Algal Blooms in River Thames | 03 Mar 2025

Source: DTE 

A study has revealed that climate change is increasing the risk of algal blooms in the River Thames (England) despite an 80% reduction in phosphorus loads over four decades. 

• An algal bloom is the overgrowth of microscopic algae or algae-like bacteria in fresh, salt, or brackish waters. 

Key Findings: 

• Rising river temperature is driving the growth of spring diatom blooms and summer cyanobacterial (blue-green algae) blooms, which deplete oxygen, harm aquatic life, and increase drinking water treatment costs. 
  • Algal blooms also restrict recreational activities like fishing and swimming. 
• Despite an 80% reduction in phosphorus since 1985, its concentration remains above safe limits, sustaining algal growth. 
  • Excess nitrogen and phosphorus block sunlight and deplete oxygen, threatening marine ecosystems. 

River Thames: 

• It is 346 km long (Longest in England, second longest in the UK after River Severn). 
• It originates from Thames Head, Gloucestershire, and drains into the North Sea via the Thames Estuary, with Nore sandbank at its mouth. 
  • London is on the bank of Thames. 
• It supplies two-thirds of London’s drinking water and has been a vital trade route.