Metals and polycyclic aromatic hydrocarbons in environmental matrices of the Fleet Lagoon, UK and toxicological investigations using the marine polychaete Hediste diversicolor.

Abstract

Contamination within the marine environment is ubiquitous and may contain both metals and polycyclic aromatic hydrocarbons (PAH’s) individually or within complex mixtures. Contamination may bind directly to organic particles within sediment and may remain undisturbed or re-released during periods of hydrodynamic activity. Sediment may therefore act as both source and sink for complex mixtures of contamination and bio-accumulate in sediment dwelling organisms including the marine polychaete Hediste diversicolor. Following exposure, an organism may deploy a variety of biochemical, cellular, molecular and behavioural alterations to maintain homeostasis and reduce the effects of the insult. Biomarkers are used within environmental monitoring to forecast adverse outcome pathways via the assessment of endpoints including those of cellular, molecular, behavioural, tissue, systemic and organism responses and alterations. However, research is primarily conducted upon bioaccumulation and adverse outcome pathways of exposure to individual contaminants although environmentally, mixtures of contaminants including metals and PAH’s are omnipresent. Concentrations of metals and PAH’s in the environmental matrices of the Fleet Lagoon, Dorset, UK were analysed in order to obtain environmentally relevant concentrations of contaminants. Specific metals and PAH’s were found to exceed the Threshold and Potential effects limits of the Canadian sediment quality guidelines. Granulometric composition showed spatial variance throughout the lagoon where all sites were identified as extremely poorly to moderately poorly sorted. Relationships between sediment fractions, Cu, Zn and Pb were identified. Additionally, both metals and PAH’s were found to bioaccumulate in H diversicolor. Total metal sediment analysis and worm tissue concentration were not relational excluding As, where a positive correlation was identified. Sediment digestion using BCR sequential extraction revealed a positive relationship between worm tissue concentrations for Cu. However, proteinase K sediment digestion identified positive correlation between Cu, Pb and worm tissue concentration. Furthermore, BCR sequential extraction was found to overestimate the bioavailable fraction. Isomer source analysis identified that PAH’s found at all sites excluding site 2, were from pyrolytic origins. PAH’s at site 2 were identified as being from petrogenic sources. Exposure investigations using the environmentally relevant concentrations of Pb and pyrene found in sediment of the Fleet lagoon identified that both contaminants, alone and in combination negatively affect burrowing rates of H diversicolor. Although, burrowing rates of the combined Pb and pyrene exposure groups were faster than those exposed to Pb alone. Acetylcholinesterase was inhibited by both Pb and pyrene (alone and in combination) although more notably by pyrene. However, burrowing rates to not correlate to AChE activity. The presence of pyrene in combination with Pb was found to reduce Pb assimilation by H diversicolor. Furthermore, both Pb and pyrene were found to produce reactive oxygen species which may not be suitably controlled by glutathione-s-transferase, cytochrome P450, superoxide dismutase as 8-OHdG adducts post exposure were identified. Additionally, potential inhibition of both GST and CYP450 were observed during the assimilation phases for all exposure groups. Energetic alterations following exposure were identified in all exposure groups suggesting that exposure to these contaminants induces high energetic demands in H diversicolor. Results from this study demonstrate for the first time that the bioaccumulation of Pb and pyrene by H diversicolor elicit behavioural, biochemical and energetic changes which may have negative effects on populations which reside in marine environments where Pb and pyrene are present.