METAL LEGACIES OF THE FAL ESTUARY: THEIR EXTENT AND IMPLICATIONS FOR ESTUARINE ORGANISMS

The Fal estuary in Cornwall (UK) has experienced centuries of heavy metal contamination, associated with historical mining and current inputs within the catchment. Recent designation of the estuary within the Fal and Helford Special Area of Conservation (SAC) has resulted in concern over the influence of metal contamination on the area. This paper examines whether metal contamination, particularly the legacy in sediments, is still influencing the Fal estuary in 2013. A weight of evidence approach was undertaken, combining chemical analyses with assessments of acute and chronic effect, in the Fal and a reference estuary (Avon, Devon). Biomarkers of sublethal exposure (Metallothionein induction, MT) and effect (Total Oxyradical Scavenging Capacity [TOSC] and immunotoxicology) were measured in the bioindicator species, Scrobicularia plana. The influence of metals was investigated in two defined branches of the estuary, Restronguet Creek and the Fal SAC. Elevated metal concentrations and bioavailabilities were evident across sediments of the Fal estuary, at levels exceeding Sediment Quality Guidelines. Metal contamination was greatest in Restronguet Creek, however significant elevations were also observed in the Fal SAC. This suggests that inputs from Restronguet Creek and the neighbouring catchments are still having an influence on sediment quality in the SAC. Sediments from the Fal estuary were highly toxic to Tisbe battagliai, inducing high rates of lethality after 48 hour exposure. Metal contamination was also highly bioavailable to S.plana. Body burdens exceeded baseline values, for zinc (Zn), iron (Fe) and lead (Pb), suggesting that they may be metals of concern. S.plana from the Fal estuary exhibited sublethal effects in response to environmental stress, in the form of elevated metallothionein (MT) induction and haemocyte counts. However, no alterations were observed in TOSC, a biomarker of oxidative stress. Overall, the results suggest that the legacy of metal contamination is still influencing the Fal estuary in 2013. Complex physical, chemical and biological processes and known mixtures of contaminants in sediments, provide challenges in deducing cause and effect. However, correlations suggest that body burdens of lead may have an influence on S.plana. Integration of chemical measurements with biomarkers and bioassays of effect have been shown to be an 2 effective method for assessing the condition of the Fal estuary. As well as highlighting sites of concern, that may require further investigative study and environmental management. Methodological developments and conclusions drawn from this project, may also inform other monitoring programmes of European Marine Sites and areas of conservational significance.In collaboration with the Marine Biological Association (MBA), Plymouth, U