A world-first study has found that petroleum-based oil, even in small amounts, causes coral reef fish to engage in risky behaviours, endangering both their lives and the health of the reefs around them.

Just as one too many cocktails can cloud a person’s judgement, oil—in concentrations equivalent to only a couple of drops in a swimming pool—can cause coral reef fishes to make poor decisions.

The study, published today in Nature Ecology & Evolution, focused on behaviour and performance in six fish species from the Great Barrier Reef.

Co-author Dr Jodie Rummer from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University says the oil radically changes how the fishes behaved. “The fish were unable to identify friend from foe and they stopped travelling in groups. The fishes also had trouble selecting suitable habitats, swam toward open waters, and could not swim away quickly from danger.”

Rummer adds that the study focused on larvae, the juvenile stage when fish are especially vulnerable. She said that even in healthy populations of reef fishes, less than one percent of embryos and larvae typically reach adulthood.

The oil concentrations used in the study are already common along many polluted coastlines in industrialised regions worldwide. Laboratory exposure to higher oil concentrations caused higher death rates as well as changing the fish’s behaviour.

The study found that limiting industrial pollution near reefs—especially oil—may be critical for reef preservation. Coral reef ecosystems are already under threat from a range of stressors, including widespread coral bleaching due to climate change and overfishing.

Fish on coral reefs are critically important for keeping the entire ecosystem alive. Some fishes form the basis of food chains for larger predators (and for humans), whereas others are responsible for removing sea weed that would otherwise kill the live corals.

“If an oil spill were to occur, this study suggests there could be major consequences for reef fish, coral reefs, and the people working in fisheries and tourism,” says the lead author Dr. Jacob Johansen, from the University of Texas. “Over the past 35 years, many of the world’s coral reefs have declined. Still, many governments continue to allow industrial activities, including oil drilling and exploration, in sensitive reef habitats.”

‘Oil exposure disrupts early life-history stages of coral reef fishes’ is published in the July 18 issue of Nature Ecology & Evolution.

Article supplied by James Cook University.



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