The zinc isotopic composition of siliceous marine sponges: Investigating nature's sediment traps

• Published in: Chemical Geology
• Main Authors: Hendry, Katharine Rosemary, Andersen, Morten B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2013
• Subjects: QD Chemistry; QE Geology; Southern Ocean
• Online Access: https://orca.cardiff.ac.uk/id/eprint/48616/; https://doi.org/10.1016/j.chemgeo.2013.06.025; https://orca.cardiff.ac.uk/id/eprint/48616/1/OA-20132014-06.pdf

The Zinc (Zn) content and isotopic composition of marine biogenic opal has the potential to yield information about the nutrient availability, utilisation and export of particulate organic matter from surface to deep waters. Here, we report the first measurements of the Zn isotopic composition of deep-sea marine sponge skeletal elements – spicules - collected in the Southern Ocean. Our results highlight different Zn uptake and isotopic fractionation behaviour between the two major siliceous sponge clades (hexactinellids and demosponges), which is most likely linked to sponge feeding strategy. Hexactinellid spicule Zn isotopic compositions are not fractionated with respect to seawater, most likely due to Zn transport via the open internal structure of the sponges. In contrast, demosponge spicules exhibit a wide range of Zn isotopic compositions that are related to the opal Zn concentration, most likely reflecting variable Zn isotope compositions in the organic matter particles on which they feed, and internal fractionation processes.