Coral reef Destruction: The Impact of Novel Syndromes

Research project P 14052 The Impact of Novel Syndromes Arnfried ANTONIUS 11.10.1999 Coral reefs constitute an essential part of the global, marine ecosystem. They inhabit hard bottom, shallow water areas of tropical oceans, roughly from the Tropic of Cancer to the Tropic of Capricorn. The health -condition of these coral reefs, or, more to the point, their survival or demise may influence the global ecosystem just as much as, for instance, the fate of tropical rain forests. Among many other parameters, our quality of life may well also depend on the wellbeing of coral reefs. Since over 20 years alarming observations on reef deterioration came to light and were the specific focus of the FWF project : "Coral Reef Health Problems: Causes and Effects", which was conducted from summer 1996 to 1999. Among many other results, such as the present health-condition of reefs in all three oceans, which turned out to be alarming enough, several novel, hitherto unknown coral-destroying syndromes were discovered, which together amount to a tremendous force accelerating coral reef destruction. Two of these are especially dangerous because of frequent occurrence and wide distrubution. Investigating these two coral diseases in detail is the aim of this project. The respective pathogens could not be more different, one being a plant, the other an animal. The plant pathogen is a new coralline red alga. The genus, up to now, was known from one mediterranean species only, now we know a second one from the Caribbean Sea and this one overgrows and kills reef-corals. This species, Metapeyssonelia corallepida, is responsible for the destruction of roughly 50% of reef areas in Central America and in Florida over the past 20 years. Basic problems not only of the life-cycle, of reproduction and disribution have to be investigated in detail, but also, and especially, the mechanisms of transmission of the disease. Also the question why this alga was never observed in the past, while it is destroying coral reefs today, still awaits an answer. Only if we know more about the biology of this killer-alga, can we hope to devise any corrective measures. The animal pathogen is a new species of colonial ciliates, which are unicellular organisms. Untold numbers of this microorganism, Halofolliculina corallasia, form black bands on coral colonies. They advance slowly across the surface of the coral, completely destroy and dissolve the live coral tissue, and leave in their wake not only denuded, but also eroded skeletal surface. This plague seems to be widely distributed in the Indo-Pacific and has, so far, been documented in the Red Sea, in the Indian Ocean and on the Great Barrier Reef of Australia. Large numbers of important reef-builders, such as staghorn corals, fall prey to this disease. Here again, we are faced with the question why this disease was totally unknown in years past, while it constitutes such a devastating force today. Of these two novel syndromes, we presently know that they exist, and the kind of devastations they cause in coral reefs, but not much else. The project proposed here will be devoted to a detailed investigation of the respective pathogens, as well as an exact analysis of the conditions under which outbreaks occur. Only knowledge of these hard facts will enable us to further preservation of endangered coral reefs.