1. Wetlands in arid regions are characterized by their great heterogeneity, often including endemic species that contribute to regional aquatic biodiversity. In the Patagonian steppe, most lakes are naturally fishless and sustain a rich aquatic biodiversity, including endemics; however, many of these lakes have been stocked with Oncorhynchus mykiss (rainbow trout) during recent decades. The introduction of predatory fish into aquatic ecosystems naturally devoid of these organisms can produce profound alterations in the structure of the original communities and in the configuration of their biotic assemblages.
2. Aquatic invertebrates play important roles in both the structure and functioning of freshwater ecosystems, including their contribution to global biodiversity and their cascading effects across ecosystem boundaries.
3. The aim of this study was to assess the effect of introduced non-native fish on the pleustonic macroinvertebrate assemblage. Samples were taken from 10 shallow Patagonian lakes (five fishless and five stocked with fish) in two consecutive warm periods.
4. Lakes with fish had higher conductivity and phosphate values. Higher inter-annual differences were also observed in lakes with fish for phytoplanktonic chlorophyll a, nitrate, phosphate, conductivity, and water temperature.
5. The community structure (relative abundance of different taxa, species composition, and diversity index) was affected by the presence of rainbow trout, with the differences mainly driven by the relative abundance of Ostracoda, Hyalella, Chironomidae, and Haliplus species.
6. This approach can be used to assess the required conservation actions in shallow Patagonian steppe lakes, which have been listed as priority areas for waterbird conservation. Specifically, this study provides a baseline for monitoring future trends of the macroinvertebrate communities and for evaluating conservation and management efforts over time.

中文翻译：

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来自干旱巴塔哥尼亚沿岸植被湖泊的水生大型无脊椎动物：鱼类引进对群落结构的影响

1. 干旱地区的湿地具有极大的异质性，通常包括有助于区域水生生物多样性的特有物种。在巴塔哥尼亚草原，大多数湖泊自然没有鱼，并维持着丰富的水生生物多样性，包括特有的；然而，近几十年来，这些湖泊中的许多湖泊都放养了Oncorhynchus mykiss（虹鳟鱼）。将掠食性鱼类引入自然没有这些生物的水生生态系统，可以对原始群落的结构及其生物组合的配置产生深远的影响。
2. 水生无脊椎动物在淡水生态系统的结构和功能中发挥着重要作用，包括它们对全球生物多样性的贡献及其跨越生态系统边界的级联效应。
3. 本研究的目的是评估引入的非本地鱼类对 pleusonic 大型无脊椎动物组合的影响。在连续两个温暖时期从 10 个巴塔哥尼亚浅湖（5 个无鱼和 5 个有鱼）采集样本。
4. 有鱼的湖泊具有更高的电导率和磷酸盐值。在有鱼类的湖泊中也观察到浮游植物叶绿素a、硝酸盐、磷酸盐、电导率和水温的较大年际差异。
5. 群落结构（不同分类群的相对丰度、物种组成和多样性指数）受虹鳟鱼存在的影响，差异主要由介形纲、透明藻、摇蚊科和鲽鱼物种的相对丰度驱动。
6. 这种方法可用于评估巴塔哥尼亚草原湖泊中所需的保护行动，这些湖泊已被列为水鸟保护的优先领域。具体而言，这项研究为监测大型无脊椎动物群落的未来趋势以及评估保护和管理工作提供了一个基线。