NEXT-GENERATION SEQUENCING FOR STUDYING MICROBIAL COMMUNITIES DURING CYANOBACTERIAL ALGAL BLOOMS

Abstract

Increasing evidence reports adverse effects of climate change on freshwater ecosystems and harmful algal blooms in particular, but response mechanisms of such heterogeneous communities are poorly understood. Environmental DNA (eDNA) analysis is a suitable and efficient tool for resolving biodiversity within complex ecosystems. Specifically, full length 16S rRNA next-generation nanopore sequencing, combined with barcoding, was implemented in the work to resolve the structure of plankton communities in LMWE mesocosm experiment. Portable nanopore sequencing technology provides time-efficient and cost-effective analysis of environmental data, with taxonomic resolution up to genera. Since laboratory cultures have limitations in reflecting complex phytoplankton communities, mesocosm facilities were used as experimental setups for studying the variability of these communities. The effect of stratification on microbial composition dynamics was assessed for eight weeks using 12 outdoor mesocosm tanks, with three temperature regimes, varying nutrient levels, and two sampling depths. In total, 192 water samples were collected, followed by eDNA extraction, amplification, and sequencing. Obtained results revealed successful classification (up to 99.93%) of over 1200 genera in each mesocosm tank. Classified taxa of heterotrophic bacteria included low-abundance (<0.01%) genera. Temporal analysis of obtained data revealed changes in microbial dominance throughout the Microcystis spp. bloom development. Principal component analysis coupled with ADONIS test revealed a significant correlation between environmental factors and heterotrophic bacteria community composition. Moreover, varying temperature regimes had a significant effect on community structure throughout 7 the experiment. Microbial communities during stratification and mixing periods were shown to form statistically significant clusters, with Microcystis spp. contributing the most to dissimilarity. Obtained results provide insights into the effect of stratification and temperature on microbial community composition