在2021年7月底,法国大西洋沿岸出现了一束丁香花,持续了六个星期。REPHY监测网络和公民参与项目PHENOMER为其观察做出了贡献。9月6日达到3,600,000个细胞/L的最大浓度,在法国海岸线上从未记录过的水平。卫星观测证实,9月初,水华达到最高丰度和空间延伸,9月4日占地3200平方公里。文化的建立,形态学和ITS-LSU测序将该物种鉴定为L.polyedra。thecae显示出特征性的表格,有时有腹孔。花的色素组成与培养的L.polyedra相似,证实浮游植物生物量由该物种主导。开花之前是Leptocylindrussp。,在Lepidodinium上发展,并通过升高的夜光闪烁浓度而成功。之后,在开花开始的地方观察到相对较高的Alexandriumtamarense。7月中旬异常高的降水增加了卢瓦尔河和Vilaine河的河流流量,这可能通过提供营养来促进浮游植物的生长。具有大量鞭毛藻的水团的特征是海表温度高和热盐分层。在开花发展期间风很低,在把它漂到海上之前.在开花结束时的浮游生物中观察到囊肿,浓度高达30,000个囊肿/L,相对丰度高达99%。花朵存入了种子库,囊肿浓度高达100,000个囊肿/g干沉淀物,特别是在细粒沉积物中。水华引起缺氧事件,并且在贻贝中记录了高达747μg/kg的叶黄素浓度,低于3,750μg/kg的安全阈值。牡蛎,蛤仔和鸟笼也被叶梭毒素污染,但浓度较低。已建立的培养物没有产生可检测水平的叶黄素,尽管在沉积物中检测到了叶黄素。不寻常的环境夏季条件引发了开花,以及建立相当多的种子银行,提供重要的发现,以了解未来沿法国海岸线的有害藻华。
At the end of July 2021, a bloom of Lingulodinium polyedra developed along the French Atlantic coast and lasted six weeks. The REPHY monitoring network and the citizen participation project PHENOMER contributed to its observation. A maximum concentration of 3,600,000 cells/L was reached on the 6th of September, a level never recorded on French coastlines. Satellite observation confirmed that the bloom reached its highest abundance and spatial extension early September, covering about 3200 km2 on the 4th of September. Cultures were established, and morphology and ITS-LSU sequencing identified the species as L. polyedra. The thecae displayed the characteristic tabulation and sometimes a ventral pore. The pigment composition of the bloom was similar to that of cultured L. polyedra, confirming that phytoplankton biomass was dominated by this species. The bloom was preceded by Leptocylindrus sp., developed over Lepidodinium chlorophorum, and was succeeded by elevated Noctiluca scintillans concentrations. Afterwards, relatively high abundance of Alexandrium tamarense were observed in the embayment where the bloom started. Unusually high precipitation during mid-July increased river discharges from the Loire and Vilaine rivers, which likely fueled phytoplankton growth by providing nutrients. Water masses with high numbers of dinoflagellates were characterized by high sea surface temperature and thermohaline stratification. The wind was low during the bloom development, before drifting it offshore. Cysts were observed in the plankton towards the end of the bloom, with concentrations up to 30,000 cysts/L and relative abundances up to 99%. The bloom deposited a seed bank, with cyst concentrations up to 100,000 cysts/g dried sediment, particularly in fine-grained sediments. The bloom caused hypoxia events, and concentrations of
yessotoxins up to 747 μg/kg were recorded in mussels, below the safety threshold of 3,750 μg/kg. Oysters, clams and cockles also were contaminated with
yessotoxins, but at lower concentrations. The established cultures did not produce
yessotoxins at detectable levels, although
yessotoxins were detected in the sediment. The unusual environmental summertime conditions that triggered the bloom, as well as the establishment of considerable seed banks, provide important findings to understand future harmful algal blooms along the French coastline.