Climate Change Metagenomic Record Index

    Microbial community composition in the sediment at naturally CO2-rich sites and its implications for ocean acidification research

    MGnify Record MGYS00000554

    Description
    Microbial processes are fundamental in nutrient cycling and remineralization in marine sediments. To understand how ocean acidification (OA) may influence sediment microbial diversity and activity, naturally CO2-rich sites are increasingly being used. However, the characterization of naturally CO2-rich sites is often limited to OA-related variables, neglecting additional variables that may obscure OA effects, especially when the CO2 increase is caused by geological processes. Here, we reevaluated the factors affecting changes in microbial communities at volcanic CO2 seeps in Papua New Guinea based on a comprehensive characterization of the conditions in the sediment. Microbial community composition was assessed using molecular fingerprinting and amplicon sequencing. pH was among the factors significantly, yet not mainly, explaining changes in microbial community composition. In-situ microprofiles and trace element concentrations further showed a variation in the strength of the hydrothermal signature of the sediment at similar pH allowing the identification of sites which may better represent future OA than others. At these sites, changes in the microbial community may have implications for element cycling in the sediment. We recommend focusing on a detailed environmental characterization in future OA research, to ensure better comparability between studies and a more reliable selection of naturally CO2-rich sites.

    Related Publications

    Pubmed Record 26887661

    Abstract Text
    To understand how ocean acidification (OA) influences sediment microbial communities, naturally CO2-rich sites are increasingly being used as OA analogues. However, the characterization of these naturally CO2-rich sites is often limited to OA-related variables, neglecting additional environmental variables that may confound OA effects. Here, we used an extensive array of sediment and bottom water parameters to evaluate pH effects on sediment microbial communities at hydrothermal CO2 seeps in Papua New Guinea. The geochemical composition of the sediment pore water showed variations in the hydrothermal signature at seep sites with comparable pH, allowing the identification of sites that may better represent future OA scenarios. At these sites, we detected a 60% shift in the microbial community composition compared with reference sites, mostly related to increases in Chloroflexi sequences. pH was among the factors significantly, yet not mainly, explaining changes in microbial community composition. pH variation may therefore often not be the primary cause of microbial changes when sampling is done along complex environmental gradients. Thus, we recommend an ecosystem approach when assessing OA effects on sediment microbial communities under natural conditions. This will enable a more reliable quantification of OA effects via a reduction of potential confounding effects.