The seabed is deteriorating rapidly, warn the McGill scientists

The acidification of the oceans caused by the high levels of CO2 produced by humans causes the decomposition of the ocean floor.

Human activity causes rapid decomposition of the seabed, as we know it, warns a research team from Canada and the United States whose scientists are associated with McGill University in Montreal.

The bottom of the ocean is normally a limestone white in deep water. It consists mainly of calcite (CaCO3), a mineral from the skeletons and shells of a large number of planktonic organisms and corals.

An important role

The seabed plays a vital role in regulating the acidity of the ocean. In fact, the calcite solution neutralizes CO2 and prevents the water from becoming too acidic.

But now, especially in some areas such as the North Atlantic and the southern seas, the soil is brown.

The CO2 level is so high and the water is so acidic that the calcite dissolves. And human activity is largely responsible.

It takes decades, if not centuries, before CO2 reaches the bottom of the ocean, because almost all CO2 produced by human activity is always at the surface. -Olivier Sulpis, Ph.D. in the Department of Earth and Plane Sciences at McGill.

"But one day it will penetrate the deep waters, it will spread to the bottom and accelerate the dissolving of the calcite particles," says Olivier Sulpis, who is currently doing his doctoral studies at the Department of Earth Sciences and McGill Planets.

The areas most affected by the decline of the seabed. Photo: McGill University / Olivier Sulpis

Huge pressure

According to the doctoral student, what we are seeing now is just a foretaste of the fate that the seabed is likely to undergo in the coming decades, because CO2 emissions in the atmosphere are exceptionally high.

We must at least go back to the disappearance of the dinosaurs in order to find fast CO2 emissions. -Olivier Sulpis

This speed prevents the established natural mechanisms from counteracting their effects, which can ultimately even increase more with regard to the level of acidity in the oceans.

This study shows that human activity dissolves the geological profile of the ocean floor. This is important because this geological history provides evidence of anthropogenic and natural changes.

-Brian Arbic, physical oceanographer at the University of Michigan

Predict the evolution of the seabed.

Researchers now want to develop different scenarios of CO2 emissions to determine how the dissolution of the ocean floor will evolve over the coming centuries.

Information needed to accurately assess the long-term effects of acidification by humans in marine ecosystems.

The Bay of Baffin, on the Arctic Circle. The conclusions of an expert report from the Arctic monitoring and evaluation program are clear: the rapid acidification of the Arctic Ocean threatens the fragile ecosystem of the region. Photo: CP / CP / Jonathan Hayward

Expensive studies

Deepwater sampling is a difficult and expensive operation. For this reason, researchers in the laboratory have created micro-environments that reproduce the seabed, soil flows, temperature and chemical properties of seawater, as well as the composition of sediments.

Their experiments led to their understanding of the decomposition of calcite in marine sediments. They have also been able to accurately measure the dissolution rate on the basis of different environmental variables.

By comparing pre-industrial dissolution rates with those of today, they were able to determine the role of people in general dissolution rates.

Just as climate change does not only affect polar bears, ocean acidification is not just about coral reefs. -David Trossman, University of Texas at Austin

"Our study shows that the effects of human activity on the seabed are visible in many areas and that the resulting increase in acidification may affect our ability to understand Earth's climate history, Trossman says.

The details of this work are published in the PNAS (in English).

RCI / McGill University / Radio Canada