Measuring Groundwater Health

ESR scientists studying groundwater aquifers in Canterbury and Southland are seeing a reduction in biological diversity due to an increase in nutrient concentrations.

The research project, which was presented today at the Water New Zealand Conference in Hamilton, is looking at what the organisms that exist in underground aquifers can tell us about the health of groundwater supplies.

Scientists have been studying four sites in Canterbury and three sites in Southland to set up a database of organisms present and look at the diversity occurring between sites.

ESR scientist Louise Weaver says the ecosystem in groundwater plays a vital role in processing contaminants such as nitrates that end up there from a range of land uses.

“The perception is that groundwater is a sterile environment. However, there are organisms there that form a complex ecosystem that can protect the water as part of nutrient cycling.”

But these natural underground communities of organisms are coming under stress from the cumulative effects of a range of contaminants coming from the land.

Dr Weaver says that by looking at the whole range of organisms that are there and how they change in response to contaminants, scientists can start building a picture of the health of the groundwater environment. Changes in water quality will be seen in changes to biological diversity.

The scientists have been looking at the bacteria, fungi, protozoa and macroinvertebrates in the groundwater at the seven sites as well as the water chemistry.

Dr Weaver says one of the challenges has been identifying the organisms that play a part in removing the nitrates.

She says changes in above ground ecosystems are well understood because they have been studied intensively for so long. By comparison some of the macroinvertebrates and microorganisms in groundwater systems have yet to be identified.

“At the moment there is so much fundamental research we don’t know. There is a whole range of organisms that have specific functions, habitats and inter-relationships, which are currently poorly understood.”

The project is part of wider research looking to develop an index, similar to the macroinvertebrate community index which is used in surface water, to get an indication of the health of the groundwater resource.

Dr Weaver says New Zealand scientists are at a very early stage of developing a groundwater index, and refining systems for getting accurate samples of the vast array of macroinvertebrates and microbial organisms that are there.

Aside from the inherent conservation values in the array of organisms present in groundwater, Dr Weaver says research to identify and characterise what is there would have another benefit.

“If we understand the processes and the organisms involved in more detail then there’s the potential to actually use them for bio-remediation - in the future you could put in some of these organisms into the system to drive the removal of contaminants even further.”

The research has been made possible through MBIE’s Strategic Science Investment Fund (SSIF) and is aligned with the Biological National Challenges (Biological Heritage) funding in collaboration with NIWA.

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