The Helgoland Roads time series is one of the longest and most detailed time series in the world. It comprises daily phytoplankton counts accompanied by physico-chemical measurements. As such, it provides valuable long-term record of changes and their underlying causes in the phytoplankton community around Helgoland. This work provides an updated check-list of the phytoplankton species encountered at the Helgoland Roads LTER station with additional taxonomic assessments from live net samples and scanning electron microscope surveys. Since the last check-list was published 11 additional taxa have been recorded for the first time comprising 9 diatom and 2 dinoflagellate species. Of the 9 diatom species 3 were Chaetoceros species: Chaetoceros anastomosans, C. pseudocurvisetus and C. lorenzianus (the latter identified by their resting cysts) which were all first recognised in September 2009. The toxic dinoflagellate Dinophysis tripos, and the bipolar centric diatom Odontella longicruris both were first observed in September 2015. The latest new record is the potentially toxic dinoflagellate Alexandrium ostenfeldii, first recorded in August 2017. All of the first records (with the exception of Dinophysis tripos) were first observed in semi-quantitative surveys based on live samples and SEM demonstrating that adding less frequent but very detailed assessments can complement high frequency counts of fixed samples as long as these data of different origin are linked efficiently to the individual sampling event and all metadata including representative pictorial metadata are recorded in a consistent manner. In this manner the enhanced checklist serves as a baseline against which long-term changes in phytoplankton potentially related to ecosystem state can be addressed.

中文翻译：

---

Helgoland Roads时间序列站的更新浮游植物清单，其中包含11项硅藻和鞭毛藻新记录

Helgoland Roads时间序列是世界上最长，最详细的时间序列之一。它包括每日浮游植物计数以及物理化学测量。因此，它为Helgoland周围浮游植物群落的变化及其潜在原因提供了有价值的长期记录。这项工作提供了在Helgoland Roads LTER站遇到的浮游植物物种的最新检查清单，还包括来自活网样品和扫描电子显微镜调查的其他分类学评估。自上次发布检查清单以来，首次记录了11个其他分类单元，其中包括9个硅藻和2个鞭毛藻。在9种硅藻物种中，有3种是Chaetoceros种：Chaetoceros anastomosans，C。pseudocurvisetus和C.