Don’t be crabby: Why ocean acidification makes our friendly crustaceans lose their minds.

Before we get started, you might want to check out this quick video summarizing ocean acidification:

Ocean acidification is a hot topic in science right now, mostly because it’s something new that scientists don’t know much about. Our oceans are currently decreasing in pH faster than it has ever happened on Earth…like, ever. This creates lots of opportunity for novel experiments, because us humans are endlessly curious. Plus, the more species whose futures we can predict, the more we can say “I told you so!” when 100 years down the road all hell breaks loose.

For this exact reason, I decided to look at how ocean acidification affects crab feeding behaviour. More specifically, I wanted to determine if crabs would be able to take advantage of the decreased defense ability of mussels in high CO2. Since mussels create weak shells and secrete less byssal threads (doohickeys that attach them to rocks) in high CO2, many scientists think that their predation will increase in the upcoming decades. However, with a series of precise measurements performed at exactly the right time in perfectly ideal conditions, I have determined that this is not the case. Crabs actually experience their own issues at high CO2, which prevents them from capitalizing on the opportunity to pig out on mussels. This is both good and bad news…It’s good because it means that mussels might not actually be in as much trouble as we thought (putting aside their structural issues). The bad news is, us humans have done it yet again: I’ve found another species that is negatively impacted by our careless CO2 emissions.

To give you an idea of just how bothered the crabs really were in high CO2, check out the pictures below:


Much like a barrel of monkeys, when we pulled out one crab, we pulled them all out. This only happened in the elevated CO2 treatment, and while I have no idea why acidification might cause crabs to form a chain and “never let go, Jack”, it seems pretty obvious that something funky’s going on here.


Many crabs in the high CO2 tank were adamant on escaping throughout the entire 20 minute trial. They would repeatedly try to climb out of the tank, often resorting to holding themselves out of the water like this little guy.

Now, if you didn’t catch my sarcasm earlier I’ll make it easier for you: my experiment was far from perfect. As in any scientific experiment, methods can always be improved and for every answer you come up with 3 more questions. So, it remains to be seen whether the negative impacts on crab behaviour were purely due to acidification, or whether temperature and oxygen levels (neither of which were strictly monitored during the trials) were adding to the situation. But that’s science kids! As much as we want it to, it can never be perfect.


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