When it comes to the investigation of key ecosystems in the world, we often omit salt from the ecological recipe. In fact, despite occupying almost half of the volume of inland waters and providing crucial services to humanity and nature, inland saline ecosystems are often overlooked in discussions regarding the preservation of global aquatic resources of our planet. As a result, our knowledge of the biological and geochemical dynamics shaping these environments remains incomplete and we are hesitant in framing effective protective strategies against the increasing natural and anthropogenic threats faced by such habitats. Hypersaline lakes, water bodies where the concentration of salt exceeds 35 g/l, occur mainly in arid and semiarid areas resulting from hydrological imbalances triggering the accumulation of salts over time. Often considered the ‘exotic siblings’ within the family of inland waters, these ecosystems host some of the most extremophile communities worldwide and provide essential habitats for waterbirds and many other organisms in already water-stressed regions. These systems are often highlighted as natural laboratories, ideal for addressing central ecological questions due to their relatively low complexity and simple food web structures. However, recent studies on the biogeochemical mechanisms framing hypersaline communities have challenged this archetype, arguing that newly discovered highly diverse communities are characterised by specific trophic interactions shaped by high levels of specialisation. The main goal of this review is to explore our current understanding of the ecological dynamics of hypersaline ecosystems by addressing four main research questions: (i) why are hypersaline lakes unique from a biological and geochemical perspective; (ii) which biota inhabit these ecosystems and how have they adapted to the high salt conditions; (iii) how do we protect biodiversity from increasing natural and anthropogenic threats; and (iv) which scientific tools will help us preserve hypersaline ecosystems in the future? First, we focus on the ecological characterisation of hypersaline ecosystems, illustrate hydrogeochemical dynamics regulating such environments, and outline key ecoregions supporting hypersaline systems across the globe. Second, we depict the diversity and functional aspects of key taxa found in hypersaline lakes, from microorganisms to plants, invertebrates, waterbirds and upper trophic levels. Next, we describe ecosystem services and discuss possible conservation guidelines. Finally, we outline how cutting-edge technologies can provide new insights into the study of hypersaline ecology. Overall, this review sheds further light onto these understudied ecosystems, largely unrecognised as important sources of unique biological and functional diversity. We provide perspectives for key future research avenues, and advocate that the conservation of hypersaline lakes should not be taken with ‘a grain of salt’.

中文翻译：

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盐保存：对高盐生态系统的生态学和保护的回顾

当谈到对世界主要生态系统的调查时，我们经常会从生态配方中省略盐。事实上，尽管占据了近一半的内陆水域并为人类和自然提供了至关重要的服务，但在有关保护我们星球的全球水生资源的讨论中，内陆盐碱生态系统经常被忽视。因此，我们对塑造这些环境的生物和地球化学动力学的了解仍然不完整，我们在制定有效的保护策略以应对这些栖息地面临的日益增加的自然和人为威胁时犹豫不决。盐分浓度超过 35 g/l 的水体超咸水湖主要出现在干旱和半干旱地区，这是由于水文失衡导致盐分随时间积累而造成的。这些生态系统通常被认为是内陆水域家族中的“外来兄弟姐妹”，拥有世界上一些最极端的社区，并为已经缺水的地区的水鸟和许多其他生物提供了必要的栖息地。这些系统通常被强调为自然实验室，由于其相对较低的复杂性和简单的食物网结构，非常适合解决核心生态问题。然而，最近关于构建高盐群落的生物地球化学机制的研究对这一原型提出了挑战，认为新发现的高度多样化群落的特点是由高度专业化形成的特定营养相互作用。i ) 为什么从生物和地球化学的角度来看，高盐湖是独一无二的；( ii ) 哪些生物群栖息在这些生态系统中，它们如何适应高盐条件；( iii ) 我们如何保护生物多样性免受日益增加的自然和人为威胁；和（四) 哪些科学工具将帮助我们在未来保护高盐生态系统？首先，我们关注高盐生态系统的生态特征，说明调节此类环境的水文地球化学动力学，并概述支持全球高盐系统的关键生态区。其次，我们描述了在高盐湖中发现的关键类群的多样性和功能方面，从微生物到植物、无脊椎动物、水鸟和上层营养级。接下来，我们描述生态系统服务并讨论可能的保护指南。最后，我们概述了尖端技术如何为高盐生态研究提供新的见解。总体而言，这篇综述进一步揭示了这些未被充分研究的生态系统，这些生态系统在很大程度上未被视为独特生物和功能多样性的重要来源。