Tracing Termohaline Properties and Productivity of Shelf Water Masses with Stable Isotopic Composition of Benthic Foraminifera
Abstract
We explore the applicability of stable isotopic ratios of four foraminiferal epifaunal species: Pseudononion atlanticum, Cibicides fletcheri, Hoeglundina elegans, Hanzawaia boueana; and of five infaunal foraminiferal species: Bulimina marginata, Cassidulina subglobosa, Buccella peruviana, Uvigerina peregrina, Angulogerina angulosa to identify bottom water masses on a continental shelf. Samples were collected along the Argentinean-Uruguayan and Brazilian Atlantic Coast during the winter 2003 and summer 2004. Results show that the stable isotopic composition of living and dead foraminifera is associated with environmental variables (latitude, water depth, temperature, salinity and nutrients) showing a general trend of higher δ18O and δ13C values with increasing latitude reflecting the influence of cooler water masses. Specifically, the δ18O data from Uvigerina peregrina, Hoeglundina elegans and Pseudononion atlanticum follow meridional temperature gradients with the presence of relatively warm Subtropical Shelf Water indicated by lower δ18O values at the northern sites (27°S) and colder Sub Antarctic Shelf Water with higher δ18O values toward the southern sites (to 37°S). Angulogerina angulosa and Pseudononion atlanticum δ18O values correlated better with salinity than temperature. Positive correlation of δ13C and water depth in the epifaunal foraminiferal species of Cibicides fletcheri seems to be consistent (R2=1) in both winter and summer, followed by Pseudononion atlanticum (winter, R2=0,2849; summer, R2=0,4996). The positive correlation of δ13C and water depth in the infaunal foraminiferal species are best expressed by Angulogerina angulosa (winter, R2=1) and Buccella peruviana (winter, R2=0,6797; summer, R2=0,4672). Positive correlation of δ13C and water depth indicate that productivity seems to increase with the depth in both epifaunal (flourishes under oligothrofic environments) and infaunal foraminifera (needs more organic-enriched sediments).; ;
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMGC33C1027E
- Keywords:
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- 1041 GEOCHEMISTRY / Stable isotope geochemistry;
- 4804 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL / Benthic processes;
- benthos