The benthic foraminiferal community in a naturally CO2-rich coastal habitat in the southwestern Baltic Sea.

Haynert, Kristin, Schönfeld, Joachim, Polovodova-Asteman, I. and Thomsen, Jörn (2012) The benthic foraminiferal community in a naturally CO2-rich coastal habitat in the southwestern Baltic Sea. Open Access Biogeosciences (BG), 9 . pp. 4421-4440. DOI 10.5194/bg-9-4421-2012.

[img]
Preview
Text
2012_Haynert_etal_Biogeosc_final.pdf - Published Version
Available under License Creative Commons Attribution.

Download (961Kb) | Preview
[img]
Preview
Text
bg-9-4421-2012-supplement.pdf - Supplemental Material
Available under License Creative Commons Attribution.

Download (306Kb) | Preview

Supplementary data:

Abstract

It is expected that the calcification of foraminifera will be negatively affected by the ongoing acidification of the oceans. Compared to the open oceans, these organisms are subjected to much more adverse carbonate system conditions in coastal and estuarine environments such as the southwestern Baltic Sea, where benthic foraminifera are abundant. This study documents the seasonal changes of carbonate chemistry and the ensuing response of the foraminiferal community with bi-monthly resolution in Flensburg Fjord. In comparison to the surface pCO2, which is close to equilibrium with the atmosphere, we observed large seasonal fluctuations of pCO2 in the bottom and sediment pore waters. The sediment pore water pCO2 was constantly high during the entire year ranging from 1244 to 3324 μatm. Nevertheless, in contrast to the bottom water, sediment pore water was slightly supersaturated with respect to calcite as consequence of higher alkalinity (AT) for the most time of the year. Foraminiferal assemblages were dominated by two calcareous species, Ammonia aomoriensis and Elphidium incertum, and the agglutinated Ammotium cassis. The one year-cycle was characterized by seasonal community shifts. Our results revealed that there is no dynamic response of foraminiferal population density and diversity to elevated sediment pore water pCO2. Surprisingly, the fluctuations of sediment pore water undersaturation (Ωcalc) co-vary with the population densities of living Ammonia aomoriensis. Further, we observed that most of the tests of living calcifying specimens were intact. Only Ammonia aomorienis showed dissolution and recalcification structures on the tests, especially at undersaturated conditions. Therefore, the benthic community is subjected to constantly high pCO2 and tolerates elevated levels as long as sediment pore water remains supersaturated. Model calculations inferred that increasing atmospheric CO2 concentrations will finally lead to a perennial undersaturation in sediment pore waters. Whereas benthic foraminifera indeed may cope with a high sediment pore water pCO2, the steady undersaturation of sediment pore waters would likely cause a significant higher mortality of the dominating Ammonia aomoriensis. This shift may eventually lead to changes in the benthic foraminiferal communities in Flensburg Fjord, as well as in other regions experiencing naturally undersaturated Ωcalc levels.

Document Type: Article
Additional Information: WOS:000312667300017
Keywords: Biogeochemistry, Coastal Ocean; Biogeochemistry: Sediment; Baltic Sea; Flensburg Fjord; OCEAN ACIDIFICATION; CARBON-DIOXIDE; MORPHOLOGICAL ABNORMALITIES; REDUCED CALCIFICATION; FLENSBURG FJORD; TEPIDA CUSHMAN; CORAL-REEFS; SEAWATER; CO2; ENVIRONMENTS
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-B Experimental Ecology - Benthic Ecology
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-9-4421-2012
ISSN: 1726-4170
Projects: Boknis Eck, Future Ocean
Date Deposited: 26 Sep 2012 09:09
Last Modified: 17 Jul 2013 08:55
URI: http://oceanrep.geomar.de/id/eprint/15424

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...