Link between sewage-derived nitrogen pollution and coral disease severity in Guam

The goals of this study were to evaluate the contribution of sewage-derived N to reef flat communities in Guam and to assess the impact of N inputs on coral disease. We used stable isotope analysis of macroalgae and a soft coral, sampled bimonthly, as a proxy for N dynamics, and surveyed Porites spp., a dominant coral taxon on Guam's reefs, for white syndrome disease severity. Results showed a strong influence of sewage-derived N in nearshore waters, with delta N-15 values varying as a function of species sampled, site, and sampling date. Increases in sewage-derived N correlated significantly with increases in the severity of disease among Porites spp., with delta N-15 values accounting for more than 48% of the variation in changes in disease severity. The anticipated military realignment and related population increase in Guam are expected to lead to increased white syndrome infections and other coral diseases. (C) 2013 Elsevier Ltd. All rights reserved.