Coral Disease

by Bernardo Vargas-Angel

A notable increase in coral disease is one of the most recent concerns pertaining to the resilience of coral reefs worldwide, particularly in light of mounting natural and anthropogenic impacts. Acute diseases have resulted in dramatic coral loss and significant changes in community structure, diversity, and ecosystem function. For example, Acropora white band disease has been recognized as one of the major factors leading to live coral cover reductions of up to 98% in areas of the Florida Keys and the Caribbean.  This loss of coral cover and associated phase-shifts in coral community structure has led to an increase in macroalgae cover and reduced rates of coral reef accretion.

For many years, the threat of coral diseases in the Pacific had been regarded as relatively unimportant based on limited impact sources, inaccessibility, and the spatial vastness of the region. However, increasing evidence indicates an escalating abundance and prevalence of disease throughout Pacific locations, including the Great Barrier Reef, the Marshall Islands, Palau, and the Philippines, as well as the Red Sea and east Africa. The 2002/2003 outbreak of white syndrome in the northern and southern sectors of the Great Barrier Reef, when disease levels increased 20- to 150-fold on outer-shelf reefs, was cause for great concern.

For most coral diseases, the lack of ecological and pathological data hinders a clear understanding of disease causation, virulence, and transmissibility. Moreover, the association between disease and environmental stress still remains largely unknown. Current research supports a connection between environmental deterioration and diminished coral immune capacity, and thus, environmental stress could influence coral disease by altering host/pathogen interactions. Because coral diseases may act synergistically with other stressors, there is reason to believe that management practices may be able to, at least in part, influence the impact of disease.

During this expedition, coral biologists are surveying for coral disease along twenty five meter transects and comparing the results to data from previous years and other areas of the pacific.  Data collected by the scientific crew are pivotal to long-term biological and oceanographic monitoring of U.S Pacific coral reef ecosystems, including the assessment and evaluation for coral diseases.