The effects of anthropogenic pressures in coastal areas are extensively studied in temperate but not in tropical zones, where their impact might be amplified by high water temperatures and upwelling phenomena. Sedimentary features and benthic metabolism were studied during the non upwelling (NUPW) and upwelling (UPW) seasons in Taganga Bay (Colombia). The bay is impacted by a submarine outfall of virtually untreated, organic and nutrient-rich wastewater. Samplings were performed in November 2017 (NUPW) and in January–February 2018 (UPW) at 4 stations located in the proximity and 100, 750 and 1800 m far from the outfall, respectively, at depths between 22 and 28 m. Aerobic respiration, denitrification, dissimilative nitrate reduction to ammonium (DNRA) and nutrient fluxes were measured. The influence of the outfall was detectable 750 and 1800 m away from the point pollution source, where δ13C data suggested that ~ 40 and ~ 20% of organic inputs were terrigenous, respectively. In the proximity of the outfall benthic oxygen demand peaked and the presence of Beggiatoa mats suggested reoxidation of sulphides, that were abundant in pore water. Under sulfidic conditions, DNRA was the major driver of nitrate demand, whereas at stations far from the outfall, denitrification dominated nitrate consumption. Organic matter and nitrate inputs to the bay during the UPW season enhanced the effects of the outfall by increasing aerobic respiration and DNRA. Higher N availability during the UPW season reversed fluxes of molecular nitrogen and turned the sediments of 3 out of 4 sites from net sinks to net N2 sources. Results from this study suggest that the analysis of sediments allows tracing the impact of the outfall and that such impact is enhanced during the upwelling season. In tropical areas, marine outfalls and upwelling may act in synergy and contribute to ecosystem deterioration due to high temperatures, increase of microbial respiration, sulphide toxicity and benthic biodiversity loss.

中文翻译：

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受污水排放口影响的热带沿海地区（塔甘加湾，哥伦比亚加勒比）沉积特征和氮底栖代谢的空间和季节变化

沿海地区人为压力的影响在温带地区得到了广泛研究，但在热带地区却没有，因为高水温和上升流现象可能会放大它们的影响。在塔甘加湾（哥伦比亚）的非上升流 (NUPW) 和上升流 (UPW) 季节研究了沉积特征和底栖代谢。该海湾受到潜艇排放口的影响，该排放口排放出几乎未经处理的有机和营养丰富的废水。采样于 2017 年 11 月 (NUPW) 和 2018 年 1 月至 2 月 (UPW) 在位于附近和距排污口 100、750 和 1800 m 处的 4 个站点分别进行，深度在 22 和 28 m 之间。测量了有氧呼吸、反硝化、异化硝酸盐还原成铵 (DNRA) 和养分通量。在距点污染源 750 和 1800 m 处可检测到排放口的影响，其中 δ13C 数据表明，分别有~40% 和~20% 的有机输入是陆源的。在排污口附近，底栖需氧量达到峰值，并且 Beggiatoa 垫的存在表明孔隙水中丰富的硫化物发生了再氧化。在硫化条件下，DNRA 是硝酸盐需求的主要驱动力，而在远离排污口的站点，反硝化作用主导了硝酸盐的消耗。UPW 季节期间向海湾输入的有机物和硝酸盐通过增加有氧呼吸和 DNRA 增强了排放口的影响。UPW 季节更高的氮可用性逆转了分子氮的通量，并将 4 个地点中的 3 个地点的沉积物从净汇变为净 N2 源。这项研究的结果表明，对沉积物的分析可以追踪排放口的影响，而且这种影响在上升流季节会增强。在热带地区，海洋排放口和上升流可能协同作用，并因高温、微生物呼吸增加、硫化物毒性和底栖生物多样性丧失而导致生态系统恶化。