The damaging impact of low salinity on the sharp stuff growing on rocks (ie: barnacles)

Have you been to a rocky beach and noticed something on the rocks that seems to want to scratch your bare feet as you are looking for fun organisms in the water? Well you may be surprised to learn that they are also REAL, and likely ALIVE organisms. They are called barnacles, and here is a little video for you to see how they look when they are in action:

This week in Biology 326 we wanted to test the impact of salinity stress on the barnacle species Balanus glandula. We collected rocks from two regions with a large difference in the salinity of their water (Bamfield: 30ppt; Vancouver: 15ppt). Additionally, within these two regions, there are also local differences in salinity which we were able to use in our experiment.


Balanus glandula (picture taken during lab)

We counted the proportion of juveniles found on each rock and discovered that rocks which were in a lower local salinity environment had a smaller proportion of juveniles on them. Secondly, we learned that the rocks from Bamfield (higher salinity) had larger barnacles on them compared to the rocks from Vancouver (lower salinity). Furthermore, the rocks from higher local salinities also had larger barnacles on them compared to the rocks from lower local salinities.

These results pointed towards low salinity causing stress on the barnacles and decreasing their ability to grow.

However, we wanted to do further testing by setting up three different baths with salinities at 12, 20 and 20ppt and used each of these while testing two different questions: beats per minute and proportion of barnacles feeding per rock. What we found for the beats per minute experiment was that as the test salinity was increased (from 12 to 28) the number of beats per minute increased significantly, as we had expected.

What we found in the feeding experiment was that low salinity stress limited the proportion of barnacles feeding when looking at the difference in the local salinities as well as our test salinities. However, there was an interesting result which suggested that the barnacles from Vancouver (lower salinity) were feeding proportionally more than those from Bamfield (higher salinity)….not what we had expected! We can only speculate on what may have caused this result, but we think it may have to do with the barnacles in Vancouver being accustomed to feeding all the time because it is possible that the seawater here has fewer nutrients than that of Bamfield. Or that since we used seawater from Vancouver to create our test salinities, the barnacles from Vancouver had some sort of advantage.

All in all, if a barnacle (or any other organism) isn’t occupying an area that is optimal for its growth and physiological functions, it will face long-term negative consequences in some cases. Low salinity stress was found to generally have a negative impact on these barnacles.


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