Reinterpreting radiocarbon records in bamboo corals – new insights from the tropical North Atlantic

Qian Liu*, Laura F. Robinson, Erica Hendy, Maria G. Prokopenko, Joseph A. Stewart, Timothy D.J. Knowles, Tao Li, Ana Samperiz

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

Abstract

Deep-sea bamboo corals (family Isididae) have been used as archives for reconstructing changes in the past ocean. However, uncertainties remain regarding the interpretation of geochemical signals from their organic nodes, specifically the water depth of the signals recorded by the coral. Here we explore this question by measuring radiocarbon (14C) and nitrogen (15N) isotopic compositions of the organic nodes in six bamboo corals collected from the central and eastern tropical Atlantic between 700 m and 2000 m water depth. By comparing coral 14C to measured seawater data, regional shallow-water coral records and climate-model outputs, we find contrasting results between the two regions. Our bamboo coral 14C results from the eastern tropical Atlantic support previous studies that suggest organic node carbon is sourced primarily from the mixed layer of the ocean. By contrast, the 14C of bamboo coral organic nodes from the oligotrophic central Atlantic better correlates with the 14C content of the subsurface deep chlorophyll maximum layer rather than the surface mixed layer. Combined with nitrogen isotope data, this observation suggests that sinking and/or ambient zooplankton feeding on phytoplankton from the deep chlorophyll maximum layer can contribute a significant proportion of the diet of bamboo corals. These results suggest that the carbon source for bamboo corals organic nodes may not always reside in the mixed layer, especially in oligotrophic regions, which has implications for 14C-based age model development in bamboo corals.
Original languageEnglish
Pages (from-to)296-308
Number of pages13
JournalGeochimica et Cosmochimica Acta
Volume348
Early online date21 Mar 2023
DOIs
Publication statusPublished - 1 May 2023

Bibliographical note

Funding Information:
We acknowledge the crew and researchers on board the research cruise JC094 (Equatorial Atlantic in 2013) who obtained the samples for this study. We thank Oliver Andrews for his support on Earth System Model data extraction and analysis. We thank Christopher Coath, Carolyn Taylor for their help with laboratory work. We thank Abby Ren, Jesse Farmer, and an anonymous reviewer for their beneficial comments. Funding was provided by NERC grants awarded to L.F.R. (NE/S001743/1 and NE/R005117/1), China Scholarship Council to Q. L. and OCE-NSF1949984 to M.G.P.

Publisher Copyright:
© 2023 The Author(s)

Keywords

  • Deep-sea bamboo corals
  • Organic node
  • Bomb radiocarbon (C)
  • Deep chlorophyll maximum
  • Tropical Atlantic

Fingerprint

Dive into the research topics of 'Reinterpreting radiocarbon records in bamboo corals – new insights from the tropical North Atlantic'. Together they form a unique fingerprint.

Cite this