Oysters that survive and grow in waters with high levels of acidity develop a smaller and brittle shell that breaks more easily.
This consequence of climate change has a great impact on the marine flora and fauna and puts at risk the future of one of the most appreciated seafood: oysters.
One of the lesser-known consequences of climate change is the increase in the levels of water acidity in seas and oceans, with a great impact on marine flora and fauna and which jeopardizes the future of one of the most valued seafood: oysters.
“Oysters, like the rest of the bivalve molluscs, use calcium and carbonate to make their shells. The acidification of the water makes this process difficult and causes the small oysters to die before the shell can be built, “explained Professor of Planetary Sciences at the University of California at Davis, Tessa Michelle Hill.
Hill, geochemist and oceanographer, participated in a conference on increasing sea acidity levels organized by the National Press Foundation of the United States. in San Francisco with the co-founder and vice president of the oyster farming company Hog Island Oyster Co, Terry Sawyer.
“The production cycle for oysters is around a year and a half, but in recent times there have been cases in which we have reached a mortality rate of 100% of the ‘harvest’,” Sawyer said. the most delicate moment is the first week of life of the bivalve.
The responsible for the seas around the planet are increasingly acidic is the excess of carbon dioxide (30% of all emissions to the atmosphere of this gas are absorbed by the ocean), which makes the pH ( scale at which the acidity is measured) go down considerably.
Thus, for example, according to data from the Environmental Protection Agency of the United States (EPA), the level of acidity in the waters of the Canary Islands (Spain) increased from an average of 8.10 pH (lower acidity) in 1990 to an average of 8.07 (higher acidity) in 2010, a pattern that is repeated in seas and oceans around the world.
“These levels of acidity are a great threat to any living being that has a shell: oysters, mussels, sea urchins, barnacles, barnacles … and also for small crustaceans that in turn constitute the main diet for larger fish,” said Hill. .
Oysters that survive and grow in waters with high levels of acidity develop a smaller, brittle shell that breaks more easily, and Hill’s team is studying whether, in addition to the shell, the animal itself is also smaller, something that It has already been proven that it happens in the case of mussels.
Such is the magnitude of the problem that Sawyer, whose company was founded in Tomales Bay ( California ) 36 years ago and employs 260 people, doubts the future viability of the industry, since the alternatives found to date result very expensive and limit production.
This is the case of the hatcheries, water tanks built on land in which the growth of the oysters is controlled while they develop their shell before depositing them in aquatic farms in the sea, a process that allows them to be protected from acidity, but it is very expensive its cultivation
In addition to hindering or even preventing the construction of shells in bivalves, high levels of acidity in the water also affect the behavior and reproduction of other marine animals.
Acidification, however, also has “winners” in marine ecosystems, since algae and other aquatic plants benefit from excess carbon dioxide, which allows them to grow faster and achieve greater size.
“We have to change and adapt at full speed, or else in a short time we will run out of business. One of the strategies we are pursuing is to promote sales and dishes based on winning species such as seaweed, “Sawyer added.
Svilen Petrov, Maritime Herald, 20 March 2019. Article.
