Rena oil spill an unfortunate lesson

Blogpost by Nathan Argent – October 7, 2011 at 16:40

The Container ship Rena inexplicably crashed into the Astrolabe Reef, about seven kilometres north of Motiti Island, near Tauranga early on Wednesday. It is carrying 1700 tonnes of heavy fuel oil, some of which has already started to leak into the sea.

Since then, fears of a potential environment disaster have grown as the leaking oil has spread threatening wildlife, including whales, birds and seals. Indeed, Environment Minister Nick Smith was quoted as saying that the spill from the ship “had the potential to be New Zealand’s most significant maritime pollution disaster in decades”. This is very disturbing news.

Oiled seabirds have already been found dead close to the Rena and more birds have been spotted in the water, covered in oil. It is also potentially disastrous for the blue whales and dolphins presently calving in the area, as well as numerous other marine species.

Response teams have so far been unable to deploy oil booms to contain the spill. The response so far as been to use a dispersant called Corexit  9500 – which is being sprayed on the water to disperse the oil. Corexit is the same chemical used in the Gulf of Mexico to deal with the oil from BP’s Deepwater Horizon spill.

Unfortunately ‘dispersal’ essentially means never cleaning up the oil. It will just stay out there and continue to pollute the marine environment. The reason being that Corexit acts like a surfactant and attracts the oil. The oil then forms globules and sinks to the bottom.

Some studies have shown that Corexit 9500 is four times as toxic as the oil itself.  Both are now going into the ocean water. It’s not a good situation.

As the authorities battle to get the spill under control and mitigate against the worst environmental effects, we also hope that this incident gives the Government pause for thought with regards to it’s deepwater oil drilling plans. This accident is an unfortunate reminder of just how difficult it is to deal with oil spills at sea. It’s a slow spill in a relatively accessible place, and the weather and sea conditions have been favourable yet even so, it is testing NZ’s response capability to the limits.

It’s shaping up to be a significant disaster but, bad as it is, it will be a walk in the park compared to what would happen if we had a Deepwater Horizon type spill.

Greenpeace has offered Maritime NZ the support of our inflatable boats, experienced drivers and volunteers to assist in the oil clean up and the New Zealand Wildlife Health Centre is calling for volunteers to assist in the recovery and rehabilitation of oiled wildlife but as yet there is little anyone can do.

Despite the best intentions, the oil spill response team in Tauranga will not be able to do enough. There is no ‘enough’.

The tools we have to respond to oil spills are orders of magnitude too small to combat the damage they do. We can’t fix oil spills; we can only prevent them. And we can only prevent the really catastrophic spills by saying no to deep sea oil drilling.

Sign the no deep sea oil petition here


8 comments on “Rena oil spill an unfortunate lesson

  1. What studies have shown Corexit 9500 to be four times more toxic than heavy fuel oil? This is th usual Greenpeace bullshit without facts. A number of countries, including New Zealand, Australia, the US (EPA) and others around the Med have done extensive ecotoxicology work on this and found that is is about as toxic as washing up liquid, when used properly, in water deep enough to dilute it and the dispersed oil to parts per billion. Its times like this I wish a overnment was strong enough to walk away from an industry-caused disaster like this and say to the know-it-alls from Greenpeace and the like “since you are so expert, you come with your resources and you take respnsibiility for cleaning it up, and we will sit on the sidelines and criticise you”. People who throw stones at others trying to resolve a difficult situation, not of their making, are nothing short of cowards. Grow some stones and find a way to assist if you actually do have expertise – otherwise get out of the way of those who have a dirty, difficult and tough job to do on a beach and in the sea, far away from your plush downtown Auckland offices.

  2. Thank you for your response Paul, all input especially on a subject as serious as this is invaluable. Please find links to some info on Corexit 9500 below and feel free to comment. Please also know that I am sure many people appreciate the amazing efforts of clean up crews that have to deal with this mess as a part of their job…they certainly have my respect. It is the chemicals used in question here not the hard work of crews and volunteers aho are only trying to help and are more than likely unaware if these findings.


    • Avalon, I appreciate your confidence in other blogs and on-line newspapers but the,material you are quoting may not exist. I have searched the on-line peer-reviewed scientific literature for the paper attributed to Anita George-Ares and James R. Clark for Exxon Biomedical Sciences, Inc. titled “Acute Aquatic Toxicity of Three Corexit Products: An Overview”, and can find no record of it. I have found this one ( – where the same authors report low to moderate toxicity) Please let me know the actual link as this would of great value tome in my work. Secondly, you may wish to visit the EPA webpages and review the letters and directives there regarding EPA directives to BP and the findings of the toxicity tests. These are at I cant find an official directive for them to stop using this dispersant – there are some that seek them to lower the amount being used and others requesting monitoring. Corexit was also not banned in Britain as is erroneously reported in many sites. It was unable to pass a test for toxicity when applied to rocky shore animals. This is a good thing as it was never designed to be used in rocky shores. It is designed to be used in a depth of water greater than 20m to allow the oil droplets to disperse into suspension so natural processes can break them down – light and bacteria primarily.

      In this spill response, HFO is the oil spilled. It is a very toxic and nasty substance, full of ashphaltenes and other carcinogenic substances, hence anyone working with it requires safety gear. There is lots I could tell you but space does not permit. Have a look at This appears to be reputable and independent science site, with similar links. The others you sent me to are not. One even suggests that the whole incident in the Gulf is a US Government conspiracy to rain toxic chemicals all across the US population. Sad people.

  3. As you mentioned above, this is the actual report and a link for anyone wanting to read it.

    “All products approved after 1 April 1996 have been required to pass both the Sea/Beach and Rocky Shore Toxicity Tests. Any products coming up for renewal that have only passed the Sea/Beach toxicity test in the past are required, before they can be renewed, to pass the Rocky Shore Test also. The following products have been removed from the list of approved products because they did not pass the Rocky Shore Test when submitted for renewal:”

    Chemkleen OSDA JAC (removed from list 21/01/1998)

    Corexit 9527 (removed from list 30/07/1998)

    Corexit 9500 (removed from list 30/07/1998).
    Existing stocks of these products may still be used away from rocky shorelines in appropriate conditions. Approval should be sought from the relevant licensing authority before any proposed use.


    Also found this:

    Photoenhanced toxicity of aqueous phase and chemically dispersed weathered Alaska North Slope crude oil to Pacific herring eggs and larvae.

    Barron MG, Carls MG, Short JW, Rice SD.


    P.E.A.K. Research, 1134 Avon Lane, Longmont, Colorado 80501, USA.


    The photoenhanced toxicity of weathered Alaska North Slope crude oil (ANS) was investigated in the eggs and larvae of Pacific herring (Clupea pallasi) with and without the chemical dispersant Corexit 9527. Oil alone was acutely toxic to larvae at aqueous concentrations below 50 microg/L total polycyclic aromatic hydrocarbons (tPAH), and median lethal (LC50s) and effective concentrations (EC50s) decreased with time after initial oil exposure. Brief exposure to sunlight (approximately 2.5 h/d for 2 d) significantly increased toxicity 1.5- to 48-fold over control lighting. Photoenhanced toxicity only occurred when oil was present in larval tissue and increased with increasing tPAH concentration in tissue. Ultraviolet radiation A (UVA) treatments were less potent than natural sunlight, and UVA + sunlight caused greater toxicity than sunlight alone. The toxicity of chemically dispersed oil was similar to oil alone in control and UVA treatments, but oil + dispersant was significantly more toxic in the sunlight treatments. The chemical dispersant appeared to accelerate PAH dissolution into the aqueous phase, resulting in more rapid toxicity. In oil + dispersant exposures, the 96-h no-observed-effect concentrations in the UVA + sunlight treatment were 0.2 microg/L tPAH and 0.01 microg/g tPAH. Exposure of herring eggs to oil caused yolk sac edema, but eggs were not exposed to sun and UVA treatment did not cause phototoxicity. These results are consistent with the hypothesis that weathered ANS is phototoxic and that UV can be a significant and causative factor in the mortality of early life stages of herring exposed to oil and chemically dispersed oil.

    PMID: 12627655 [PubMed – indexed for MEDLINE

    Also this:

    An initial probabilistic hazard assessment of oil dispersants approved by the United States National Contingency Plan.

    Berninger JP, Williams ES, Brooks BW.


    Institute of Biomedical Studies, Baylor University,Waco, Texas, USA.


    Dispersants are commonly applied during oil spill mitigation efforts; however, these industrial chemicals may present risks to aquatic organisms individually and when mixed with oil. Fourteen dispersants are listed on the U.S. Environmental Protection Agency (U.S. EPA) National Oil and Hazardous Substances Pollution Contingency Plan (NCP). Availability of environmental effects information for such agents is limited, and individual components of dispersants are largely proprietary. Probabilistic hazard assessment approaches including Chemical Toxicity Distributions (CTDs) may be useful as an initial step toward prioritizing environmental hazards from the use of dispersants. In the present study, we applied the CTD approach to two acute toxicity datasets: NCP (the contingency plan dataset) and DHOS (a subset of NCP listed dispersants reevaluated subsequent to the Deepwater Horizon oil spill). These datasets contained median lethal concentration (LC50) values for dispersants alone and dispersant:oil mixtures, in two standard marine test species, Menidia beryllina and Mysidopsis bahia. These CTDs suggest that dispersants alone are generally less toxic than oil. In contrast, most dispersant:oil mixtures are more toxic than oil alone. For the two datasets (treated separately because of differing methodologies), CTDs would predict 95% of dispersant:oil mixtures to have acute toxicity values above 0.32 and 0.76 mg/L for Mysidopsis and 0.33 mg/L and 1.06 mg/L for Menidia (for DHOS and NCP, respectively). These findings demonstrate the utility of CTDs as a means to evaluate the comparative ecotoxicity of dispersants alone and in mixture with different oil types. The approaches presented here also provide valuable tools for prioritizing prospective and retrospective environmental assessments of oil dispersants.

    Copyright © 2011 SETAC.

    PMID: 21425326 [PubMed – indexed for MEDLINE

    Also this:

    Comparative toxicity of oil, dispersant, and oil plus dispersant to several marine species.

    Fuller C, Bonner J, Page C, Ernest A, McDonald T, McDonald S.


    Conrad Blucher Institute, Texas A&M University-Corpus Christi, Corpus Christi, Texas 78412, USA.


    Dispersants are a preapproved chemical response agent for oil spills off portions of the U.S. coastline, including the Texas-Louisiana coast. However, questions persist regarding potential environmental risks of dispersant applications in nearshore regions (within three nautical miles of the shoreline) that support dense populations of marine organisms and are prone to spills resulting from human activities. To address these questions, a study was conducted to evaluate the relative toxicity of test media prepared with dispersant, weathered crude oil, and weathered crude oil plus dispersant. Two fish species, Cyprinodon variegatus and Menidia beryllina, and one shrimp species, Americamysis bahia (formerly Mysidopsis bahia), were used to evaluate the relative toxicity of the different media under declining and continuous exposure regimes. Microbial toxicity was evaluated using the luminescent bacteria Vibrio fisheri. The data suggested that oil media prepared with a chemical dispersant was equal to or less toxic than the oil-only test medium. Data also indicated that continuous exposures to the test media were generally more toxic than declining exposures. The toxicity of unweathered crude oil with and without dispersant was also evaluated using Menidia beryllina under declining exposure conditions. Unweathered oil-only media were dominated by soluble hydrocarbon fractions and found to be more toxic than weathered oil-only media in which colloidal oil fractions dominated. Total concentrations of petroleum hydrocarbons in oil-plus-dispersant media prepared with weathered and unweathered crude oil were both dominated by colloidal oil and showed no significant difference in toxicity. Analysis of the toxicity data suggests that the observed toxicity was a function of the soluble crude oil components and not the colloidal oil.

    PMID: 15648769 [PubMed – indexed for MEDLINE]

      • Avalon, thanks for the links and the informative dialogue. . I am aware of the litigation in the US regarding alleged health effects on workers of dispersants and oil. Whilst environmental effects are inevitable in a spill, if only because oil shouldnt be there in the amounts a spill creates, the effects on workers and other people is awful, sad and entirely avoidable. The Gulf spill is unprecedented. We will learn a lot from this huge and nasty experiment, but if dispersants become an non-option for response then any future oil spill will cause different (and very obvious) effects on the environment, and on economic and social values. Remember that the HFO in the water in Tauranga is less than the Gulf spill volumes and quite different in chemistry that Louisiana crude. Many Bay of Plenty birds feed by targeting surface sheens (indicating baitfish presence normally) and so oil on the water will cause bird mortality and dispersing the oil will cause it to be suspended in the water column for days to weeks potentially creating ecotoxicity to demersal and benthic species – pretty much “Hobson’s choice”. Would be better for oil not to be spilled, but when it is the responders face awful choices about what to do and what they can actually do. Monday morning quarterbacks can comment all they like, but until you are put in the decision-making role, its “all care, but no responsibility”. If we keep shooting the responders and the decisonmakers for doing the best they can with the tools they have available, we will get poor outcomes. Hopefully science will deliver better, more effective and more environmentally and much less health-effecting ways of dealing with the inevitable oil spills. This will be my last post – got to go back to work and actually work on saving the planet from people’s stupidity.

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