It’s not the barnacles’ mere existence that commands the sea service’s hefty monetary investment. It’s their Herculean ability to literally glue themselves to the surface of Navy vessels with a permanence that confounds everyone -- from Sailors to scientists.
“Barnacles attach themselves to the exterior of a ship and over time they grow and become extremely difficult to remove,” said Dr. Christopher Spillmann, a research physicist at the U.S. Naval Research Laboratory and member of a team at NRL conducting extensive research on combatting the Navy’s barnacle dilemma.
“It costs the Navy in money, manpower, materials and supplies,” Spillmann said. “Barnacles increase drag and fuel consumption, decrease efficiency … you’ve got to remove them somehow, whether it’s scraping a ship underwater or dry docking it. There’s a lot of costs associated with that.”
A baby barnacle is known as a nauplius. The nauplius grows for about two to three weeks usually, munching on plankton, then transforms into a cyprid.
Cyprids cannot eat. En route to barnacle adulthood, its only mission in life is to find a home, preferably where other cyprids are hanging out, and attach itself to any surface – often that of a ship.
It uses swimming appendages to find that surface, two antennules used as feet to walk around, smell for other barnacles and probe the surface for a suitable spot to settle.
“That’s its only goal at that point,” said Dr. Kathy Wahl, a section head in NRL’s chemistry division. Wahl is leading the barnacle research project, with Spillmann and Dr. Christopher So, a materials research scientist.
“[The cyprid] is looking for a place where other barnacles might be,” Wahl continued. “It takes its feet, sticks to a surface and lays its glue down permanently,” she said. Then it molts. “Turns itself inside out and starts to form the shape of a barnacle.”
Research on barnacles and how to prevent them from attaching to Navy ships has been ongoing for decades, So said.
According to Wahl, some of the most effective surface treatments, such as tributyl tin, have been banned for environmental reasons, so there is a push to develop new, less toxic alternatives, she said.
“The Navy has a different duty cycle,” Wahl began. “In port for months at a time, compared to commercial shipping vessels. Solutions that might work well on a hull in nearly constant motion may not release or limit growth of fouling as well after a prolonged time in port,” she said.
Cleaning and grooming tools are being developed, but the challenge there is to balance removing foulers while limiting coating damage, Spillmann added.
So Wahl and her team took a different approach.