Around 100 Mt of phosphogypsum (PG) have been deposited in large stacks on the salt marshes of the Tinto River estuary in Huelva (SW Spain), covering about 1000 ha. These stacks contain extremely acidic water (pH < 2) with high concentrations of pollutants which can cause emissions into their surroundings, generating important environmental concerns. Despite many chemical, geological or hydrological studies have been conducted to characterize the PG stacks of Huelva, the microbial community inhabiting this extreme environment remains unexplored. Using a 16S/18S-rRNA-high throughput sequencing approach, we have uncovered the main taxonomic groups able to live in the acidic metal-contaminated water, which is in direct contact with the PG, demonstrating for the first time the existence of a huge diversity of microbial species in these extreme conditions. In addition, the physicochemical characteristics of the water sampled have been analyzed. These studies have revealed that the most abundant bacteria found in two different leachate samples of the PG stacks belong to the genera Acidiphilium, Pseudomonas, Leptosprillum, Acidithrix, or Acidithiobacillus, typically found in acid mine drainage (AMD) environments, which in total represent around 50% of the total bacterial community. Biodiversity of eukaryotes in PG water is lower than that of prokaryotes, especially in the water collected from the perimeter channel that surrounds the PG stacks, where the pH reaches a value of 1.5 and the activity concentrations exceed 300 Bq L⁻¹ for ²³⁸U or 20 Bq L⁻¹ for ²¹⁰Po, values which are from four to five orders of magnitude higher than those usually found in unperturbed surface waters. Even so, an unexpected diversity of algae, fungi, and ciliates have been found in the PG stacks of Huelva, where chlorophyte microalgae and basidiomycetes fungi are the most abundant eukaryotes. Additional bioinformatics tools have been used to perform a functional analysis and predict the most common metabolic pathways in the PG microbiota. The obtained data indicate that the extreme conditions of these PG stacks hide an unexpected microbial diversity, which can play an important role in the dynamics of the contaminating compounds of the PG and provide new strains with unique biotechnological applications.

大约 100 公吨磷石膏 (PG) 堆积在韦尔瓦（西班牙西南部）廷托河河口的盐沼上，占地约 1000 公顷。这些烟囱含有极酸性的水（pH < 2），含有高浓度的污染物，会导致排放到周围环境中，从而产生重要的环境问题。尽管已经进行了许多化学、地质或水文研究来表征韦尔瓦的 PG 堆，但居住在这种极端环境中的微生物群落仍未被探索。使用 16S/18S-rRNA 高通量测序方法，我们发现了能够生活在与 PG 直接接触的酸性金属污染水中的主要分类群，首次证明在这些极端条件下存在巨大多样性的微生物物种。此外，还对水样的理化特性进行了分析。这些研究表明，在 PG 堆的两个不同渗滤液样品中发现的最丰富的细菌属于该属 嗜酸菌属、假单胞菌属、钩端螺旋菌属、嗜酸菌属或酸性硫杆菌属，通常存在于酸性矿山排水 (AMD) 环境中，它们总共占总细菌群落的 50% 左右。PG 水中真核生物的生物多样性低于原核生物，特别是在从围绕 PG 堆的周边通道收集的水中，其中 pH 值达到 1.5 并且活性浓度超过 300 Bq L ^-1对于²³⁸ U 或20 Bq L ^-1为²¹⁰Po，值比通常在未受干扰的地表水中发现的值高 4 到 5 个数量级。即便如此，在韦尔瓦的 PG 堆中发现了意想不到的藻类、真菌和纤毛虫多样性，其中叶绿体微藻和担子菌是最丰富的真核生物。其他生物信息学工具已用于执行功能分析并预测 PG 微生物群中最常见的代谢途径。获得的数据表明，这些 PG 堆栈的极端条件隐藏了意想不到的微生物多样性，这可以在 PG 污染化合物的动力学中发挥重要作用，并提供具有独特生物技术应用的新菌株。