In the last five years we've seen a remarkable acceleration in the use of environmental DNA (eDNA) monitoring to better understand ecosystems and mitigate any impacts.
The key benefit of this relatively new technology is it can be used to genetically confirm the presence of a species in the environment without requiring a direct sighting or physical collection of a living individual. All organisms shed DNA into the environment, and eDNA monitoring enables the scanning of water, air, or soil to trace these tiny remnants.
Rapid advances in technology have made eDNA even more versatile and through access to the growing body of global data, analysis techniques and computing power, the accurate processing of samples can now be achieved very quickly. In some cases, gone are the days when you needed an expensive laboratory to process eDNA samples with the generation of results now possible while in the field.
The use of eDNA is proving beneficial in many areas. For example, in environmental protection it can be used to test for pathogens or invasive species. It can also be used to study migration patterns or to detect rare or hard to find species.
A recent project in Australia provides an excellent example of how eDNA can be used to analyse the distribution of wildlife.
Exploiting the use of eDNA to justify additional water access
Situation |
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Due to limited water availability, a mining industry client applied to the State Government for a variation to licence conditions related to entitlements and releases from a local reservoir. This included a request to temporarily cease environmental water releases to a local creek containing significant Australian species including platypus and fish (Mountain Galaxias). The cessation of the releases had the potential to reduce flow across more than 16 kilometres of the creek and reduce connectivity resulting in a series of isolated pools. This was a naturally occurring event prior to the construction of the reservoir. Provided water quality and habitat conditions remained at suitable levels, it was thought the isolated pools could provide refuge habitat to platypus and Mountain Galaxias during cease-to-flow events. However, the location and number of refuge pools were unknown, as was the distribution of platypus and Mountain Galaxias in the creek. This made it challenging to develop a monitoring program to assess changes in ecological values. |
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Solution |
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To support the client’s application and address concerns related to ecological risks, GHD recommended a three stage monitoring program that aimed to:
During stage 1, eDNA and standard survey techniques determined that platypus and Mountain galaxias were distributed throughout the creek. The location of key pools that may provide refuge habitat for platypus and Mountain Galaxias during future cease-to-flow events were identified based on water quality and a newly developed Habitat Suitability Index (HSI). Of the 20 pools assessed, five were selected for ongoing monitoring to investigate changes in distribution of the two species during cease-to-flow events. Stage 2 monitoring during cease-to-flow events was undertaken between March and December 2019, with additional testing occuring over a six month period in 2020. Results have been encouraging in that water quality and habitat in refuge pools have persisted at suitable levels and the refuge pools have the capacity to continue to support platypus and Mountain galaxias. This has been confirmed by the eDNA monitoring that indicate these two species remain in the refuge pools. eDNA is a developing tool that requires validation. A key challenge was managing the issue of both false negatives and false positive results (See Figure 1). During Stage 2, the findings of the eDNA were validated using trigger motion cameras deployed in situ to document the presence of platypus. This mitigated the occurrence of both false positives and false negatives.
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Result |
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The positive eDNA detections that were validated using trigger motion cameras for platypus and visual sightings of Mountain galaxias, provided evidence that these species were persisting in the refuge pools during cease-to-flow events. The combination of these techniques provided a robust and validated approach, which contributed to further development of eDNA monitoring, and provided benefits to the client and the State Government. The case study is a good example of the benefits of eDNA and also highlights the importance of other techniques to help overcome some of eDNAs shortcomings and provide more robust data outcomes. In this particular case, GHD was able to develop a rigorous and defensible approach to water management that ultimately enabled on site water conservation without compromising waterway health. This enable more efficient use of water resources and justified changes to the client’s licence conditions. For continued protection of platypus and Mountain galaxias, site-specific trigger values related to water quality and habitat were developed to indicate if risks to the species increases should cease-to-flow events occur over an extended period. Mitigation options, such as flushing flows from the reservoir, have recently been implemented to maintain water quality and habitat at suitable levels to enable the persistence of refuge pools for ecosystem benefit. With experience and careful planning, this examples demonstrates that it’s possible to develop tailored programs to suit a variety of needs and design monitoring programs which are meaningful, adaptive and can be communicated quickly and effectively. |
About GHD
At GHD, our aquatic scientists provide leadership on the investigation and management of marine and freshwaters, to help our clients achieve better ecological, resource efficiency and human health outcomes. We collaborate with our clients and other disciplines to contribute high quality inputs to all stages of the project lifecycle, including planning and permitting, design and implementation, monitoring and evaluation.
For more information, connect with our aquatic sciences professional:
Peter Lind
Senior Scientist Aquatic Ecology
T: +61 3 86878369
Email Peter Lind