Subterranean carbon flows from source to stygofauna: a case study on the atyid shrimp Stygiocaris stylifera (Holthuis, 1960) from Barrow Island (WA)

ABSTRACT

Groundwater biota are crucial for the ecological functioning of subterranean ecosystems. However, while knowledge of the taxonomic diversity of groundwater invertebrates (stygofauna) is increasing, functional ecological information is still limited. Here, we investigate seldom empirically tested assumptions around stygofaunal trophic plasticity in coping with oligotrophic habitats. We focus on Barrow Island (Western Australia), an ideal natural laboratory due to the occurrence of natural oil seeps in association with aquifers. The trophic position and food source use of the endemic atyid shrimp Stygiocaris stylifera (Holthuis, 1960) were assessed via δ¹³C and δ¹⁵N stable isotope analysis (SIA). Background information on the environmental conditions was gathered through hydrochemical data and δ¹³C SIA combined with ¹⁴C data from dissolved inorganic/organic carbon and particulate organic carbon from groundwater samples. Our results indicate carbon enrichment in proximity to the natural oil seepage coupled with changes in trophic positions of S. stylifera from higher consumers/predators to biofilm grazers/decomposers. These results are consistent with an increased involvement of hydrocarbon seeps and associated microbial communities in the carbon flows and confirm potential for the trophic flexibility in stygofauna. Further investigations involving other trophic groups will help elucidate the functioning of the ecosystems at a community level.

KEYWORDS:

• Biofilm
• carbon-13
• carbon-14
• groundwater ecology
• hydrocarbons
• isotope ecology
• nitrogen-15
• stygofauna
• organic matter
• trophic webs

Disclosure statement

Survey design and site selection for the overarching project was a collaborative process involving Chevron Australia, Stantec Australia Pty Ltd and Enpoint Consultants. Dr Nicholas Stevens was employed by Stantec Australia Pty Ltd from 2010 to 2020.

Additional information

Funding

The work presented in this paper was funded by Chevron Australia and forms part of an overarching project undertaken by Stantec Australia Pty Ltd. Curtin University was funded on a consultancy basis by Stantec to support Saccò and Blyth’s contribution to the project. Matthew Jones of Enpoint Consultants was engaged by Chevron Australia. Nicholas Stevens, Fiona Taukulis and Erin Thomas received salary from Stantec Australia Pty Ltd during the project.