Continuous dumping of crushed rocks by bulk carriers along the Great Barrier Reef route may counteract the acidification of ocean water caused by fossil fuel burning, but will lead to unknown side effects on the marine environment and coral reefs, according to a study by an Australian agency. .
In what is described as a “first-rate assessment,” CSIRO scientists found that it was theoretically possible to return the clock to the effects of decades of burning fossil fuels, but the radical step came with “as yet undefined risks.”
In addition to causing the atmosphere and oceans to warm, rising levels of CO2 in the atmosphere from burning fossil fuels have also changed the pH of the ocean, making it difficult for corals to form their skeletons, a process known as calcification.
The study’s lead scientist, Dr. Mathieu Mongin, said researchers are now forced to consider the viability of radical reef rescue interventions due to the lack of global action on the climate crisis.
One reef expert, Prof. Terry Hughes, described the concept of adding materials to the waters of the Great Barrier Reef, as modeled in the study, as “reckless.”
Reef scientists are studying the viability of a number of local interventions to try to gain time for the world’s largest coral reef system.
A supply system has already been tested to spray trillions of nanosized ocean salt crystals to illuminate clouds that can be located to cool the reef during the summer, when corals are at risk of bleaching.
The new study, published Tuesday in the journal Environmental Research Letters, raises the concept of using an existing shipping route to use alkaline material that can raise water’s pH levels, making it less acidic.
The study uses real pH measurements made by sensors on a ship owned by mining company Rio Tinto, which travels from Weipa to the Gladstone route – a trip that usually takes four days.
Mongin and colleagues used these measurements to test and calibrate their computer model, which simulates the material released over two years using the ocean and weather conditions between January 2014 and December 2015.
Mongin, a carbon chemist and model at CSIRO, said: “Because there is a lack of action on climate change and emissions reduction, this is forcing us to study these interventions.
“We need to study all the warnings and this will need to be done with our research colleagues and reef managers.”
The study looked at the potential effects of adding 90,000 tonnes of shredded olivine – a common mineral – over three days. Ocean currents then spread the solution over the reef.
Mongin said the modeling shows that the material must be constantly added to ocean waters to maintain elevated pH levels.
“On the day you stop, you return to where you were within three months,” he said.
The model offers a continuous release of the material every three days for one year along the reef to compensate for four years of ocean acidification caused by current CO2 emissions.
“We are not advocating for this intervention,” Mongin said. “We are dealing with the current state of the Great Barrier Reef. We see that this is coming and we do not see any action and it is difficult for us to think about it.
“But my job is to test it so that the public knows what might happen if we don’t act now. We go beyond our comfort zone, but we have to do it. “
Scientists have already conducted a small experiment on a coral pier in the southern part of the Great Barrier Reef, showing that adding an alkaline solution to the water increases the rate at which corals can build skeletons.
Professor Hughes of James Cook University’s Center for Coral Reef Research said the concept of adding 90,000 tonnes of olivine “every three days for a century” was “reckless.”
He said: “The study does not examine the environmental impacts of manipulating aquatic chemistry on a huge scale, other than acknowledging that light levels will be reduced.
“The Australian government has spent hundreds of millions of dollars in recent years to reduce water pollution on coastal reefs. Deliberately reducing light levels through GBR would have a huge detrimental effect on corals, seagrass and other key species that use sunlight for photosynthesis. “
Dr. Kennedy Wolfe, a marine biologist at the University of Queensland who helped conduct a previous ocean acidification experiment, said it was important to understand the potential viability of large-scale conservation measures.
But he said the study showed that a “major drawback” of the approach was the need to constantly add material to the ocean.
He said: “According to the study, the chemistry of seawater will quickly return to pre-intervention levels if alkaline injections are stopped. Does this mean that a 90,000 t source of alkalinity must be added to the GBR every three days throughout eternity?
“In fact, we will probably have to add more and more alkalinity to the system to counter the continuing increase in ocean acidification due to global emissions, unless emissions are drastically reduced along with alkaline injections.”
Globally, the average pH of the world’s oceans is the lowest in about 800,000 years.
While water pH levels naturally fluctuate back and forth every day and during the seasons, a study found the highest levels of CO2 to which the corals of the Great Barrier Reef were exposed in the 1960s now represent the lowest levels. .
Dr Katarina Fabricius, Senior Principal Investigator at the Australian Institute of Marine Science, said: “Overall, it is clear that reef calcification has decreased.
“GBR has become 6% more acidic in the last 10 years. We are exactly following the trend [of CO2 levels] in the atmosphere. “
She said that while some marine species could move to escape higher temperatures, “there is no salvation for acidifying the ocean.”