSTOFF) INCREASES THE RESILIENCE OF CORAL REEFS BY ABSORBING ULTRA VIOLET RADIATIONS (UVR)-A CASE STUDY OF GULF OF KACHCHH by ROHAN THAKKER AND HITESH A. SOLANKI

Abstract

Coral reefs are especially vulnerable to predicted climate change because they bleach rapidly and dramatically in response to increased Sea Surface Temperatures (SSTs). Even an increase of 1 or 2ºC above average over a sustained period of time (i.e. a month) can cause mass bleaching. The potential severity of the predicted increases of 1-3ºC in SSTs by 2050 and 1.4-5.8ºC in Earth surface temperatures by 2100 thus becomes apparent. The Mass-coral bleaching events are generally triggered by high seawater temperatures, experiments have demonstrated that corals and reef-dwelling foraminifers bleach more readily when exposed to high energy, short wavelength solar radiation (blue, violet and ultraviolet [UVR]: ? ~ 280 - 490 nm). In seawater, colored dissolved organic matter (CDOM), also called gelbstoff, preferentially absorbs these shorter wavelengths, which consequently bleach and degrade the CDOM. Coloured Dissolved Organic Matter (CDOM), also known as gelbstoff; it primarily consists of humic acids produced by the decomposition of plant litter and organically rich soils in coastal and upland areas. Levels can be augmented by fulvic acid produced by coral reefs, seaweed decomposition or industrial effluents. CDOM absorbs UV radiation and can protect coral reefs against bleaching. Hence the surrounding ecosystems such as seagrasses and mangroves should be protected because they contribute nutrients to the coral reefs, provide nurseries for many reef species and produce coloured dissolved organic matter (CDOMs), which can be important in screening harmful solar radiation and thus protecting corals against bleaching. The Gulf of kachchh has a very unique feature where we find Corals as well as mangroves. The Mangroves need Mud & Silt deposition whereas the corals don’t. According to reports the probable mangrove areas are increasing in the GOK. That means the only source of Silt in the region i.e. the Indus River carries the Silt which doesn’t gets deposited on the Corals. But the mangroves are directly responsible for Conservation of the Corals by producing CDOM.
KEY WORDS: CDOM, Mangroves, Coral reefs.