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Corals
Coral diseases generally occur in response to biological stresses, such as bacteria, fungi and viruses, and nonbiological stresses, such as increased sea surface temperatures, ultraviolet radiation and pollutants. One type of stress may exacerbate the other (NMFS, 2001). While the pathologies, or mechanisms by which many diseases act upon the coral polyp are not well known, the effects that these diseases have on corals has been well documented. Black-band disease, discolored spots, red-band disease, and yellow-blotch/band disease appear as discolored bands, spots or lesions on the surface of the coral. Over time, these progress across or expand over the corals surface consuming the living tissue and leaving the stark white coral skeleton in their wake. Other diseases, such as rapid wasting, white-band, white-plague and white-pox, often cause large patches of living coral tissue to slough off, exposing the skeleton beneath. Once exposed, the corals limestone skeleton can be a fertile breeding ground for algae and encrusting invertebrates. The colonization and overgrowth of the exposed coral skeleton by foreign organisms often results in the health of the entire colony taking a downward spiral from which it seldom recovers. |
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