Floating plant islands keep Zilvermeer free of blue-green algae

The Zilvermeer recreation area in Mol is enjoying a summer free from the nuisance of blue-green algae, a stark contrast to numerous other ponds and swimming zones in the region experiencing outbreaks. This success is largely attributed to innovative floating plant islands that naturally enhance water quality.

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The floating plant islands work as a natural purification system: the roots of the plants feed on algae.

Introduced in 2022, these islands are densely planted with marsh and water vegetation. Their root systems act as a natural purification system, feeding on algae and absorbing essential nutrients like phosphate, which are crucial for blue-green algae growth. "This is a natural way of purifying, and it has a clear effect," stated Igor Geubbelmans, director of Zilvermeer.

The province of Antwerp invested €478,000 in the project, executed by the company Navicula. Geubbelmans explained that the plants effectively inhibit blue-green algae growth by consuming the nutrients they rely on. Additional factors contributing to the Zilvermeer's good water quality include the interconnectedness of its two large ponds, which promotes water movement and oxygenation, and the absence of direct connections to canals or rivers where algae blooms might already be present.

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The plants also extract phosphate from the water, and that is precisely a substance that blue-green algae feed on. This slows down the growth of blue-green algae.

Water quality at Zilvermeer is monitored weekly through water sampling and daily visual inspections along the banks and on the ponds. Mireille Colson, a deputy for the province of Antwerp, expressed satisfaction with the results, noting that the investment in a natural and sustainable approach has allowed the area to maintain good water quality even during prolonged hot and dry weather. While this specific approach is not being automatically replicated elsewhere due to varying water conditions, the success at Zilvermeer is prompting consideration for similar initiatives.

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The investment in Zilvermeer shows very concretely today why it is important to think ahead. By investing in a natural and sustainable approach to water quality a few years ago, we see that the area holds up well even during a long, hot and dry period.