The Foul Story - Barnacles, Ultrasonics & The Facts From Cousin Glen

Some weeks back I wrote (here) of the difficulties we had experienced with barnacles fouling the sea water inlets on Crystal Blues in estuarine waters.

Keen to find a solution, we started to investigate the new ultrasonic antifouling systems - these use a low power transducer attached to the hull, constantly exciting the hull with acoustic energy which (we are told) prevents algae and barnacle growth.  One leading manufacturer, Ultrasonic Antifouling Ltd., claimed that preventing algae growth also prevented barnacles, because the barnacles fed on the algae. I was somewhat suspicious of this claim -  I just didn't see how barnacles (which never move) could effectively feed on the algae on the hull.  See the story here, on their promotional email.

Cousin Glen at Wilson's Promontory, Victoria

So we turned to cousin Glen Burns, our oracle on all things related to marine biology.  His informative and generally hilarious response is presented here :

"Anyway...in answer to your question, barnacles do NOT rely on the slime/algae growing on the (hull) surface, they are (as you suggest) filter feeders. They don't actually suck water into the body as clams, oysters (ie bivalves) do. Barnacles are actually arthropods not molluscs, so they have legs like crabs. Their legs are hairy and  modified into filter feeding appendages. They open their shell and reach out with their hairy legs to "sweep" any organic particles in to their mouths. You can watch them do this... if you have the patience to sit and watch a barnacle. Who said marine biology wasn't exciting!  Lots of particulate organic matter in estuaries and harbours means lots of food for barnacles and therefore a pain in the bum for boaties, constantly trying to keep the little critters from fouling hulls, intakes etc.

Searching For A Mate - Scary

So what do you do about it? Antifouling paint, either toxic or ablative obviously works on the outside. Scrape them off, dig them out, regularly replace bits...there is no easy answer. I'd be really interested to hear how the ultrasonic system works. What's that saying about "Build a better mousetrap and the world will beat a pathway to your door"...I reckon the same goes for barnacles...come up with a cheap, easy, environmentally friendly solution and boaties everywhere will be on bended knees in thanks!!    By the way, just another tidbit of information for you re barnacles. Being arthropods they practice internal fertilization. 

Now, being cemented to the substrate,  barnacles obviously can't get up and go looking for a mate so the penis is actually capable of extending out and over to neighbouring barnacles to facilitate insemination.  Which means that if you're a barnacle, size really does matter!  The further you can reach with your penis the more individuals you can mate with and thus pass on your genetic information to the next generation. Which is why the humble barnacle has the longest penis (relative to its body size) of any animal on the planet! Depending on the species,  the penis may be 10 times the individuals body length. So Ley, thanks goodness Neil isn't a barnacle or you'd be dealing with a schlong nearly 20 metres long!!"

Thanks Glen ... I think.  Maybe too much information.   Anyway, I have noticed that the "algae is barnacle food" claim is not repeated on the company website.  Equally, the product may work really well, even if we don't really know exactly why.  So we'll probably try it soon - stay posted, and please feel free to add your comments or opinions to this post.