ASSESSMENT OF WATER-QUALITY IN ESTUARINE AND COASTAL WATERS OF ENGLAND AND WALES USING A CONTAMINANT CONCENTRATION TECHNIQUE

Water samples were taken from over 40 estuarine, nearshore and offshor e sites in the U.K. during two CEFAS research cruises in 1993, The sam ples were processed using a bulk hexane extraction and concentration p rocedure and bioassayed using the marine harpacticoid copepod Tisbe ba ttagliai, This process allowed the toxic effects of non-polar organic contaminants to be measured at all sites, expressed as the concentrati on factor required to elicit a 48 h median lethal response. Total hydr ocarbons (THC)and polycyclic aromatic hydrocarbons (PAH) were also qua ntified to estimate their contribution to sample toxicity. Extracted c ontaminants were concentrated < 10-300-fold for estuarine sites, 100-6 00-fold for nearshore sites and 350- > 1000-fold for offshore sites be fore toxicity was observed. A tentative water contamination ranking of the studied estuaries was established as Tees > Wear > Mersey > Tyine > Blyth, Poole Harbour, Southampton Water > Ribble, Dee, Lune. Chemic al 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 fluores cence and toxicity. The results indicate that hydrocarbons may make a significant potential contribution to the toxicity of estuarine and co astal waters with a selected 10 PAH compounds estimated to be responsi ble 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 concen tration factors required at near and offshore sites suggest that hexan e extractable contaminants were not present at chronically toxic conce ntrations in the untreated seawater. However, at some estuarine sites, low concentration factors (< 200-fold) suggested that these waters ma y be exhibiting chronic biological effects that are not always demonst rated by conventional bioassay-based monitoring. Crown Copyright (C) 1 998 Published by Elsevier Science Ltd. All rights reserved.