The Effects of Contaminated Rena Sediments on Juvenile Paua (Haliotis iris)

Abstract

The grounding of the MV Rena on Otaiti resulted in the release of heavy fuel oil and container debris contaminants into the surrounding environments including the rocky shores of the adjacent Mōtītī Island. This is the habitat where significant populations of benthic paua reside. Paua (Haliotis iris) are a staple and consistent food source for Mōtītī Island. Being an offshore island with no amenities, Mōtītī Island residents are reliant on the ocean as a pataka kai (food cupboard) and are therefore acutely aware of environmental influences to the harvest of kaimoana. This thesis aimed to address concerns relating to the effects of contaminated boundary layer water emanating from contaminated ‘Rena’ sediment on juvenile paua. Research was focused in two areas: 1) the sublethal behavioural effects of contaminated Rena sediment to Paua and 2) the accumulation of trace metals in the edible tissue and viscera mass. The experiments were carried out with the use of a close circuit aquaria in a laboratory environment, followed by a field experiment. In all experiments, paua in control treatments were healthy by comparison to paua exposed to treatments with Rena contaminated sediments and copper as judged by survivorship and behaviour. The most likely cause of of behavioural aberrations and mortality observed was deemed to be copper as demonstrated by Diffusive Gradient in thin film (DGT) and ambient water analyses in both experiments. Copper that is bioavailable can increase quickly in the edible tissue and viscera mass as was identified as the visceral mass of Rena and copper exposed paua had a higher mean concentration of this and other trace metals. On Otaiti, the effects to paua from the Rena ship wreck and lost container contents, know to include a medly of metals and other contaminants, is not likely to be limited to copper alone. Results demosntrate the relevance of examining the effects of water borne contaminated plumes emanating from complex mixtures of contaminants. This is rarely done in ecotoxicological studies which tend to focus on individual contaminant compounds.