Acid Oceans Could Drastically Cut Down One of The World's Biggest Oxygen Producers

New study reveals that as our seas get more acidic, the small floating creatures that provide up to a fifth of our world's oxygen will be in jeopardy.

Diatoms will be deprived of the silica building blocks they require to make their protective shells, which come in a variety of beautiful opaline designs.

According to studies, this might cut their numbers by up to 26% by the end of the century.

"Diatoms are one of the most important plankton groups in the ocean," says GEOMAR Helmholtz Centre for Ocean Research Kiel marine researcher Jan Taucher.

"Their decline could lead to a significant shift in the marine food web or even a change for the ocean as a carbon sink."

These single-celled algae account for 40% of the ocean's photosynthetic biomass, making them an important part of the biological pump that removes CO2 from the sky and stores it in the ocean's depths.

They are one of the reasons the seas have been able to absorb a large portion of the extra CO2 produced by humans.

However, as our extra CO2 dissolves in saltwater, it interacts to produce additional hydrogen ions, raising the acidity of the water. Since industrialisation, the changing ocean chemistry has resulted in a 10% drop in carbonate concentrations.

Because calcium carbonate is component of most marine organisms' shells and exoskeletons, having less carbonate makes it more difficult for it to develop.

Calcium carbonate dissolves when the carbonate concentration becomes too low. The shells of certain creatures are eroding.

Diatoms, on the other hand, are considered to be reasonably resistant to ocean acidification and may even benefit from CO2 rises since they construct their elaborate glass dwellings out of totally different elements.

The outer shells of phytoplankton, known as frustules, are made of silica that floats on the ocean's surface waters.

However, the current study uncovers a characteristic that earlier investigations had overlooked. It turns out that when the pH of the water decreases, these essential silica building blocks dissolve more slowly, causing more of it to sink deeper into the ocean before becoming light enough to float.

This results in more silica on the ocean floor, far out of reach of the diatoms who utilize light to convert CO2 into oxygen, water, and carbohydrates, preventing them from constructing their frustule dwellings.

Taucher and his colleagues discovered this by putting varied quantities of CO2 into enormous oceanic "test tubes" (mesocosms) to predict future warming scenarios.

They next analyzed the dead-diatom-filled silt obtained in samples taken at various depths. This, together with modeling based on prior diatom silica chemistry research, indicated a dramatic drop in floating silica, implying that diatoms might reduce by up to a quarter by 2200.

Given that phytoplankton is one of the ocean's major producers, such a large loss will have serious consequences for other species on our planet.

"Associated consequences for ecosystem functioning and carbon cycling are more difficult to assess," the researchers write in their report, noting that they did not account for various physiological and ecological processes that might have a domino impact on the remainder of the food web.

Regardless, the findings demonstrate how unforeseen feedback processes in Earth's systems may significantly alter environmental and biological changes that we may believe we understand, demonstrating that we still have a lot to learn about how our planet and its life forms are connected.

"This study once again highlights the complexity of the Earth system and the associated difficulty in predicting the consequences of man-made climate change in its entirety," says Ulf Riebesell, a marine scientist at GEOMAR.

"Surprises of this kind remind us again and again of the incalculable risks we run if we do not counteract climate change swiftly and decisively."