Sewage pollution levels in the Mersey estuary are as high as they were in the 1980s, despite extensive clean-up efforts, according to a study by Durham University researchers.

By examining dried seaweed, which acts as a historical record, they compared pollution levels over the past 200 years. The study found that the River Mersey and its estuary are still heavily polluted with nitrogen from sewage, prompting calls for immediate action.

The Environment Agency stated its commitment to “protecting and improving water quality.”

The Mersey, once considered the most polluted river in Western Europe in the 1980s, saw a significant clean-up campaign following public outcry.

Last year, a record number of species were found in the river, which the Mersey Rivers Trust celebrated as “the greatest river recovery in Europe.” The river now hosts species such as rays, scorpion fish, eels, and the rare venomous bluemouth rockfish.

The study, published in the journal Environmental Science: Advances by geochemists Freya Alldred and Prof. Darren Grocke, utilised herbaria from the World Museum Liverpool. These dried seaweed collections date back to the 1780s and capture historical environmental conditions. This innovative use of herbaria revealed significant nitrogen pollution over two centuries.

Prof. Grocke expressed astonishment at the elevated pollution levels, attributing the problem primarily to population growth and inadequate infrastructure, and called for immediate remedial action.

Of the record levels of species being recorded in the River Mersey, he said: “They’re probably sporadic and not living there all the time and just venturing in and out.”

He added: “Although that conflicts with the evidence we have, if you go round the Liverpool Mersey area you’ll see [they] don’t have many mussels and other organisms that live on the rocks… and they normally help filter the water.

“So if we could even try and get those ecosystems back that will help clean the river up as well.”

Professor Jamie Woodward from the University of Manchester described the estuary as a “hot-spot for sewage dumping,” labelling it unacceptable and a public health threat.

The Environment Agency said: “We are committed to protecting and improving water quality.

“Our team works tirelessly to enforce regulations, conduct monitoring, and collaborate with stakeholders to address sources of pollution.”

The Mersey Rivers Trust acknowledged ongoing improvements in water quality since the late 1980s, citing advancements in sewage treatment.

“As a result we are seeing a lot more different species of fish in the estuary than 40 years ago and the return of shark, dolphin and porpoise.”

The charity said it was working with a range of organisations “to assess the water quality and ecological health of the Mersey to help determine the further actions required to continue improvements to river health”.

It added: “The study by Durham University is an interesting additional data contribution and we hope to discuss the work with the authors of the study in the near future.”

Liverpool City Region Mayor Steve Rotheram has previously announced plans to make the River Mersey sewage-free by 2030.

 

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