While those across the marine sector recover from the blow delivered this week by the breakdown in negotiations to address ocean plastic pollution, corners of the scientific community suggest that the subject at the top of the world’s agenda right now ought instead to be the worsening threat of ocean acidification.

Once thought to be the concerns of surface level layers of the ocean, headlines over the past week indicate that ocean acidification is now sinking into marine regions as deep as 1,500 metres – posing new threats to the marine life and organisms that dwell there, including sea butterflies, sea snails, and cold-water corals.

It’s long been established that the uptake of carbon dioxide impacts the acidity of the ocean’s surface. Earlier this year, scientists called upon world leaders gathered at COP16 this October to turn greater attention to the growing concerns over ocean acidification by addressing the global carbon emissions crisis and the impacts of climate change upon biodiversity and the environment.

The ocean is, after all, the largest natural sink of carbon dioxide, responsible for the absorption of around a quarter of the world’s annual emissions. As those emissions increase, so too does the impact of ocean acidification.

And one such impact, new studies have revealed, is that it is reaching deeper waters and impacting ecosystems in a way that few have fully understood, until now.

It was the work of Jens Daniel Müller and his colleague, Nicolas Grube at the Federal Institute of Technology Zurich in Switzerland that brought this to world’s attention this week, having developed a 3D reconstruction of how carbon dioxide moves through the ocean, based on global measurements of currents and other circulation patterns. By using this model to estimate how the carbon dioxide the oceans have absorbed since 1800, the team of researchers have been able to illustrate just how greenhouse gas emissions have affected deep-water acidity since the start of the industrial revolution.

What was found was there is a clear indication of acidification down to depths as far as 1,000 metres below the surface across most of the ocean. This went deeper still in some areas, such as the North Atlantic – where the Atlantic Meridional Overturning Current (AMOC) routinely carries carbon from the surface to deeper waters – where acidification has reached depths of 1,500 metres beneath the surface.

In the research paper (published recently in Science Advances under the title ‘Progression of Ocean Interior Acidification over the Industrial Era’) Müller and Grube position that ocean acidification driven by the uptake of human-caused C02 represents “a major threat to ocean ecosystems” while drawing attention to the matter that, even now, “little is known about its progression beneath the surface”…