ABSTRACT

Lacustrine environments from Northern Patagonia are exposed to volcanic events from the Southern Volcanic Zone. Chironomid larvae are an important paleo-proxy because, in addition to their environmental sensitivity, their chitinous cephalic capsules are well preserved in lacustrine sediments, allowing their recovery and identification. We analysed the effects of a recent volcanic eruption (Puyehue-Cordón Caulle Volcanic Complex 2011) on the chironomid community based on their cephalic remains accumulated following the ash deposition process. Two pulses of ash deposition were distinguished: a first stage comprising the immediate coarse ash fall and a delayed finer volcanic deposition. An abrupt decline in chironomid taxa and their densities were noted during the first coarse pulse, followed by an attempt of community recovery through the second finer pulse, characterised by main taxa turnover, observing an alternative community functional structure. Based on these results and comparing with past volcanic depositions, we observed different chironomid responses according to their particular ecological habits, and we noted possible percolation effects, mainly in coarse tephras, and probably a delayed record of very low abundance taxa. Our results suggest caution in analysing chironomid assemblages within and adjacent to tephra deposition as local volcanic eruption could affect chironomid community with possible consequences on paleoreconstructions.

摘要

巴塔哥尼亚北部的湖泊环境受到南部火山带火山活动的影响。摇蚊幼虫是一个重要的古代生物，因为除了它们对环境的敏感性之外，它们的几丁质头囊在湖相沉积物中保存完好，使得它们能够被回收和识别。我们根据火山灰沉积过程中积累的头颅遗骸，分析了最近的一次火山喷发（2011 年 Puyehue-Cordón Caulle 火山群）对摇蚊群落的影响。火山灰沉积有两个脉冲：第一阶段包括立即的粗灰沉积和延迟的较细的火山沉积。在第一个粗脉冲期间，注意到摇蚊类群及其密度突然下降，随后尝试通过第二次更精细的脉冲来恢复群落，其特征是主要类群更替，观察替代的群落功能结构。基于这些结果并与过去的火山沉积进行比较，我们根据其特定的生态习性观察到了不同的摇蚊响应，并且我们注意到可能的渗滤效应，主要是在粗粒火山灰中，并且可能是非常低丰度类群的延迟记录。我们的结果表明，在分析火山灰沉积内部和附近的摇蚊组合时要谨慎，因为当地火山喷发可能会影响摇蚊群落，并可能对古矿石构造产生影响。我们根据其特定的生态习性观察到了不同的摇蚊响应，并且我们注意到可能的渗透效应，主要是在粗粒土中，并且可能是非常低丰度类群的延迟记录。我们的结果表明，在分析火山灰沉积内部和附近的摇蚊组合时要谨慎，因为当地火山喷发可能会影响摇蚊群落，并可能对古矿石构造产生影响。我们根据其特定的生态习性观察到了不同的摇蚊响应，并且我们注意到可能的渗透效应，主要是在粗粒土中，并且可能是非常低丰度类群的延迟记录。我们的结果表明，在分析火山灰沉积内部和附近的摇蚊组合时要谨慎，因为当地火山喷发可能会影响摇蚊群落，并可能对古矿石构造产生影响。