Boat users on the Menai are leading the way on innovative water quality testing programme

Diffusive Gradient in Thin-films (DGT) samplers have been deployed across the Strait. The samplers are being used to help us understand average levels of nitrate and phosphate in the Menai Strait and its adjoining estuaries.

So how do they work?

Unlike a traditional water sample, which tells us what is happening at one place and point in time, Diffusive Gradients in Thin-films (DGTs) continuously collect dissolved substances from the surrounding water over an extended period. The small samplers are attached below the waterline using cable ties and remain submerged throughout the sampling period.

As the water passes through a thin disc of hydrogel the nitrate and phosphate bind to the layer beneath. Following a deployment period of two weeks, the samplers will be retrieved and sent to Bangor University for analysis to calculate time-averaged nutrient concentrations.

The project is part of a wider community-led marine observatory being developed across the Menai Strait and adjoining estuaries. By working with local boat owners, businesses and organisations, the aim is to build a coordinated network of evidence that can help us better understand the Strait and support future action, protection and management.The project will also allow us to explore how this approach can complement more traditional monitoring methods.

Why nitrate and phosphate?

Nitrate and phosphate are important nutrients in aquatic environments. They occur naturally, but increased inputs from sources such as agricultural runoff, wastewater and urban drainage can contribute to changes in coastal and estuarine ecosystems.

Understanding how nutrient levels vary across the Strait and its tributaries can help build a clearer picture of the pressures affecting this interconnected environment.

The Menai Observatory is bringing together community knowledge and scientific evidence to help us understand the Strait and inform its future stewardship.

A huge thank you to Seacoast Safari, Seawake and Plas Menai for helping us get the first samplers into the water and supporting this community-led monitoring programme.