Current thinking on how the Toxoplasma gondii parasite invades its host is incorrect, according to a study published today in Nature Methods describing a new technique to knock out genes. The findings could have implications ...
Definition. Coral bleaching is a process whereby the coral colonies lose their colour, either due to the loss of pigments by microscopic algae (zooxanthellae) living in symbiosis with their host organisms (polyps), or because these zooxanthellae have been expelled.
Note the extreme bleaching in this Diploria at the Grotto, San Salvador, Bahamas. Coral Reef Bleaching. Coral reef bleaching occurs when corals undergo great stress. The symbiotic algae, zooxanthallae, is expelled or its photosynthetic pigments harmed--thus the coral appears white. The corals may be weakened to the point of death. A number of environmental factors, both natural and anthropogenic, can cause bleaching.