Coral reefs are the most diverse marine ecosystems on the planet, and have been subject to considerable damage during last few decades (80% in the last 30 years). The dramatic decline of coral reefs is manly due to the emergence of infectious diseases, including yellow band, red band, black band, white band and white plague. The last three account for 60% of reported coral diseases in the Caribbean Sea. The etiology and physiopathology of coral diseases, however, remain poorly understood, because, the diagnosis has been based on limited and ambiguous signs, there is no reliable microbiological data, and there is a poor distinction of the microbiota associated with the disease. Recent evidence suggests that an imbalance in the structure of bacterial communities is an important factor determining the origin and progression of coral diseases. In this proposal we aim to design a diagnosis and monitoring DNA microarray tool for each of the three most prevalent coral diseases in the Caribbean of Colombia. This tool will detect characteristic patterns of diversity and abundance of bacterial populations that are associated to disease. This technology will provide a better interpretation of the dynamics of bacterial communities in coral diseases and might contribute to design strategies to manage and protect the vast biodiversity supported by coral reefs.