August 12, 2026: More than 1,500 commercial vessels that have remained idle in and around the Persian Gulf since February could pose a major marine biosecurity threat when they eventually leave the region, according to researchers.
Scientists warn that ships stranded by the prolonged disruption in the Strait of Hormuz have had more time to accumulate marine organisms on their hulls. When these vessels resume their journeys, they could transport invasive species, parasites and diseases to ports around the world, potentially triggering what researchers describe as an international marine biosecurity “super-spreader” event.
The economic consequences of the Strait of Hormuz disruption have received considerable attention, but the potential ecological consequences of prolonged vessel layups have received far less focus.
Why idle ships become a risk
Ships that remain stationary for extended periods can quickly accumulate biofouling the build up of marine organisms such as algae, shellfish, worms and other organisms on their underwater surfaces.
The problem can be particularly serious in warm, tropical waters. When vessels eventually move to another region, the organisms attached to their hulls can travel with them and potentially establish themselves in a new marine environment.
These introduced species can compete with native organisms and damage ecosystems, fisheries, aquaculture operations and coastal industries. Some can also carry parasites or diseases.
The Persian Gulf already contains more than 50 recorded marine non native species, while several species native to the region have been transported to other parts of the world.
Why the Strait of Hormuz is especially important
The Strait of Hormuz is one of the world’s critical maritime chokepoints. Researchers identify 24 major chokepoints in global maritime trade, but only four have no practical alternative routes. These include the Strait of Hormuz, the Øresund Strait, the Bosporus and Dardanelles and the Bohai Strait.
Disruptions at such locations can force large numbers of ships to remain at anchor or be taken out of service.
Similar vessel layups have occurred during previous global crises. The financial crisis of 2008, for example, resulted in thousands of vessels being taken out of service following a sharp decline in international trade.
Seasonal closures can also cause fishing fleets to remain stationary for extended periods, creating similar biofouling concerns.
Potential risks for Australia and New Zealand
Researchers say Australia and New Zealand could eventually receive vessels carrying organisms accumulated in the Strait of Hormuz region.
The number of affected ships arriving in these countries may be limited during the first month after the strait reopens, but researchers estimate that a significant number of potentially invasive organisms could reach the region within a year.
Both countries already have strict marine biosecurity systems designed to detect and manage invasive species.
New Zealand, for example, strengthened monitoring during the COVID-19 pandemic when cruise ships were temporarily laid up. Ships with significant biofouling were required to leave New Zealand waters or undergo cleaning and maintenance to meet biosecurity requirements.
However, managing biofouling risks from commercial vessels making short port visits remains difficult.
Steps to reduce the threat
Researchers have recommended several measures to reduce the risk of marine biological invasions from vessels leaving the Persian Gulf.
Ships could undergo inspections before departure to estimate the amount of biofouling on their hulls. Environmental DNA testing around vessels could also help identify potential biological threats.
Where possible, vessels should be cleaned before leaving the region. Researchers stress that cleaning operations must safely capture organisms and debris rather than releasing them into the surrounding water.
Authorities should also track the routes of vessels leaving the Gulf and identify their first destinations so that receiving ports can assess potential biosecurity risks.
Ports and national agencies could use rapid monitoring and environmental DNA techniques to detect newly introduced species at an early stage. Establishing international alert and information sharing networks would also allow authorities to respond quickly when a new biological threat is detected.
A global biosecurity challenge
Researchers say the situation highlights an often-overlooked environmental consequence of disruptions to global shipping.
While the immediate focus of a Strait of Hormuz closure may be on energy supplies, trade and shipping, prolonged vessel layups can create biological risks that may continue even after maritime traffic resumes.
Preventing a potential wave of marine invasions will require coordination between shipping companies, ports and national biosecurity agencies.
Early inspection, safe hull cleaning, route monitoring and rapid detection could help reduce the possibility that ships leaving the Strait of Hormuz region become carriers of invasive marine species to ecosystems far beyond the Persian Gulf.