Offshore wind farms are built to generate renewable electricity, but their interaction with marine ecosystems is receiving increasing attention. Research at Teesside Offshore Wind Farm suggests that infrastructure installed primarily to protect turbine foundations could also provide habitat for marine species.
The study examined Ridgeway’s Filter Unit Rockbags, installed more than a decade ago for scour protection, to assess whether they had produced measurable ecological benefits alongside their engineering function.
From scour protection to habitat
Scour protection prevents seabed erosion around turbine foundations caused by underwater currents. Conventional approaches commonly use rock armour, but Filter Unit Rockbags introduce additional structural complexity through varied surfaces, voids and spaces.
Over time, these features can be colonised by marine organisms and begin to resemble aspects of a natural reef.
Teesside provided a useful opportunity to study this effect over the long term. The 62 MW wind farm has 27 turbines, of which 11 required scour protection following advice from engineering consultants Ramboll. These were fitted with Filter Unit Rockbags, while the remaining turbines did not require additional protection.
This created treated and control areas within the same wind farm, allowing researchers to compare ecological conditions while considering factors such as water depth, tides and proximity to river outflows.
Looking beneath the surface
The survey was carried out with marine specialists FjordStrong using baited remote underwater video systems (BRUVs).
Across the wind farm, researchers completed:
Because the technique is non-invasive, marine life could be observed with limited disturbance.
The study reported a number of differences around turbines fitted with the Rockbags. According to Ridgeway, these areas produced a net increase of 38% in observed species across the wind farm, together with 2.2 times higher abundance of cod-family fish, ten times higher edible crab abundance and three times higher lobster abundance.
These findings are reported by Ridgeway, with a scientific paper still in preparation.
Could offshore structures become fish nurseries?
One of the study’s more interesting observations concerned juvenile fish.
Researchers repeatedly observed juveniles passing through the Rockbag mesh while larger predators were excluded. This suggests the structures could function as artificial fish nurseries, providing protected areas during important early life stages.
Larger species also appeared to use the structures differently. Lobsters, which were too large to enter the mesh, occupied crevices between stacked units. One observed lobster measured approximately 40 cm and weighed around 4 kg.
This contrast between homogeneous soft sediment and the more complex hard substrate created by the Rockbags is central to the study. Ridgeway also highlights reported increases in fish, gadid, edible crab and lobster abundance.
This physical complexity could be important because habitat structure influences shelter, feeding opportunities and interactions between species.
Measuring marine net gain
Biodiversity net gain (BNG) is increasingly established in terrestrial development, but applying similar principles offshore is more difficult.
There is currently no universally agreed metric for marine biodiversity gain. The Teesside study therefore considered several indicators:
The results suggest that engineering infrastructure can potentially contribute to these measures, although further research is required before conclusions can be applied across different offshore environments.
From one wind farm to wider application
The project involved cooperation between Ridgeway, FjordStrong and EDF Power Solutions UK & Ireland, which operates Teesside Offshore Wind Farm. Access to a working wind farm allowed ecological research to take place in real operating conditions without interrupting electricity generation.
Several questions remain. Researchers want to understand how these habitats develop over longer periods, whether similar outcomes occur in other marine environments and whether design changes could further improve ecological performance.
Standardising marine BNG metrics will also be important if ecological enhancement is to become a measurable part of offshore project design.
The Teesside results nevertheless point towards a different way of thinking about offshore infrastructure. Scour protection will always have an engineering purpose, but designing it with habitat complexity in mind could allow the same installation to perform another function beneath the water.
As offshore wind expands, the opportunity may be not simply to minimise environmental impacts, but to investigate where carefully designed infrastructure can make a positive contribution to marine ecosystems.
Read the complete Industrial Insight feature from Ridgeway on scour protection, artificial fish nurseries and marine biodiversity at Teesside Offshore Wind Farm in PES Wind: https://pes.eu.com/exclusive-articles/ten-years-on-scour-protection-turned-reef-at-teesside-offshore-wind-farm