Background Aquatic ecosystems are greatly altered by urban development, including the complete loss of natural habitat due to water diversions or channel burial. However, novel freshwater habitats also are created in cities, such as effluent-dependent streams that rely on treated wastewater for flow. It is unclear how diverse these novel ecosystems are, or how quickly aquatic species are able to colonize them. In this study, we (1) quantify odonate (Insecta, Odonata) colonization of a novel effluent-dependent river reach, (2) examine how drying events affect odonates in these novel habitats, and (3) explore whether effluent-dependent streams can support diverse odonate assemblages. Methods We conducted monthly odonate surveys at three sites along the Santa Cruz River (Tucson, AZ, USA) between June 2019 and May 2020. One site was in a long-established effluent-dependent reach (flowing since the 1970s) that served as a reference site and two sites were in a newly-established reach that began flowing on June 24, 2019 (it was previously dry). We compared odonate species richness, assemblage composition, and colonization patterns across these reaches, and examined how these factors responded to flow cessation events in the new reach. Results Seven odonate species were observed at the study sites in the new reach within hours of flow initiation, and species rapidly continued to arrive thereafter. Within 3 months, species richness and assemblage composition of adult odonates were indistinguishable in the new and reference reaches. However, drying events resulted in short-term and chronic reductions in species richness at one of the sites. Across all three sites, we found over 50 odonate species, which represent nearly 40% of species known from the state of Arizona. Discussion Odonates were surprisingly diverse in the effluent-dependent Santa Cruz River and rapidly colonized a newly established reach. Richness levels remained high at study sites that did not experience drying events. These results suggest that consistent discharge of high-quality effluent into dry streambeds can be an important tool for promoting urban biodiversity. However, it remains to be seen how quickly and effectively less vagile taxa (e.g., mayflies, caddisflies) can colonize novel reaches. Effluent-dependent urban streams will always be highly managed systems, but collaboration between ecologists and urban planners could help to maximize aquatic biodiversity while still achieving goals of public safety and urban development.

中文翻译：

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如果你建造它，它们就会来：蜻蜓在一条依赖污水的新河段迅速定殖

背景 城市发展极大地改变了水生生态系统，包括由于引水或渠道掩埋而导致自然栖息地的完全丧失。然而，城市中也创造了新的淡水栖息地，例如依赖处理过的废水流动的依赖污水的溪流。目前尚不清楚这些新的生态系统有多么多样化，或者水生物种能够以多快的速度殖民它们。在这项研究中，我们 (1) 量化新的依赖污水的河流河段的 odonate (Insecta, Odonata) 定殖，(2) 检查干燥事件如何影响这些新栖息地中的 odonates，以及 (3) 探索依赖污水的溪流是否可以支持不同的 odonate 组合。方法 我们在 2019 年 6 月至 2020 年 5 月期间在圣克鲁斯河（美国亚利桑那州图森）沿岸的三个地点进行了每月 odonate 调查。一个站点位于一个长期建立的依赖污水的河段（自 1970 年代开始流动），用作参考站点，两个站点位于一个新建立的河段，该河段于 2019 年 6 月 24 日开始流动（以前是干涸的）。我们比较了这些河段的 odonate 物种丰富度、组合组成和定殖模式，并检查了这些因素如何对新河段的流量停止事件作出反应。结果 在流动开始数小时内，在新河段的研究地点观察到 7 种齿形物种，此后物种迅速继续到达。3个月内，成虫齿形动物的物种丰富度和群落组成在新区和参考区没有区别。然而，干燥事件导致其中一个地点物种丰富度的短期和长期减少。在所有三个站点中，我们发现了超过 50 种 odonate 物种，占亚利桑那州已知物种的近 40%。讨论 Odonates 在依赖污水的圣克鲁斯河中的多样性令人惊讶，并迅速在新建立的河段殖民。在没有经历干燥事件的研究地点，丰富度水平仍然很高。这些结果表明，将高质量的污水持续排放到干涸的河床中可以成为促进城市生物多样性的重要工具。然而，不太灵活的类群（例如，蜉蝣、石蝇）如何迅速和有效地在新河段定殖还有待观察。依赖污水的城市河流将始终是高度管理的系统，但生态学家和城市规划者之间的合作可以帮助最大限度地提高水生生物多样性，同时仍然实现公共安全和城市发展的目标。