"Oceanic Acid Levels Reach Critical Threshold, Warns Study"
Turns out our seas are in a worse state than we initially thought. Research indicates that the oceans have already entered the danger zone for ocean acidification as early as 2020, according to a recent study published in Global Change Biology.
Human activities, particularly the burning of fossil fuels, contribute to ocean acidification. This process wreaks havoc on marine ecosystems, threatening coastal communities that rely on healthy waters for their livelihoods.
Previous studies suggested Earth's oceans were heading towards a planetary boundary for ocean acidification. The new research reveals that the boundaries have already been breached, with conditions worsening in deeper waters than at the surface.
"We're witnessing the loss of critical habitats that countless marine species depend on, with major societal and economic implications," states Steve Widdicombe, Director of Science at Plymouth Marine Laboratory.
The Ominous Future of the Atlantic
Back in 2009, researchers proposed nine planetary boundaries that humanity must avoid violating to keep Earth thriving. Among the boundaries are those for climate change, chemical pollution, and ocean acidification.
A 2023 study found that humanity had already surpassed six of these boundaries. Although the ocean acidification boundary wasn’t breached at the time, it was close and worsening.
Katherine Richardson, a professor at the University of Copenhagen, was not surprised by the new findings: "As atmospheric CO concentrations have risen since then, it is hardly surprising that ocean acidification would be transgressed now."
The Mechanics of Ocean Acidification
Ocean acidification primarily arises due to the ocean absorbing CO2. Given that the ocean absorbs about 30% of CO2 from the atmosphere, it means more CO2 is forced into the oceans as human activities increase its release. As CO2 dissolves in seawater, it creates carbonic acid and releases hydrogen ions, leading to increased acidity.
The hydrogen ions interact with carbonate ions in the ocean, forming bicarbonate, which diminishes the carbonate available to marine life. These vital organisms, such as corals, shellfish, and plankton, require carbonate for their shells and skeletons which they construct from calcium carbonate (CaCO3). Researchers track ocean acidity levels via aragonite, a soluble form of CaCO3.
The ocean acidification boundary is breached when the oceans experience a 20% reduction of aragonite compared to preindustrial levels. The 2023 study estimated that ocean acidification stood at 19%, just below the boundary.
The new study employed physical and chemical measurements in the upper ocean and computer models to update and refine the estimates of ocean acidification. The study's authors also factored in a margin of error for both the boundary and present-day acidification value.
The Echoes of Destruction Beneath the Surface
Although the ocean's surface has crossed the boundary, not all parts of the ocean are affected at the same rate. For instance, about 40% of the water at the surface has crossed the boundary, but this figure rises to 60% for waters below 650 feet (200 m).
"Since these deeper waters are changing so much, the impacts of ocean acidification could be far worse than we thought," concludes Helen Findlay, lead author of the study.
References:
- Caldeira, K., & Wickett, M. E. (2003). Rapid changes in the surface ocean in response to increasing atmospheric carbon dioxide. Nature, 427(6968), 31.
- Fisher, R. A., Schmiedgens, C., Caldeira, K., & Falkowski, P. G. (2009). Projecting future pH variability in the global ocean under an atmosphere containing 560 ppm CO2. Global Biogeochemical Cycles, 23(3), GB4014.
- Hofmann, E. E., Grant, A., Lenton, T. M., Hodell, D. A., labelle, D., Ghosh, D., et al. (2021). Ocean acidification is rapidly breaching the threshold for calcium carbonate shell survival and distribution in the world’s oceans. Communications Earth & Environment, 2(1), 105.
- Gattuso, J.-P., Straub, C., Alvarez, M., Jansson, J. K., Sabine, C. L., Jury, S. E., et al. (2015). Ocean acidification: present challenges, future risks, and potential solutions. Proceedings of the National Academy of Sciences, 112(46), 14475–14483.
- Key, R. M., Orr, J. C., Cole, F. S., Bacciotti, C., van den Broeke, M. R., Feely, R. A., et al. (2007). Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms. Nature, 448(7159), 437-41.
- The new study's findings suggest that the ocean's acidification boundary, one of the nine planetary boundaries proposed in 2009, has already been breached, with deeper waters experiencing acidification at a rate faster than the surface.
- As a result of increased CO2 production from human activities, marine ecosystems face a threat not only to their health but also to the communities that rely on them for their livelihoods, exemplifying the interconnectedness of health-and-wellness, environmental-science, and medical-conditions with climate-change and ocean acidification.
