Dynamic bacterial community response to Akashiwo sanguinea (Dinophyceae) bloom in indoor marine microcosms

Abstract

We investigated the dynamics of the bacterial composition and metabolic function within Akashiwo sanguinea bloom using a 100-L indoor microcosm and metagenomic next-generation sequencing. We found that the bacterial community was classified into three groups at 54% similarity. Group I was associated with “during the A. sanguinea bloom stage” and mainly consisted of Alphaproteobacteria, Flavobacteriia and Gammaproteobacteria. Meanwhile, groups II and III were associated with the “late bloom/decline stage to post-bloom stage” with decreased Flavobacteriia and Gammaproteobacteria in these stages. Upon the termination of the A. sanguinea bloom, the concentrations of inorganic nutrients (particularly PO43−, NH4+ and dissolved organic carbon) increased rapidly and then decreased. From the network analysis, we found that the A. sanguinea node is associated with certain bacteria. After the bloom, the specific increases in NH4+ and PO43− nodes are associated with other bacterial taxa. The changes in the functional groups of the bacterial community from chemoheterotrophy to nitrogen association metabolisms were consistent with the environmental impacts during and after A. sanguinea bloom. Consequently, certain bacterial communities and the environments dynamically changed during and after harmful algal blooms and a rapid turnover within the bacterial community and their function can respond to ecological interactions.

Core bacteria associated with Cochlodinium polykrikoides(Dinophyta) blooms: diversity and function

“…Generally, bacteria can promote the growth of HABs through the release of EPS (Jung et al, 2021;Kang et al, 2021) or inhibit HABs (Jung et al, 2008). Bacteria can utilize the EPS released by HABs and play important roles in biogeochemical cycling in oceans (Azam, 1998;Jung et al, 2021). Our results generally confirm previous reports (Grossart et al, 2005;Sapp et al, 2007), which found that phycospheres harbour host-specific bacteria based on the ability of bacteria to utilize different types of organic matter.…”

“…Bacterial communities can respond to phytoplankton blooms (Pinhassi et al, 2004), and HABs are known to be closely associated with host-specific bacteria (Mayali et al, 2011). Generally, bacteria can promote the growth of HABs through the release of EPS (Jung et al, 2021;Kang et al, 2021) or inhibit HABs (Jung et al, 2008). Bacteria can utilize the EPS released by HABs and play important roles in biogeochemical cycling in oceans (Azam, 1998;Jung et al, 2021).…”

“…Extraction of bacterial genomic DNA and metabarcoding analyses using 16S rDNA were performed as described in our previous report (Kang et al, 2021) and in the Supplementary Information (Table S1). Then, the amplified PCR products were analysed using a next-generation sequencing platform (Mi-Seq, Illumina, San Diego, CA, USA), and raw sequencing data (Fastq files) were analysed using the bioinformatics processes described in Jung et al (2021) and in the Supplementary Information.…”

“…Thus, the relationships between bacteria and HABs are a promising study area in bacterial ecology, which may provide insights into how bacteria interact with HAB development (Andersson et al, 2010). Although some recent reports have suggested that specific bacteria are associated with HABs (Jung et al, 2021;Kang et al, 2021), ecological studies on these interactions are lacking. Moreover, the ecological interaction and function between bacteria and phytoplankton can be difficult to explain fully, because the phycosphere habitat may determine how communities are organised; for example, it can provide ecological niches where species interactions, such as competition, mutualism, and predation, occur, in addition to providing a suitable environment (Sapp et al, 2007;Zhou et al, 2019).…”

“…With advanced molecular technologies, several ecological studies have used metabarcoding approaches to understand the changes in microbial dynamics (Kang et al, 2021) and strengthen biological monitoring in the ocean (Jung et al, 2018). Our previous studies have revealed changes in the dynamics of bacterial communities in natural ecosystems (i.e., "what is there") (Kim et al, 2016) as well as in bacterial functional roles associated with phytoplankton dynamics (i.e., "why is it there") (Jung et al, 2021). In the present study, we explored the changes in the environmental characteristics and functional roles of core bacterial communities during C. polykrikoides HABs and estimated the core bacteria and environments in the phycosphere of C. polykrikoidesHABs.…”