The Discovery That Changed Marine Antifouling

The Science of Making Barnacles Swim Away

At any given time, billions of barnacles are glued to rocks and things submerged in seawater.

This volcano-shaped crustacean has plagued anything that floats for millennia, developing remarkably sophisticated survival strategies that let it swim, find a suitable surface, settle, and cement itself firmly in place. These behaviours have evolved over millions of years, making the barnacle exceptionally successful in its natural environment.

Unlucky for boat owners and ship operators, the humble barnacle can’t tell the difference between a metal hull and a rock, or a whale or a pier… and because of this, they have plagued the maritime industry for millennia.

This tiny creature creates a remarkably large problem for the global shipping industry.

Barnacles glued on ship hulls create billions of dollars in extra fuel costs for the cargo and passenger shipping fleet every year. They drive up harmful emissions, wreck hull paint when forcibly removed, and interfere with proper mechanical functions.

This small but mighty creature is a total pest for the shipping industry and leisure boat owners.

At I-Tech, we are obsessed with them and how to stop them and have been for over 25 years.

But what catalysed the gathering of some of the best minds in marine biology and chemistry to understand this extraordinary biofouling organism and how to stop its worldwide ship hull domination?

To understand that, we need to rewind to the 1990s.

The first discovery: the 90s

The 1990s are perhaps best remembered for the rise of the internet, the arrival of mobile phones into everyday life and some unforgettable fashion and pop culture. But alongside all of those moments that defined the 90s, a scientific discovery was taking place in a laboratory in Gothenburg – one that would eventually change the course of marine antifouling technology forever.

In the late 90s, researchers found that medetomidine, a compound widely used in pharmacology to sedate mammals, had an antifouling effect against barnacles.

This was a colossal discovery, but at this time, the inhibitory effects were not understood.

Scientists at the time thought it might have something to do with barnacle glue. This substance and its antifouling effects needed a lot more lab time….

The Eureka Moment: the 2000s

In early 2000, the Swedish Foundation for Strategic Environmental Research (MISTRA) funded a multidisciplinary research programme focused on marine paints. Under this project, researchers at the University of Gothenburg and Chalmers University of Technology were investigating new approaches to antifouling.

Medetomidine was one of the substances they investigated, and researchers set out to understand how this pharmacological compound inhibited barnacle settlement.

Scientists worked on this day in-day out. Then came the unexpected observation that would set everything in motion – it wasn’t the glue. It was the swimming legs.

Swim away, swim away!

When swimming barnacle larvae – specifically the cyprid stage of Balanus improvisus – encountered very low concentrations of medetomidine being released from a wet coating, the larvae changed their behaviour. Scientists observed that the barnacle larvae’s swimming legs couldn’t stop kicking when in the presence of medetomidine, forcing them to move away from a coated surface.

For antifouling scientists, this was triumphant. Add to the gravity of the discovery, the barnacle larvae were not being killed; the effects were reversible.

This was highly significant, since at the time, and still largely to this day, antifouling technologies largely rely on mechanisms that kill fouling organisms. Whereas Medetomidine offered a completely different possibility: instead of killing barnacles, could they simply be put into a swimming mode and forced to stay away.

However, discovering the effect that medetomidine was having on barnacle larvae led to more vital questions:

• How was Medetomidine making barnacle larvae swim away?
• How could a molecule used extensively for its sedative effects in mammals cause such a dramatic behavioural response in a microscopic crustacean larva from the sea?
• Could this curious reaction be turned into a reliable, practical way of preventing barnacle fouling?

The finding was clear. The mechanism behind it was not.

Unlocking that mystery would become the next chapter in the Selektope story.

Find out more in the next article in the series.