Abstract Heavy metals (HMs) enter the marine environment through a variety of sources, especially in areas such as submarine canyons acting as conduits for terrigenous pollutants to the deep sea. HMs exert toxic effects at different levels of biological organization, yet several marine microbes have the capacity to tolerate HMs. However, the relationships between microbes, their tolerance mechanisms and the concentration of HMs in the marine environment are poorly investigated. We evaluated the occurrence and distribution of HMs and culturable HM-resistant microorganisms in sediments collected in two submarine canyons and the adjacent slope in the NE Ligurian margin (Mediterranean Sea), down to 2000 m depth, and explored the role of contaminants in modulating community adaptation to metals. HM concentrations exhibited wide spatial variability across the whole study area, without showing significant differences between canyon and open slope environments, exception made for higher Cd concentrations recorded in one canyon. Benthic microbial abundance was negatively correlated with Cd concentration, while viable counts of HM-resistant microorganisms indicated tolerance of HMs in the order Zn2+ > Cu2+ > Hg2+ > Cd2+. Differences in the tolerance patterns were observed among sampling stations, with microbial communities generally tolerating up to three HMs. Cd2+ was the less tolerated metal, with microbial growth in the presence of this metal observed only for 50 ppm, and only at five of the eleven sampled stations. Our results show the existence of complex multitolerance patterns in deepsea sediments subjected to anthropogenic influence, suggesting that microbial HM tolerance develops under different ways and mechanisms that have to be elicited. Also, they highlight the opportunity for further exploitation of the potential of HM-resistant deep sea microbes for the remediation of contaminated marine areas, or for their use as bioindicators of human impact down to the deep sea.

中文翻译：

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利古里亚东北缘（西地中海）海底峡谷及邻近大陆坡沉积物中重金属抗性微生物

摘要 重金属（HMs）通过多种来源进入海洋环境，特别是在海底峡谷等区域，作为陆源污染物进入深海的通道。HMs 在不同层次的生物组织中发挥毒性作用，但一些海洋微生物具有耐受 HMs 的能力。然而，微生物、它们的耐受机制和海洋环境中 HMs 浓度之间的关系研究得很少。我们评估了 HMs 和可培养的 HM 抗性微生物在 NE 利古里亚边缘（地中海）的两个海底峡谷和相邻斜坡收集的沉积物中的发生和分布，深达 2000 米，并探讨了污染物在调节群落中的作用对金属的适应。HM 浓度在整个研究区域表现出广泛的空间变异性，在峡谷和开阔斜坡环境之间没有显示出显着差异，但在一个峡谷中记录的更高 Cd 浓度是例外。底栖微生物丰度与 Cd 浓度呈负相关，而 HM 抗性微生物的活计数表明 HMs 耐受性的顺序为 Zn2+ > Cu2+ > Hg2+ > Cd2+。在采样站之间观察到耐受模式的差异，微生物群落通常耐受多达三种 HM。Cd2+ 是耐受性较差的金属，在这种金属存在下仅观察到 50 ppm 的微生物生长，并且仅在 11 个采样站中的 5 个站观察到。我们的研究结果表明，在受到人为影响的深海沉积物中存在复杂的多耐受模式，这表明微生物对 HM 的耐受性是在不同的方式和机制下发展起来的。此外，它们强调了进一步开发抗重金属深海微生物的潜力以修复受污染海洋区域或将其用作人类对深海影响的生物指标的机会。