Abstract
Microcystis blooms have occurred in upper San Francisco Estuary (USFE) since 1999, but their potential impacts on plankton communities have not been fully quantified. Five years of field data collected from stations across the freshwater reaches of the estuary were used to identify the plankton communities that covaried with Microcystis blooms, including non-photosynthetic bacteria, cyanobacteria, phytoplankton, zooplankton, and benthic genera using a suite of analyses, including microscopy, quantitative PCR (qPCR), and shotgun metagenomic analysis. Coherence between the abundance of Microcystis and members of the plankton community was determined by hierarchal cluster analysis (CLUSTER) and type 3 similarity profile analysis (SIMPROF), as well as correlation analysis. Microcystis abundance varied with many cyanobacteria and phytoplankton genera and was most closely correlated with the non-toxic cyanobacterium Merismopoedia, the green algae Monoraphidium and Chlamydomonas, and the potentially toxic cyanobacteria Pseudoanabaena, Dolichospermum, Planktothrix, Sphaerospermopsis, and Aphanizomenon. Among non-photosynthetic bacteria, the xenobiotic bacterium Phenylobacterium was the most closely correlated with Microcystis abundance. The coherence of DNA sequences for phyla across trophic levels in the plankton community also demonstrated the decrease in large zooplankton and increase in small zooplankton during blooms. The breadth of correlations between Microcystis and plankton across trophic levels suggests Microcystis influences ecosystem production through bottom-up control during blooms. Importantly, the abundance of Microcystis and other members of the plankton community varied with wet and dry conditions, indicating climate was a significant driver of trophic structure during blooms.
Highlights
As a powerful competitor in the water column, and the most common harmful cyanobacteria bloom species in freshwater, the presence of the cyanobacterium Microcystis spp. shapes freshwater plankton communities and ecosystem processes worldwide (Harke et al, 2016; Paerl et al, 2018)
Microcystis can influence the growth of phytoplankton and other cyanobacteria within blooms by excretion of substances that inhibit or stimulate growth through allelopathy (Kearns and Hunter, 2001; Singh et al, 2001; De Figueiredo et al, 2006; Suikkanen et al, 2006; Dunker et al, 2013; Zhang et al, 2013; Bittencourt-Oliveira et al, 2015; Song et al, 2017; Wang et al, 2017)
Similar associations between Microcystis and green algae and diatoms were measured for Microcystis blooms in upper San Francisco Estuary (USFE) in 2004, 2005, and 2014 (Lehman et al, 2008, 2010, in press)
Summary
As a powerful competitor in the water column, and the most common harmful cyanobacteria bloom species in freshwater, the presence of the cyanobacterium Microcystis spp. shapes freshwater plankton communities and ecosystem processes worldwide (Harke et al, 2016; Paerl et al, 2018). Microcystis engages in resource exploitation and interference strategies to shape plankton communities (Dunker et al, 2013; Zhang et al, 2013; Bittencourt-Oliveira et al, 2015) Both the microcystin toxin and other secondary metabolites it produces, including lipopolysaccharides, inhibit phytoplankton, cyanobacteria, and non-photosynthetic bacteria through impacts on growth and cell membrane structure. The versatility Microcystis displays to survive and shape the plankton community in its favor may partially explain why it is the most common of the freshwater cyanobacteria worldwide (Harke et al, 2016) and expected to increase with the adverse conditions associated with climate change (Paerl and Huisman, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
