Hellenic Centre for Marine Research, Institute of Marine Biological Resources and Inland Waters, 46.7km Athens-Sounio Ave., Anavyssos 19013, Greece.
Hellenic Centre for Marine Research, Institute of Marine Biological Resources and Inland Waters, 46.7km Athens-Sounio Ave., Anavyssos 19013, Greece.
Sci Total Environ. 2017 Dec 15;603-604:639-650. doi: 10.1016/j.scitotenv.2017.06.078. Epub 2017 Jun 28.
Water stress is a key stressor in Mediterranean intermittent rivers exacerbating the negative effects of other stressors, such as pollutants, with multiple effects on different river biota. The current study aimed to determine the response of macroinvertebrate and fish assemblages to instream habitat and water chemistry, at the microhabitat scale and at different levels of water stress and pollution, in an intermittent Mediterranean river. Sampling was conducted at high and low summer discharge, at two consecutive years, and included four reaches that were targeted for their different levels of water stress and pollution. Overall, the macroinvertebrate fauna of Evrotas River indicated high resilience to intermittency, however, variation in community structure and composition occurred under acute water stress, due to habitat alteration and change in water physico-chemistry, i.e. water temperature increase. The combined effects of pollution and high water stress had, however, pronounced effects on species richness, abundance and community structure in the pollution impacted reach, where pollution sensitive taxa were almost extirpated. Fish response to drought, in reaches free of pollution, consisted of an increase in the abundance of the two small limnophilic species, coupled with their shift to faster flowing riffle habitats, and a reduction in the abundance of the larger, rheophilic species. In the pollution impacted reach, however, the combination of pollution and high water stress led to hypoxic conditions assumed to be the leading cause of the almost complete elimination of the fish assemblage. In contrast, the perennial Evrotas reaches with relatively stable physicochemical conditions, though affected hydrologically by drought, appear to function as refugia for fish during high water stress. When comparing the response of the two biotic groups to combined acute water stress and pollution, it is evident that macroinvertebrates were negatively impacted, but fish were virtually eliminated under the two combined stressors.
水分胁迫是地中海间歇性河流的主要胁迫因素，加剧了其他胁迫因素（如污染物）的负面影响，对不同的河流生物群产生多种影响。本研究旨在确定大型底栖无脊椎动物和鱼类群落对河流栖息地和水化学的响应，在微观生境尺度上，并在不同程度的水分胁迫和污染下，在一条地中海间歇性河流中。采样在夏季高、低流量下进行，连续两年进行，包括四个目标是不同程度水分胁迫和污染的河段。总体而言，Evrotas 河流的大型底栖无脊椎动物区系对间歇性表现出很高的恢复力，然而，由于栖息地的改变和水理化性质的变化，即水温升高，群落结构和组成在急性水分胁迫下发生了变化。然而，污染和高水分胁迫的综合影响对污染影响河段的物种丰富度、丰度和群落结构产生了显著影响，其中污染敏感类群几乎灭绝。在没有污染的河段，鱼类对干旱的反应是两种小型淡水鱼类数量的增加，加上它们向更快流动的急流栖息地的转移，以及较大的洄游鱼类数量的减少。然而，在污染影响的河段，污染和高水分胁迫的综合作用导致缺氧条件，这被认为是鱼类几乎完全灭绝的主要原因。相比之下，常年有水流的 Evrotas 河段虽然受干旱影响，但理化条件相对稳定，似乎是鱼类在高水分胁迫期间的避难所。在比较两个生物群对急性水分胁迫和污染的综合响应时，很明显，大型底栖无脊椎动物受到负面影响，但鱼类在两种综合胁迫因素下几乎被消灭。
