Publication Date:
2024-02-02
Description:
We have analyzed the stable carbon isotopic composition of the diunsaturated C37 alkenone in 29 surface sediments from the equatorial and South Atlantic Ocean. Our study area covers different oceanographic settings, including sediments from the major upwelling regions off South Africa, the equatorial upwelling, and the oligotrophic western South Atlantic. In order to examine the environmental influences on the sedimentary record the alkenone-based carbon isotopic fractionation (Ep) values were correlated with the overlying surface water concentrations of aqueous CO2 ([CO2(aq)]), phosphate, and nitrate. We found Ep positively correlated with 1/[CO2(aq)] and negatively correlated with [PO43-] and [NO3-]. However, the relationship between Ep and 1/[CO2(aq)] is opposite of what is expected from a [CO2(aq)] controlled, diffusive uptake model. Instead, our findings support the theory of Bidigare et al. (1997, doi:10.1029/96GB03939) that the isotopic fractionation in haptophytes is related to nutrient-limited growth rates. The relatively high variability of the Ep-[PO4] relationship in regions with low surface water nutrient concentrations indicates that here other environmental factors also affect the isotopic signal. These factors might be variations in other growth-limiting resources such as light intensity or micronutrient concentrations.
Keywords:
-; Alkenone, Ep; Alkenone, unsaturation index UK37; Alkenone C37:2, δ13C; Amazon Fan; Angola Basin; Brazil Basin; Calculated; Cape Basin; Carbon dioxide, total; DEPTH, sediment/rock; Elevation of event; Equatorial Atlantic; Event label; Gas chromatography; GeoB; GeoB1008-6; GeoB1016-3; GeoB1028-4; GeoB1032-2; GeoB1041-1; GeoB1105-3; GeoB1117-3; GeoB1214-2; GeoB1413-1; GeoB1501-1; GeoB1503-2; GeoB1505-3; GeoB1508-1; GeoB1515-2; GeoB1703-5; GeoB1706-1; GeoB1710-2; GeoB1711-5; GeoB1712-2; GeoB1713-6; GeoB1719-5; GeoB1903-1; GeoB2102-1; GeoB2109-3; GeoB2125-2; GeoB2204-1; GeoB2215-8; GeoB3117-3; GeoB3603-1; Geosciences, University of Bremen; Giant box corer; GIK17843-1; GKG; Gravity corer (Kiel type); JOPSII-6; Latitude of event; Longitude of event; M12/1; M16/1; M16/2; M20/2; M23/2; M23/3; M34/1; M6/6; M9/4; Mass spectrometer Finnigan MAT 252; Meteor (1986); Mid Atlantic Ridge; MUC; MultiCorer; Namibia Continental Margin; NE-Brazilian continental margin; Nitrate; off Kunene; Phosphate; Sea surface temperature, annual mean; SL; SO84; Sonne; Southern Cape Basin; ST. HELENA HOTSPOT; Victor Hensen; Walvis Ridge; West Angola Basin
Type:
Dataset
Format:
text/tab-separated-values, 249 data points
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