The Zoological Society of London’s State of the Thames report, suggests that the once highly-polluted river is in the midst of an ecological revival. The river has seen improvements in its dissolved oxygen and phosphorus levels, as well as improvements in bird and marine mammal populations.
The report did find that nitrate levels and fish populations were headed in the wrong direction and that climate change posed a significant risk to life, both flora and fauna. The increase in nitrates stems in part from agricultural runoff and can significantly worsen algae blooms.
The report suggests further study is needed to understand the small decline in the fish population. The river has seen the average temperature and sea-level rise due to climate change.
Overall, the report indicates that the Thames is far healthier than back in 1957 when scientists at the Natural History Museum declared certain areas of the river biologically dead. From that low point, the Thames has been making a slow comeback.
The identification of sharks in the river is a sign of improved environmental health, indicating that the environment and thus the food chain is currently healthy enough to support an apex predator.