This is World Water Week and I have been writing a lot of water-related posts lately. Water is a resource that we all take for granted and water management comes with many challenges. In addition to the challenges of obtaining potable water, changes in ocean chemistry due to global warming affect many industries particularly fisheries. One of the industries that is severely affected is oyster farming.
Whiskey Creek Shellfish Hatchery on Netarts Bay in Oregon raises oyster larvae for shellfish growers from Mexico to Canada. The hatchery’s oyster larvae or ‘seed’ began dying by the millions in 2007. The same year, in Washington, wild oyster larvae also died in Willapa Bay. The bay has been the heart of the Pacific Northwest’s oyster industry since the 1850s. Taylor Shellfish Farms, the Pacific Coast’s largest grower, also lost most of its larvae that year and the situation was dire. Both Taylor and Whiskey Creek provide nearly all the seed for the West Cost growers. Subsequently, they produce more than a quarter of the 700 million farmed oysters in America.
Eventually, a larvae-eating bacterium called Vibrio tubiashii was found to be the culprit. Nonetheless, despite new filters being attached to the oyster tanks, larvae still died in epic numbers. In 2008, the remaining larvae at Whiskey Creek also died. At the same time, the water in Netarts Bay became more acidic and this was the water in the hatchery’s tanks. Each summer, the north wind pushed back the water along the coast of Oregon, allowing cold offshore water to surge into the land. At the time the larvae died there had been a strong upwelling.
According to researchers, this provides the ideal conditions for Vibrio growth as ‘blooms’ appear to be linked to “warmer waters in estuaries and the oxygen-starved “dead zones” that have showed up this decade off the coast of Oregon and Washington.” Scientists also report that the bacterium can thrive in oxygen-starved waters, feasting on decaying plant and animal matter littering the seafloor. However when it is brought to the surface, it can also flourish in warm, well-oxygenated waters.
This phenomenon of ocean acidification leaves shellfish more vulnerable than any other kind of marine life. Oyster farming is the perfect example of how acidification of oceans leads to economic catastrophes. Oceans of the world act as huge carbon sinks and colder waters near the ocean floor hold more CO2 than surface waters. Many different kinds of phytoplankton on the ocean’s surface absorb CO2 for photosynthesis, much like plants on land. When they die, they sink and decompose releasing CO2 into the water. CO2 dissolved in water forms carbonic acid and the upwelling of oceans creates a huge ‘mixer’ that supports marine life and oceanic food chains. However when carbonic acid content increases in the water due to excess carbon emissions, it wreaks havoc on shellfish including corals.
Ocean acidification due to global warming thus has a direct impact on people that depend on the ocean for their livelihood. Currently the oyster farms have adapted their methods to survive such fluctuations in acid levels and as a result, have had good harvests over the last two years. However, it is only a matter of time before adaptation becomes impossible.
Image Credit: Pacific Oyster. Wiki Media Commons