Inter catchment comparisons of groundwater communities from the Lower Murray Darling Basin

Anthropogenic activities threaten groundwater ecosystems and biota through changes to groundwater levels and contamination. Groundwater ecosystem assessment and monitoring is complicated due to restricted access and the cryptic habits of groundwater biota. The aim of this study was to compare the composition of groundwater biota between catchments of the lower Murray Darling Basin using DNA metabarcoding and identify the role of water quality in shaping the biological communities. Alluvial aquifers were sampled from within the Lachlan (15), Murray (11) and Murrumbidgee (9) catchments. Prokaryotes, eukaryotes and metazoans were targeted using 16S rDNA, 18S rDNA and COI primers, respectively. Water quality variables including water level, salinity, temperature, pH, nutrients, metals were measured to identify correlative relationships between the abiotic and biotic features of each catchment. Results indicated catchments harboured distinct prokaryotic and eukaryotic communities and showed relationships between prokaryotic, eukaryotic and metazoan assemblages and fluctuations in salinity, pH dissolved oxygen and nutrients. Metazoan analysis showed no significant differences among catchments but a strong correlation with nitrogen levels. This illustrates how water quality variables alter prokaryote, eukaryote and metazoans compositions in groundwater ecosystems and emphasises the impacts of anthropogenic activities, highlighting the need to manage groundwater health and protect their unique biota.