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| 04/07/16

Pacific coast acidification requires urgent regional response


The waters off North America’s Pacific coast from British Columbia down to California are steadily acidifying, according to a blue-ribbon panel of ocean scientists who have recommended that regional governments sharply step up their response to the human-induced phenomenon.

The same carbon dioxide (CO2) emissions that contribute to global warming have a second, lesser known effect. Oceans absorb roughly between 30 and 40 percent of atmospheric CO2, and as the gas dissolves, it reacts with the water and forms carbonic acid, which inhibits shell growth in marine organisms, among other impacts.

A team of 20 researchers was convened by ocean management agencies from BC, Washington, Oregon and California three years ago to studying the phenomenon off their respective coasts. The researchers issued their findings this week.

The process occurs the world over, but the panel, which includes former PICS director Tom Pedersen, concluded that there are specificities to the West Coast that “dramatically heighten the potentially devastating effects” and will ensure that this region faces some of the earliest, most challenging changes in ocean carbon chemistry.

Over the course of 30-50 years, ocean currents carry Asian waters that have absorbed CO2 from the atmosphere to the West Coast. During this transit, they sink deep below the surface and CO2 levels rise even further as natural processes break down sinking organic matter, produce CO2 and also deplete dissolved oxygen. Coastal upwelling then pulls these CO2-rich and oxygen-poor waters to the surface, which then spread across the full length of the West Coast’s continental shelf.

In addition, because these physical and biogeochemical processes take many decades to play out, even if the rise in atmospheric CO2 emissions could immediately be halted, the West Coast would still be faced with steadily more CO2-rich waters for at least another 30 years.

The panel acknowledged that local actions are insufficient to wholly undo the impacts of acidification and hypoxia, but ocean management officials can improve local conditions by implementing better controls on nutrients and organic matter pollution that flow from land into coastal waters, as these substances provide nourishment for algae and bacteria that, in turn, can exacerbate the hypoxia and acidification.

They also encouraged the conservation and restoration of seagrass and kelp beds, which remove CO2 from coastal waters as they grow and have the potential to offset the acidification. Small-scale and short-term studies on such effects now need to be upscaled to larger proof-of-concept studies across a range of habitats to see under which conditions this CO2 removal works best to counteract the problem.

They also called for sweeping revisions to state and provincial water-quality regulations to take into account the effects of acidification, as most rules were written long before researchers were aware of the problem. The panel also encouraged the enhancement of a coast-wide monitoring network to assist with adaptation planning.

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