Chemical contamination of marine ecosystems represents a major concern for the detrimental consequences at different levels of biological organization. However, the impact of chronic contamination on the diversity and assemblage composition of benthic prokaryotes is still largely unknown, and this limits our understanding of the potential implications on ecosystem functioning. The Bagnoli-Coroglio bay (Gulf of Naples, Tyrrhenian Sea) is a typical example of coastal area heavily contaminated by metals and hydrocarbons, released for decades by industrial activities, which ceased at the beginning of nineties. In the present study we analyzed the abundance, diversity and assemblage composition of benthic prokaryotic assemblages at increasing distance from the historical source of contamination in relation to the heavy hydrocarbons (C > 12), polycyclic aromatic hydrocarbons (PAHs) and heavy metal concentrations in the sediments. Prokaryotic abundance in the sediments differed among sites, and was mostly driven by environmental factors rather than by contamination levels. Conversely, the richness of prokaryotic taxa was relatively high in all samples, was driven by contamination levels and decreased significantly with increasing contamination (15–38%). Moreover, our results indicate large variations in the composition of the benthic prokaryotic assemblages among sites, mostly explained by the different levels and types of chemical contaminants found in the sediments. Overall, our findings suggest that chemical contaminants, even after decades from the end of their release, can profoundly influence the richness and turnover diversity of the benthic prokaryotic assemblages, in turn promoting a high diversification of the benthic bacterial and archaeal assemblages by selecting those lineages more adapted to specific mixtures of different contaminants. Our results open new perspectives for understanding of the long-term effects of chemical contamination on the benthic prokaryotic assemblages and the ecological processes they mediate.

海洋生态系统的化学污染代表了对生物组织不同层面的有害后果的主要关注。然而，长期污染对底栖原核生物多样性和组成组成的影响仍然是未知之数，这限制了我们对生态系统功能潜在影响的理解。Bagnoli-Coroglio海湾（第勒尼安海那不勒斯海湾）是沿海地区典型的例子，该地区受到金属和碳氢化合物的严重污染，几十年来由于工业活动而释放出来，该活动在90年代初就停止了。在本研究中，我们分析了底栖原核生物组合物的丰度，多样性和组合物组成，与历史上较重的碳氢化合物相关的污染源距离越来越远（C> 12），沉积物中的多环芳烃（PAHs）和重金属浓度。沉积物中原核生物的丰度在不同地点之间有所不同，并且主要由环境因素而不是由污染水平驱动。相反，在所有样品中，原核生物分类的丰富度都相对较高，这是由污染水平驱动的，并且随着污染的增加而显着降低（15-38％）。此外，我们的研究结果表明，不同地点底栖生物原核组合物的组成存在很大差异，这主要是由于沉积物中发现的化学污染物的水平和类型不同所致。总体而言，我们的发现表明，即使从污染物释放开始已经过了几十年，化学污染物仍会深刻影响底栖原核生物种群的丰富度和周转多样性，通过选择更适合不同污染物的特定混合物的血统，进而促进底栖细菌和古细菌的高度多样化。我们的结果为了解化学污染对底栖原核生物群及其介导的生态过程的长期影响开辟了新的前景。