Marine invasions are of increasing concern for biodiversity conservation worldwide. Gelatinous macrozooplankton contain members, which have become globally invasive, for example the ctenophore Mnemiopsis leidyi or the hydromedusae Blackfordia virginica. B. virginica is characterised by a large salinity tolerance, with a brackish-water habitat preference, and by a metagenic life history strategy with an alternation between sexually reproducing planktonic medusae and asexually reproducing benthic polyps to complete the life cycle. In this study we analysed 8 years of ichthyoplankton survey data (2010–2017) from the Kiel Canal and 14 ichthyoplankton summer surveys in the central Baltic Sea (2008–2017). We report the first presence of B. virginica in northern Europe, namely from the southwestern Baltic Sea and the Kiel Canal. In the Kiel Canal, B. virginica was first sporadically sighted in 2014 and 2015 and has developed persistent populations since summer 2016. Changes in size-frequency distributions during summer 2016 indicate active recruitment in the Kiel Canal at salinities between 7 and 13 and temperatures > 14 °C. Close vicinity to and direct connection with the southwestern Baltic Sea, where B. virginica was observed during 2017, indicate that the Baltic Sea and other brackish-water habitats of Northern Europe are at risk for colonisation of this non-indigenous species. Our results highlight that monitoring activities should consider gelatinous macrozooplankton for standard assessments to allow for the detection of non-indigenous species at an early stage of their colonisation.

中文翻译：

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非本地水母Blackfordia virginica（Mayer，1910年）在波罗的海的首次记录

海洋入侵日益引起全球生物多样性保护的关注。胶质巨足动物包含已成为全球侵入性的成员，例如c虫Mnemiopsis leidyi或水生水母Blackfordia virginica。维尔京芽孢杆菌的特点是耐盐碱度高，对咸水栖息地的偏爱，以及通过有性繁殖的浮游水母和无性繁殖的底栖性息肉之间的交替来完成生命周期的成因生命史策略。在这项研究中，我们分析了基尔运河8年（2010–2017年）的浮游鱼类调查数据和14个波罗的海中部（2008–2017年）浮游鱼类夏季调查数据。我们报告了北欧最早出现的维吉尼亚B. virginica，即波罗的海西南部和基尔运河。在基尔运河，B。维吉尼亚州于2014年和2015年首次出现零星，自2016年夏季以来一直在迁徙。2016年夏季，大小频率分布的变化表明，在盐度介于7和13之间且温度高于14°C时，基尔运河正在积极招募。2017年在波罗的海西南部紧邻并与之直接相连，这表明波罗的海和北欧的其他微咸水生境有被该非本土物种定居的风险。我们的结果强调，监测活动应考虑使用胶质巨浮游动物进行标准评估，以便在其定殖的早期阶段检测到非本地物种。