Parth Shah, Ankit Yadav, Rigterink Sonja, Mazzini Ilaria, Russell James, Anoop Ambili, Waldmann Nicolas
Dr. Moses Strauss Department of Marine Geosciences, Charney School of Marine Sciences, University of Haifa, 3498838 Haifa, Israel.
Department Physical Geography, Faculty of Geoscience and Geography, Georg-August University Göttingen, Germany; Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Sector-81, Mohali, Punjab 140306, India.
Sci Total Environ. 2023 Nov 25;901:165835. doi: 10.1016/j.scitotenv.2023.165835. Epub 2023 Jul 28.
Lake systems respond physically, chemically, and biologically to hydro-climatic change and variability, and these responses are documented in the sediments. Individual proxies and lacustrine environments may respond to climate variations in a nonlinear way, making it difficult to determine the direction and extent of a climatic shift. Here we investigate the response of lake ecosystem to climatic and environmental changes using a suite of paleo-proxies including ostracods, chironomids, and n-alkanes distribution from paleolake 'Gayal el Bazal (Yemen)'. A previous study from this site has provided a continuous, and high-resolution dataset providing an understanding of precipitation during the last ca 1200 years, particularly during Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). However, the response of the lake ecosystem to these changing hydro-climate conditions, including water-level, salinity, and productivity, remains unknown. The n-alkanes dataset shows that during pluvial interval such as the MCA, the lake experienced an increase in nutrient input resulting in enhanced aquatic productivity. Concurrently, ostracods assemblage displays an increased abundance of swimmer species (like Bradleytriebella lineata and Fabaeomiscandona cf. breuili), suggesting an indirect response between ostracods and climate shifts. The chironomid community during the MCA interval is dominated by taxa belonging to the subfamilies of Chironomini, suggesting a warm, shallow, productive environment with macrophyte vegetation. The LIA interval is marked by increased abundance of higher-chain length n-alkanes, suggesting increased contribution from higher plants. Furthermore, ostracod distribution revealed increased abundance of non-swimmer species like Vestalenula cylindrica., which thrive under saline conditions in the lake. Changes in abundances of Tanytarsini during the LIA interval, which are associated with higher oxygen levels, suggest changes in lake productivity. As a result, the overall patterns in biological indicators reveal that their individual abundance and species/tribe distribution fluctuates in response to changes in the climate and hydrological conditions.
湖泊系统会在物理、化学和生物方面对水文气候变化及变率做出响应，而这些响应记录在沉积物中。单个代理指标和湖泊环境可能以非线性方式对气候变化做出响应，这使得确定气候转变的方向和程度变得困难。在此，我们利用一套古代理指标，包括来自古湖“盖亚勒·巴扎勒（也门）”的介形虫、摇蚊和正构烷烃分布，来研究湖泊生态系统对气候和环境变化的响应。此前对该地点的一项研究提供了一个连续的高分辨率数据集，有助于了解过去约1200年的降水情况，尤其是中世纪气候异常（MCA）和小冰期（LIA）期间的降水情况。然而，湖泊生态系统对这些不断变化的水文气候条件（包括水位、盐度和生产力）的响应仍不为人知。正构烷烃数据集表明，在诸如MCA这样的多雨期，湖泊经历了营养输入增加，导致水生生产力增强。同时，介形虫组合显示游泳物种（如细纹布拉德利介和布雷乌利法贝奥小玻璃介）的丰度增加，这表明介形虫与气候转变之间存在间接响应。MCA期间的摇蚊群落以摇蚊亚科的分类群为主，表明是一个有大型植物植被的温暖、浅水、高产环境。小冰期以较高链长正构烷烃丰度增加为特征，表明高等植物的贡献增加。此外，介形虫分布显示非游泳物种如柱状韦斯塔勒介的丰度增加，这些物种在湖泊的咸水条件下茁壮成长。小冰期期间与较高氧水平相关的坦塔西尼摇蚊丰度变化表明湖泊生产力发生了变化。因此，生物指标的总体模式表明，它们的个体丰度以及物种/类群分布会随着气候和水文条件的变化而波动。
