Environmental toxicity after Rena

Professor Chris Battershill, the University of Waikato’s Chair in Coastal Science, is leading research to explore environmental toxicology in the Bay of Plenty.

Underwater survey of marine life

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Scientists have begun long-term monitoring of marine life in its natural environment. This helps to identify contaminants that may be slow to accumulate in biological systems.

Rights: Bay of Plenty Polytechnic, The University of Waikato Te Whare Wānanga o Waikato

Current information on pollutants not relevant to New Zealand

Chris noted that the grounding of Rena in October 2011 on the Astrolabe Reef demonstrated that New Zealand’s information base concerning species resilience to pollutants is minimal. When the Rena incident occurred, people relied on information in the literature that described how pollutants are likely to affect marine organisms in general. This information mostly relates to studies done in other countries and is often based on experiments that are carried out in laboratories (rather than in the natural setting). It isn’t relevant to New Zealand species or to pollutants in New Zealand settings. Much of the literature describes how a specific pollutant might affect a species. In real life situations – in the environment – marine organisms are exposed to mixtures of possible contaminants. Mixtures can be much more potent and deadly than individual streams of pollutants. Mixtures are also often more bioavailable (more easily absorbed by organisms) than a single pollutant.

Relevant field research needed

Chris recognised the need to produce and develop an information base on common pollutants that are relevant to New Zealand marine situations. It should be:

• based on New Zealand species

• based on New Zealand conditions

• carried out in realistic field situations to reflect real life.

Much of the current information does not reflect real situations. The experiments are carried out in laboratories where toxicity is measured according to lethal dose 50 (LD50). LD50 is defined as a dose required to kill half the members of a particular animal population. However, many contaminants don’t kill an animal outright (such as they would in a laboratory bioassay), but they may damage an animal’s reproductive system so that they are unable to reproduce. The species then is effectively ecologically dead but becomes so over a longer period of time and at a much lower concentration of pollutants than an LD50 assay would show.

Monitoring marine life in its natural environment

LD50 is still useful to compare toxicity of different pollutants to particular organisms but it is also necessary to see what is happening in nature. It is important to run field experiments to look at the effects of a mixture of pollutants on marine life. There also needs to be long-term monitoring of marine life to examine contaminants that may be slow to accumulate in biological systems.

The marine life existing around Astrolabe has been exposed to oil and other contaminants from the Rena. Research will look at the reproductive response of marine life exposed to these mixtures. Scientists will consider whether the oil has damaged the physiology of marine life and also what effects other bioactive compounds released (such as antifouling paints) may have. They will do this by counting numbers of species in specific areas over time as well as taking biopsies from samples. In a biopsy, scientists will look for aberrations in reproductive organ development in particular.

While it looks as if we have averted a major oil spill, we need to be careful about checking long-term effects of any catastrophic pollution event.

Pollutant mixtures

As fresh oil weathers in the ocean, it loses its toxicity. However, dispersants such as Corexit (used to disperse the Rena oil) solubilises the oil and makes it more bioavailable. Dispersants may dilute and disperse oil, but they also enable it to get into animals more easily and quickly.

Mixtures of contaminants can be potent

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Mixtures of contaminants leached from the Rena could be toxic to marine life. Scientists look for signals in marine life that might come from such mixtures.

Rights: Maritime New Zealand

The chemical cryolite, which is used in the aluminium smelting process, was on board the Rena. This cryolite had already been used and is considered relatively inert when dry and stored correctly, but if it is released and exposed to other chemicals, it can be dangerous to animal life.

For several months after the grounding of the Rena, cryolite was in a soup of many other things in the ship’s hull, such as diesel, hydraulic fuel and possibly pool-cleaning chlorinated compounds. With such a mixture, it is highly possible some interactive chemistry was taking place. Toxins may have leached out into the environment. In this research, scientists will look for signals that might come from such contaminant mixtures. For example, if heavy metal or trace element levels peak in bivalves, it may demonstrate that pollutants coming from the ship have affected them.

An update

In July 2015, Chris gave a final report to the Rena Recovery Plan Governance Group. He said, "No evidence of long term reproductive damage to oil covered species or communities has been observed. Contamination around Otaiti (Astrolabe Reef) however remains a concern due to early signs of trophic (food chain) accumulation of metals in some species within the immediate debris field of the Rena.”