General · 16th October 2014
Nothing that anyone can say anymore actually overstates the seriousness of the problems facing the world's oceans. The present rates of industrial overfishing are simply unsustainable. The increasing amounts of chemical pollution are calamitous. The ubiquitous masses of plastic garbage are unconscionable. And then, like pneumonia in a palliative care unit, there's carbon dioxide.
About one-third of the billions of tonnes of carbon dioxide we emit into the atmosphere from burning fossil fuels dissolves into the world's oceans to form carbonic acid. This acidifying process is occurring about 10 times faster than it did 55 million years ago when a natural event — probably volcanic activity in carbon-rich areas of Earth's strata — caused the mass extinction of bottom-dwelling marine life, according to a 2010 study by researchers from the University of Bristol, England.
Our carbon dioxide emissions have two more lethal effects on the oceans. The first is planetary warming, which also warms the oceans — albeit more slowly — but by the same amount that the atmosphere is warmed. The oceans are a finely tuned ecology in which water temperatures are so critical that even a degree or two can have huge effects. The other effect, related to warming, is reduced quantities of dissolved gases, particularly oxygen. Fish studies show that predator fish with high metabolic rates such as marlin are already disappearing from some areas of tropical oceans; other studies suggest that ocean oxygen levels could be reduced by 7% at the century's end. Oceanic “dead zones”, of which more than 400 now exist, are the result of depleted oxygen levels. The so-called “deadly trio” of acidity, warming and deoxygenation is exposing ocean ecologies to unprecedented stresses.
This is no longer scientific theory or a remote abstraction. Early in 2014, ocean acidity killed 10 million scallops near Qualicum Beach on Vancouver island — three years of product worth $10 million died when the normal pH of 8.2 dropped to 7.1. (Like the Richter Scale for earthquakes, the pH scale is also logarithmic so a drop of 1.0 is ten times more acidic). Scallop farmers are now doubting the viability of growing these shellfish in local waters.
Growing other shellfish is also becoming problematic. For decades, nearby Baynes Sound has been one of the most productive commercial shellfish farming areas on the west coast of North America. Now the acidic seawater is beginning to kill the larvae that grow the fragile seed stock for their oysters, clams, mussels, geoducks and other shellfish. The only way to reliably use the local seawater is to treat it with calcium carbonate .
The same problem is occurring along the coasts of Washington, Oregon and California. Acidity is causing naturally resident larvae to disappear from parts of Washington so oyster growers are having to import factory grown larvae for seed stock. A problem that began as occasional has now become persistent. Some growers have shifted production to Hawaii where the ocean is — as yet — not as acidic. Unless we immediately and dramatically reduce our carbon dioxide emissions, scientists expect that by 2050 not even the shells of mature animals will be able to survive the acidity. At some point before then, the animals at the bottom of the food chain that need a calcium-based shell will be unable to grow one and the entire marine ecology will begin collapsing.
Meanwhile, the global warming that is heating the oceans is creating other disturbing effects. A layer of heated surface water on the ocean tends to stay locked in place because of its relatively lower density, thus inhibiting the mixing process that keeps the entire ocean properly oxygenated. When oxygen-depleted deep water does eventually come to the surface, the effects can be devastating. Such upwellings of the hypoxic California Current caused massive animal death — events that were unknown prior to 2000.
This is now a problem of global dimensions. Coral reefs, where most of the ocean's fish species live, are bleaching and dying from warmer water. Acidity is adding to the devastation, while the deoxygenation is exacerbating it. In some places, such as the Caribbean, most of the coral reefs are now dead. Within five decades or so, all coral reefs are predicted to be white and lifeless wastelands, their once brilliant vitality replaced by “jellyfish, pathogenic microorganisms and toxic glooms of algae” (NewScientist, Oct. 12/13).
In just the last few months, on the west coast of North America, from Alaska to British Columbia and California, seastars have been dying in massive numbers — their legs fall off as if they have leprosy and then they just decompose into a pile of goo. No one knows, as yet, the cause of this “seastar wasting syndrome”. A virus? Something triggered by changes in the ocean's temperature and chemistry? Marine biologists are unequivocal in their concern. They don't know what it is, how to stop it, or what the ultimate consequences will be for the ecosystem when a key animal dies en masse. “It's pretty shocking,” said one. “I'm quite scared, to be honest,” said another.
How serious is this? Perhaps an anecdote best answers the question. About a decade ago, a conference of marine biologists were presented with the data on current and anticipated atmospheric carbon dioxide emissions. A few quick calculations revealed the implications for the world's oceans. One biologist made a dash for the toilets to vomit. Another went into clinical depression for a month. Unlike these scientists, most of the public and their politicians still don't understand the significance of what is happening to our oceans.