Celebrating the First Ever World Lake Day: Why Lakes Matter

Image: Adobe Stock, Wallagoot Lake in Bournda National Park, South Coast NSW, Australia

Today is the first ever United Nation’s World Lake Day. The need to protect our lakes and maintain their biodiversity is essential more than ever. Lakes play a key role in climate regulation, keeping our planet cool through absorbing floodwaters, and storing carbon.

Lakes are vulnerable to pollution. One of the largest threats to lakes is eutrophication, which is the over-enrichment of water by nutrients such as nitrogen and phosphorus. Fertilizers, fossil-fuel combustion, and other human activities drive the growth of harmful algal blooms. They’re a threat to human health, biodiversity, and quality of water. Satellite data shows that nearly half of the world’s large lakes have experiences algal blooms, with their size and frequency intensifying.

Nitrogen feeds algal blooms, boosts cyanobacteria buoyancy (leading to surface scums), and even triggers toxins that harm ecosystems. That’s why scientists are increasingly focused on how nitrogen moves through lake systems, and how it can be removed naturally.

Today, we’re highlighting the research of Environment Institute member Professor Justin Brookes and his colleagues. Their recently published study enhances our understanding of nitrogen removal mechanisms in both the water column and sediments of large shallow lakes.

What did they discover?

Around 43% of nitrogen removal happens in the water column, and different processes take the lead depending on where you look.

In the water column the main process is anaerobic ammonium oxidation (anammox). This is when bacteria convert ammonium and nitrite straight into nitrogen gas. In the sediments, the dominant process is denitrification where bacteria convert nitrate into nitrogen gas.

There are also seasonal differences. Water column anammox is strong in spring and winter and is influenced by nitrate and ammonium. Sediment denitrification is stronger in springtime as it’s influenced by chlorophyll, a measure of algae growth and productivity.

So why does this matter? Because these processes are dynamic, reflecting how the sediments and water column remove nitrogen. The balance shifts depending on seasons and the nutrient availability in the algal activity.

This research helps scientists understand how shallow lakes can respond to pollution, and assist in the design of better strategies to restore water quality.

As we celebrate and highlight the first World Lake Day, studies like this remind us that protecting lakes means looking below the surface at the microbial processes that keep our waters healthy.

Read the full study here.