Data from: Getting to the root of organic inputs in groundwaters: stygofaunal plant consumption in a calcrete aquifer

Groundwater environments interact with and support subterranean biota as
well as superficial aquatic and terrestrial ecosystems. However, knowledge
of subterranean energy flows remains incomplete. Cross-boundary
investigations are needed to better understand the trophic structures of
groundwater ecosystems and their reliance on carbon inputs from
aboveground. In this study we used carbon and nitrogen stable isotope
analyses combined with radiocarbon fingerprints to characterise organic
flows in groundwater ecosystems. We coupled these data with DNA
metabarcoding of the gut contents of consumers to further elucidate
organic matter sources and shifts in diet preferences. Samples were
collected from the arid zone Sturt Meadows calcrete aquifer under low
rainfall (LR) and high rainfall (HR) conditions. Bayesian modelling of
Δ14C, δ13C and δ15N data indicated that primary consumers (copepods)
incorporated mainly particulate organic carbon (POC) under LR but during
HR shifted to root derived material (either exudates or direct root
grazing). By contrast, diets of secondary consumers (amphipods) were
dominated by root material under both LR and HR. Our DNA
metabarcoding-based results indicate that amphipods relied primarily on
root inputs from perennial trees
(likely Eucalyptus and Callitris) during the
dry season (LR). Under HR, diets of both amphipods and copepods also
included organic material derived from a broad range of more shallow
rooted shrubs, and ephemeral herbs and grasses. Our findings illustrate
the complexity of functional linkages between groundwater biota and
terrestrial surficial ecosystems in environments where aboveground
productivity, diversity and organic matter flux to groundwater are
intimately linked to often episodic rainfall.