So here is a subject that, far more than toothbrushes or Downton Abby (see Action 4) really keeps me up at night. Ocean acidification is a very serious and very present danger of increased CO2 in our atmosphere; and we are already seeing evidence of its effects.
Ocean acidification describes a process by which carbon dioxide in the atmosphere is absorbed by the ocean, lowering its pH. Its lucky for us that the oceans have this capacity; the ocean annually absorbs about a quarter of the CO2 we create through fossil fuel burning and related activities. But this absorption comes at a price; absorbing CO2 causes the pH to decline (which, for our purposes, we can call increasing ocean acidity, even though they’re not exactly the same), which has already been estimated at about 0.1 units of pH, and could get up to 0.5 units by the end of this century. That might not sound like a big change, but since the pH scale is logarithmic, we are talking about an approximately 30% increase in ocean acidity already, and a possibility of a 150% increase in ocean acidity by 2100.
What does increased acidity mean for our oceans? This chemical shift has implications for the most basic building blocks of oceanic food webs, our coral reefs and our oceanic plankton. Both these life forms use calcium carbonate as the fundamental building blocks of their skeletons. Decreasing pH means that, to simplify things a bit, there are more protons floating around waiting to grab those carbonate ions, and keep them out of reach of all the things that need them in order to grow and survive. This, as you can guess, is not good news for all the ocean life that depends on carbonates, nor the things that depend on these things that are CaCO3 based. It might not be bad news for jellyfish and stuff that isnt dependent on these calcium carbonates; but for a lot of the rest of our ocean food webs, and all us people who like to eat and enjoy these things, its extremely bad news.
This is not just some chemical theory, either: we are seeing the effects of acidification right now: recently our aquaculture facilities in the pacific northwest have seen near total failures of larval oyster development, which may be due in part to natural upwellings of low-pH waters but appear also likely to be exacerbated by anthropogenically derived acidification. And acidification is also extremely bad news for coral reefs, as these changing conditions are linked to reductions in reef productivity and increases in bleaching events.
So, the upshot of this is – you guessed it- if we want to have a chance and reducing the worst of these impacts, we need to reduce greenhouse gas emissions! However, there are additional proactive steps that we can take to manage and adapt to these changing ocean conditions too. The good news is that some local changes in acidification might be mitigated by steps we can take locally, including reducing nutrient runoff, as nitrogen additions can also contribute to ocean acidification at local and regional scales. A recent article and accompanying publicly available podcast from the Ecological Society of America discusses some important steps that ocean managers can, and should, be taking to be proactive about acidification, including understanding our ocean carbon baseline and local-scale variability, and understand where and why some reefs may be more sensitive than others to acidification in order to identify priorities for protection. We certainly need to prepare for and adapt to the changes that will very likely come our way even if we start reducing emissions as soon as possible, because, as I’ve talked about, there is plenty of forward momentum on increased CO2, and we will be seeing these impacts at global scales no matter how proactive we are.
Here in Washington, there is some movement to see what we can do at a state level to understand and manage for acidification. Senator Ranker, who represents the San Juan Islands, has just introduced legislation to establish an advisory council on ocean acidification, so today I sent him an email thanking him for this important step and asking him what else we as citizens can do to support this legislation. Will an advisory council be the solution to these grave concerns? Certainly not by itself. But in a world of government bureaucracy where we have many agencies with different goals and priorities for protecting and managing natural resources, having a group of folks with an overarching goal to make these agencies and institutions work better together to address acidification seems like a good step to take.