Environmental constraints on Holocene cold-water coral reef growth off Norway: insights from a multiproxy approach
Raddatz, J.; Liebetrau, V.; Trotter, J.; Rüggeberg, A.; Flögel, S.; Dullo, W.-C.; Eisenhauer, A.; Voigt, S.; McCulloch, M. (2016). Environmental constraints on Holocene cold-water coral reef growth off Norway: insights from a multiproxy approach. Paleoceanography 31(10): 1350-1367. https://dx.doi.org/10.1002/2016PA002974 In: Paleoceanography. American Geophysical Union: Washington, DC. ISSN 0883-8305; e-ISSN 1944-9186, more |  |
| Keywords | Desmophyllum pertusum (Linnaeus, 1758) [WoRMS]
Marine/Coastal | | Author keywords | cold-water corals; Lophelia pertusa; boron isotopes; Holocene; pHupregulation; Li; Mg |
| Authors | | Top | - Raddatz, J.
- Liebetrau, V.
- Trotter, J.
| - Rüggeberg, A., more
- Flögel, S.
- Dullo, W.-C.
| - Eisenhauer, A.
- Voigt, S.
- McCulloch, M.
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| Abstract | High-latitude cold-water coral (CWC) reefs are particularly susceptible due to enhanced CO2 uptake in these regions. Using precisely dated (U/Th) CWCs (Lophelia pertusa) retrieved during research cruise POS 391 (Lopphavet 70.6°N, Oslofjord 59°N) we applied boron isotopes (δ11B), Ba/Ca, Li/Mg, and U/Ca ratios to reconstruct the environmental boundary conditions of CWC reef growth. The sedimentary record from these CWC reefs reveals a lack of corals between ~6.4 and 4.8 ka. The question remains if this phenomenon is related to changes in the carbonate system or other causes. The initial postglacial setting had elevated Ba/Ca ratios, indicative of meltwater fluxes showing a decreasing trend toward cessation at 6.4 ka with an oscillation pattern similar to continental glacier fluctuations. Downcore U/Ca ratios reveal an increasing trend, which is outside the range of modern U/Ca variability in L. pertusa, suggesting changes of seawater pH near 6.4 ka. The reconstructed bottom water temperature at Lopphavet reveals a striking similarity to Barent sea surface and subsea surface temperature records. We infer that meltwater pulses weakened the North Atlantic Current system, resulting in southward advances of cold and CO2-rich Arctic waters. A corresponding shift in the δ11B record from ~25.0‰ to ~27.0‰ probably implies enhanced pH up-regulation of the CWCs due to the higher pCO2 concentrations of ambient seawater, which hastened mid-Holocene CWC reef decline on the Norwegian margin. |
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