The closure of the strategic Strait of Hormuz has created conditions for an extreme global biodiversity threat, with marine biologists warning that more than 1,500 stranded commercial vessels could spread invasive aquatic species across the world’s oceans once maritime trade resumes. According to an international team of researchers, ships remaining motionless in the Gulf since the waterway shut down on 28 February have allowed dense marine communities to encrust their hulls, creating a potential bio-invasion super-spreader event unlike any previous shipping disruption.
The Perfect Storm of Idle Shipping and Marine Growth
Commercial vessels typically remain at anchor in harbors for only one to three days, a timeframe that severely limits the growth of organisms on submerged surfaces. However, the unexpected closure of the Strait of Hormuz following the outbreak of the US-Israel war on Iran has left more than 1,500 vessels trapped in the Gulf for months. According to Prof Mario Tamburri of the University of Maryland Center for Environmental Science, lead author of the new research, this prolonged stagnation has transformed ship hulls into floating habitats.
If you had to design the worst-case scenario, you could not have done it differently, Tamburri said, describing the situation as a perfect storm. As these vessels finally prepare to sail, their encrusted hulls—populated by microbes, algae, barnacles, and other invertebrates—risk hitchhiking to ports across the globe. When these organisms are moved into new regions, they can outcompete native wildlife, cause local extinctions, and permanently alter marine ecosystems.
Hardy Gulf Organisms Pose Global Port Risks
The Gulf is already a known hotspot for marine invasions, with scientific studies identifying dozens of non-native species introduced primarily by commercial shipping operations. According to researchers, the region’s extreme heat and salinity act as a natural filter, leaving behind organisms that are exceptionally resilient. These hardy life forms make particularly aggressive invaders when introduced to new environments.
Ports sharing warm, salty conditions similar to the Gulf face the highest immediate danger. Tamburri highlighted India and Singapore among the specific global locations where local authorities should place ports on high alert. Beyond ecological disruption, invasive species can devastate local fisheries, clog power plant cooling systems, and demand billions of dollars annually in management costs, according to the study.
Ballast Water Risks and the Call for Strict Monitoring
The threat extends beyond what is visible on ship hulls. Individual vessels may have already released millions of larvae into Gulf waters during their months-long lay-up. As shipping resumes, parasites and pathogens hidden within biofouling communities, alongside organisms carried in ballast water, threaten to spread rapidly through the interconnected global shipping network.
To mitigate the crisis, Tamburri urged governments and shipping companies to inspect and clean vessels before they depart the Gulf wherever possible. Port authorities expecting incoming traffic should simultaneously increase monitoring for invasive species and establish rapid-response plans. Comparing the biological risk to public health management, Tamburri emphasized that early detection is essential, noting that responses should mirror efforts to track infectious diseases like the flu or COVID-19.
The International Maritime Organization (IMO) echoed these warnings. A spokesperson for the agency stated that biofouling remains a key vector for the transfer of invasive aquatic species, noting a severe risk if ships cannot remove fouling after prolonged stays in a single area. The IMO recommends that ship operators follow existing biofouling guidelines as far as possible while the organization develops a standalone legally binding instrument for control and management.
Did You Know?
While standard port stops last less than 72 hours, vessels trapped in the Gulf have remained stationary for months, allowing dense layers of barnacles, algae, and mussels to establish permanent footholds on submerged metal surfaces.
Frequently Asked Questions
Why are ships currently trapped in the Gulf?
More than 1,500 commercial vessels have been stuck in the Gulf since the Strait of Hormuz closed on 28 February following the outbreak of the US-Israel war on Iran.
What makes the marine organisms in the Gulf so dangerous?
According to researchers, the Gulf’s extreme heat and salinity produce exceptionally hardy organisms that can easily survive long journeys and outcompete native wildlife in similar environments elsewhere in the world.
Which regions are at the highest risk of marine invasion?
Ports with warm and salty environments similar to the Gulf, such as those in India and Singapore, face the highest risk of receiving invasive species from returning commercial vessels.
What can authorities do to prevent a bio-invasion?
Experts recommend that shipping companies inspect and clean vessel hulls before departure, while destination ports should enhance ecological monitoring, adopt rapid-response plans, and follow International Maritime Organization biofouling guidelines.
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