Ocean Pollution

Marine life thriving in River Thames

Written by Oceanographic Staff

The UK’s River Thames, pronounced biologically dead around 60 years ago, is now home to myriad marine species, new study finds.

After the Thames was declared biologically dead in 1957, the State of the Thames Report, conducted by the Zoological Society of London (ZSL), highlights the positive changes that since happened. According to the study, the river has been revived, with hundreds of wildlife species now calling the famous river that flows through London their home.

While seahorses, eels, seals and shark species such as tope, starry smooth hound and spurdog sharks can now be found living in the river, the first major report into the state of the Thames in 60 years, estimates that 115 species of fish can be found in the estuary too. The river has also seen an increase in its bird and natural habitat range since the 1990s. Another positive finding: the water quality has improved with dissolved oxygen concentrations showing an increase from 2007 to 2020.

Alison Debney, for ZSL, said: “Estuaries are one of our neglected and threatened ecosystems. They provide us with clean water, protection from flooding, and are an important nursery for fish and other wildlife. The Thames Estuary and its associated ‘blue carbon’ habitats are critically important in our fight to mitigate climate change and build a strong and resilient future for nature and people. This report has enabled us to really look at how far the Thames has come on its journey to recovery since it was declared biologically dead, and, in some cases, set baselines to build from in the future.”

The findings are bittersweet, however. Some fish species inhabiting the Thames’ tidal areas showed a slight decline. The cause of this hasn’t been determined yet. The biggest threat to the Thames, according to the report, is climate change which has increased the river’s temperature by 0.2C annually. It also led to higher water levels. This could heavily impact the wildlife found in the Thames in the near future.

Another big talking point in the study is sewage discarded into the Thames. Unfortunately, nitrates from sewage are getting worse, according to the report. Together with phosphates, nitrates enter rivers and lakes through untreated sewage, waste and fertilisers. These, in turn, can cause algae and certain plants to grow rapidly which can lead to algal blooms. This heavily reduces the amount of oxygen in the water and poses a suffocation risk to fish and other marine animals.

The report hopes that the announced ‘super sewer’, the Thames Tideway Tunnel, which will open in 2025 will improve the nitrate levels in the Thames. The 24-kilometre-long, 61-metre-deep sewer is said to capture 39 million tonnes of untreated sewage annually which would usually end up in the Thames.

For more from our Ocean Newsroom, click here.

Photography courtesy of Unsplash.

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