Past responses of modern phytoplankton and subfossil diatoms to volcanism in an Andean lake (central Chile)

Laguna del Maule is a volcanic basin lake in the Central Chilean Andes that contains a peculiar and poorly understood algal flora from an ecological perspective. We present a comprehensive list of modern phytoplankton and limnological parameters (measured in 2011 and 2015), as well as a subfossil diatom assemblage spanning the past ∼700 years. We examined the relationship between the past assemblages and two Holocene tephra layers, pH, and the impact of recent warming. Chlorophyll values (1.3–1.8 µg l⁻¹) are indicative of an oligotrophic lake. Counts (past and modern specimens) totalled two hundred fifty-four taxa: Bacillariophyceae (239, mainly subfossil), Chlorophyta (4), Chrysophyta (3), Cryptophyta (3), Cyanophyta (3) and Dinophyta (2). Diatom groups included: twelve centric (the most abundant specimens) and two hundred twenty-seven pennate taxa; of the latter, thirty-three were araphid and one hundred and ninety-four were either monoraphid or biraphid. An increased richness was observed after deposition of the tephra layers, along with different diatom assemblages associated with each tephra. Alkaliphilous-circumneutral taxa dominated, in concordance with the alkaline basin conditions of Laguna del Maule. A recent megadrought brought a shift from planktic to benthic diatoms, as coastal areas expanded, fostering a higher diversity of biraphid genera. Records of past and present dynamics of Andean lacustrine microorganisms are necessary to further evaluate responses to critical global environmental change and for high-altitude aquatic ecosystem conservation efforts.

Laguna del Maule（毛勒湖）是智利中部安第斯山脉中的火山盆地湖泊，拥有一类从生态学视角来看颇为特殊且研究程度极低的藻类植物区系。本数据集提供了2011年与2015年测定的现代浮游植物完整名录及湖沼学参数，同时包含一段跨度约700年的亚化石硅藻组合记录。本研究分析了历史硅藻组合与两处全新世火山灰层、水体pH值之间的关联，以及近期气候变暖产生的影响。叶绿素含量（1.3–1.8 μg·L⁻¹）指示该湖泊为贫营养型水体。本次共计数得到254个分类单元的标本（涵盖历史与现代样本），其中包括硅藻门（Bacillariophyceae，239种，以亚化石为主）、绿藻门（Chlorophyta，4种）、金藻门（Chrysophyta，3种）、隐藻门（Cryptophyta，3种）、蓝藻门（Cyanophyta，3种）以及甲藻门（Dinophyta，2种）。硅藻类群可分为12种中心硅藻（为丰度最高的类群）与227种羽纹硅藻；其中33种为无壳缝类群，剩余194种均为单壳缝或双壳缝类群。火山灰层沉积后，硅藻物种丰富度显著提升，且每一处火山灰层均对应有独特的硅藻组合。喜碱-近中性类群占据优势，这与毛勒湖的碱性盆地环境特征相符。近期发生的特大干旱引发了硅藻群落从浮游型向底栖型的转变：随着沿岸区域扩张，双壳缝属类群的多样性也随之升高。安第斯山区湖泊微生物的历史与现代动态记录，可为进一步评估其对全球重大环境变化的响应，以及开展高海拔水生生态系统保护工作提供关键支撑。