Stuck cargo ships are picking up some unwanted passengers

A legion of experts were racing to reopen a shipping channel through the Key Bridge wreckage, but Mario Tamburri wondered if anyone was thinking about the muck.

And the slime.

Specifically, that briny brew of microbes, macroalgae and invertebrates — known to the maritime industry as biofouling — that grows along a ship’s waterline over time.

The clock started ticking for ships stranded in the Port of Baltimore when the Dali crashed into the Key Bridge on March 26. Through his research for the University of Maryland Center for Environmental Science, Tamburri knew biofouling would beginning accumulating within days, even hours, on ships idling in warming water.

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Four weeks later, the first vessel left the port. Tamburri worried about the native Chesapeake species teeming around the hull. If they survived the voyage across the globe, would they invade delicate ecosystems abroad?

“We can’t just worry about what’s coming in [to the Chesapeake Bay],” Tamburri said. “We have to think about what’s coming out, too.”

Barnacles and other organisms can be seen on the topmost band of biofouling that has accumulated on the N.S. Savannah on Tuesday, April 9, 2024. More organisms grow below the water. (Kylie Cooper/The Baltimore Banner)

Commercial, fishing and recreational vessels have long contributed to the spread of invasive species, which can cause unintended ecological damage and cost jurisdictions millions of dollars to manage.

Ships have carried stubbornly resilient aquatic invertebrates like the Bugula neritina, a type of bryozoan that can cause health issues for sea life all over the world, including the Chesapeake Bay. Even Maryland’s famous blue crabs stowed away on cargo ship bound for warm Mediterranean waters, where they’ve since exploded in population.

International authorities and industry leaders are increasingly concerned with how ships treat the water that gets stored and expelled from their holds. Far fewer regulations exist for biofouling, even though it is responsible for more than half of all invasive species attributed to commercial vessels.

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Maryland has no laws, regulations or formal guidelines in place related to biofouling, according to the Maryland Port Administration.

Some places such as New Zealand are increasingly requiring vessels to provide evidence of biofouling management prior to arrival. California also has biofouling regulations aimed at minimizing the transfer of nonindigenous species.

These days, new cargo ships are painted with a copper- or zinc-based antifouling coating. However, the coating’s potency deteriorates over time and doesn’t perform as well on stationary ships, Tamburri said.

Biofouling can also be removed by underwater divers and in-water cleaning systems. Some jurisdictions such as Maryland don’t allow cleanings because they can brush heavy metals from the surface of the ship into the water.

The Maryland Port Administration proactively contributed funding to Tamburri’s research into the effectiveness of such technologies. In 2018, Tamburri and his team tested a cleaning system designed by Subsea Global Solutions, a Miami-based ship maintenance company with an international presence, that also captures organisms and debris.

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University of Maryland researcher Mario Tamburri explains the stages of biofouling on Tuesday, April 9, 2024. (Kylie Cooper/The Baltimore Banner)

The study gave the company an opportunity to test their tech on a particularly filthy ship, the NS Savannah. The historic vessel is parked indefinitely in the Port of Baltimore, to the delight of mussels and barnacles (probably.)

The exercise showed Subsea officials that they needed to expand the capacity for capturing debris from the water to keep up with the water flow, said Executive Vice President Rick Shilling.

“We were filtering down to one micron, thinner than smoke,” Shilling said.

Maritime industries have an incentive to clean their hulls, he added. The less sludge on the bottom of ships, the more efficiently it uses fuel and moves through the water.

“If we’re able to keep ships efficient, minimize our biofouling risks and at the same time keep our air cleaner, to me it’s a triple win for industry and also a win for the environment,” Shilling said.

Tamburri said his research is intended to one day inform regulations. Before that happens, the stranded cargo ships and their stowaways will be long gone.

Lillian Reed

lillian.reed@thebaltimorebanner.com