Abstract

The free-floating American duckweed, Lemna minuta, is an invasive species now widespread in Europe. Yet, its impact on freshwater ecosystems has been poorly investigated. In this study, the effects of the presence of this invasive duckweed on water quality, and aquatic plant and invertebrate communities were evaluated in sites in Central Italy. Water chemical and physical factors and community descriptors were analyzed to identify these effects. Surveys were carried out across 17 paired aquatic sites. Site pairs were similar in microclimate, hydrogeology and water quality, but differed in relation to the presence/absence of L. minuta floating mats. In sites with mats, light and dissolved oxygen in water were negatively correlated with increasing mat coverage and thickness. The limited light and hypoxic conditions under mats inhibited plant growth and had a selective impact on the invertebrate community. Sites with L. minuta had aquatic communities with a lower plant taxa richness and a contrasting composition, compared with those in sites without. At sites with mats some plants were unaffected, but the majority of plant taxa documented at sites without Lemna were no present at sites with Lemna or were very rare (macroalgae, submerged rhizophytes). As for invertebrates, hypoxic-tolerant taxa dominated under mats (Ostracoda, Copepoda, Isopoda), whilst those more sensitive to oxygen depletion, or obligate herbivores, or those with a winged stage or swimming on water surface, were rare or absent (Ephemeroptera, Amphipoda, Chironomus, Notonecta). Lemna minuta mats presence was associated with alterations in the underlying aquatic ecosystem, severely threatening the conservation of these habitats. Active management strategies, including spread-prevention techniques, or mechanical removal combined with biological control, are required to conserve these habitats.

中文翻译：

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外来入侵植物Lemna minuta Kunth主导的水体的生境变化和植物和无脊椎动物群落的变化

摘要

自由浮游的美国浮萍Lemna minuta是现在在欧洲广泛传播的一种入侵物种。然而，对其对淡水生态系统的影响的研究很少。在这项研究中，在意大利中部评估了这种侵入性浮萍的存在对水质，水生植物和无脊椎动物群落的影响。分析了水的化学和物理因素以及群落描述符以识别这些影响。在17个成对的水生地点进行了调查。位点对在小气候，水文地质学和水质方面相似，但在存在/不存在小。金龟子方面存在差异浮垫。在有垫子的地方，水中的光和溶解氧与垫子的覆盖范围和厚度增加呈负相关。席子上有限的光照和低氧条件抑制了植物的生长并对无脊椎动物群落产生了选择性的影响。与没有L. minuta的地区相比 ，水生生物群落的植物类群丰富度较低，组成相反。在带有垫子的站点上，一些植物没有受到影响，但是在没有Lemna的站点上记录的大多数植物类群在带有Lemna的站点上不存在或非常罕见（巨藻，浸没的根瘤菌）。至于无脊椎动物，则在垫子（Ostracoda，Copepoda，Isopoda）下以耐缺氧类群为主，而对缺氧或专性草食动物更敏感的人，或有翅阶段或在水面上游泳的人很少或不存在（表翅目，两栖动物，Chironomus，Notonecta）。Lemna minuta mats的存在与底层水生生态系统的变化有关，严重威胁了这些生境的保护。为了保护这些栖息地，需要采取积极的管理策略，包括防扩散技术或机械清除与生物防治相结合。