The Southeast Asia and Melanesia region has extensive nickel (Ni)-rich lateritic regoliths formed from the tropical weathering of ultramafic rocks. As the global demand for Ni continues to rise, these lateritic regoliths are increasingly being exploited for their economic benefit. Mining of these regoliths contributes to the enrichment of coastal sediments in trace metals, especially Ni. The present study used high-throughput sequencing (metabarcoding) to determine changes in eukaryote (18s v7 recombinant DNA [rDNA] and diatom-specific subregion of the 18s v4 rDNA) and prokaryote (16s v4 rDNA) community compositions along a sediment Ni concentration gradient offshore from a large lateritized ultramafic regolith in New Caledonia (Vavouto Bay). Significant changes in the eukaryote, diatom, and prokaryote community compositions were found along the Ni concentration gradient. These changes correlated most with the dilute-acid extractable concentration of Ni in the sediments, which explained 26, 23, and 19% of the variation for eukaryote, diatom, and prokaryote community compositions, respectively. Univariate analyses showed that there was no consistent change in indices of biodiversity, evenness, or richness. Diatom richness and diversity did, however, decrease as sediment acid extractable-Ni concentrations increased. Threshold indicator taxa analysis was conducted separately for each of the 3 targeted genes to detect changes in taxa whose occurrences decreased or increased along the acid extractable-Ni concentration gradient. Based on these data, 46 mg acid extractable-Ni/kg was determined as a threshold value where sensitive species began to disappear. In the case of the estuarine sediments offshore from lateritized ultramafic regolith in New Caledonia, this is recommended as an interim threshold value until further lines of evidence can contribute to a region-specific Ni sediment quality guideline value. Environ Toxicol Chem 2021;40:1894–1907. © 2021 SETAC

中文翻译：

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元条形码揭示了沿热带海洋沉积物镍梯度的底栖真核生物和原核生物群落组成的变化

东南亚和美拉尼西亚地区有大量富含镍 (Ni) 的红土风化层，这些风化层由超镁铁质岩石的热带风化形成。随着全球对镍的需求持续增长，这些红土风化层正越来越多地被开发以获取经济利益。这些风化层的开采有助于沿海沉积物富集痕量金属，尤其是镍。本研究使用高通量测序（元条形码）来确定真核生物（18s v7 重组 DNA [rDNA] 和 18s v4 rDNA 的硅藻特异性亚区）和原核生物（16s v4 rDNA）群落组成沿沉积物 Ni 浓度梯度的变化从新喀里多尼亚（瓦武托湾）的一个大型红土化超镁铁质风化层离岸。真核生物、硅藻、沿Ni浓度梯度发现了原核生物群落组成。这些变化与沉积物中镍的稀酸可萃取浓度最相关，这分别解释了真核生物、硅藻和原核生物群落组成变化的 26%、23% 和 19%。单变量分析表明，生物多样性、均匀度或丰富度指数没有一致的变化。然而，随着沉积物酸可萃取镍浓度的增加，硅藻的丰富度和多样性确实降低了。对 3 个目标基因中的每一个分别进行阈值指示分类群分析，以检测其出现率随酸可提取镍浓度梯度减少或增加的分类群的变化。基于这些数据，46 mg 酸可提取物-Ni/kg 被确定为敏感物种开始消失的阈值。对于新喀里多尼亚红土化超镁铁质风化岩近海的河口沉积物，建议将其作为临时阈值，直到进一步的证据可以为特定区域的镍沉积物质量指导值做出贡献。环境毒物化学2021；40:1894–1907。© 2021 SETAC