Tackling marine growth on your offshore assets

Why offshore energy assets are at risk

A new generation of structures is entering the marine environment in considerable numbers: wind turbines, wave and tidal energy devices, and their associated cabling infrastructure. These assets are critical to the low-carbon energy transition, and biofouling can pose a threat to their performance, structural integrity and the surrounding environment.

The impacts fall into three areas.

Operational

Marine growth can interfere with day-to-day operations in several ways:

• Obscured sensors and damaged connectors: Growth can block sensors, damage wet connectors and interfere with moving parts.

• Harder inspections: It can conceal structural damage, making it more difficult to spot fatigue or defects during subsea inspections.

• Distorted survey data: Different types of marine growth absorb or scatter sound waves, which can affect multibeam and sonar surveys.

• Reduced efficiency: Where surfaces have been precisely engineered for performance, marine growth can impair flow-sensitive components, anchors and cables.

Structural

Over time, marine growth can compromise the physical integrity of offshore assets:

• Coating damage: It can wear down anti-fouling coatings, making structures more vulnerable to further colonisation.

• Increased loading: Growth adds hydrodynamic load and friction, amplifying the forces acting on infrastructure.

• Restricted movement: It can stiffen components designed to flex, changing how they respond to environmental forces. This increases the risk of mooring failures.

• Overheating risk: A layer of growth on cables can affect their thermal properties, raising the chance of overheating.

• Reduced protection: The effectiveness of cathodic protection systems may also be compromised.

Environmental

Marine growth doesn't just affect assets. It can affect ecosystems too:

• Non-native species: Marine growth communities can include non-native species, helping them spread into new areas by acting as stepping stones and food sources.

• Habitat disruption: Offshore structures can create new habitats that interfere with existing ecosystems in the surrounding area.

• Cleaning debris: In-water cleaning campaigns can generate debris that impacts local marine life.

Understanding marine growth before you build

With these risks in mind, it's important to include a biofouling assessment at the pre-consent stage of offshore development. This gives you a clearer picture of how your assets may be affected over their lifespan.

A good starting point is a desktop study, which interprets existing marine growth data to inform early planning. The quality of supporting data is key, as is the experience of the people behind it. We draw on historic datasets, in-house marine growth specialists and a deep understanding of client and regulatory requirements.

But historical data tends to cover national or regional trends, and marine growth is often site-specific in both composition and growth rate. Settlement panels offer a practical way to study marine growth in situ, typically during the pre-construction phase of offshore wind and marine energy projects. They can be attached to existing equipment already scheduled for deployment and recovery, such as metocean monitoring devices. Different materials or coatings can also be tested at this stage, supporting final engineering decisions.

The site-specific data these panels provide reduces the need for extrapolation from broader datasets, meaning structures can be designed with the local marine growth community in mind, whether the goal is to deter or endure its effects.

What happens in the laboratory

Once recovered, settlement panels are returned to the laboratory for analysis. Weight in water can be calculated through displacement measurements, providing important information to inform engineering design. Corrosion rates can also be evaluated on relevant materials, informing material selection and estimating asset longevity.

A detailed examination of the marine growth community highlights key species, faunal compositions and any non-native species colonising these structures.

These studies help us identify challenges and potential data gaps, evaluate the effectiveness of different surface materials and coatings, and assess growth at different depths to predict colonisation patterns. Together, this evidence gives you a stronger foundation for design decisions, maintenance planning and regulatory compliance, helping to reduce risk and protect your investment over the long term.

Managing marine growth throughout the asset life cycle

Understanding marine growth before construction is only part of the picture. Ongoing subsea inspections and maintenance are essential to protect performance, meet regulatory requirements and extend asset lifespan. This is particularly important for offshore wind farms, where assets are expected to operate for 25 years or more. 

Inspections and structural monitoring

We use our fleet of remotely operated vehicles (ROVs) and uncrewed surface vessels (USVs), controlled by our global network of remote operations centres, to conduct detailed subsea inspections of underwater infrastructure safely, efficiently and sustainably. Regular monitoring builds a clearer picture of how marine growth is developing on an asset over time, which is essential for informed maintenance planning.

Community monitoring

The species that make up a marine growth community directly affect how a structure responds. A soft community of algae, soft corals and anemones creates different challenges compared to one dominated by hard species like mussels. Understanding the composition matters because it shapes both engineering and maintenance decisions.

Sample collection and expert taxonomic analysis can build a full picture of a marine growth community. Advances in environmental DNA (eDNA) capabilities are also opening new possibilities. eDNA can detect non-native species in the water column before they settle and establish themselves. Once detected, predictions can be made about how invasive a species may become based on local environmental conditions and biological traits.

eDNA and remote monitoring

We're innovating eDNA collection as part of our remote and autonomous survey capabilities. Autosamplers can collect biodiversity data over extended periods when paired with fixed assets such as buoys, moorings or platforms. Through the BeWild project, we’re also collecting eDNA samples from USVs and ROVs. This provides ongoing insight into marine growth communities without the need for repeated crewed mobilisations.

Cleaning

Biofouling cleaning campaigns use ROV-delivered high-pressure water jets and rotary nylon brush techniques to remove growth without damaging structural coatings. Getting the timing and method right is important, as cleaning too aggressively or at the wrong stage can do more harm than good.

Let's talk about your project

From early-stage assessment through to subsea inspections, monitoring, and cleaning, a joined-up approach to marine growth gives offshore assets the best chance of long-term performance. Every site is different, and the more you understand about what's growing on your infrastructure, the better equipped you are to manage it.

If you'd like to discuss how marine growth could affect your project, or how to manage it on existing infrastructure, our specialists are ready to help.