Two anchor lines beneath France’s first floating wind turbine spent four years underwater, and mussels, anemones, and soft corals made parts of the ropes up to 32% thicker

France is boosting its wind capacity by deploying floating structures offshore, but marine organisms threaten their structural integrity.

The nation has set ambitious interim climate goals, with fast-approaching deadlines.

To meet these targets, renewable energy capacity must quickly expand to replace fossil fuels in power generation.

Using advanced anti-fouling coatings and conducting routine underwater inspections will help France secure its offshore floating future.

Offshore wind deployment has especially become a strategic necessity, but the ocean presents engineering challenges.

What will help address the effects of biological communities on floating structures?

How green targets will help drive a carbon-free society

In 1850, France’s reliance on fossil fuels began and continued for over a century.

Coal was the primary driver of the nation’s industrial growth, but production gradually declined.

By the 1920s and later 1930s, France gained energy independence after securing domestic oil and natural gas production.

An oil crisis triggered a high dependence on imports, leading to the nation’s Mesmer Plan.

This plan entailed constructing a major fleet of nuclear power plants, which has dominated France’s electricity generation.

Despite this, the historic reliance on fossil fuels has generated nearly 418 million tons of carbon dioxide equivalent per year.

To diversify its energy portfolio and break this dependence, a decarbonization strategy was established.

The plan is to phase out coal by 2030 and oil by 2045. By 2050, the nation aims to phase out natural gas for energy purposes.

The key to these targets is to rapidly expand clean power generation.

Making offshore wind a strategic necessity

Ocean deployment has become strategic in France, as available land for onshore deployment is extremely limited.

France’s operational offshore wind capacity has reached roughly 2 gigawatts.

This is set to increase with many projects nearing full commercial launch.

However, traditional offshore turbines are secured to the seabed with fixed-bottom foundations.

This means that conventional deployment is limited to shallow coastal waters.

As a result, the technology cuts off access to the best wind resources in France.

To reach the deeper waters, the nation pivoted toward floating offshore wind installations.

These platforms are tethered to the seafloor with mooring cables and anchors.

This bypasses depth barriers and positions the technology as the core pillar of France’s future energy security.

But experts are concerned about the impact of local marine life on the platforms’ structural integrity.

Researchers conducted a four-year study of a floating wind turbine to establish how certain sea animals affect the installation.

Tracking the hidden underwater growth

Approaching waves threaten floating wind turbines’ integrity, but that is not all.

A comprehensive study conducted by Nantes Université and Fondation OPEN-C revealed a threat growing underwater.

France’s first operational floating turbine, FLOATGEN, was monitored during the study timeline. Its two mooring lines were specifically tracked.

The goal was to track the evolution of marine growth spatially and temporally from the surface to the seabed.

Three distinct biological zones along the tethers

The water surface was colonized by hard-bodied species like mussels and barnacles.

The intermediate depths were dominated by mobile organisms like crustaceans and swimming crabs.

Soft-bodied species like soft corals and anemones took over the deeper, darker zones.

Over four years, these marine organisms’ coverage and thickness increased significantly in the deeper sections.

This caused the floating turbines’ structural ropes to swell by up to 32 percent.

The accumulated growth is known as biofouling, and these findings prove that it is a major engineering variable.

To scale floating wind capacity in France, the variable must be integrated into structural lifespan models.

Unexpected mooring line thickening will raise hydrodynamic drag and weight, which accelerates mechanical stress and fatigue.

This, in turn, unnecessarily increases the frequency of maintenance and its costs.

Using advanced anti-fouling coatings and conducting routine underwater inspections will help France secure its offshore floating future.

The research findings can be reviewed using: Dubois, A., Schoefs, F., Cognie, B., Reynaud, M., Soulard, T., & Dumay, J. (2025). Spatio-temporal evolution and engineering implications of biofouling communities on floating wind turbine mooring lines. Estuarine, Coastal and Shelf Science, 320, 109302.