Assessment of water quality in estuarine and coastal waters of england and wales using a contaminant concentration technique

Abstract

Water samples were taken from over 40 estuarine, nearshore and offshore sites in the U.K. during two CEFAS research cruises in 1993. The samples were processed using a bulk hexane extraction and concentration procedure and bioassayed using the marine harpacticoid copepod Tisbe battagliai. This process allowed the toxic effects of non-polar organic contaminants to be measured at all sites, expressed as the concentration factor required to elicit a 48 h median lethal response. Total hydrocarbons (THC) and polycyclic aromatic hydrocarbons (PAH) were also quantified to estimate their contribution to sample toxicity. Extracted contaminants were concentrated <10–300-fold for estuarine sites, 100–600-fold for nearshore sites and 350- > 1000-fold for offshore sites before toxicity was observed. A tentative water contamination ranking of the studied estuaries was established as Tees > Wear > Mersey > Tyne > Blyth, Poole Harbour, Southampton Water > Ribble, Dee, Lune. Chemical analysis revealed a weak but statistically significant correlation (−0.36 to −0.43) between total hydrocarbon concentrations in water and the concentration factor required to elicit a median lethal response. There was no correlation between a control determinand, algal fluorescence and toxicity. The results indicate that hydrocarbons may make a significant potential contribution to the toxicity of estuarine and coastal waters with a selected 10 PAH compounds estimated to be responsible for up to 18% of the total toxicity at one specific site. However, the cause of the majority of the toxic response remains unidentified. Although the technique is based on an acute endpoint, the high concentration factors required at near and offshore sites suggest that hexane extractable contaminants were not present at chronically toxic concentrations in the untreated seawater. However, at some estuarine sites, low concentration factors (<200-fold) suggested that these waters may be exhibiting chronic biological effects that are not always demonstrated by conventional bioassay-based monitoring.