A prolonged standstill of commercial shipping in the Strait of Hormuz, stemming from an escalated conflict between the United States and Iran, poses an unexpected and severe environmental threat, according to a new study. Marine scientists are warning that the thousands of vessels idled in the Persian Gulf and Gulf of Oman could become 'super-spreaders' of invasive marine species across the globe.
Since hostilities began on February 28, 2026, more than 1,500 commercial ships have been stranded, with many remaining stationary for nearly five months. This extended period of inactivity has created ideal conditions for the accumulation of marine organisms, a process known as biofouling, on ship hulls.
Biofouling: A Looming Ecological Disaster
The study, published in the journal Biological Invasions, was led by the University of Maryland Center for Environmental Science (UMCES) with contributions from the Woods Hole Oceanographic Institution (WHOI). It highlights how biofouling begins with microscopic bacteria and slime, progressing to dense layers of algae, barnacles, mussels, and other invertebrates. Once these ships eventually resume their journeys, these organisms could be transported to ports worldwide, establishing themselves in new ecosystems where they could outcompete native species and disrupt local environments.
"Marine invasive species have profound ecological and economic impacts on coastlines across the globe and are extremely difficult, if not impossible, to eradicate once they become established," stated Carolyn Tepolt, a WHOI biologist and co-author of the study. She emphasized that the shipping disruption has inadvertently fostered ideal conditions for warm-water species from the Gulf to spread.
International Recommendations and Economic Impacts
The International Maritime Organization (IMO) recommends that vessels idle for more than 30 days undergo biofouling management before sailing. However, many stranded ships have far exceeded this period, coinciding with the peak growth and reproduction season for numerous marine organisms. Beyond ecological risks, biofouling also significantly reduces a vessel's efficiency, increasing fuel consumption and greenhouse gas emissions. Even a thin layer of slime can boost emissions by 20-25%, while barnacle growth can raise them by over 50%, according to IMO estimates.
Historical precedents underscore the danger: the Asian green mussel, native to the Indian and Pacific oceans and prevalent in Gulf waters, previously spread to the Caribbean and South Atlantic, causing significant ecological damage.
Urgent Calls for Action
Researchers are urging ship operators, port authorities, and regulators to enhance biofouling management, expand monitoring at high-risk ports, and coordinate international response measures. In-water hull cleaning before departure is identified as a critical step to mitigate the risk of invasive species spread. Reports indicate that divers have already begun cleaning operations in Gulf ports, with costs for a single vessel potentially reaching up to $8,000.
While global attention has largely focused on the economic and geopolitical fallout of the Strait of Hormuz situation, scientists warn that the most enduring consequence might be an invisible ecological threat, carried across oceans on the hulls of these stranded ships, demanding immediate and concerted global action.