Populations of the shallow-water Caribbean elkhorn coral, Acropora palmata, are being decimated by white pox disease, with losses of living cover in the Florida Keys typically in excess of 70%. The rate of tissue loss is rapid, averaging 2.5 cm 2 ⅐day ؊1 , and is greatest during periods of seasonally elevated temperature. In Florida, the spread of white pox fits the contagion model, with nearest neighbors most susceptible to infection. In this report, we identify a common fecal enterobacterium, Serratia marcescens, as the causal agent of white pox. This is the first time, to our knowledge, that a bacterial species associated with the human gut has been shown to be a marine invertebrate pathogen.

Black-band disease affects many species of tropical reef-building corals, but it is unclear what factors contribute to the disease-susceptibility of individual corals or how the disease is transmitted between colonies. Studies have suggested that the ability of black-band disease to infect coral is enhanced by different stressors. We examined the effect of both water temperature and mechanical injury on the ability of this disease to infect the reef coral Montastraea faveolata, and investigated the possibility of an interaction between the 2 stressors. Under laboratory conditions, Phormidium corallyticum was able to successfully invade all injured fragments but no uninjured fragments of M. faveolata, irrespective of temperature regime. We also determined whether the local coral-feeding butterflyfish Chaetodon capistratus was involved in the inter-colony transfer of black-band disease. In aquaria, the presence of C. capistratus increased the rate at which the disease spread from infected to non-infected fragments of M. faveolata. Both corals that were protected from and those that were exposed to fish predation contracted the disease. Hence, either direct oral transmission of the pathogen from colony to colony and/or indirect fecal transmission could be occurring. Variables such as potential stressors and/or disease vectors on a reef could contribute to the patterns of blackband disease observed in the field.

No abstract