Post provided by Chloe Robinson
It doesn’t come as a surprise that healthy wetland systems are linked with freshwater quality. Wetlands form vital habitats for global biodiversity, help combat climate change through storage of carbon and offer defenses against flooding. Freshwater resources, including wetlands, are under increasing pressure from over-abstraction, pollution and habitat destruction among other threats, which is directly contributing to the current global freshwater crisis that threatens people and our planet.
February 2nd each year is World Wetlands Day, which aims to raise global awareness about the vital role of wetlands. This year, the 2021 campaign highlights the contribution of wetlands to the quantity and quality of freshwater on our planet. Water and wetlands are connected in an inseparable co-existence that is vital to life, our well-being, and the health of our planet. In this blog post, Associate Editor Chloe Robinson, will explore why wetlands are so important and the new DNA-based methods being used to monitor wetland health.
Water is life: The role of wetlands
Wetlands only cover 6% of the Earth’s surface, but they are one of the most undervalued freshwater habitats. They are typically defined as a place where the land is covered by water for prolonged periods of time. The movement, distribution, and quality of water is the driving force behind the wetland structure, function and therefore the biodiversity observed.
In terms of maintaining water quality, wetlands are considered the ‘filters of the world’. They extract pollutants such as phosphorus and heavy metals from the water and store them in their soils, they also transform dissolved nitrogen into nitrogen gas. These ecosystem services not only benefit the local wildlife that call wetlands their home, but also their human neighbors. It is predicted that between 300 million and 400 million people live close to, and depend on, wetlands.
In Canada alone, boreal forests are pivotal for maintaining quality for two-thirds of the country’s drinking water. These boreal forests contain 85% of the country’s wetlands, which highlights the importance of wetlands for drinking water quality. In the UK, groundwater makes up around 30% of England’s drinking water supply, of which wetlands help maintain through seasonal recharging. With heavy reliance on wetlands comes heavy costs when these wetland systems become degraded, polluted, over-extracted and ultimately, lost.
Water-scarce wetlands: is there a way out?
The current freshwater crisis, driven by water scarcity, is being felt in every corner of the Earth. 1.1 billion people worldwide lack access to water, and inadequate sanitation is also a problem for an additional 2.4 billion people. Wetlands have been heavily impacted by freshwater pressures, with over half of the world’s wetlands having been lost since 1900. Loss of habitat ultimately results in loss of biodiversity and in the UK, over 10% of freshwater and wetland species are threatened with extinction.
With these alarming statistics and the general doom and gloom surrounding the state of freshwater ecosystems, it is easy to feel sombre and disheartened when considering the future of the world’s wetlands. However, not all is lost. One way to prevent further wetland loss is to use efficient and robust monitoring techniques to track the quality of freshwater systems and alert us to potential degradation before the ecological integrity of the system is lost.
Freshwater health via DNA biomonitoring
One of the most efficient ways to investigate freshwater health is to use DNA-based methods to assess the presence of freshwater macroinvertebrates, such as fly larvae, worms and snails, which are present within wetlands and river systems. Some larval stages of macroinvertebrate species, such as mayflies, caddisflies and stoneflies act as bioindicators of freshwater health in river systems, whereas species such as damselflies and dragonflies are bioindicators of wetland systems.
Known as DNA metabarcoding, this method enables whole communities of species to be identified by collecting, extracting and sequencing the DNA that species leave behind in their environment. These DNA sequences are then compared against reference databases to identify the sequences down to the species level. What is so effective about this method, is there is no need to visually identify the bugs, the DNA pipelines used to classify the sequences are easy to update and these DNA samples can also be re-analysed to look for DNA from different groups of species, such as fish.
DNA metabarcoding has been used to assess wetland ecosystem health in numerous studies. One group conducted a large-scale study in Canada, which looked at detecting ecosystem change within North America’s largest inland delta, the Peace-Athabasca delta. Delving further into the intricate data DNA samples can provide, another study employed this method to create ecological networks to investigate boreal wetland ecological health. Beyond inland wetlands and macroinvertebrates, this method has also been applied in a study concerning detecting fish in coastal wetlands for understanding seasonal fluctuation of fish diversity.
This method can also be used to investigate how successful and effective wetland restoration efforts have been in restoring ecosystem function. In conjunction with community-based monitoring, Darcie Quamme at Integrated Ecological Research is using DNA metabarcoding, as part of the STREAM project, to look at environmental and biodiversity changes pre- and post- wetland restoration in British Columbia (Canada). This method is enabling a real-time view of how wetland biodiversity is changing in relation to water quality and stabilization of wetland environmental conditions.
Our world wetlands are in trouble, and with increasing pressures on freshwater, the outlook is bleak. However, DNA-based methods have revolutionized how we investigate freshwater health and provide vital tools for looking at relationships between wetlands and their associated biodiversity, in order to best conserve and prevent further losses. To save wetlands, we need to continue developing and utilizing robust techniques to improve the information we can obtain from the environment.
Take part in the global celebration #WorldWetlandsDay