As part of the Rena Long Term Environmental Recovery Programme commissioned by the Ministry for the Environment in response to the grounding of the MV Rena on Astrolabe Reef (Otaiti), an experimental study of ecotoxicological effects was initiated to examine potential effects of major pollutants discharged from or associated with the Rena shipwreck. This project is one of the first examinations of ship wreck and oil spill pollution in New Zealand. Research will aid responses to future oil pollution events such as ship groundings and oil industry pollution. The container ship MV Rena ran aground on Astrolabe Reef in the Bay of Plenty in October 2011 and discharged approximately 350 tonnes of heavy fuel oil (HFO). During the response HFO was treated with approximately 3 m³ of the oil dispersant Corexit 9500 at sea. Other pollutants associated with the Rena grounding included general cargo and other goods classified as environmentally hazardous, in particular, 560 tonnes of sodium hexafluoroaluminate or cryolite. Given the almost total absence of toxicity data relevant to HFOs, Corexit 9500 and other contaminant mixtures on New Zealand marine species, this project sought to assess the acute sublethal toxicity of these contaminants to a range of culturally, ecologically and commercially important species. Sub-adult snapper (Pagrus auratus), spotted wrasse (Notolabrus celidotus) and red rock lobster (Jasus edwardsii) were exposed to 1:1000 cryolite, 1:10000 HFO (HFO WAF), 1:400000 Corexit 9500 and 1:40 HFO/Corexit 9500 combination (HFO CEWAF: 1:10000 HFO, 1:400000 Corexit 9500) for up to 96 h followed by recovery for up to 10 d. These concentrations and exposure durations were viewed as being environmentally realistic. Fish were necropsied and examined for haematology and accumulation of polycyclic aromatic hydrocarbons (PAHs). Exposure to toxicants caused no lethality but did indicate sub-lethal effects. Measurements of blood parameters indicated two main effects in fish of erythrocyte swelling and haemoconcentration. The overall pattern of response in fish appeared to be a greater degree of erythrocyte swelling in response to the HFO WAF treatment. HFO WAF and HFO CEWAF treatments caused changes in leukocyte differential counts indicating negative responses of immunosuppression in fish. Corexit 9500 and cryolite exposure caused negligible/minimal changes in haematology in all species. Haematological assessment of Jasus edwardsii indicated immune effects of HFO WAF, HFO CEWAF and cryolite exposure as evident by changes in differential haemocyte counts. Bile PAHs in fish and red rock lobster reached levels several orders of magnitude higher than controls. Corexit 9500 increased PAH body burden when combined with oil, however in fish it also appeared to accelerate depuration of PAHs during post-exposure recovery. Depuration was not as evident in red rock lobster. Exposure to HFO appeared to stimulate an increase in melanomacrophages in the spleen of Pagrus auratus. Overall HFO exposure with or without the addition of Corexit 9500 caused apparent sublethal changes in haematology that mostly recovered by 10 d post-exposure.