Groundwater ecosystems consist of simple foodwebs with microbes (archaea, bacteria and fungi) providing biofilms on which protozoans and stygofauna (highly adapted groundwater invertebrates) graze. It is apparent biota provide a range of ecosystem services significant for water quality and quantity. Microbes perform a range of metabolic functions important for biogeochemical cycling of carbon, sulfur, iron and nitrogen. Similarly, stygofauna and protozoans are believed to perform a range of functions from grazing and promoting microbial growth, through to maintaining pathways for water flow within aquifers. Thus the maintenance of these ecosystems services within groundwater resources is vital for industries such as agriculture, which in many parts of the world is heavily reliant on irrigation from groundwater.
Previous studies indicate the significant biodiversity of groundwater fauna, however relatively few studies have studied groundwater microbial communities, mainly due to difficulties in using traditional methods to culture these organisms. With advances in technology, it has now become relatively easy (albeit expensive) to study the potential microbial function and diversity within environmental data though the use of metagenomics and DNA sequencing.
The study utilised a combination of both traditional (pumping and netting) techniques as well as DNA community profiling (metabarcoding) of 16S rDNA and 18S rDNA, to characterise groundwater biota (stygofauna and microbes) from three catchments within the Murray-Darling Basin, eastern Australia with data collected between 2015-2016. A number of differences in the compositional structure of biota under irrigated or non-irrigated lands were demonstrated, including differences in relative abundances of nitrogen cycling microbes and stygofauna communities. Such findings suggest agricultural activities can alter groundwater biotic composition and functions, which may in turn influence biogeochemical cycling and ecosystem services provided by groundwater ecosystems.