Cyanobacterial Akinete Distribution, Viability, and Cyanotoxin Records in Sediment Archives From the Northern Baltic Sea

Abstract

Cyanobacteria of the order Nostocales, including Baltic Sea bloom-forming taxa Nodularia spumigena, Aphanizomenon flosaquae, and Dolichospermum 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 Anabaena. Potentially planktonic species of Dolichospermum 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.

Effect of Ultraviolet-C Radiation on the Morphology of Cyanobacteria Nostoc sp. LBALBR-2 Isolated from Supply Reservoir (Belém, Pará, Brazil)

“…Akinetes are generally recognized as resistance cells, with thick walls, that accumulate protein reserves in the form of cyanophycin granules. Akinetes are produced when environmental conditions are unfavorable (Calijuri et al, 2006;Mehnert et al, 2014;Wood et al, 2021), with temperature being one of the main factors responsible for the formation of akinetes, as some cyanobacteria initiate the production of akinetes at temperatures between 20°C and 25°C, such as Aphanizomenon ovalisporum (Cirés et al, 2013), and the absence of this cell occurs at temperatures below 21°C, as in the cyanobacterium…”

Identification of cyanobacteria overwintering cells and environmental conditions causing growth: Application for preventative management

“…The extent that benthic populations overwinter and transfer to the planktonic phase has not been reported in the literature identified during this review. Wood et al, 2021) prior to dilution, filtration or density separation techniques. However, careful consideration of sonication duration and intensity is important to minimize or avoid damage to cells (Rajasekhar et al, 2012).…”

Joint FAO-IOC-IAEA technical guidance for the implementation of early warning systems for harmful algal blooms

“…Akinetes, a type of resting stage, are produced by some cyanobacteria (Wood et al, 2021). The akinetes may act as seed population for cyanobacteria blooms.…”