The state of ocean acidification

Ocean acidification is often thought of as a future impact of our changing climate. But exactly what is it, what are its impacts and is it really a problem of the future?

As reported in the CSIRO and Bureau of Meteorology’s latest State of the Climate report, oceans around Australia are acidifying 10 times faster than at any point in the last 300 million years. When coupled with ocean warming and deoxygenation, this is putting considerable pressure on our marine environments. Recent research from CSIRO and AIMS has highlighted the changing conditions on the Great Barrier Reef. Drawing on over a decade of observations collected as part of Australia’s Integrated Marine Observing System (IMOS) the team found that the Reef’s rich carbonate seafloor is not buffering against ocean acidification, a process that might offset ocean acidification.

The future is now for the Great Barrier Reef

New research published by the Australian Institute of Marine Science (AIMS) and CSIRO has shown that ocean acidification is no longer a thing of climate projections, but a present-day reality.

Bleached corals with small fish in background
The oceans are slowing climate change by absorbing excess heat, but changes in carbon chemistry of sea water is contributing to coral bleaching. © CSIRO, Christopher Doropoulos.

Dr Katharina Fabricius, a Senior Principal Research Scientist at AIMS said people talk about ocean acidification in terms of 50 years’ time, but for the first time our study shows how fast ocean acidification is already happening on the Great Barrier Reef.

Dr Bronte Tilbrook is a Senior Principal Research Scientist at CSIRO who leads IMOS’ observational projects for CO2 and ocean acidification. He is a co-author of the new research and said that it shows that acidification is rapidly changing the conditions that support the growth of corals on the Reef.

The study has filled this important knowledge gap by analysing 10 years of CO2, pH and aragonite saturation state data (2009–2019). These data were collected as part of Australia’s IMOS network at two long-term monitoring stations, located 650 kilometres apart at contrasting locations on the central and south Great Barrier Reef.

The researchers found the range of CO2 concentrations measured today were already greater than the range expected 60 years ago, even after accounting for the effects of temperature, nutrients, salinity, and daily and seasonal changes.

“We know now that oceans are taking up about 23% of the excess CO2 from the air. They actually provide a service to humanity by slowing climate change. But the price to pay is that the seawater’s carbon chemistry is changing, and we didn’t know it was happening in dynamic coastal waters at such fast rates,” Dr Fabricius said.

“Ocean acidification is not just a climate change issue, but can be addressed and managed in its own right,” added Dr Fabricius.

Fion Brown & Chris Gerbing, CSIRO ECOS, 25 November 2020. Full article.

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