Conference proceeding
Pteropods as oceanographic proxies; testing the impact of dissolution on stable isotopes and comparing modern and core-top samples
American Geophysical Union Fall Meeting, Vol.2019
Dec 2019
Abstract
Pteropods are used as biological indicators of ocean acidification in the modern ocean due to the sensitivity of their thin aragonitic shells to changes in ocean chemistry. However, despite their importance, they are underutilized as environmental proxies. Here we present the stable isotopic composition of the shells of 67 Heliconoides inflatus specimens from 17 sediment trap samples (1996 - 1998) in the Cariaco Basin, Venezuela. These measurements were compared to hydrographic measurements taken during the CARIACO timeseries, as well as the calculated delta (super 18) O of seawater. Pteropod shell condition, a measure of the amount of dissolution that a pteropod shell has undergone, was assessed to determine whether dissolution affects shell stable isotopic composition. The shells in this study ranged from transparent and pristine, to opaque-white and displaying surface layer dissolution. We found no correlation between pteropod shell condition and delta (super 18) O and delta (super 13) C. Comparisons between the temperature and salinity of the water column and shell delta (super 18) O suggest that H. inflatus calcifies at a depth of 40 m in the Cariaco Basin, shallower than the most recent calcification estimate for this species of 75 m. The isotopic composition of an additional 48 H. inflatus shells from a Cariaco Basin core top sample (192 m water depth; nearly equal 1000 yr BP) were also measured. Specimens from the sediment trap display an offset in both delta (super 13) C (0.4 ppm) and delta (super 18) O (0.2 ppm) relative to that of specimens from the core top. This offset is comparable to values reported from a study on planktic foraminifera, another group of calcareous plankton, with the delta (super 18) O values capturing an increase in seawater temperature and the delta (super 13) C values reflecting an increase in isotopically light carbon associated with the burning of fossil fuels (delta (super 13) C). Both planktic foraminifera (G. sacculifer) and pteropods (H. inflatus) from the same core top sample were radiocarbon dated, however, the resulting ages vary by 880 years. This discordance is currently unexplained, though the few other studies radiocarbon dating both foraminifera and pteropods also find non-overlapping ages. This research reaffirms that the stable isotopic composition of pteropod shells are reliable recorders of water column chemistry, and can preserve a signal of environmental variability in the shallow sedimentary record.
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Details
- Title
- Pteropods as oceanographic proxies; testing the impact of dissolution on stable isotopes and comparing modern and core-top samples
- Creators
- R. L. Oakes - Academy of Natural Sciences of Drexel University Philadelphia, PA USA United StatesC. V. DavisJ. A. SessaAnonymous
- Publication Details
- American Geophysical Union Fall Meeting, Vol.2019
- Conference
- American Geophysical Union Fall Meeting (2019)
- Publisher
- American Geophysical Union
- Resource Type
- Conference proceeding
- Language
- English
- Academic Unit
- Academy of Natural Sciences of Drexel University; Biodiversity, Earth, and Environmental Science (BEES)
- Identifiers
- 991021013171504721