[Photo taken at Pachena Bay, BC, 2012]

Bamfield, BC is a place that is close to the hearts of all who have been there. It is a quaint village nestled in the rugged landscape of the west coast of Vancouver Island, with a population of 155 locals (as of 2011) and a lively, modern marine science center that brings in hundreds of students each year. This is where I was introduced to scientific research, starting with the world of ocean acidification.

colinbates3_webIn 2012 I had the pleasure of earning a summer research position with Dr. Chris Harley and Kat Anderson. Harley single-handedly wrote a very important paper in the marine ecology world, detailing some alarming changes in the ecology of intertidal regions as a result of climate change. Climate change is having far-reaching, unanticipated effects on the relationships between predators and prey in marine ecosystems, significantly altering their frequency, distributions, and the number of species that can persist. This is a really big deal, and the attention that scientists are giving this issue has been on the rise. But what about everyone else? The trouble with the ocean is that we seldom see what is beneath its surface – the average person is probably much more familiar with the problems of bee health, global desertification, and the shrinking polar ice cap. The reason is that these are all things we can see, whereas the troubles in the ocean are largely invisible. But that doesn’t make them any less real. It may be surprising to learn, then, that these changes in ocean chemistry are predicted to be one of the most profound ecological alterations in recent history.

To explain what is happening, we need to think about where carbon is coming from and where it’s going. We all know by now that we are responsible for releasing huge amounts of CO2 emissions into the atmosphere and this is having catastrophic effects on the global climate, but what is maybe not so apparent is that this carbon doesn’t all stay in the atmosphere. There is carbon flux between the atmosphere and the ocean, which is acting as a carbon sink dissolving formerly-atmospheric-carbon into the water. In fact, one third of all anthropogenic (i.e. human-produced) carbon emissions in the past 200 years has been absorbed by the ocean (!!!). Once the carbon is dissolved, it is converted into carbonic acid, thus increasing the ocean acidity (and decreasing the pH). This process is what we fittingly call “ocean acidification” – it’s a mouthful to say (and cumbersome to type) so we often abbreviate it as simply “OA.”

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Simplified diagram of the ocean acting as a carbon sink. Diagram from Helen Amass:  https://www.tes.com/news/school-news/

The predicted increase in ocean acidity is by about 0.5 pH units in the next 100 years. This might not seem like much, but it’s important to remember that the pH scale is logarithmic; therefore, something that is pH 7 is actually 10x more acidic than something that is pH 8. Doing the math, a decrease of 0.5 pH units means that in 100 years, the ocean is predicted to be more than 3x more acidic than it is today. To put this into perspective, if the pH of your own blood dropped by that much, it would make you extremely sick and you would probably die. Now, I’m not saying that all sea life will be dead in 100 years (it won’t be), but I am trying to reinforce how much of an impact changes in pH can have on carefully balanced biological systems.

Sea life is also sensitive to changes in ocean chemistry, and there are many ways the marine ecosystem can be thrown off balance. For example, calcifying invertebrates (things with calcium carbonate shells, like snails and limpits) can’t grow as well in acidic conditions. These invertebrates normally feed on algae (e.g. seaweeds or phytoplankton), which conversely grows just fine – sometimes even better – in acidic conditions. This is not only because the algae is not being eaten as much, but also because for them, the dissolved carbon is actually a beneficial resource. Thinking back to basic plant biology, this makes sense: terrestrial plants (plants that grow on the land) take up CO2 for photosynthesis and release oxygen, and algae has to do something similar. Since they live mostly submerged in the ocean, they don’t have ready access to CO2 gas in the air like terrestrial plants do, so instead they take up the dissolved carbon.

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The damage that acidic conditions can do to calcifying invertebrates. Photo courtesy of David Littschwager/National Geographic Society, obtained from http://www.pmel.noaa.gov/co2/ story/What+is+Ocean+Acidification%3F

Hey! If algae is taking up the carbon, why do we have an ocean acidification problem at all? The answer is for two reasons: one is that there is so much extra carbon that the algae can’t possibly use it all, and the other is that carbon is not the only limiting resource for the algae to grow (they also need other key nutrients, like nitrogen and phosphorous). But this still leads to an intriguing idea – can we grow more algae to help balance the pH in the ocean? Some researchers think we can do this by creating controlled blooms of phytoplankton, which are microscopic algae like diatoms and radiolarians. These are good candidates; diatoms alone already take up huge amounts of carbon (they are responsible for 20% of the impact of all algae combined), and would just need a local influx of fertilization to feed a massive bloom. But like so many ways we have proposed to undo our mistakes, this would likely create yet another: when these carbon-sequestering plankton die, they sink to the ocean floor, out of sight and out of mind. But this sequestration lasts for just a few human generations, so it is by no means a permanent solution – it just means that our great grandchildren will have to deal with it, instead of us.

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