The Solent Strait: Water quality trends within a heavily trafficked marine environment, 2000 to 2020.

This study presents an important long-term historical analysis of water quality in an internationally crucial waterway (the Solent, Hampshire, UK), in the context of increasing adoption of open-loop Exhaust Gas Cleaning Systems by shipping. The pollutants studied were acidification (pH), zinc, and benzo [a] pyrene, alongside temperature. We compared baseline sites to locations likely to be impacted by pollution. The Solent's average water temperature is slightly increasing, with temperatures at wastewater sites significantly higher. Acidification suggests a complex story, with a highly significant small overall increase in pH during the study period but significantly different values at wastewater and port sites. Zn concentrations have significantly reduced but increased in enclosed waters such as marinas. BaP showed no long-term trend with values at marinas significantly and consistently higher. The findings provide valuable long-term background data and insights that can feed into the upcoming review of the European Union's Marine Strategy Framework Directive and ongoing discussions about the regulation of, and future monitoring and management strategies for coastal/marine waterways.

The impact of an annual major recreational boating event on water quality in the Solent Strait.

A long-term historical analysis of the impacts of recreational boating on marine surface water quality during a regatta (Cowes Week) in an internationally crucial waterway, the Solent Strait (Hampshire, UK) is presented. Water quality indicators studied included nitrogen concentration, bacterial indicators, and oxygen saturation, at three sampling sites at/near Cowes during 2001-2019. Findings include that sewage discharge from recreational boats is the key contributor to localised faecal contamination of marine surface waters, putting bathers and shellfisheries at risk. Bathing water quality monitoring and pollution warning systems should be strengthened prior to and during this type of regatta and access to bathing water areas may need to be restricted. These findings have implications for the regulation, future monitoring and management strategies for discharges from recreational boats during extended regattas. Adequate and affordable local facilities for recovering sewage wastewater from recreational boats should be provided alongside appropriate mechanisms for communication to sailors.