As it turns out Barnacle Boy and Mermaid Man, or maybe just Barnacle Boy in this case have more on their hands than just EVILLLLLL! Apparently barnacles have to fight the monster that is low salinity levels as well. Salinity is an important factor in barnacle ecology because salinities fluctuate depending on weather and other factors such as tidal cycles. Salinity has a variety of influences on barnacles including larval development, growth, and feeding.
The purpose of the experiment we conducted was to determine the effects of changing salinity on barnacle behavior. To test this we set up three water tanks with different salinities of 12, 20 and 28 parts per trillion. Parts per trillion is exactly what it sounds like, very miniscule difference in saltiness for us but it could be the difference between life and death in barnacles. We first looked at feeding behavior by counting the number of barnacles that were brave enough to extend their dainty little cirri from their operculum to feast on the food particles in the water. It takes them an eternity to get going, but once they do, these guys don’t mess around! Imagine if human possessed appendages that allowed us to just shovel loads of food into our mouths down our digestive tracts, my life would be made.
Barnacle with cirri fully extended. Our experimental setup. Barnacles at low salinity
Photo from: refusing to open up their operculum.
We not only looked at barnacle feeding behavior at different salinities but we did so with a twist. We selected barnacles from both Bamfield and Vancouver regions to participate in this eating contest. We wanted to see if the visitors from Bamfield who normally experience much higher salinities would be done by the lower salinity levels compared to the home team from Vancouver who normally experience lower salinity levels anyways.
Our results were very intriguing. We found that greater proportion of barnacles from Vancouver were feeding at higher salinities of 20 and 28 ppt, but both Vancouver and Bamfield barnacles were equally dismayed by the low salinity at 12 ppt. This shows that Vancouver barnacles did have home field advantage and we see this as potential evidence to support the idea that Vancouver barnacles are better adapted to larger ranges of salinities more so than Bamfield barnacles because of the differences in salinity fluctuations within their natural habitats. It is also important to note that at low salinities of 12 both Vancouver and Bamfield both displayed very low proportions of feeding indicating that extremely low salinities are a major stressor regardless of where they come from.
For more on Barnacles:
Wonderful video of barnacles feeding
Another up close and personal view of a barnacle extending its cirri
Finally, a good scientific paper on the mechanisms behind barnacle feeding