Mn∕Ca intra- and inter-test variability in the benthic foraminifer <i>Ammonia tepida</i>

TitreMn∕Ca intra- and inter-test variability in the benthic foraminifer Ammonia tepida
Type de publicationArticle de revue
AuteurPetersen, Jassin, Barras, Christine , Bézos, Antoine, La, Carole, de Nooijer, Lennart Jan, Meysman, Filip JR, Mouret, Aurélia, Slomp, Caroline P, Jorissen, Frans
EditeurEuropean Geosciences Union
TypeArticle scientifique dans une revue à comité de lecture
Année2018
LangueAnglais
DateJanvier 2018
Numéro1
Pagination331-348
Volume15
Titre de la revueBiogeosciences
ISSN1726-4170
Résumé en anglais

The adaptation of some benthic foraminiferal species to low-oxygen conditions provides the prospect of using the chemical composition of their tests as proxies for bottom water oxygenation. Manganese may be particularly suitable as such a geochemical proxy because this redox element is soluble in reduced form (Mn2+) and hence can be incorporated into benthic foraminiferal tests under low-oxygen conditions. Therefore, intra- and inter-test differences in foraminiferal Mn∕Ca ratios may hold important information about short-term variability in pore water Mn2+ concentrations and sediment redox conditions. Here, we studied Mn∕Ca intra- and inter-test variability in living individuals of the shallow infaunal foraminifer Ammonia tepida sampled in Lake Grevelingen (the Netherlands) in three different months of 2012. The deeper parts of this lake are characterized by seasonal hypoxia/anoxia with associated shifts in microbial activity and sediment geochemistry, leading to seasonal Mn2+ accumulation in the pore water. Earlier laboratory experiments with similar seawater Mn2+ concentrations as encountered in the pore waters of Lake Grevelingen suggest that intra-test variability due to ontogenetic trends (i.e. size-related effects) and/or other vital effects occurring during calcification in A. tepida (11–25% relative SD, RSD) is responsible for part of the observed variability in Mn∕Ca. Our present results show that the seasonally highly dynamic environmental conditions in the study area lead to a strongly increased Mn∕Ca intra- and inter-test variability (average of 45% RSD). Within single specimens, both increasing and decreasing trends in Mn∕Ca ratios with size are observed. Our results suggest that the variability in successive single-chamber Mn∕Ca ratios reflects the temporal variability in pore water Mn2+. Additionally, active or passive migration of the foraminifera in the surface sediment may explain part of the observed Mn∕Ca variability.

URL de la noticehttp://okina.univ-angers.fr/publications/ua18559
DOI10.5194/bg-15-331-2018
Lien vers le document

https://www.biogeosciences.net/15/331/2018/

Titre abrégéBiogeosciences