Intensifying ocean acidity from carbon emissions hitting Pacific shellfish industry  

The SMH has a look at the toll carbon emissions are taking on the oceans - Intensifying ocean acidity from carbon emissions hitting Pacific shellfish industry.

For more than a century, Bill Taylor's family has used the calm, protected waters of Puget Sound to raise oysters, planting billions of larvae in underwater beds and then harvesting them to ship to some of the finest restaurants in the world.

But then something went wrong. After the hatchery produced peak levels of seven billion larvae in 2006 and 2007, the numbers began to drop precipitously. In 2008, it had just half as many larvae. By 2009, it produced less than a third of the peak.

Up and down the Pacific Coast, from California to British Columbia to Alaska, other shellfish farms experienced the same decline: Something was happening to their larvae at the formative stage of life when they build their shells. No one in the industry knew why "We didn't know that much about the water because we didn't have any problems," Taylor said. Once the larvae started dying off, they tested the water: It was much too acidic.

Scientists testing the water up and down the Pacific Coast found evidence of the same steep decline in pH. Studies have found more acidic water in Alaska is stunting the growth of red king crabs and tanner crabs. Plummeting pH levels across the Eastern Seaboard have been impacting the shellfish industry for decades.

The economic impacts of rising acidity can be devastating. At its peak in 1952, U.S. producers harvested 72 million pounds of eastern oysters, according to data collected by the National Marine Fisheries Service. In 2012, the last year for which data is available, farmers hauled in just 23.8 million pounds. Producers haven't harvested more than 30 million pounds since 1996.

In a new study published online in the scholarly journal Progress in Oceanography, a team of scientists from the National Oceanic and Atmospheric Administration found rural areas in southern Alaska are at high risk of losing hundreds of millions of dollars in commercial and subsistence fishing stocks. Declining seafood harvests will impact about 20 per cent of Alaska's population, which relies on subsistence fishing for significant amounts of their diet, the NOAA report found.

The acidification of the world's oceans frightens scientists, who see it as evidence of a rapidly changing climate. Though not as evident as increasingly powerful storms or devastating droughts, ocean acidification may be the clearest example of man's impact on the changing climate.

Acidification happens as a result of increased carbon in the atmosphere. The top layer of the world's oceans, perhaps the first 100 metres, absorb the elements in the atmosphere. The more carbon, the more acidic the water becomes. Currents take that layer of surface water and plunge it into the depths of the Pacific; decades later, the water is forced back to the surface as it reaches the West Coast, a process scientists call upwelling.