Predicting the ecological effects of metals in marine sediments

Udochi, Solomon (2020) Predicting the ecological effects of metals in marine sediments. Doctoral thesis, University of East Anglia.

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Despite advances in the regulation of marine pollution, there remains considerable uncertainty about metal concentrations in sediments that can elicit adverse ecological effects. A key gap has been the work that relates metal contamination to ecological endpoints in field-contaminated sites. Consequently, the main aim of this thesis was to assess dose-response relationships of metals in marine sediments: to determine what chemical measures of contamination best predict ecological effects and the threshold concentrations at which these effects begin to occur. The study was conducted, primarily, in the Fal and Hayle estuaries, Cornwall, England, which are grossly contaminated by mine drainage. I assessed physicochemical characteristics of sediments and porewater at twelve study sites over a two-year period and in three different seasons. To quantify exposure to benthic fauna, I measured metal contamination using Diffusion Gradients in Thin Films (DGT), Equilibrium Partitioning (EqP) derivations, and traditional measures: total porewater (PW), organic carbon-normalised porewater (PW Cu/OC), acid-extractable (AEM), and total sediment (Sed) concentrations. I quantified ecological effects using the occurrence of pollution-tolerant nematode communities (PICT) and nematode community structure defined by univariate diversity indices and multivariate techniques. The EqP model downplays dietary toxicity. Therefore, I assessed the importance of dietary toxicity and the validity of the EqP in predicting (non-)toxicity of copper to a deposit-feeding snail, Peringia ulvae. Overall, the results reveal a combination of metal uptake routes that raises questions about regulatory guidelines based on single measures. Where dissolved metals were important predictors, DGT offered little above PW. Where sediment-bound metals were important, Sed proved more useful than widely considered. In both instances, the EqP performed poorly. This thesis also showed that medium to long-term redox changes in Fal and Hayle sediments can remobilise metals at potentially toxic concentrations. Recommendations for metal regulation in marine sediments are provided.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Chris White
Date Deposited: 20 Dec 2021 15:16
Last Modified: 20 Dec 2021 15:16


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