A global synthesis of the current knowledge on the taxonomic and geographic distribution of major coral diseases

Although knowledge on the diseases affecting corals has been accumulating exponentially since the 2000s, even more effort is required to summarize and guide further investigation. Here, we used the Web of Science database to review 226 studies published, between 2000 and 2020, to identify the major geographic and taxonomic gaps in the literature, and propose future directions for the study of coral diseases. We classified the studies according to the ocean, ecoregion, coral species, disease types, approach (e.g., observational or experimental), and depth. In total, 22 types of diseases were reported for 165 coral species. Acropora spp. was the most studied taxa with 12 types of diseases and 8.2% of the records. Black band, white plague, white syndromes, skeletal eroding, dark spot, and yellow band were the six most common diseases, accounting together for 76.8% of the records. As expected, most studies were conducted in the Caribbean and Indo-Pacific (34.0% and 28.7%, respectively), but only in 44 of the 141 global ecoregions that harbour corals. Observational approaches were the most frequent (75.6% of the records), while experimental approaches accounted for 19.9% and were mainly done on Acropora. The vast majority of studies (∼98%) were performed in shallow waters (<30 m depth). We conclude that over the past two decades, coral diseases have been assessed on a very small fraction of coral species, in very few locations around the globe, and at a limited range of their depth distribution. While monitoring bleaching is mandatory for reef ecology and conservation, the ecoepidemiology of coral diseases deserves more space in the research agenda of reef ecosystems.