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Planktonic foraminiferal area density as a proxy for carbonate ion concentration: A calibration study using the Cariaco Basin ocean time series

Planktonic foraminiferal area density as a proxy for carbonate ion concentration: A calibration study using the Cariaco Basin ocean time series
Planktonic foraminiferal area density as a proxy for carbonate ion concentration: A calibration study using the Cariaco Basin ocean time series
Biweekly sediment trap samples and concurrent hydrographic measurements collected between March 2005 and October 2008 from the Cariaco Basin, Venezuela, are used to assess the relationship between [CO32?] and the area densities (?A) of two species of planktonic foraminifera (Globigerinoides ruber (pink) and Globigerinoides sacculifer). Calcification temperatures were calculated for each sample using species-appropriate oxygen isotope (?18O) temperature equations that were then compared to monthly temperature profiles taken at the study site in order to determine calcification depth. Ambient [CO32?] was determined for these calcification depths using alkalinity, pH, temperature, salinity, and nutrient concentration measurements taken during monthly hydrographic cruises. The ?A, which is representative of calcification efficiency, is determined by dividing individual foraminiferal shell weights (±0.43 µg) by their associated silhouette areas and taking the sample average. The results of this study show a strong correlation between ?A and ambient [CO32?] for both G. ruber and G. sacculifer (R2?=?0.89 and 0.86, respectively), confirming that [CO32?] has a pronounced effect on the calcification of these species. Though the ?A for both species reveal a highly significant (p?<?0.001) relationship with ambient [CO32?], linear regression reveals that the extent to which [CO32?] influences foraminiferal calcification is species specific. Hierarchical regression analyses indicate that other environmental parameters (temperature and [PO43?]) do not confound the use of G. ruber and G. sacculifer ?A as a predictor for [CO32?]. This study suggests that G. ruber and G. sacculifer ?A can be used as reliable proxies for past surface ocean [CO32?].
foraminifera, carbonate ion, area density, ocean acidifiation, calcification
0883-8305
363-376
Marshall, Brittney J.
4c1f0ae8-6038-427b-b58f-eb151adf1815
Thunell, Robert C.
932169c7-0406-4112-a5b6-5da5422485e8
Henehan, Michael J.
e64fc230-0233-4660-9811-8252e8a1ddf9
Astor, Yrene
befc2b32-4cc8-439c-b20e-63c23a3a1a27
Wejnert, Katherine E.
c6151fd7-553d-4f6a-842c-a448eb4f6c78
Marshall, Brittney J.
4c1f0ae8-6038-427b-b58f-eb151adf1815
Thunell, Robert C.
932169c7-0406-4112-a5b6-5da5422485e8
Henehan, Michael J.
e64fc230-0233-4660-9811-8252e8a1ddf9
Astor, Yrene
befc2b32-4cc8-439c-b20e-63c23a3a1a27
Wejnert, Katherine E.
c6151fd7-553d-4f6a-842c-a448eb4f6c78

Marshall, Brittney J., Thunell, Robert C., Henehan, Michael J., Astor, Yrene and Wejnert, Katherine E. (2013) Planktonic foraminiferal area density as a proxy for carbonate ion concentration: A calibration study using the Cariaco Basin ocean time series. Paleoceanography, 28 (2), 363-376. (doi:10.1002/palo.20034).

Record type: Article

Abstract

Biweekly sediment trap samples and concurrent hydrographic measurements collected between March 2005 and October 2008 from the Cariaco Basin, Venezuela, are used to assess the relationship between [CO32?] and the area densities (?A) of two species of planktonic foraminifera (Globigerinoides ruber (pink) and Globigerinoides sacculifer). Calcification temperatures were calculated for each sample using species-appropriate oxygen isotope (?18O) temperature equations that were then compared to monthly temperature profiles taken at the study site in order to determine calcification depth. Ambient [CO32?] was determined for these calcification depths using alkalinity, pH, temperature, salinity, and nutrient concentration measurements taken during monthly hydrographic cruises. The ?A, which is representative of calcification efficiency, is determined by dividing individual foraminiferal shell weights (±0.43 µg) by their associated silhouette areas and taking the sample average. The results of this study show a strong correlation between ?A and ambient [CO32?] for both G. ruber and G. sacculifer (R2?=?0.89 and 0.86, respectively), confirming that [CO32?] has a pronounced effect on the calcification of these species. Though the ?A for both species reveal a highly significant (p?<?0.001) relationship with ambient [CO32?], linear regression reveals that the extent to which [CO32?] influences foraminiferal calcification is species specific. Hierarchical regression analyses indicate that other environmental parameters (temperature and [PO43?]) do not confound the use of G. ruber and G. sacculifer ?A as a predictor for [CO32?]. This study suggests that G. ruber and G. sacculifer ?A can be used as reliable proxies for past surface ocean [CO32?].

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More information

Published date: June 2013
Keywords: foraminifera, carbonate ion, area density, ocean acidifiation, calcification
Organisations: Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 355634
URI: https://eprints.soton.ac.uk/id/eprint/355634
ISSN: 0883-8305
PURE UUID: 4afd8a23-c2ac-4cad-b949-d9d1e1c5f9f5

Catalogue record

Date deposited: 09 Aug 2013 10:50
Last modified: 20 Apr 2018 16:32

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