Some of our purest water relies on a delicate balance of life - bacteria, crustaceans and invertebrates - that filter and feed on water-borne pollutants.
NIWA ecologist and crustacean expert Graham Fenwick is embarking on a new study of ancient groundwater ecosystems to better understand how they work.
Though out of sight, he says these ecosystems play a vital role in our environment.
These alluvial aquifers are typical of the big plains systems in Canterbury, Blenheim and Hawke’s Bay.
“The water percolating into the ground carries with it dissolved organic carbon, the building blocks of life as we know it. It is created by plants photosynthesising using light - all animals eat organic carbon to provide the energy to live. “
This organic carbon gets carried into the groundwater where it is too dark for plants to grow and forms biofilms – the slightly slimy coating on the underside of a stone in a river is a biofilm.
Invertebrates browse the biofilms and keep them under control to stop them clogging up the whole system.
The problem comes, Fenwick says, when pollutants enter these aquifers. And we don’t really understand what impact this has on them.
“Where we get organic enrichment of the ground water through human activities - industrial or faming effluent - it stimulates bacteria and also larger populations of these invertebrates. If you take out the invertebrates then there is a chance that the ground water system could become clogged.“
He says we know nitrates are toxic to a host of invertebrates living in rivers, but there is very little evidence how much nitrate is safe in aquifers.
He hopes his research will help understand the bio-diversity that exists in these aquifers.
Many of the species that we’re dealing with here are completely unknown to science, potentially we’ve got species that are unique to individual catchments.” he says.