About the Class

Ocean acidification is sometimes called the evil twin of climate change. It's driven by the carbon dioxide being added to the atmosphere, which is changing the chemistry of the oceans. These changes can influence how hard it is to make a shell, or how easy it is for plants and algae to grow. Ocean acidification can effect anything from the survival of tiny oysters to the sense of smell in fish. In this session we will start with some basics about how the ocean waters are changing. Then we will look at some of the more common responses among different kinds of organisms, including some that are common in the Salish Sea. We will explore what we do and don't know about what happens when things get complicated, like when temperature and carbon dioxide are changing at the same time, or in coastal waters that have many other influences. Finally we will take a look as what we know about what the future holds and how people and policy makers are addressing the coming changes.

Follow-up session questions and answers:

Some years ago Cliff Mass of UW argued that the oyster spat mortality could not have been caused by increased atmospheric CO2 because it was too abrupt. There was some talk about changes in currents bringing more deep low-pH water to the surface. What is the state of that argument today?
It is very well established at this point that low pH does cause oyster spat mortality and that this was the root of the issues that local oyster growers experienced back in 2009. The source of the low pH was is a combination of the long term atmospheric CO2 trends, and wind driven circulation that episodically brings low-pH water to the surface. That upwelling mechanism is certainly very important in the Salish Sea, however the long term atmospheric trends are also important, especially looking to the future as the two overlay each other.

Considering that oceans absorb CO2, what effects, if any, has the carbon emissions from the recent large scale forest fires had on ocean pH in the PNW.
I don't know of any studies on this question specifically, however it has been shown that local CO2 emissions to matter. CO2 is well mixed on the scale of a year or so in the atmosphere, but local sources can have effects on shorter time scales, so the forest fires could have had an effect on local waters in the days right around those events.

Anything in the fossil record which can inform what the oceans could be like with increased temperature and acidification in line with the 2 degree warming scenario? 4 degree?
There are times in the past, seen in marine sediment cores where the sediment goes black, because there are no more light colored shells being deposited, at times when ocean pH was low. There are times when coral reefs were pretty much wiped out as well. The presence of calcifying organisms like these is the most straightforward evidence to be seen. The paleo record is really not my specialty though.

What is the physical mechanism for the forecast decrease in nutrient supply? Increased surface stable stratification because of warming?
Yes, that is right. Nutrient supply, and therefore productivity are projected to decrease because when surface waters warm, they are more buoyant/less dense. Therefore mixing is reduced and nutrients in the surface layer are more quickly depleted, and less efficiently replenished from nutrient rich deeper waters.

What is sensitivity of jellyfish to acidification vis a visfish? Are we headed for a jellyfish ocean in future?
Well, jellyfish in general are pretty robust to low pH and low oxygen. However, they also are generally really patchy, and often have bloom and bust kind of life cycles making it somewhat difficult to track abundance over time. I would say the idea that we are headed for a jellyfish ocean does not have much evidence as of yet. There are a lot of moving parts in they system and it is very hard to predict what will unfold.

Perhaps a silly question, but is there any hope that shell producing organisms will adapt/evolve in resilient ways that are not yet known/discovered and continue to survive with the expected + acidification?
Yes, that's a great question. As we mentioned in the talk, there has been evidence of this in oysters that are being bred to develop new features. There is also an interesting story with corals that have evolved in an area that has naturally high CO2. They are thriving under these conditions. Adaptation is certainly possible. There are two parts of this that work against this as major ray of hope. One is that changes are happening very fast relative to what has happened in the past. The other is that there could be some real physiological/chemical thresholds that it is not really possible to get around, depending on how far changes go. So, overall I would say that things are likely to change, and that organisms will likely adapt to some extent. We just don't know how those things will all mesh together in terms of who will be be winners and losers.

So far, have you seen any reduction in water acidification at a local level? And if so, how was it accomplished?
There are not any large scale efforts going on locally on drawing down CO2 or increasing pH. There is a test project with kelp in the hood canal that is pretty small scale, but showing some interesting early results. We know that eelgrass beds can alter chemistry locally as well. These are all on a very localized scale in terms of space and time.

China and India have some of the highest carbon contributions. But they were not on your chart. What is happening to deal with their issues.
The chart really focuses on individual actions, and the average person in China and India is not really going on long plane flights, and usually doesn't have a car and eats a plant based diet already. The per-capita impact is usually much bigger in the countries represented on the graph. Of course every nation needs to participate in cutting carbon emissions, and that is the work of treaties and of the citizens of every country.

Is the rate of CO2 uptake in the ocean slowing? thought I read something about this at some point...
Yes, this is due to something called the Revelle factor. Basically, the more CO2 that is absorbed in the oceans, the less efficient they become at doing so. So, over time the proportion of CO2 that ends up in the oceans will go down and more will stay in the atmosphere.


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