How snails freshen up when having a meltdown

We all know that the temperatures on Earth are rising. You’ve probably seen the pictures of polar bears lost in the middle of the sea on a small piece of melting ice, but have you ever thought what this means for the animals that live under the icy covered oceans of polar regions.

When ocean temperatures rise, it causes increasing amounts of sea ice to melt each year. This sea ice is basically fresh water. So when it melts, it can cause the salinity of the water column to plummet. Melting sea ice also means there is an increasing area of, non-ice covered, open ocean. Because ice is so efficient at reflecting incoming solar radiation back to space, the less there is, the more light gets absorbed into the ocean, causing further heating of the ocean. This is known as a positive feedback.


For my individual project in Biology 326, I wanted to study how the tolerance and grazing activity of the common periwinkle, Littorina littorea, would change as polar oceans become more fresh and light levels increase. Two experiments were run. First, I timed how long it would take a periwinkle to escape from 1-liter mesocosm and repeated this over a wide range of salinities to help determine if the grazers would be able to tolerate a fresher ocean.Second, I set up a 2-day experiment where I had 6 different salinities. Each bottle had some kelp, which was weighed before and after the trails to determine how much kelp was lost. At each salinity there where 4 mesocosms. 2 bottles were exposed to light, 1 with snails and one without snails. The other two bottles were darkened with foil, again, 1 with snails and one without. The bottles without snails were used as the controls, which determine how much kelp was lost from decomposition and not from grazing by the periwinkles.

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Photos by: Jeff Joss

What I found out from my study is that light had no affect on the amount of kelp mass lost by decomposition or grazing. However, I did find out that snails and kelp don’t like to be in low salinity waters. At low salinities, the amount of kelp lost increased and the snails wanted to get out of the water a whole lot quicker. This may suggest that as climate change continues, the distribution of snails at kelp may drastically change.

For more information on polar climates, check out:


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