Rainfall as a trigger of ecological cascade effects in an Australian groundwater ecosystem

Mattia Saccò,Debashish Mazumder,Steven J B Cooper,William F Humphreys,Kliti Grice,Quan Hua,Nicole E White,Christian Griebler,Colin Smith,Mahsa Mousavi-Derazmahalleh,Matthew Campbell,Alison J Blyth

doi:10.1038/s41598-021-83286-x

Abstract

Groundwaters host vital resources playing a key role in the near future. Subterranean fauna and microbes are crucial in regulating organic cycles in environments characterized by low energy and scarce carbon availability. However, our knowledge about the functioning of groundwater ecosystems is limited, despite being increasingly exposed to anthropic impacts and climate change-related processes. In this work we apply novel biochemical and genetic techniques to investigate the ecological dynamics of an Australian calcrete under two contrasting rainfall periods (LR—low rainfall and HR—high rainfall). Our results indicate that the microbial gut community of copepods and amphipods experienced a shift in taxonomic diversity and predicted organic functional metabolic pathways during HR. The HR regime triggered a cascade effect driven by microbes (OM processors) and exploited by copepods and amphipods (primary and secondary consumers), which was finally transferred to the aquatic beetles (top predators). Our findings highlight that rainfall triggers ecological shifts towards more deterministic dynamics, revealing a complex web of interactions in seemingly simple environmental settings. Here we show how a combined isotopic-molecular approach can untangle the mechanisms shaping a calcrete community. This design will help manage and preserve one of the most vital but underrated ecosystems worldwide.

Highlights

Groundwaters host vital resources playing a key role in the near future
To elucidate carbon flows through the stygofaunal community we focused on the essential amino acids Valine (Val), Phenylalanine (Phe) and Arginine (Arg), as these compounds must be integrated through diet and cannot be synthetised internally by the fauna[14,34]
The Principal Components Analysis (PCA) using the Kyoto Encyclopedia of Genes and Genomes (KEGG) orthologs function prediction showed that cyclopoids from both rainfall periods (C[LR] and C[high rainfall regime (HR)]) clustered close to the harpacticoids (H[LR]) and amphipods (AM1[LR], AM2[LR] and AM3[LR]) from the LR regime (Fig. 2b)

Summary

Introduction

Groundwaters host vital resources playing a key role in the near future. Subterranean fauna and microbes are crucial in regulating organic cycles in environments characterized by low energy and scarce carbon availability. We show how a combined isotopic-molecular approach can untangle the mechanisms shaping a calcrete community This design will help manage and preserve one of the most vital but underrated ecosystems worldwide. Stable isotope chemistry (SIA—Stable Isotope Analysis, CSIA—Compound Specific Stable Isotope Analysis) and molecular biology (eDNA—environmental DNA, DNA metabarcoding, etc.) are two disciplines providing new perspectives in the study of ecological dynamics in freshwater e nvironments[11]. These techniques are still mainly employed in marine and surface terrestrial environments, and their application in groundwaters is in its infancy[14]

Methods

Results

Conclusion