Diatoms: Tiny Algae with a Big Role in River Health

Diatoms are single celled algae encased in silica. When viewed under a microscope their communities can resemble a beautiful kaleidoscope of life. Understanding which diatom species are present provides an insight into the health of a river.

Rivers are lifelines of biodiversity, supporting countless species and providing essential ecosystem services to communities worldwide. Yet, they face mounting threats from pollution, habitat destruction, and the growing pressures of climate change. Understanding and maintaining river health is critical to preserving these vital ecosystems. Enter diatoms: microscopic heroes that reveal the secrets of a river’s well-being.

Diatoms are single-celled algae encased in intricate silica shells that look like tiny works of art under a microscope. These organisms are more than just visually fascinating; they are biological indicators of ecosystem health. Diatoms are highly sensitive to changes in their environment, such as shifts in water quality, nutrient levels, pollution, and pH. Each species of diatom has specific environmental preferences, so the presence—or absence—of certain species provides a snapshot of water conditions over time.

This sensitivity is why diatoms have become a cornerstone of water quality monitoring. In the UK, the Environment Agency uses diatoms extensively to assess river health. Their approach is based on the fact that diatoms reflect the cumulative effects of environmental stressors, unlike single-point chemical tests, which provide only a momentary view. For instance, elevated nutrient levels from agricultural runoff or subtle changes in pH caused by industrial discharges can alter diatom communities in ways that are easily detectable through population analysis. This makes them an invaluable tool for long-term monitoring and sustainable management of aquatic ecosystems.

Diatom monitoring is a key component of the Water Framework Directive (WFD), an ambitious European Union policy aimed at achieving “good ecological and chemical status” in all water bodies. The WFD emphasizes the importance of using biological indicators like diatoms to make holistic assessments of water quality. The integration of diatom-based monitoring under the directive has been highly regarded because it provides a reliable, cost-effective, and scientifically robust way to track changes in freshwater ecosystems.

At our lab, we take diatom monitoring a step further by using cutting-edge environmental DNA (eDNA) sequencing techniques. Traditional diatom identification relies on microscopy, which can be time-consuming and requires specialised expertise to identify species based on their morphology. eDNA sequencing, on the other hand, allows us to analyse genetic material from diatoms. This approach is not only faster but can also more precise, enabling us to detect rare or cryptic species that are often overlooked with traditional methods.

By extracting DNA from a rock scraping sample, we can generate detailed data on diatom communities in a fraction of the time it would take using microscopy. This information is invaluable for monitoring river health, identifying pollution hotspots, and evaluating the success of restoration projects. For example, if a diatom community indicates poor water quality in a particular stretch of river, targeted interventions can be implemented to address the underlying issue, such as reducing agricultural runoff or improving wastewater treatment.

The data collected through diatom monitoring has far-reaching implications. It not only supports conservation efforts but also informs policy decisions and helps ensure compliance with environmental regulations. Furthermore, as climate change alters rainfall patterns and increases the frequency of extreme weather events, diatoms can provide early warning signs of ecosystem stress, allowing for more proactive management strategies.

Diatoms may be microscopic, but their significance in protecting our rivers cannot be overstated. These tiny organisms are a window into the health of our waterways, helping scientists, policymakers, and conservationists understand and address the challenges facing freshwater ecosystems. By harnessing the power of diatom-based monitoring, we can ensure that our rivers remain vibrant and resilient for generations to come.

So, next time you see a flowing river, take a moment to think about the microscopic world beneath its surface. Diatoms may be small, but their role in safeguarding the health of our rivers is enormous.