Acuinuga. Acuicultura y Nutrición de Galicia


13-03-15 |

Increasing effects of acidification on Aquaculture

New scientific evidence is detailing the growing impact of ocean acidification on marine aquaculture. From the Atlantic to the Pacific, from Argentina to New Zealand, there is increasing evidence that the progressive acidification of the oceans is causing changes in the development of algae, molluscs, crustaceans and fish. These changes are negatively affecting the cultivation of various species of commercial interest, with the subsequent loss of income and the destruction of thousands of jobs.


The production of bivalve molluscs is possibly the most affected industry on a global scale. Larvae of oysters, mussels, clams and scallops require very specific pH values in seawater in order to properly develop the calcium carbonate shells acting as their exoskeleton. If these values are not suitable, the animals cannot properly develop, growth stops and high mortalities are quickly recorded over time. 


The process of ocean acidification is the progressive decrease in the pH of seawater as a result of increased carbon dioxide levels in the atmosphere. Since the beginning of the industrial revolution, CO2 values have steadily increased from 280 ppm recorded in the mid-eighteenth century to 390 ppm in the late twentieth century. In seawater, average pH values are decreasing from 8.2 to 7.8 units expected for the end of the present century.


In the Galician estuaries or rías, ocean acidification combines with other negative impacts derived from global warming, which has been linked to the increased prevalence of certain parasites in bivalves and algal toxic blooms, pollution resulting from industrial waste, oil spills or improperly treated urban wastewater. A successful coastal management during these past years could have alleviated these effects, focusing on hatchery seed production, introducing breeding programs designed for the farming of more resistant strains, better adapted to new environmental conditions; developing innovative regeneration strategies, implementing strict water monitoring programmes, promoting the diversification of the bivalve species currently farmed,  etc. 

Time will tell if we are still in a position to correct the many mistakes made in our recent past. What seems clear, in the absence of specific estimates of the loss of natural productivity in our shellfish banks, is that a growing number of voices are denouncing the dramatic decline in most natural populations of our traditional bivalve species. If this situation is not quickly addressed, it will have serious implications in the capacity of an already compromised sector for the sustainable generation of employment and wealth.