Effects of ocean acidification on microbial community composition of, and oxygen fluxes through, biofilms from the Great Barrier Reef

Authors

  • Verena Witt,

    Corresponding author
    1. Australian Institute of Marine Science, PMB 3, Townsville MC, Qld. 4810, Australia.
    2. Coral Reef Ecology Group (CORE), Leibniz Center for Tropical Marine Ecology (ZMT), Fahrenheitstr. 6, 28359 Bremen, Germany.
    Search for more papers by this author
  • Christian Wild,

    1. Coral Reef Ecology Group (CORE), Leibniz Center for Tropical Marine Ecology (ZMT), Fahrenheitstr. 6, 28359 Bremen, Germany.
    Search for more papers by this author
  • Kenneth R. N. Anthony,

    1. Australian Institute of Marine Science, PMB 3, Townsville MC, Qld. 4810, Australia.
    Search for more papers by this author
  • Guillermo Diaz-Pulido,

    1. Griffith School of Environment and Australian Rivers Institute – Coast & Estuaries, 170 Kessels Road, Nathan Campus, Griffith University, Nathan Qld. 4111, Australia.
    Search for more papers by this author
  • Sven Uthicke

    1. Australian Institute of Marine Science, PMB 3, Townsville MC, Qld. 4810, Australia.
    Search for more papers by this author

E-mail v.witt@aims.gov.au; Tel. +61-7-47534483; Fax +61-7-4772 5852.

Summary

Rising anthropogenic CO2 emissions acidify the oceans, and cause changes to seawater carbon chemistry. Bacterial biofilm communities reflect environmental disturbances and may rapidly respond to ocean acidification. This study investigates community composition and activity responses to experimental ocean acidification in biofilms from the Australian Great Barrier Reef. Natural biofilms grown on glass slides were exposed for 11 d to four controlled pCO2 concentrations representing the following scenarios: A) pre-industrial (∼300 ppm), B) present-day (∼400 ppm), C) mid century (∼560 ppm) and D) late century (∼1140 ppm). Terminal restriction fragment length polymorphism and clone library analyses of 16S rRNA genes revealed CO2-correlated bacterial community shifts between treatments A, B and D. Observed bacterial community shifts were driven by decreases in the relative abundance of Alphaproteobacteria and increases of Flavobacteriales (Bacteroidetes) at increased CO2 concentrations, indicating pH sensitivity of specific bacterial groups. Elevated pCO2 (C + D) shifted biofilm algal communities and significantly increased C and N contents, yet O2 fluxes, measured using in light and dark incubations, remained unchanged. Our findings suggest that bacterial biofilm communities rapidly adapt and reorganize in response to high pCO2 to maintain activity such as oxygen production.

Ancillary