Wood Steffaney M, Kremp Anke, Savela Henna, Akter Sultana, Vartti Vesa-Pekka, Saarni Saija, Suikkanen Sanna
Marine Research Centre, Finnish Environment Institute, Helsinki, Finland.
Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, Germany.
Front Microbiol. 2021 Jun 15;12:681881. doi: 10.3389/fmicb.2021.681881. eCollection 2021.
Cyanobacteria of the order Nostocales, including Baltic Sea bloom-forming taxa , and spp., produce resting stages, known as akinetes, under unfavorable conditions. These akinetes can persist in the sediment and germinate if favorable conditions return, simultaneously representing past blooms and possibly contributing to future bloom formation. The present study characterized cyanobacterial akinete survival, germination, and potential cyanotoxin production in brackish water sediment archives from coastal and open Gulf of Finland in order to understand recent bloom expansion, akinete persistence, and cyanobacteria life cycles in the northern Baltic Sea. Results showed that cyanobacterial akinetes can persist in and germinate from Northern Baltic Sea sediment up to >40 and >400 years old, at coastal and open-sea locations, respectively. Akinete abundance and viability decreased with age and depth of vertical sediment layers. The detection of potential microcystin and nodularin production from akinetes was minimal and restricted to the surface sediment layers. Phylogenetic analysis of culturable cyanobacteria from the coastal sediment core indicated that most strains likely belonged to the benthic genus . Potentially planktonic species of could only be revived from the near-surface layers of the sediment, corresponding to an estimated age of 1-3 years. Results of germination experiments supported the notion that akinetes do not play an equally significant role in the life cycles of all bloom-forming cyanobacteria in the Baltic Sea. Overall, there was minimal congruence between akinete abundance, cyanotoxin concentration, and the presence of cyanotoxin biosynthetic genes in either sediment core. Further research is recommended to accurately detect and quantify akinetes and cyanotoxin genes from brackish water sediment samples in order to further describe species-specific benthic archives of cyanobacteria.
念珠藻目蓝细菌，包括在波罗的海形成水华的分类群以及其他物种，在不利条件下会产生休眠阶段，即厚壁孢子。这些厚壁孢子可以在沉积物中持续存在，若有利条件恢复则会萌发，它们既代表过去的水华，也可能对未来水华的形成有贡献。本研究对来自芬兰湾沿海和开阔海域的微咸水沉积物档案中的蓝细菌厚壁孢子存活、萌发及潜在的蓝藻毒素产生进行了表征，以了解波罗的海北部近期水华扩张、厚壁孢子持久性及蓝细菌生命周期。结果表明，蓝细菌厚壁孢子能够在波罗的海北部沿海和公海位置分别高达40多年和400多年的沉积物中持续存在并萌发。厚壁孢子丰度和活力随垂直沉积物层的年龄和深度而降低。从厚壁孢子中检测到的潜在微囊藻毒素和节球藻毒素产生量极少，且仅限于表层沉积物。对沿海沉积物岩芯中可培养蓝细菌的系统发育分析表明，大多数菌株可能属于底栖属。潜在的浮游物种只能从沉积物近表层复苏，对应估计年龄为1 - 3年。萌发实验结果支持了厚壁孢子在波罗的海所有形成水华的蓝细菌生命周期中并非都发挥同等重要作用的观点。总体而言，在任何一个沉积物岩芯中，厚壁孢子丰度、蓝藻毒素浓度与蓝藻毒素生物合成基因的存在之间几乎没有一致性。建议进一步开展研究，以准确检测和量化微咸水沉积物样本中的厚壁孢子和蓝藻毒素基因，从而进一步描述特定物种的蓝细菌底栖档案。
