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<p>Concentration and flux of nitrogen in mangrove wetlands and coral reefs are modified by chemical and hydrodynamic mechanisms determined by natural and anthropic factors. Nearby anthropic activities impact ecosystems making them vulnerable, mainly due to nutrient flow increase which modifies biogeochemical cycles and trophic dynamics. Here, spatial-temporal variability of N in three tropical coastal ecosystems under different levels of anthropic pressure were studied; 1) trophic dynamics of mangroves in the Colombian Pacific using stable isotopes (δ<span><sup>13</sup></span>C, δ<span><sup>15</sup></span>N); 2) quantification of δ<span><sup>15</sup></span>N in octocorals from the northwestern region of Cuba as an indicator of wastewater pollution, and 3) determination of the trophic status of coastal and continental sites in the Mexican Caribbean using Karidy’s index and CE-CCA-001-89. In the mangrove food web, a value of 5 ‰ for δ<span><sup>15</sup></span>N was found, principally in systems with modified trophic structures close to tourist and urban centers. In octocorals, δ<span><sup>15</sup></span>N was significantly higher in reefs close to polluted river basins, evidencing a positive and significant correlation with the concentration of fecal and total coliforms, fecal streptococci, heterotrophic and sulfate-reducing bacteria. The nutrients analyzed in the Mexican Caribbean, exceeded the permissible limit for the protection of marine life, with Karidy’s index suggesting in some sites concentrations of nitrates in a mesotrophic and eutrophic state, principally during the months of highest tourist influx. The results confirm the effect and vulnerability of these ecosystems towards anthropic N, which could result in a reduction of ecosystem services and diversity.</p>

The Sunbittern (Eurypyga helias), despite having a wide distribution, is poorly studied and with few records in its area of distribution. Updating the distributions of species allows us to understand distributional patterns which are useful in ecology and conservation, especially for rare or threatened species. Given this situation for E. helias and the new records outside its historical range, here we present its updated distribution and a new record in the south of the Middle Magdalena Valley in Colombia. Using occurrences with preserved specimens and photographic records we build an Ecological Niche Model using the algorithm implemented in MaxEnt. The new record was found in the municipality of La Belleza, Santander in northern Colombia. Its range extends approximately 200 km south of its historical distribution. In Venezuela, it could reach the northern part near the foothills of the Cordilleras Central and Oriental. In Bolivia to the south over the Chiquitano Forest. In Central America, it extends to the lowlands near the Cordillera Central and the Cordillera Volcánica Central, and in North America to southern Mexico. The model suggests that tropical lowlands are more suitable for the species than cold temperate zones, also, the Middle Magdalena Valley is a suitable area, however, the species prefers forested and preserved areas. Some distribution patterns could be explained by different biogeographical barriers, but phylogeographical analyzes are needed to test this hypothesis.