de Moel, Hans; Ganssen, Gerald M; Peeters, Frank J C; Jung, Simon J A; Kroon, Dick; Brummer, Geert-Jan A; Zeebe, Richard E (2010): Geochemistry and morphometry on planktonic foraminifera. PANGAEA, https://doi.org/10.1594/PANGAEA.746072, Supplement to: de Moel, H et al. (2009): Planktic foraminiferal shell thinning in the Arabian Sea due to anthropogenic ocean acidification? Biogeosciences, 6, 1917-1925, https://doi.org/10.5194/bg-6-1917-2009
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About one third of the anthropogenic carbon dioxide (CO2) released into the atmosphere in the past two centuries has been taken up by the ocean. As CO2 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 CO2 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 Globigerinoides ruber 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 14C and d13C 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 (d13C and d18O) 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 14C 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.
Median Latitude: 10.821433 * Median Longitude: 51.964733 * South-bound Latitude: 10.774300 * West-bound Longitude: 51.944200 * North-bound Latitude: 10.915700 * East-bound Longitude: 51.975000
Date/Time Start: 1992-06-02T00:00:00 * Date/Time End: 1993-03-01T00:00:00
905B * Latitude: 10.915700 * Longitude: 51.944200 * Date/Time: 1993-03-01T00:00:00 * Elevation: -1567.0 m * Location: Indian Ocean * Campaign: NIOP-C2 * Basis: Tyro * Method/Device: Box corer (BC)
Datasets listed in this publication series
- de Moel, H; Ganssen, GM; Peeters, FJC et al. (2010): Shells weights from sediment core 905B. https://doi.org/10.1594/PANGAEA.746074
- de Moel, H; Ganssen, GM; Peeters, FJC et al. (2010): Radiocarbon analysis of foraminifera tests from core top of box corer BC21WP7. https://doi.org/10.1594/PANGAEA.746073
- de Moel, H; Ganssen, GM; Peeters, FJC et al. (2010): Stable isotope measurements on G. ruber from the core top of BC21WP7. https://doi.org/10.1594/PANGAEA.746071
- de Moel, H; Ganssen, GM; Peeters, FJC et al. (2010): Shells weights from the core top of BC21WP7. https://doi.org/10.1594/PANGAEA.746068
- de Moel, H; Ganssen, GM; Peeters, FJC et al. (2010): Wall thicknesses of thick and thin shells from the core top of BC21WP7. https://doi.org/10.1594/PANGAEA.746069
- de Moel, H; Ganssen, GM; Peeters, FJC et al. (2010): Weights of foraminifera shells from surface water. https://doi.org/10.1594/PANGAEA.746076