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Ocean Acidification Changes Abiotic Processes but Not Biotic Processes in Coral Reef Sediments

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dc.contributor Max Planck Society
dc.contributor Max Planck Inst Marine Microbiol
dc.contributor Australian Inst Marine Sci
dc.contributor Australian Institute Of Marine Science
dc.contributor Microsensor Grp DE BEER, DIRK FINK, ARTUR DEN HAAN, JOOST CHENNU, ARJUN UTHICKE, SVEN 2019-02-24T18:33:24Z 2019-02-24T18:33:24Z 2020-09-02T03:44:53Z 2019-02-24T18:33:24Z 2019-02-24T18:33:24Z 2020-09-02T03:44:53Z 2017-01-01
dc.identifier.citation Fink A, den Haan J, Chennu A, Uthicke S, de Beer D (2017) Ocean acidification changes abiotic processes but not biotic processes in coral reef sediments. Frontiers in Marine Science 4: 73
dc.description.abstract In coral reefs, sediments play a crucial role in element cycling by contributing to primary production and the remineralization of organic matter. We studied how future ocean acidification (OA) will affect biotic and abiotic processes in sediments from two coral reefs of the Great Barrier Reef, Australia. This was investigated in the laboratory under conditions where water-sediment exchange was dominated by molecular diffusion (Magnetic Island) or by porewater advection (Davies Reef). OA conditions (+Delta pCO(2): 170-900 mu atm, Delta pH: 0.1-0.4) did not affect photosynthesis, aerobic and anaerobic organic matter remineralization, and growth of microphytobenthos. However, microsensor measurements showed that OA conditions reduced the porewater pH. Under diffusive conditions these changes were limited to the upper sediment layers. In contrast, advective conditions caused a deeper penetration of low pH water into the sediment resulting in an earlier pH buffering by dissolution of calcium carbonate (CaCO3). This increased the dissolution of Davis Reef sediments turning them from net precipitating (-0.8 g CaCO3 m(-2) d(-1)) under ambient to net dissolving (1 g CaCO3 m(-2) d(-1)) under OA conditions. Comparisons with in-situ studies on other reef sediments show that our dissolution rates are reasonable estimates for field settings. We estimate that enhanced dissolution due to OA will only have a minor effect on net ecosystem calcification of the Davies Reef flat (<4%). However, it could decrease recent sediment accumulation rates in the lagoon by up to 31% (by 0.2-0.4 mm year(-1)), reducing valuable reef space. Furthermore, our results indicate that high-magnesium calcite is predominantly dissolving in the studied sediments and a drastic reduction in this mineral can be expected on Davis Reef lagoon in the near future, leaving sediments of an altered mineral composition. This study demonstrates that biotic sediment processes will likely not directly be affected by OA. Ensuing indirect effects of OA-induced sediment dissolution on biotic processes are discussed.
dc.description.sponsorship We thank the MPI Microsensor group technicians for preparing the microsensors and M. Kebben for building the flumes. We are grateful to S. Noonan, K. Hohmann, and V. Hubner and the SeaSim technical staff for their continuous support during the experiments and C. Vogt for the XRD analyses. This study was funded by German Ministry for Research and Education (BMBF) project on the Biological Impacts of Ocean Acidification (BIOACID, grant 03F0666C) and a BMBF grant (01DR14002).
dc.language English
dc.subject Hyperspectral Imaging
dc.subject Marine & Freshwater Biology
dc.subject Coral Reef Sediments
dc.subject Magnesium Calcites
dc.subject Microphytobenthos
dc.subject Ocean Acidification
dc.subject Environmental Sciences & Ecology
dc.subject Sediment Dissolution
dc.subject Environmental Sciences
dc.subject Microsensors
dc.title Ocean Acidification Changes Abiotic Processes but Not Biotic Processes in Coral Reef Sediments
dc.type journal article
dc.identifier.doi 10.3389/fmars.2017.00073
dc.identifier.wos WOS:000457690600073

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