This study investigated two mining lakes located in the north of Lower Austria. These lakes arose 45 years ago when open cast lignite mining ceased. The lakes are separated by a 7-m wide dam. Due to the oxidation of pyrite, both lakes have been acidified and exhibit iron, sulphate, and heavy metal concentrations several orders of magnitude higher than in circumneutral lakes. The water column of both lakes is divided into two layers by a pronounced chemocline. The smaller mining lake (AML), with pH close to of 2.6, is the most acidic lake in Austria, whereas flooding with stream water and by drainage from the surrounding fields neutralized the adjacent larger pit lake. The goal of our study was to investigate the effect of flooding on its physical, chemical and biological properties, in comparison to the pristine AML. Even relative to other extremely acidic lakes, the flora and fauna in the AML was reduced and composed of only two flagellate, one ciliate, and one rotifer species. The simplified pelagic food web in the mixolimnion consisted of heterotrophic bacteria, the mixotrophic flagellates Chlamydomonas acidophila and Ochromonas sp., the ciliate Oxytricha sp., and the rotifer Cephalodella sp. The latter two are as yet undescribed new species. The heliozoan Actinophrys sp. that may act as top predator occurred only in low abundance. The euglenid Lepocinclis buetschlii formed a stable deep chlorophyll maximum (DCM) at 7 m depth. Highest cell numbers of L. buetschlii in the DCM exceeded 108 L−1. The neutralized mining lake harboured higher plankton diversity similar to that of natural circumneutral lakes. A peak of at least 16 different phytoplankton taxa was observed during summer. The zooplankton consisted of several copepod species, daphnids and other cladocerans, and at least six different rotifer species. Several fish species occurred in the neutralized lake. Although the effect of non-permanent flooding was largely sustainable, interannual fluctuations of the pH affected the plankton community and reduced its species diversity.

中文翻译：

---

与中和的采矿湖相比，奥地利酸化程度最高的湖泊

本研究调查了位于下奥地利北部的两个采矿湖。这些湖泊形成于 45 年前，当时露天褐煤开采停止。湖泊被一个 7 米宽的大坝隔开。由于黄铁矿的氧化，两个湖泊都被酸化，铁、硫酸盐和重金属的浓度比中性湖泊高几个数量级。两个湖泊的水柱被明显的趋化层分成两层。较小的采矿湖 (AML) 的 pH 值接近 2.6，是奥地利酸性最强的湖泊，而河水泛滥和周围田地的排水中和了相邻的较大坑湖。与原始 AML 相比，我们研究的目的是调查洪水对其物理、化学和生物特性的影响。即使相对于其他极端酸性的湖泊，AML 中的动植物群也减少了，仅由两种鞭毛虫、一种纤毛虫和一种轮虫物种组成。mixolimnion 中简化的远洋食物网由异养细菌、混合营养鞭毛虫 Chlamydomonas acidophila 和 Ochromonas sp.、纤毛虫 Oxytricha sp. 和轮虫 Cephalodella sp. 组成。后两个是尚未描述的新物种。日光动物 Actinophrys sp。可能作为顶级捕食者的那只发生在低丰度的情况下。Euglenid Lepocinclis buetschlii 在 7 m 深度形成了稳定的深叶绿素最大值 (DCM)。DCM 中布氏乳杆菌的最高细胞数超过 108 L-1。中和的采矿湖具有更高的浮游生物多样性，类似于天然的环中性湖泊。在夏季观察到了至少 16 种不同浮游植物分类群的峰值。浮游动物包括几种桡足类、水蚤和其他枝角类动物，以及至少六种不同的轮虫。在中和的湖中出现了几种鱼类。尽管非永久性洪水的影响在很大程度上是可持续的，但 pH 值的年际波动影响了浮游生物群落并降低了其物种多样性。