An Ocean of Problems

Photo Credit: WSeigmund

Yellow-shore crab Credit: WSeigmund



Everyone knows there’s a ‘c’ in carbon dioxide, but do they know about all the carbon dioxide in the sea? Burning fossil fuel creates carbon dioxide which can be absorbed by the ocean and when combined with water produces carbonic acid. This breaks down into bicarbonate ions and hydrogen ions. An increase in hydrogen ions causes an increase in pH, which has huge consequences for all marine organisms.

Diagram Credit: Oceana

Diagram Credit: Oceana

Ocean acidification is becoming known as ‘the other CO2 problem’ and is having negative affects on sea life. It interferes with many processes. Ocean acidification is not as well known a problem as climate change, but is a major issue nonetheless.

The Biology 326 class decided to investigate how ocean acidification may affect the ability of yellow-shore crabs, Hemigraphus oregonensis, to tolerate seriously cold temperature. Yellow-shore crabs are the tiny greenish crabs that are found under rocks in the low tide zone. Intertidal species brave fluctuations in environmental conditions. Intertidal temperatures get below freezing in winter and so it is of interest how these little green critters function in cold and different pH’s.

To do this we put yellow-shore crabs in 1 L jugs for a week. One jug had more CO2 than the other, resulting in that jug having a lower pH. We then put a few crabs at a time in an ice bath, which is exactly what it sounds like. After they were so cold they stopped moving and became unresponsive, we flipped them over on their backs and recorded the time it took them to wake up and get back on their feet. Their recovery time gives us a good approximation of how tolerant they are to the cold.


Crabs in their 1 L experimental containers Photo Credit: Meghan Terpenning

We also tried to measure the minimal temperature that crabs remained active by recording the temperature at which they became unresponsive – which is known as the chill coma. Because the machine that controls the temperature took longer than expected to make the water cold, we could collect very little data for this.

We found that crabs in our low pH treatments actually recovered from their chill coma faster than those in our control pH treatments and suggesting that low pH crabs were actually more cold tolerant. This is one way that ocean acidification can affect marine life. However, we cannot know what the long term affects will be. More study should be put into the effects of ocean acidification on marine life, as well as other environmental changes resulting from human activity.

Ocean Acidification can be lessened by emitting less carbon dioxide. By simple changes in our everyday lives we can reduce emissions of fossil fuels and cause less carbon dioxide to wind up in our oceans, slowing the effects of ocean acidification. To learn more about this click here.


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