Discovering the biodiversity of our wetlands
Discovering the biodiversity of our wetlands
February 2nd marks the day that the world shines an extra light on one of the most productive environments; our wetlands.
For Aotearoa New Zealand, wetlands are extremely valuable both culturally and ecologically, supporting a rich biodiversity and enacting key ecosystem services such as filtering nutrients and contaminants, sediment, and controlling floodwaters. With only ~10% of wetlands remaining since human settlement, these environments support a disproportionately high number of Aotearoa’s threatened plant and animal species.
Birds and fish species which rely on wetland habitats often have very specific habitat requirements, are highly vulnerable to change, and are often more difficult to observe and monitor than compared to those in other environments. Some of these species include fernbird, marsh and spotted crake, brown teals, kōkopu, long-fin eel, inanga and mudfish.
Current wetland monitoring is mainly focused on larger plant, bird and fish species, all of which can be relatively slow to respond to environmental changes making them less able to show small improvements or declines at the broader ecosystem scale. There is also lots still unknown about the ecosystem dynamics and interactions with the wider environment and how this may change through time.
eDNA offers an opportunity to explore and monitor ecosystems at multiple levels, not just what we are able to easily see, hear and identify under a microscope (figure 1). This new lens can allow us to better understand some of these ecosystem changes including those from restoration and conservation work.
Sampling eDNA in slow-mixing, standing environments is quite different to sampling from high-mixing, flowing environments like rivers which continually deliver genetic material on a ‘natural conveyor belt’. There is also often more suspended algae and other organic material floating around in these waters, making the filtering of eDNA more difficult.
Figure 1: Biodiversity wheel of the organisms detected from Te Harakeke Wetland Complex . These samples were collected as a part of a pilot case study by Greater Wellington Regional Council and Wilderlab in September, 2021.
We’ve been doing some collaborations with regional councils and other environmental groups to help establish the best ways to sample eDNA from wetlands as a way to more safely monitor and regularly survey these vulnerable environments.
Using sampling strategies such as compositing - pooling water samples into a container instead of sampling directly from the environment - has been shown to be a good way of overcoming the issue of low water mixing and ‘patchiness’ of eDNA distributions. This method is being investigated by several different environmental agencies alongside other visual and auditory surveys.
In overseas examples, researchers have found that eDNA can perform the same, if not better, results to conventional visual and auditory surveys (Doi et al., 2017; Zou et al., 2020; Neice & McRae, 2021; Wikston, 2021), making it a useful tool in the toolbox for monitoring rare, vulnerable and cryptic wetland species.
Figure 2: Visiting the Te Harakeke Wetland Complex with scientists from Greater Wellington Regional Council in September, 2021.
As our understanding and knowledge continues to grow, we hope to help Aotearoa make everyday a day to celebrate our wetlands!
If you have any questions about using eDNA for monitoring wetlands, feel you can always get in touch with the Wilderlab team at info@wilderlab.co.nz.
References:
Doi, H., Katano, I., Sakata, Y., Souma, R., Kosuge, T., Nagano, M., … Tojo, K. (2017). Detection of an endangered aquatic heteropteran using environmental DNA in a wetland ecosystem. Royal Society Open Science, 4(7), 170568.
Neice, A. A., & McRae, S. B. (2021). An eDNA diagnostic test to detect a rare, secretive marsh bird. Global Ecology and Conservation, 27, e01529.
Wikston, M. J. H. (2021). Comparative Efficacy of eDNA and Conventional Methods for Monitoring Wetland Anuran Communities (Trent University (Canada)). Retrieved from https://search.proquest.com/openview/480704b92e6ede0dc7a47c4c17cdf650/1?pq-origsite=gscholar&cbl=18750&diss=y
Zou, K., Chen, J., Ruan, H., Li, Z., Guo, W., Li, M., & Liu, L. (2020). eDNA metabarcoding as a promising conservation tool for monitoring fish diversity in a coastal wetland of the Pearl River Estuary compared to bottom trawling. The Science of the Total Environment, 702, 134704