- Dona Paula, Goa, India.
- +91-0832- 2450327
- iiosc2020[at]nio[dot]org
| Abstract Submission No. | ABS-2022-06-0076 |
| Title of Abstract | Organic matter cycling in evolving hypoxic environments: the roles of oxygen availability and benthic faunal communities |
| Authors | Greg Cowie*, Carol White, Clare Woulds |
| Organisation | University of Edinburgh |
| Address | The School of GeoSciences, University of Edinburgh Edinburgh, Midlothian, United Kingdom Pincode: EH9 3FE Mobile: 7722655919 E-mail: glcowie@glg.ed.ac.uk |
| Country | United Kingdom |
| Presentation | Poster |
| Abstract | Continental margin sediments are key sites of carbon cycling and sequestration. Factors including oxygen exposure time and sedimentation rate are important controls on eventual C preservation, but the least well understood aspect is the role of benthic fauna. Seafloor faunal communities exert influence via a number of activities, including digestion, bioturbation/bioirrigation, respiration, and microbial stimulation. In addition, oxygen and OC (food) availability are known to influence faunal size and abundance, and thus benthic biological processing of OC. Consequently, complex relationships exist between benthic faunal communities, sediment geochemistry and oxygen availability, which have been challenging to deconvolve. The Arabian Sea oxygen minimum zone provides a natural laboratory to study the interplay of these factors, and to assess how ecosystems and biogeochemical cycling may respond to projected environmental change. Isotope tracing experiment were performed at three sites exhibiting contrasting oxygen and OC concentrations, and faunal communities. Experiments were performed at ambient oxygen concentrations, and under oxygen saturations manipulated upwards and downwards by 5%. Both upward and downward oxygen manipulations led to increases in bacterial C uptake and decreases in total community respiration (except at the lowest oxygen site). Increases in oxygen availability favoured faunal C uptake, but the relative benefits to foraminifera and macrofauna varied amongst sites. Downward manipulations of oxygen always led to an increased dominance of foraminiferal C uptake over macrofaunal uptake, but led to a decrease in faunal uptake overall. Thus, both upward and downward oxygen manipulations affected the pathways of benthic organic carbon cycling, with implications for the impacts of future spreading of hypoxia on ecosystem function. |