Planktic foraminiferal shell thinning in the Arabian Sea due to anthropogenic ocean acidification?

Article English OPEN
de Moel, H. ; Ganssen, G. M. ; Peeters, F. J. C. ; Jung, S. J. A. ; Kroon, D. ; Brummer, G. J. A. ; Zeebe, R. E. (2009)
  • Publisher: COPERNICUS GESELLSCHAFT MBH
  • Journal: BIOGEOSCIENCES (issn: 1726-4170, eissn: 1726-4189)
  • Related identifiers: doi: 10.5194/bg-6-1917-2009
  • Subject: /dk/atira/pure/subjectarea/asjc/1900/1904 | Ecology | /dk/atira/pure/subjectarea/asjc/1100/1105 | QH540-549.5 | QE1-996.5 | Ecology, Evolution, Behavior and Systematics | QH501-531 | Geology | Life | Earth-Surface Processes

About one third of the anthropogenic carbon dioxide (CO<sub>2</sub>) released into the atmosphere in the past two centuries has been taken up by the ocean. As CO<sub>2</sub> invades the surface ocean, carbonate ion concentrations and pH are lowered. Laboratory studies indicate that this reduces the calcification rates of marine calcifying organisms, including planktic foraminifera. Such a reduction in calcification resulting from anthropogenic CO<sub>2</sub> emissions has not been observed, or quantified in the field yet. Here we present the findings of a study in the Western Arabian Sea that uses shells of the surface water dwelling planktic foraminifer <i>Globigerinoides ruber</i> in order to test the hypothesis that anthropogenically induced acidification has reduced shell calcification of this species. We found that light, thin-walled shells from the surface sediment are younger (based on <sup>14</sup>C and δ<sup>13</sup>C measurements) than the heavier, thicker-walled shells. Shells in the upper, bioturbated, sediment layer were significantly lighter compared to shells found below this layer. These observations are consistent with a scenario where anthropogenically induced ocean acidification reduced the rate at which foraminifera calcify, resulting in lighter shells. On the other hand, we show that seasonal upwelling in the area also influences their calcification and the stable isotope (δ<sup>13</sup>C and δ<sup>18</sup>O) signatures recorded by the foraminifera shells. Plankton tow and sediment trap data show that lighter shells were produced during upwelling and heavier ones during non-upwelling periods. Seasonality alone, however, cannot explain the <sup>14</sup>C results, or the increase in shell weight below the bioturbated sediment layer. We therefore must conclude that probably both the processes of acidification and seasonal upwelling are responsible for the presence of light shells in the top of the sediment and the age difference between thick and thin specimens.
  • References (62)
    62 references, page 1 of 7

    Anderson, D. M. and Archer, D.: Glacial-interglacial stability of ocean pH inferred from foraminifer dissolution rates, Nature, 416, 70-73, 2002.

    Asami, R., Yamada, T., Iryu, Y., Quinn, T. M., Meyer, C. P., and Paulay, G.: Interannual and 5 decadal variability of the western Pacific sea surface condition for the years 1787-2000: Reconstruction based on sTable isotope record from a Guam coral, J. Geophys. Res.-Oceans, 110, C05018, doi:10.1029/2004JC002555, 2005.

    Barker, S. and Elderfield, H.: Foraminiferal Calcification Response to Glacial-Interglacial Changes in Atmospheric CO2, Science, 297, 833-836, 2002.

    10 Barker, S., Broecker, W., Clark, E., and Hajdas, I.: Radiocarbon age offsets of foraminifera resulting from differential dissolution and fragmentation within the sedimentary bioturbated zone, Paleoceanogr., 22, PA2205, doi:10.1029/2006PA001354, 2007.

    Berger, W. H.: Planktonic Foraminifera: Selective solution and the lysocline, Mar. Geol., 8, 111-138, 1970.

    15 Beveridge, N. A. S. and Shackleton, N. J.: Carbon isotopes in recent planktonic foraminifera: A record of anthropogenic CO2 invasion of the surface ocean, Earth Planet. Sci. Lett., 126, 259-273, 1994.

    Bijma, J., Spero, H. J., and Lea, D. W.: Reassessing Foraminiferal STable Isotope Geochemistry: Impact of the Oceanic Carbonate System, in: Use of Proxies in Paleoceanography: 20 Examples of the South Atlantic, edited by: Fisher, G. and Wefer, G., Springer-Verlag, New York, 489-512, 1999.

    Bohm, F., Joachimski, M. M., Lehnert, H., Morgenroth, G., Kretschmer, W., Vacelet, J., and Dullo, W.-C.: Carbon isotope records from extant Caribbean and South Pacific sponges: Evolution of [delta]13C in surface water DIC, Earth Planet. Sci. Lett., 139, 291-303, 1996.

    25 Bo¨hm, F., Haase-Schramm, A., Eisenhauer, A., Dullo, W. C., Joachimski, M. M., Lehnert, H., and Reitner, J.: Evidence for preindustrial variations in the marine surface water carbonate system from coralline sponges, Geochemistry Geophysics Geosystems, 3(3), 1019, doi:10.1029/2001GC000264, 2002.

    Broecker, W. and Clark, E.: An evaluation of Lohmann's foraminifera weight dissolution index, 30 Paleoceanogr., 16, 531-534, 2001.

  • Related Research Results (1)
  • Metrics
    1
    views in OpenAIRE
    0
    views in local repository
    0
    downloads in local repository
Share - Bookmark