Prolonged Gulf Crisis Raises Biofouling Risks for Idled Vessels

Source: Maritime Executive / Courtesy Pole Star Global

Ship operators are facing unusual operating conditions in the Gulf shipping market. Prolonged disruption and instability have left a large number of vessels anchored for extended periods across the Arabian Gulf.

According to AIS data collected by MarineTraffic and published by Weathernews, as of mid-June 2026, 958 vessels were affected, with 63% having remained at anchor for 100 days or more. The scale and duration of these anchorage periods indicate that the disruption is having a significant impact on vessel operations in the region.

Beyond the direct impact on schedules and operational performance, prolonged periods at anchor create favorable conditions for marine organisms to grow on the submerged sections of a vessel’s hull. This can increase fuel consumption and affect operational efficiency, while also creating biofouling management requirements when vessels return to service and call at ports in jurisdictions with stringent regulations.

How Do Prolonged Anchorage Periods Increase Biofouling?

The process of marine growth forming on a vessel’s hull can begin just minutes after the hull surface comes into contact with seawater. Initially, a layer of organic matter and microorganisms forms on the surface. This biofilm then develops further as bacteria, algae and other microorganisms become established.

Over the following weeks or months, larger organisms such as barnacles, mussels, tubeworms, sea squirts and seaweed can attach to the hull. If left uncontrolled, this layer of marine growth increases surface roughness and hydrodynamic drag, affecting vessel operating efficiency.

For shipowners, the consequences can include lower operating speeds, higher engine loads, increased fuel consumption and higher emissions. A 2025 survey by Jotun of 1,000 shipowners and operators found that 50.4% of respondents had experienced higher fuel consumption and reduced operational performance due to ineffective biofouling management.

Importantly, the survey reflects vessel operating conditions in general and does not specifically measure the impact of prolonged anchorage periods such as those currently occurring in the Gulf.

Gulf Conditions Favor Marine Growth

The Arabian Gulf presents a number of conditions that can support marine growth on vessel hulls. Relatively high water temperatures can accelerate the growth of algae, barnacles and other marine organisms. Port and industrial activity, together with nutrient-rich waters in some coastal areas, may also create favorable conditions for marine growth.

Vessels waiting for cargo, operational instructions, security conditions or berth availability for extended periods may therefore face an increased risk of accumulating biofouling on their submerged hulls.

Limited vessel movement may also reduce the effectiveness of an antifouling system, depending on the type of coating, operating conditions and system specifications. High salinity in the Gulf may limit the growth of certain species, but it does not eliminate the risk of biofouling.

Biofouling Can Become a Compliance Issue

A biofouled vessel can act as a vector for the spread of invasive species to other ecosystems. This is one of the reasons why an increasing number of countries are introducing biofouling management requirements for ships.

According to Jotun’s 2025 survey, 41% of respondents said they had faced penalties related to biofouling, while 38% had been denied port access for failing to meet relevant requirements. In addition, 49% said they had avoided ports with strict biofouling regulations.

Several markets have established relatively specific requirements:

●    Australia: Under the Biosecurity Act 2015, shipowners and operators can demonstrate that biofouling risks are being managed through measures such as cleaning the hull within 30 days before arrival, maintaining a Biofouling Management Plan and Record Book, or applying an approved management method.

●    New Zealand: Vessels arriving in New Zealand must provide evidence of biofouling management in accordance with the Craft Risk Management Standard and meet pre-arrival declaration requirements. Vessels that do not meet the requirements may be subject to additional treatment measures, including hull cleaning or other control measures.

●    United States: The state of California applies biofouling management requirements to vessels of 300 GT or more, including a Biofouling Management Plan and Record Book. Vessels that have remained idle for extended periods may be subject to additional review or monitoring by the authorities.

●    Brazil: NORMAM-401, introduced in 2025 with new requirements taking effect from June 2026, establishes biofouling management requirements for vessels operating in Brazilian waters. The requirements focus on controlling the level of biofouling and reducing the risk of introducing invasive species into local ecosystems.

Security Risks Also Need to Be Considered

Prolonged anchorage also creates vessel security concerns. Vessels that remain idle for extended periods may become targets for unauthorized parties seeking access to their underwater hulls and attempting to carry out illicit activities.

In some cases, organized criminal groups may exploit underwater inspection or cleaning operations to attach illicit cargo to hard-to-observe areas such as sea chests, rudder trunks or other underwater hull structures. The cargo may then be retrieved once the vessel reaches its next port.

Cases documented by law enforcement agencies indicate that this is a risk that should be incorporated into vessel security management procedures, particularly when vessels remain at anchor for extended periods or undergo underwater work.

Before Returning the Vessel to Service

For vessels that have remained at anchor for several months, the condition of the hull should be assessed before the vessel is returned to service. Signs such as reduced speed, increased fuel consumption, higher engine loads or declining operational performance may warrant an assessment of the extent of biofouling.

Underwater inspections using divers or remotely operated vehicles (ROVs) can help assess hull condition and determine whether cleaning is required. The scope and method of cleaning should be selected based on the actual condition of the hull, the antifouling system and environmental requirements at the port where the work is carried out.

Underwater inspections should also be combined with appropriate security-control procedures to detect any objects or cargo that may have been illegally attached to the vessel’s hull.

Prolonged disruption in the Gulf could therefore have consequences extending beyond vessel schedules and day-to-day operations. For shipowners, operators and charterers, assessing hull condition before reactivation and verifying biofouling management requirements at the next port of call at an early stage can help limit operational risks.

Security-control measures should also remain in place throughout underwater inspections and cleaning operations to reduce the risk of invasive species being spread, maintain vessel operating efficiency and minimize compliance issues when vessels return to service.

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Source: Phaata.com (According to Maritime Executive)

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