This data collection activity covers baseline, geographical and temporal trend monitoring of heavy metals and chlorinated hydrocarbons in water from the marine chemistry monitoring programme. Data for water chemistry covers marine areas around Ireland and between Ireland and Canada in the North Atlantic Ocean. Water sample stations have been collected since 1991 mostly from water bottles attached to a CTD rosette and discrete water samplers. Contaminants in water monitoring has been undertaken by the Marine Chemistry team of the Marine Environment and Food Safety Services (MEFSS) section of the Marine Institute. Data 100% complete for surveys since 1991.