The δ¹⁵N in Orbicella faveolata organic matter reveals anthropogenic impact by sewage inputs in a Mexican Caribbean coral reef lagoon

Coral-reef ecosystems provide essentials services to human societies, representing the most important source of income (e.g., tourism and artisanal fishing) for many coastal developing countries. In the Caribbean region, most touristic and coastal developments are in the vicinity of coral reefs where they may contribute to reef degradation. Here we evaluated the influence of sewage inputs in the coral reef lagoon of Puerto Morelos during a period of 40 years (1970-2012). Annual δ15N values were determined in the organic matter (OM) extracted from coral skeletons of Orbicella faveolata. Average protein content in the OM was 0.33 mg of protein g-1 CaCO3 (±0.10 SD) and a 0.03% of OM relative to the sample weight (n =100). The average of N g-1 CaCO3 was 0.002% (± 0.001 SD). The results showed an increase (p < 0.001) in δ15N over the time, positively correlated with population growth derived from touristic development. These findings emphasize the need to generate urban-planning remediation strategies that consider the impact on natural environments, reduce sewage pollution, and mitigate local stressors that threaten the status of coral-reef communities in the Caribbean region.