Of Oyster shells and lobster’s tails
The ocean absorbs approximately 26% of the CO2 added to the atmosphere from human activities each year, greatly reducing the impact of this greenhouse gas on the climate.
When CO2 dissolves in seawater, carbonic acid is formed. It is this chemical reaction that leads to ocean acidification. Ocean acidity has increased by 30% since the beginning of the Industrial Revolution.
Business as usual scenarios for CO2 emissions could make the ocean up to 150% more acidic by 2100.
Who is affected?
Ocean acidification may have a strong negative impact on many plankton and zooplankton species that form the base of the marine food chain. Plankton is key to the survival of larger fish, and their decline may trigger a chain reaction through the marine food web. This will affect the multi-billion dollar commercial fisheries and shellfish industries, as well as threatening the food security for millions of the world’s poorest people.
Coral reefs may be particularly affected because of the combined impact of coral bleaching caused by increased water temperatures and ocean acidification. By the middle of this century, it is expected that coral calcification rates will decline by about one third, and erosion of corals will outpace new growth. Many reefs may no longer be sustainable. By 2100, 70% of cold-water corals will be exposed to corrosive waters. Cold-water coral ecosystems provide habitat, feeding grounds, and nursery areas for many deep-water organisms, including commercial fish species.
Acidification is also causing seawater to become corrosive to the shells and skeletons of numerous marine organisms, and is affecting reproduction and physiology of others. This is already impacting aquaculture and oyster production: Researchers at Oregon State University have definitively linked an increase in ocean acidification to the collapse of oyster seed production at a commercial oyster hatchery in Oregon, where larval growth had declined to a level considered by the owners to be "non-economically viable."
The owners of Whiskey Creek Shellfish Hatchery at Oregon's Netarts Bay began experiencing a decline in oyster seed production several years ago. "The early growth stage for oysters is particularly sensitive to the carbonate chemistry of the water," said George Waldbusser, a benthic ecologist in OSU's College of Earth, Ocean, and Atmospheric Sciences. "As the water becomes more acidified, it affects the formation of calcium carbonate, the mineral of which the shell material consists. As the CO2 goes up, the mineral stability goes down, ultimately leading to reduced growth or mortality."
Why does it matter ?
Coral reefs are the nurseries of the oceans, they are biodiversity hot spots. On some tropical coral reefs, for example, there can be 1,000 species per m². Their decline affects tourism, food security, shoreline protection and biodiversity.
Ocean acidification, along with warming surface waters, may reduce the ability of the ocean to absorb CO2, leaving more CO2 in the atmosphere and worsening its impact on the climate.
What is UNESCO doing?
UNESCO-IOC and the Scientific Committee on Oceanic Research (SCOR) sponsor the International Ocean Carbon Coordination Project (IOCCP), a monitoring and research programme. IOCCP focuses on the effect of increasing level CO2 emissions on ocean and studies the effect of ocean acidification on calcifying organisms and coral growth rates.
UNESCO-IOC is co-founder of the Ocean Acidification network, meant to provide a central source of information for ocean scientists on research activities in this area, and co-hosts the main international symposium on this issue, ‘The Ocean in a high CO2 World’.
UNESCO is proud to be a partner of the Tara Oceans expedition, a 3 year mission around the world aiming to understand how the nature and diversity of planktonic life will be affected by climate change and acidification. The impacts of plankton on life on earth are so broad that they are highly important for global human security; it is absolutely essential to get a better understanding of plankton ecosystems