Red Tide in Southampton (image) University of Southampton Caption A photo of red tide in Empress Dock, Southampton. A red tide is a term often used to describe a discolouration of estuarine or coastal waters caused by a proliferation or 'bloom' of microscopic algae. These are often red in colour but can be other colours, such as green, brown, yellow etc. Credit University of Southampton Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.