The ongoing conflict and resulting traffic disruptions in the Strait of Hormuz could trigger a widespread invasive species event, according to a new study published in the journal Biological Invasions. Scientists warn that ships stalled in the critical waterway are becoming prime sites for marine organisms to attach and multiply, creating a potential global biosecurity threat.
The Strait of Hormuz, a vital chokepoint for approximately 20% of the world's oil supply, has seen intermittent closures and disruptions since a conflict with Iran escalated in February. This has led to a significant number of vessels being idled in the Persian Gulf and the Gulf of Oman. More than 1,500 ships are reportedly stalled in the Persian Gulf, with hundreds more anchored in the Gulf of Oman.
When ships remain stationary for extended periods, a process known as biofouling occurs. This buildup can include a diverse range of marine life, from microorganisms and algae to plants and invertebrates. According to Mario Tamburri, a marine ecologist at the University of Maryland's Center for Environmental Science and lead author of the study, this accumulated marine life can then be transported to new ecosystems worldwide once the ships resume their voyages.
"Once invasive species take hold of a foreign ecosystem, it's nearly impossible to get rid of them," Tamburri stated. "We know that these invading organisms can cause millions of dollars' worth of damage and impact commercial operations like aquaculture and fisheries, and change the environment."
An example of the destructive potential of invasive species is the zebra mussel, which originated in the Caspian and Black Seas. The mussels rapidly spread through the Great Lakes in the 1980s and have since infiltrated rivers across North America. Efforts to eradicate them once established have proven largely unsuccessful.
Ships typically use anti-fouling paint to prevent marine growth. However, the effectiveness of these coatings diminishes when vessels are inactive for long durations, as seen during periods of widespread shipping slowdowns like those experienced during the COVID-19 pandemic. This prolonged stillness allows for extensive biofouling to develop.
The risk is amplified by the specific marine environment of the Strait of Hormuz. Organisms in this region are adapted to high salinity and warm temperatures, making them particularly hardy and capable of surviving long journeys to new environments. Tamburri described the current situation as a "worst-case scenario," especially as regional waters are warming further during summer months.
The combination of extensive biofouling, the accumulation of hardy species, and the sheer number and global reach of affected vessels presents a significant international biosecurity concern. These stranded ships effectively become transport vessels for invasive organisms.
Ecologists emphasize that prevention and early detection are crucial, as eradicating established invasive marine species is extremely costly and difficult. Recommended preventative measures include cleaning ship hulls before departure, ideally using specialized vacuum devices to avoid reintroducing organisms into the water. Some regions, like New Zealand, already require clean hulls for all vessels entering their waters, and international bodies are working to strengthen related regulations.