Alteration of dominant cyanobacteria in different bloom periods caused by abiotic factors and species interactions

Abstract

Freshwater cyanobacterial blooms have drawn public attention because they threaten the safety of water resources and human health worldwide. Heavy cyanobacterial blooms outbreak in Lake Taihu in summer annually and vanish in other months. To find out the factors impacting the cyanobacterial blooms, the present study measured the physicochemical parameters of water and investigated the composition of microbial community using the 16S rRNA gene and internal transcribed spacer amplicon sequencing in the months with or without bloom. The most interesting finding is that two major cyanobacteria, Planktothrix and Microcystis , dramatically alternated during a cyanobacterial bloom in 2016, which is less mentioned in previous studies. When the temperature of the water began increasing in July, Planktothrix appeared first and showed as a superior competitor for M. aeruginosa in NO 3 − -rich conditions. Microcystis became the dominant genus when the water temperature increased further in August. Laboratory experiments confirmed the influence of temperature and the total dissolved nitrogen (TDN) form on the growth of Planktothrix and Microcystis in a co-culture system. Besides, species interactions between cyanobacteria and non-cyanobacterial microorganisms, especially the prokaryotes, also played a key role in the alteration of Planktothrix and Microcystis . The present study exhibited the alteration of two dominant cyanobacteria in the different bloom periods caused by the temperature, TDN forms as well as the species interactions. These results helped the better understanding of cyanobacterial blooms and the factors which contribute to them.

Single-colony sequencing reveals phylosymbiosis, co-phylogeny, and horizontal gene transfer between the cyanobacteriumMicrocystisand its microbiome

“…Despite the absence of a core microbiome, several of the associations between Microcystis and its attached bacteria, notably Roseomonas and Rhodobacter, appear to be relatively stable over evolutionary time. These two genera have been previously reported to be correlated with Microcystis in environmental samples 41,42 . Whether these associations are beneficial to one or both partners remain to be seen, and deserve further study as possible targets for better predicting and controlling harmful Microcystis bloom events.…”

Cyanobacterial blooms contribute to the diversity of antibiotic-resistance genes in aquatic ecosystems

“…Sample acquisition and field data. Samples were collected from Meiliang Bay, the main location of cyanobacterial blooms in northern Lake Taihu as our previous study described 28 . Samples were collected during five periods (July, August and September 2016 and March and May 2017) at three locations (A: 31°31′19″ N, 120°13′49″E; B: 31°32′01″N, 120°13′15″E; C: 31°32′31″N, 120°13′33″E).…”

“…Each sample was filtered through 0.22-µm polycarbonate filters to obtain all aquatic microorganisms, which were frozen at −80 °C. The concentrations of total nitrogen (TN), total phosphorus (TP), nitrate (NO 3 − ) and ammonium (NH 4 + ) were measured in the filtered water following the methods described our previous studies 28 .…”

“…To shed light on the impacts of cyanobacterial blooms on the emergence and spread of ARGs, the different periods of cyanobacterial bloom were selected as the peak stages (July and August 2016), decline stage (September 2016) and non-bloom stage (March and May 2017) in the present study according our previous study 28 . We monitored the microbial community and the composition of ARGs in Lake Taihu, a natural freshwater lake that is eutrophic and has annual cyanobacterial blooms, during these periods by sequencing amplicons of the 16S ribosomal RNA (rRNA) gene and the internal transcribed spacer (ITS) as well as the high-throughput quantitative PCR (HT-qPCR).…”

Insights into the cyanosphere: capturing the respective metabolisms of cyanobacteria and chemotrophic bacteria in natural conditions?

“…Continental freshwater ecosystems can experience episodic cyanobacterial blooms during the summer season, caused mainly by anthropogenic activities, leading to eutrophication, rising CO 2 levels and global warming (Huisman et al ., 2018). These bloom events induce changes in physico‐chemical conditions of the ecosystems such as alternating hypoxia‐anoxia cycles, reducing penetration of light into the water column and increasing pH values (Zhang et al ., 2021). Aggregates of cyanobacteria and their immediate environment, also called cyanosphere, are colonized by a microbiome composed of bacteria potentially involved in the remineralization of the phytoplanktonic organic matter (OM), in exchange with key nutrients (Bell and Mitchell, 1972; Song et al ., 2017).…”