The Ocean’s Little Goldilocks

We have all heard the tale of Goldilocks and the three bears. In which Goldilocks enters the bears’ home and makes herself feel right at home before being driven off by the bears. Now you might wonder what does this story have to do with oceans? The bears lived in a forest not the ocean. Well, let me tell you that during my 326 lab I actually met Goldilocks, which can be seen in the picture below.

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Hemigrapsus oregonensis, our green shore crab.  (Image from: http://www.centralcoastbiodiversity.org/hairy-shore-crab-bullnbsphemigrapsus-oregonensis.html)

Yes, that’s right the ocean’s little Goldilocks is none other than the shore crab, Hemigrapsus oregonensis. These shore crabs are found living in intertidal zones preferably under rocks. It is seen in previous research that in relatively warmer temperatures, the shore crabs have a higher activity level and are also seen to feed more due to the increased metabolic demand. Similarly, other abiotic factors could also be influencing the shore crab’s physiology and survival.

These seawater properties, however, are currently changing due to climate change. Climate change is causing shifts in the ocean properties such as temperature, salinity, and acidity. In fact, it has been predicted in the coming decades the oceans will become warmer and more acidic which could be detrimental for marine organisms. This suggests that the water properties of oceans could potentially have an effect on the shore crab’s physiology.

I investigated the effect of climate change on shore crabs by performing temperature and salinity manipulations. For my experiment I placed the crab in different temperature and salinity treatments to see how feeding and crawling speed of the shore crabs would be affected. Just as Goldilocks had found the first bowl of porridge too hot, the shore crab also found the warm temperature treatment to be too hot and didn’t feed much. The low temperature was just right for the shore crabs. Similarly, low salinity treatments were just too low for the little marine Goldilocks whereas the higher salinity was just right.

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Hemigrapsus oregonensis feeding on a mussel. (Photo Credit: Manjot Sandhu)

This suggests that the shore crabs prefer particular ranges for the abiotic factors, like temperature and salinity. Fluctuations in the abiotic factors change the environment which could compromise the physiology and survival of shore crabs. In fact, if the shore crabs are not able to adapt to these changes they may be forced to leave their current habitats. In a sense, climate change could be the bears in our tale of the ocean’s little Goldilocks. If climate change causes a shift in ocean properties that could make shore crabs physiologically intolerant to their current habitat resulting in deaths and habitat loss.

 Thus, I feel it is important to monitor the fluctuations in abiotic factors to see how they might affect marine ecosystems. Because unlike the classic tale, we don’t want the bears to force ocean’s little Goldilocks out of their home.

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