Strait of Hormuz Ship Stau Could Trigger Global Biological Invasions

Biological invasion risks are mounting globally as more than 1,500 commercial vessels stranded in the Strait of Hormuz accumulate heavy biofouling on their hulls, according to a study published in the journal Biological Invasions. The ships became trapped following the closure of the Strait of Hormuz on February 28 amid escalating tensions between the United States and Iran, creating conditions that researchers warn could trigger a worldwide super-spreader event once maritime traffic fully resumes.

Strait of Hormuz Evacuation Plan Advances as Hull Accumulation Peaks

While an evacuation plan backed by the International Maritime Organization (IMO), the United States, and Iran is underway to help more than 11,000 stranded seafarers and their vessels exit through the Strait of Hormuz, the prolonged stationary period has taken a severe toll on ship hulls. According to University of Maryland Professor Mario Tamburri, the lead author of the Biological Invasions study, the situation represents a “worst-case scenario” because the shutdown coincides directly with spring and summer growth seasons.

Marine microorganisms, algae, and invertebrates can enter a rapid growth phase on submerged ship surfaces within just 10 days, according to the research. Vessels stationary for more than 30 days face extreme biofouling risks. Because marine organisms in the Persian Gulf are naturally adapted to high temperatures and high salinity, researchers warn they possess traits that make them exceptionally hardy and likely to become invasive when transported to new ports worldwide.

Global Super-Spreader Threat Targets Major International Ports

As vessels begin exiting the Persian Gulf through temporary maritime corridors established by Oman’s Navy—navigating around minefields detailed by U.S. Secretary of State Marco Rubio—their first port stops are critical. Professor Tamburri identified ports such as Jeddah, Mumbai, Colombo, Singapore, Alexandria, Piraeus, Algeciras, and Rotterdam as high-risk destinations due to short voyage times and similar environmental conditions like temperature and salinity.

Researchers point to the Asian green mussel, a species native to the Gulf, as a prime example of the danger. Already transported to Florida, the Caribbean, Australia, and South America, the mussel competes with native bivalve species and routinely clogs industrial piping systems at power plants and desalination facilities. Beyond infrastructure damage, biofouling transport can carry pathogens and parasites that threaten commercial fisheries and local marine ecosystems.

Maritime Community Unprepared for Large-Scale Biosecurity Disruption

The international maritime community lacks sufficient preparation to handle biosecurity risks stemming from large-scale shipping disruptions, according to Professor Tamburri. While regulations continue to develop through the International Maritime Organisation (IMO), officials note that full approval and implementation will take several years.

Cleaning hulls before departure is the ideal preventative measure, but regional cleaning capacity in the Gulf remains limited. Furthermore, operational, security, and logistical pressures often require ships to depart immediately once transit lanes clear, leaving ports worldwide vulnerable to sudden introductions of non-native species.

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