Diseases of corals with particular reference to Indian reefs

Abstract

Diseases are one of the factors that change the structure and functioning of coral-reef communities as they cause irreversible damage to the corals Reports on coral diseases describe the etiological agents responsible for the disease and in a few cases, Koch�s postulates have been proved The report of Black Band Disease (BBD) among the corals of Caribbean reefs kickstarted awareness on coral diseases among ecologists and naturalists leading to reports on the prevalence of new band diseases from other reefs Outbreaks of several other diseases have also been reported from other reefs around the world Other diseases reported so far are the White Band Disease (WBD), Rapid Wasting Syndrome (RWS), White Syndrome (WS), White Plaque, Shut Down reaction (SDR), Pink Line Syndrome (PLS) and bleaching in hexacorals The Pink Line Syndrome (PLS) that affected Porites lutea colonies in Lakshadweep corals is the only disease in Indian reefs investigated extensively It has been established that Phormidium valderianum, a cyanobacterium causes the PLS Histological observations showed that the tissue was destroyed in PLS The coral bleaching is the only abiotic disease known in the corals Bleaching is triggered by anomalous high water temperature during summer in which the endosymbiont zooxanthellae are expelled from the coral tissue causing a break in symbiosis Bleaching in the polluted or eutrophicated reefs delays or completely stops the recovery processes This will be a major threat to the global coral reefs as forecast by the recent IPCC report In octacorals, BBD, Red Band Disease (RBD) and Aspergillosis are reported to be affecting the colonies The Aspergillosis, caused by the fungus Aspergillus sp in gorgonians is the first coral disease in which the complete processes, such as entry and spread of the pathogen in the coral reef ecosystem, and the role of global change in the disease propagation, have been studied in detail