Intertidal critters might be overdesigned

In the rocky intertidal we find a plethora of animals and plants which appear to be severely over-designed to withstand the pounding forces of breaking waves. Barnacles might be one of the best examples of this over-engineering. They build little calcium carbonate fortresses around their body, and these are anchored to the rock. The shell of the barnacle is strong, sometimes stronger than the rock tow which it's attached.

For example, this is a shell of Balanus aquila which I found lying on the beach here in Monterey.


It's a big barnacle, usually found in the low intertidal and subtidal zones. This individual was long dead. What's unique here is that I found the entire shell, intact, and free of the rock. It was removed by something, perhaps a small boulder rolling around, and rather than being crushed, it simply broke free from the rock. We're not dealing with wimpy sandstone or mudstone rock either, this barnacle shell was ripped right out of the granite found around Monterey.

The underside of the barnacle shell is just granite. It's hard to imagine just how this shell and bit of rock broke free of the rock without the shell being crushed, but it happened. This is clearly a case where the organism (its shell in this case) was extraordinarily over-designed for the situation in which it was living.