RAPID: Aquatic refuge and recovery in the face of drought in a biodiversity hotspot

大多数关于干旱对淡水生物影响的研究都集中在短暂的季节性干旱上，而非典型的严重干旱的影响还没有被很好地理解。美国东南部最近经历了至少10年来最极端的干旱。阿拉巴马州遭受的打击尤为严重，该州近98%的地区直接受到干旱条件的影响。2016年秋季降雨不足，许多河流变成涓涓细流，而其他河流已经完全干涸；主要河流的水位达到了60多年来未曾见过的水平。阿拉巴马州是鱼类、两栖动物和无脊椎动物等淡水物种的全球生物多样性热点。这些物种中的许多都受到威胁，濒临灭绝，和/或在地球上其他地方找不到。这项研究试图确定下游避难所在物种多样性较高的水生生态系统中对严重干旱影响的作用。具体目标是：1)确定应对严重干旱的物种组成的变化；2)确定为具有不同运动能力的物种提供关键避难所的栖息地；3)在地方和区域尺度上建立严重干旱的影响和未来恢复的预测模型。两名研究生和几名本科生将参与本研究的抽样和研究活动。这项研究将为确定和保护阿拉巴马州战略生境单位提供管理工具。这项研究还将为中学生提供夏令营，并与奥本大学自然历史博物馆合作组织公民科学团体的公共外展活动。研究将评估极端干旱对栖息地利用动态的影响，以及评估水生物种对突如其来的干旱的适应能力。研究人员假设，干旱期间利用下游避难所的能力是一个瓶颈，根据物种、迁移性和在河流网络中的位置而有所不同。将对经历了异常干旱的两个流域的溪流栖息地进行采样，并与自2012年以来收集的历史基线数据进行比较，以检验这一假设。这项研究将结合干旱前的调查和阿拉巴马州两个生态区不同大小溪流的环境DNA(EDNA)数据，以及基于功能特征数据库、生活史信息和专业判断的物种特定迁徙潜力，来预测溪流动物在应对闪旱时的分布格局变化。预测和观测的模式将使用精细调查、广泛的EDNA收集和空间分析进行比较。这项调查的结果将为了解特定类群和河流群落在全球多样性热点地区对干旱干扰的一般恢复能力提供关键信息。

Most studies of the effect of drought on freshwater organisms have focused on short, seasonal droughts, while the effects of atypical intense droughts are not well understood. The southeastern United States has recently experienced the most extreme drought in at least 10 years. Alabama has been particularly hard hit, with nearly 98% of the state being directly affected by drought conditions. The lack of rainfall during Fall 2016 reduced many streams to trickles while others have completely dried; major rivers reached low levels not seen in over 60 years. Alabama is known as a global biodiversity hotspot for freshwater species of fish, amphibians, and invertebrates. Many of these species are threatened, endangered, and/or found nowhere else on Earth. This study seeks to determine the role of downstream refuges on the effect of intense droughts in aquatic ecosystems with high species diversity. The specific objectives are to: 1) determine changes in species composition in response to intense drought, 2) Identify habitat offering critical refuge from the drought to species with different movement abilities, 3) Build a predictive model of the effects of intense drought and future recovery at local and regional scales. Two graduate students and several undergraduates will be involved in the sampling and research activities of the study. This research will provide management tools to identify and protect Alabama Strategic Habitat Units. The study also will offer summer camps for middle-school students and public outreach activities to citizen science groups organized with collaboration of the Auburn University Museum of Natural History.The study will assess the impacts of extreme drought on the dynamics of habitat use as well as evaluate the resilience of aquatic species to flash drought. The investigators hypothesize that the ability to use downstream refuge during drought is a bottleneck that varies based on species vagility and position in the stream network. Stream habitats in two drainages that have experienced the exceptional drought will be sampled and compared to historic, baseline data collected since 2012 to test this hypothesis. The study will predict shifts in distribution patterns of stream fauna in response to flash drought by combining pre-drought survey and environmental DNA (eDNA) data from streams of various sizes in two ecoregions of Alabama, with species-specific vagility potential based on functional trait databases, life history information, and professional judgment. Predicted and observed patterns will be compared using fine scale surveys, broad scale eDNA collections, and spatial analysis. The results of this investigation will provide critical information pertinent to understanding the resiliency of specific taxa and stream communities in general to drought disturbance in a global hotspot for diversity.