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Shellfish help boats glide through water


Marine organisms like barnacles, algae and tubeworms stick to ships, slowing them down. Scientists are hoping to reduce this fouling by designing a new type of chemical to coat ships (Image: iStockphoto)

Scientists are trying to stop marine organisms sticking to the bottom of ships by designing an antifouling agent that mimics the non-stick surface of shellfish.

If the research is successful, the product may replace current antifouling agents that rely on heavy metals or toxic chemicals, and which international marine authorities want to phase out.

Dr Andrew Scardino, a biologist at Australia's Defence Science and Technology Organisation, reports his findings this week at the Australian Marine Sciences Association conference in Melbourne.

Scardino's research aims to reduce fouling or biofouling, when barnacles, algae, tubeworms and other marine organisms stick to ships.

"It slows the boats down considerably," he says. "A small amount of fouling can have big increase in drag, which leads to a large increase in fuel costs."

Fouling of ships can also lead to the spread of invasive marine species, he says.

In the search for greener antifouling agents, Scardino noticed shellfish had evolved their own way of keeping unwanted organisms off them.

"For certain shellfish it can be a big problem if fouling covers the opening of their valve and they can no longer filter seawater and food," he says.

When Scardino took a closer look at their surfaces he found very fine microtextures that appear to play a role in staving off unwanted organisms.

For example, he says the surface of the blue mussel (Mytilus galloprovincialis) has tiny grooves just a few micrometres apart.

Another shellfish, Tellina plicate, has tiny pyramids on its surface.

Scardino carried out experiments using an artificial surface, designed to mimic the shellfish microtextures, to check how different surfaces affect fouling.

He found as long as the distance between the pyramids or the grooves is small enough, barnacle larvae or algal spores cannot easily hold on.

But he found that over time tiny bacteria fill in the gaps and create a smooth surface, which is easy for unwanted organisms to stick to.

Scardino thought that in nature there must be something in the shell surface that kills these bacteria, or deters them from building up.

He then found that extracts from the blue mussel shell kills some kinds of bacteria-like organisms, but he has not yet isolated the exact chemical that is doing the job.

He says the plan is to develop a synthetic microtextured coating containing a broad-spectrum antibacterial that will be able to keep a wide range of fouling organisms off ships.

Another scientist presenting at the marine science conference is doing similar research with tropical sea stars.

Tags: environment, marine-biology, information-technology