 |
| Titel |
Relationship between the pore density in benthic foraminifera and bottom-water oxygen content |
| VerfasserIn |
T. Kuhnt, O. Friedrich, G. Schmiedl, Y. Milker, A. Mackensen, R. Schiebel |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060274
|
|
|
|
|
|
| Zusammenfassung |
| Reliable estimates of bottom-water oxygen contents are crucial to understand the formation of past oxygen-depleted environments. Here, we investigate the relationship between pore density in calcareous benthic foraminiferal (BF) tests and measured oxygen concentrations of the surrounding bottom-waters (BW-O2) in living (Rose Bengal stained) specimens of the shallow-infaunal species Bolivina pacifica, and the three deep-infaunal species Fursenkoina mexicana, Globobulimina turgida, and Chilostomella oolina. Used samples span a wide oxygen-gradient across oxygen minimum zones (OMZ) off Namibia and Pakistan.
Bolivina pacifica, F. mexicana and G. turgida display a significant negative exponential correlation between the pore density and BW-O2, indicating a morphological response of the foraminifers to decreasing oxygenation. Supporting previous results, we suggest that an increasing number of pores improves the ability of oxygen uptake in low-oxygen environments. This morphological response can be used to establish an independent proxy for BW-O2. The inter-specific comparison of the dependency of pore density and BW-O2 reveals a steeper gradient for B. pacifica than for F. mexicana, and G. turgida. We hypothesize that the inter-specific pore density-BW-O2-relationship may reflect their species-specific microhabitat preferences. The shallow-infaunal species B. pacifica is probably stronger affected by oxygen depletions than the two deep-infaunal species F. mexicana, and G. turgida.
Our results for the deep-infaunal species C. oolina show no significant relationship between pore density and BW-O2. This suggests that C. oolina has another life-strategy to survive sustained low-oxic conditions than increasing its pore density. Overall, we propose that the pore density of individual BF species provides a valuable independent proxy to reconstruct ancient bottom-water oxygenation.
To test the application of this proxy in fossil assemblages, we used the organic-carbon rich sapropel layer S1 in two cores from the North Agean Sea to illustrate the decrease in BW-O2 before and during the sapropel formation as well as the BW-O2 increase afterwards. |
|
|
|
|
|
|