Insignificant Response of Bacterioplankton Community to Elevated pCO2 During a Short-Term Microcosm Experiment in a Subtropical Eutrophic Coastal Ecosystem.

Yunlan Yang,Xiaowei Chen,Nianzhi Jiao,Huifang Li,Fei Zhang,Rui Zhang

doi:10.3389/fmicb.2021.730377

Abstract

Ocean acidification, as one of the major consequences of global climate change, markedly affects multiple ecosystem functions in disparate marine environments from coastal habitats to the deep ocean. Evaluation of the responses of marine microbial community to the increasing partial pressure of CO2 (pCO2) is crucial to explore the microbe-driven biogeochemical processes in the future ocean. In this study, a microcosm incubation of eutrophic coastal water from Xiamen Bay under elevated pCO2 (about 1,000 μatm) and control (ambient air, about 380–410 μatm) conditions was conducted to investigate the effect of ocean acidification on the natural bacterioplankton community. During the 5-day incubation period, the chlorophyll a concentration and bacterioplankton abundance were not significantly affected by increased pCO2. Hierarchical clustering and non-metric multidimensional scaling analysis based on Bray-Curtis similarity among the bacterioplankton community derived from the 16S rRNA genes revealed an inconspicuous impact of elevated pCO2 on the bacterial community. During the incubation period, Proteobacteria, Bacteroidetes, Actinobacteria, Cyanobacteria, and Epsilonbacteraeota were predominant in all microcosms. Despite the distinct temporal variation in the composition of the bacterioplankton community during the experimental period, statistical analyses showed that no significant difference was found on bacterioplankton taxa between elevated pCO2 and control, indicating that the bacterioplankton at the population-level were also insensitive to elevated pCO2. Our results therefore suggest that the bacterioplankton communities in the fluctuating and eutrophic coastal ecosystems appear to be adaptable to the short-term elevated pCO2.

Highlights

Human activities have triggered substantial changes in global climate systems with a preternatural rate over the past two centuries, leading to massive CO2 absorption by the world’s oceans and a reduction in the pH of seawater which is known as ocean acidification (Caldeira and Wickett, 2003; Orr et al, 2005)
To simulate atmospheric CO2 concentrations currently and by the end of this century, two levels of pressure of CO2 (pCO2) were obtained by adjusting ambient air with CO2 using an enrichment device (Wuhan Ruihua Instrument and Equipment, Wuhan, China)
The temperature of the seawater collection was 17.5°C, and this temperature was maintained during the incubation period

Summary

Introduction

Human activities have triggered substantial changes in global climate systems with a preternatural rate over the past two centuries, leading to massive CO2 absorption by the world’s oceans and a reduction in the pH of seawater which is known as ocean acidification (Caldeira and Wickett, 2003; Orr et al, 2005). Ocean uptake of CO2 changes the equilibrium of the carbonate system, and the continued release of anthropogenic CO2 may lead to another 0.3–0.4 units decline in seawater pH globally by 2100 (Orr et al, 2005; IPCC, 2013). The subsequent effects of ocean acidification on coastal life have become one of the most important issues

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Conclusion