Tab. 3: Concentrations of selected chemical species at various depths in Ace Lake

This article reviews the history, chemical stratification, biology and biogeochemistry of Ace Lake, which is one of the many marine-derived meromictic (permanently stratified) lakes in the Vestfold Hills, Eastern Antarctica. The lake has an area of 18 ha, a maximum depth of 25 m, and a salinity range from 7 to 43 g l**-1. The lake mixes to a depth of 7 m in late winter as a result of brine freeze out during ice formation. Deeper mixing is precluded by a sharp halocline. The water beneath 12 m is permanently anoxic, The lake was formed approximately 10,800 yr BP as the polar ice cap melted. Sea level rise 7,800 yr BP resulted in invasion of seawater into the initially freshwater lake. Subsequently, sea level dropped, and the now saline lake became isolated from the ocean. The biota of the lake was derived from species trapped when the connection between the lake and the ocean was cut off. The oxic zone above 12 m supports a relatively simple community which includes microbial mats, four major species of phytoplankton (including a picocyanobacterium), two copepod species, and a variety of heterotrophic flagellates and ciliates. The anoxic zone contains populations of photosynthetic sulfur, sulfate reducing, fermentative and methanogenic bacteria, which combine to remineralise organic carbon which sediments from the upper waters. Research on the physics, biology and chemistry of Ace Lake has contributed significantly to knowledge of Antarctic meromictic lakes.

本文综述了东南极洲维斯特福尔德丘陵区域众多海源meromictic湖（永久分层湖）之一的埃斯湖（Ace Lake）的演化历史、化学分层特征、生物学特性与生物地球化学过程。该湖面积达18公顷，最大水深25米，盐度范围为7~43 g·L⁻¹。受结冰过程中卤水析出的影响，该湖在晚冬时节会发生至7米水深的水体混合，而显著的盐跃层（halocline）则阻止了更深层的水体混合。12米水深以下的水体长期处于缺氧状态。该湖形成于约10800年前（BP）的极地冰盖消融时期。7800年前的海平面上升使得海水侵入了最初为淡水的湖中，此后海平面下降，这座已变为咸水的湖泊便与海洋彻底隔绝。该湖的生物区系源自湖海连通中断时被困在湖内的物种。12米以上的有氧区栖息着结构相对简单的生物群落，其中包括微生物垫、四种主要浮游植物（包含一种超微蓝细菌（picocyanobacterium））、两种桡足类，以及多种异养鞭毛虫与纤毛虫。缺氧区则栖息着光合硫细菌、硫酸盐还原菌、发酵菌与产甲烷菌种群，这些微生物共同作用，将上层水体沉降而来的有机碳进行再矿化。针对埃斯湖物理、生物与化学特性的研究，极大地丰富了学界对南极meromictic湖的认知。