Variable prevalence of diseases and compromised health conditions on hard corals around Mauritius Island, Western Indian Ocean

Although coral diseases and compromised health conditions (CHCs) are one of the most prominent threats to coral reefs globally, they have yet to be thoroughly investigated in the Western Indian Ocean. This study aimed to assess the prevalence and spatial distribution of coral diseases and CHCs around Mauritius. Six coral diseases [Growth Anomaly (GA), Skeletal Eroding Band (SEB), Brown Band (BrBD), Porites White Patch Syndrome (PWPS), White Syndromes (WSs), and Yellow Band (YB)] and four CHCs [Pink Patches (PP), Pink Spots (PS), Pink Line Syndrome (PLS), and Focal Bleaching (FB)] were spatially variable in prevalence among the 17 studied sites. The average prevalence for Mauritius was 4.88% (SD 0.52%), almost half of what has been documented from Caribbean and Pacific reefs (about 10%). Total coral colony density (R = −0.585, P < 0.001) and diseases/CHCs-affected host density (R = −0.249, P > 0.05) were negatively correlated while human population density (R = 0.085, P < 0.05) and coral cover (R = 0.045, P < 0.05) were positively correlated with coral diseases/CHCs prevalence. The prevalence of diseases/CHCs significantly differed between the reef-flat and fore-reef zones, with the latter exhibiting higher prevalence. Cluster analyses revealed that PLS, YB, and FB were mostly distributed in the fore-reef zone, while the other diseases/CHCs were mostly predominant on the reef-flats. However, coral disease/CHCs prevalence did not differ significantly (F = 2.613, P > 0.05) between protected and nonprotected zones. These findings have important implications for informing appropriate coral reef conservation and management strategies for Mauritius.