Stable isotopes used to assess pollution impacts on coastal and marine ecosystems of Cuba and México: Stable isotopes on coastal and marine ecosystems of Cuba and México

Stable isotopes of nitrogen (δ¹⁵N) have been widely used around the world to evaluate the impact of anthropogenic activities on marine ecosystems; however, in the Caribbean Sea countries, such as México and Cuba, they are rarely used. Inputs of nutrients related to urban development and tourist activities along the coasts of the Caribbean Sea have the potential to deteriorate their fragile marine ecosystems. The use of isotopic tools and elemental analysis in sentinel organisms would be useful to provide evidence of the impact generated by anthropogenic nutrients. Measurements of δ¹⁵N (‰), carbon and nitrogen content, and C:N ratios, were conducted in different sentinel groups (macroalgae, seagrasses, gorgonians, and corals) collected in five marine ecosystems with different nearby coastal development pressure in both countries. The selected ecosystems, ordered according to the level of coastal areas development (low to high), were: Jardines de la Reina (JR), Gulf of Ana Maria (GAM), Cayo Coco (CC), and Laguna Larga (LL) in Cuba, and Puerto Morelos (PM) in México. Results evidenced that the majority of sentinels inhabiting near the most developed coastal areas, in terms of population and tourism, showed higher N contents, lower C:N ratios and higher values of δ¹⁵N (e.g., PM and LL) than those near less developed coastal ecosystems (e.g., GAM and JR). Land-based nutrients from municipal wastewater constitute the primary source of N pollution. Because eutrophication represents a significant threat to the integrity of valuable coastal ecosystems, there is an urgent need to accelerate progress in wastewater treatment systems, in terms of capacity and efficiency, to significantly reduce nutrient inputs to coastal ecosystems. Otherwise, more negative changes and deteriorations to the health of coastal ecosystems, including coral reefs, are expected along the Mexican Caribbean and numerous key points of Cuba and other Caribbean countries.