Ships stuck in the Strait of Hormuz region may be biosecurity risks when they leave. What can we do?

The economic consequences of the closure of the Strait of Hormuz have garnered significant attention, but the potential ecological damage resulting from a prolonged blockade of ships has been largely neglected. Recent research reveals that the over 1,500 commercial vessels stranded in the Persian/Arabian Gulf since February present a substantial environmental threat due to the accumulation of marine biofouling organisms on their hulls.

As the strait reopens, these vessels may inadvertently disseminate these organisms to ports they visit, potentially triggering an international biosecurity crisis. Such translocation of alien marine plants, animals, parasites, and diseases can cause severe ecological damage, threaten wild fisheries, aquaculture stocks, and coastal industries, leading to significant economic losses.

However, the Strait of Hormuz's closure is not the first instance where shipping disruptions have resulted in extensive biofouling on idle vessels. In tropical waters, idle ships can rapidly build up substantial amounts of biofouling, particularly in regions prone to high temperatures and humidity. Ian Davidson highlights that while 24 global shipping choke points exist, 20 of them offer alternative routes, allowing for re-routing of vessels.

This approach, albeit slower and costlier, can mitigate the risk of mass layups. Nevertheless, only four choke points lack viable alternatives, including the Strait of Hormuz, the Oresund Strait in the Baltic Sea, the Bosporus and Dardanelles straits in the Black Sea, and the Bohai Strait in the Bohai Sea. Disruptions in these critical shipping lanes can stem from various factors such as conflicts, terrorism, piracy, environmental impacts, and even intentional measures like vessel layups due to economic oversupply or maintenance requirements.

In fact, approximately 1% of the global commercial fleet is purposefully kept idle due to economic downturns, seasonal market fluctuations, or the need for upkeep. The global financial crisis of 2008 led to mass vessel layups, with around 10% of container vessels and 25% of refrigerated vessels remaining idle. Similarly, large fishing fleets undergo seasonal layups due to regulatory closures and weather-related limitations.

When vessels remain stationary, they can accumulate substantial biofouling in a short period, especially in tropical waters. Upon their subsequent departure, these ships transport these organisms to new regions, potentially introducing invasive species to novel environments. The Persian/Arabian Gulf is home to over 50 marine non-native species, and many indigenous species have already been introduced globally.

While New Zealand and Australia are unlikely to receive a large influx of vessels trapped in and near the Strait of Hormuz in the first month post-reopening, research suggests that numerous ships carrying invasive species will arrive within a year. Both nations boast robust biosecurity regulations and stringent frameworks, including early detection and rapid response capabilities when ships with biofouling risks are identified.

For instance, Biosecurity New Zealand successfully screened cruise ships during the COVID-19 pandemic, mandating their departure from New Zealand waters or maintenance to ensure hull cleanliness and minimal biosecurity risk. However, managing biofouling on commercial vessels arriving briefly remains a challenge. To address this, we propose several actions to mitigate the biofouling risk for ships departing from the Strait of Hormuz region.

First, conducting pre-departure inspections to estimate the level of biofouling can prove beneficial. Several services in the region assist with this task, such as environmental DNA sampling near vessels to identify the level of biosecurity threat. When feasible, in-water cleaning prior to departure from the Persian/Arabian Gulf is recommended, although it should target ship biofouling and coating debris rather than introducing further contaminants into the environment.

Additionally, forecasting vessel routes, particularly the first port after departing the gulf, and communicating this information to port and national authorities can help assess biosecurity risks. National authorities and ports should implement early detection and rapid response systems using environmental DNA or rapid assessments to identify new invasion events promptly.

Establishing rapid alerts and dissemination networks to share biosecurity events is crucial in mitigating the impacts of these potential super-spreader events and similar occurrences in the future. This proactive approach requires global cooperation and action to safeguard our environments, economies, and social values from marine biological invasions and their deleterious effects.