Dissolved oxygen levels in estuarine and coastal waters around Ireland

This paper presents the status of summer oxygen conditions in estuarine and coastal waters around Ireland between 2003 and 2007. Of the 95 water bodies surveyed, 85 had oxygen levels sufficient to support aquatic life. This corresponds to a surface area of 3125 km2 or 99.4% of the total area assessed. Ten water bodies, representing a surface area of 20.2 km2, were deficient in oxygen but still capable of supporting most aquatic life. No evidence of hypoxia (<2.0 mg/l O2) or anoxia (<0.2 mg/l O2) was found. Dissolved oxygen conditions in a number of estuaries continue to improve, probably due to improved municipal waste water treatment. The implementation of measures contained in both the Nitrates and Urban Waste Water Treatment Directives, together with those of the Water Framework Directive, should ensure areas of oxygen deficiency are eliminated from Irish waters.