A new study of coral diseases in Montastraea corals in the Caribbean and Gulf of Mexico contradicts the theory that diseases are related to marine pollution.
Previous studies have suggested that there is a greater prevalence of disease and mortality in corals which are found on reefs closest to sources of pollution. However, this new study suggests that something other than pollution may be to blame.
Eric Jordan-Dahlgren, Miguel Maldonado and Rosa Rodriguez-Martinez of Mexico's Insituto de Ciencias del Mar y Limnologia, studied diseases, syndromes and health problems in colonies of the hard coral Montastraea annularis on three reefs in the Caribbean and Gulf of Mexico over a period of several years.
The three reefs surveyed including one relatively undisturbed reef in unpolluted waters, one in an area polluted by industrial pollutants and one polluted by urban pollutants.
The study showed that corals on all three of the reefs had relatively high levels of the coral disease Yellow-band syndrome, as well as a high degree of partial mortality in which parts of the coral colony die back.
Other coral diseases, such as Black-band disease and White-plague disease, weren't very common, but the team did spot a new widespread disease which they've dubbed Thin-dark line syndrome.
Since the results show no direct link between coral disease and pollution, the authors believe that some other factors are responsible:
"Our results open the possibility that regional and/or global factors may already be playing an important role in the prevalence of coral disease in the Caribbean and contradict the theory that coral disease prevalence is primarily related to local environmental degradation.
"Reasons that may partially explain these findings are the high level of potential pathogen connectivity with the Caribbean as a result of its circulation patterns coupled to the large land-derived pollutants and pathogens input into this sea; together with the surface water warming effects which stress corals and enhance pathogen activity."
For more details see the paper: Jordan-Dahlgren, E., Maldonado, M. and R. Rodriguez-Martinez (2005) - Diseases and partial mortality in Montastraea annularis species complex reefs with differing environmental conditions (NW Caribbean and Gulf of Mexico). Diseases of Aquatic Organisms. Vol. 63. No. 1.