Port Lincoln proudly proclaims itself “the Seafood Capital of Australia”; but, Norwegian energy giant Equinor threatens this status with plans to drill for oil in the Great Australian Bight. Such plans will have dramatic repercussions for the thriving aquaculture industry of Port Lincoln which relies heavily on the Bight.
Equinor plans to start operations in October next year with a drill located 370km from the nearest coastline at water depths of 2339 metres. Critics of the drill fear that an oil spill in this productive and pristine region will damage coastal communities and devastate wildlife.
What happens when oil is spilled?
Initially after an oil spill oil will spread out across the water, moving with the wind and the current. The amount of spreading depends on the action of winds, waves, water currents, oil type and temperature. At the same time the oil undergoes a number of chemical and physical changes due to weathering, evaporation, oxidation, biodegradation and emulsification.
Effect of an oil spill on the SBT population and industry
Oil spills can seriously impact the marine environment in a range of ways. Examples include:
- Physical and chemical alteration of natural habitats e.g. resulting from oil incorporation into sediments
- Physical smothering effects on flora and fauna
- Lethal or sub-lethal toxic effects on flora and fauna
- Changes in biological communities resulting from oil effects on key organisms e.g. death of zooplankton.
An oil spill in the Great Australian Bight (GAB) will inevitably have lethal and/or sub-lethal effects on the prized Southern Bluefin Tuna (SBT). Sub-lethal effects may include fin and tail rot, altered reproduction, decreased growth rates and lowered immune function. Overall, exposure to oil will reduce the chance of survival.
SBT are at a critical level that the industry sustainably manages with strict quota regulations. The recovery of the species is dependent on the strong conservation efforts at the international, national and state level. Considering the status of the species, a mass mortality event caused by an oil spill could see the extinction or reduction below recovery level.
The ability of a species to recover from exposure to toxic chemicals like that in oil depends on a number of factors. These include:
- Sensitivity/tolerance to chemicals
- Potential for (im)migration from non-impacted areas
- The reproductive dynamics i.e. generation time
- Number of offspring
In general, ubiquitous species with high reproduction rates and short generation times have a significantly higher potential for recovering than isolated species with a slow reproduction.
SBT are expected to have a low recovery potential. Firstly, SBT are considered to be a single stock since they have a single spawning ground. Consequently, an oil spill in the GAB is expected to affect the entire population of SBT. Secondly, SBT have slow reproduction rates and a long generation time. Therefore, it may take many years for the population of SBT to recover, if at all. Lastly and most importantly, the numbers of SBT are most likely not great enough to withstand the effects of oil spill.
Exposure of seafood to oil can make it unfit for human consumption. There are two ways that this can happen. First is through the presence of chemicals known as polycyclic aromatic hydrocarbons (PAHs), some of which are cancer-causing. PAHs are one of the components that make up oil.
The second way that an oil spill will make SBT unfit for human consumption is through tainting. Tainting is defined as the presence of an “off taste” that can be due to oil; however, it can also be due to natural causes. Tainting isn’t necessarily harmful; however, it can significantly decrease the marketability of the affected fish.
Even if SBT remains unaffected by the oil spill, just the perception of tainting and contamination will have significant negative effects on SBT marketability.
Port Lincoln upholds a title for clean seafood, caught in the pristine waters of the Great Australian Bight. After an oil spill, it will be possibly contaminated seafood, caught in waters thick with oil.
Australian Southern Bluefin Tuna Industry Association (ASBTIA) chief executive Brian Jeffriess says an oil spill will mean the end of the tuna industry. This could be due to loss of the species or contamination or perceived contamination of fish. Furthermore, “drilling in the Bight is not just a direct threat to tuna, but to all of the city’s aquaculture,” he said.