The risk of a major marine fuel spill in Antarctic waters is increasing, yet there are currently no adequate response methods to deal with such an event. Chemical fuel dispersants have not previously been used in Antarctica, but may offer an alternative solution for spill management. Very few data on the toxicity of physically and chemically dispersed fuels and fuel dispersants to Antarctic marine species are available, thus preventing informed management decisions. This research investigated the toxicity of three fuels commonly used in Antarctica (Special Antarctic Blend diesel, marine gas oil and an intermediate fuel oil) and of three dispersants approved for use in Australian waters (Ardrox 6120, Slickgone LTSW and Slickgone NS). Experiments were conducted on common Antarctic nearshore invertebrates including sea urchins (Sterechinus neumayeri), polychaetes (Ophryotrocha orensanzi), nemerteans (Antarctonemertes sp.) and amphipods (Paramoera walkeri).
Chemically dispersed fuel treatments contained greater proportions of higher molecular weight hydrocarbon compounds than did physically dispersed fuel treatments. Toxicity was highly correlated with dispersant type. Ardrox 6120 was the most toxic dispersant with and without fuel, followed by Slickgone LTSW. Slickgone NS was by far the least toxic and appeared to be the most effective at dispersing fuels in cold water. Dispersant type dictated toxicity relationships between physically and chemically dispersed fuel to S. neumayeri, O. orensanzi and Antarctonemertes sp., and results showed that chemically dispersed fuels were consistently more toxic when created using Ardrox 6120 or Slickgone LTSW in comparison to physically dispersed fuels. In contrast, physically dispersed fuels were more toxic compared to chemically dispersed fuels created using Slickgone NS.
Differences in toxicity were apparent between P. walkeri and the other species tested. Physically dispersed fuels were consistently more lethally toxic to P. walkeri than chemically dispersed fuels and toxicity appeared to be largely influenced by the hydrocarbon composition of water accommodated fractions. Paramoera walkeri appeared to be more sensitive to lighter hydrocarbon fractions, specifically those encompassing known toxicants including naphthalenes, hence further research is needed to identify toxicity responses to different hydrocarbon compounds. Larval and juvenile life stages of S. neumayeri and P. walkeri were more sensitive to hydrocarbons than early embryonic and adult life stages respectively.
This work represents the first study assessing the toxicity of physically and chemically dispersed fuels and fuel dispersants to a range of Antarctic marine invertebrates. These data provide valuable information for decision making to minimise impacts to marine species following a marine fuel spill event in Antarctica.