Offshore wind: from baseline to benefits in the benthic zone

When it comes to offshore wind, Australia’s marine science community is working hard to understand and document species and environmental conditions in the Declared Areas set aside for development – places like Gippsland in Victoria, the Hunter and Illawarra regions off New South Wales, and most recently off the coast of Bunbury in Western Australia. 

As the industry is new in Australia, we’re very much in “baseline mode” – completing the long-term, inter-seasonal monitoring programs that are necessary to understand which species are present in these areas. These studies will feed into the impact assessments needed for offshore wind project approvals, design, and management planning. When we talk about environmental impact assessment a lot of the focus is placed on negative effects, and how to avoid them. But there’s also an interesting conversation to have around the positive effects that offshore wind could represent – particularly for benthic habitats.

The benthic zone - an ocean of interactions

The benthic zone represents the lowest level of a body of water including sediments and substrates on the seafloor. The marine benthic environment is vast and can be extremely diverse. Key types of benthic species that we’re looking at when undertaking baseline studies include:

• Infauna – species that live in benthic sediments, such as worms, clams or burrowing shrimp.
• Epifauna – species that live on (or are attached to) the seafloor, such as sponges, scallops or crab.
• Seaweeds – algae species usually found attached to reefs, rubble or shells.
• Seagrasses – flowering plants usually found in sheltered, shallow and sandy coastal waters.

Even across the five areas that have been declared for offshore wind to date, there are big variations in benthic conditions. Not only are these zones geographically dispersed, they’re also subject to different bathymetric (water depth) and temperature conditions, positioning in relation to reserved marine areas and other marine uses, the presence of natural reefs, or otherwise...the list goes on. This is why there’s no one-size-fits-all for offshore development, and why detailed site investigation is so important.

It's undeniable that installing turbines (or any type of offshore infrastructure) will change the benthic environment. Introducing new structures changes local hydrodynamics (how the water moves), and by extension what moves with it in terms of nutrients and species. Turbine infrastructure also increases the volume and complexity of reef-like habitat available – particularly in areas where the seabed is otherwise flat and sandy.

In the context of environmental protection, we’re conditioned to consider all change as bad change. But if managed carefully, these changes could represent a positive opportunity for local marine ecosystems, and our broader goals around marine conservation.

Positive impacts possible, but research is required

Here in Australia, there are likely hundreds or even thousands of benthic species present across a single offshore wind project site. Many benthic species are ‘cryptic’ (unique from other known examples, but impossible to differentiate through physical characteristics alone), or altogether undescribed.

As a marine researcher, this is exciting. The studies we do for offshore wind will give us an unprecedented opportunity to investigate what is present in these zones. There will be vast amounts of data generated in the next decade or so about benthic ecosystems in Declared Areas, and we will likely be documenting new species and communities as we go.

To turn all of this information into management plans that not only support development approvals but make projects a vehicle through which to promote biodiversity, we need to be consistent, document well, and share information. This includes applying consistent sampling methods that are right for the conditions (you can read more about marine sampling best practices in this article by my colleague Dr Rachel Przeslawski), utilising technology to reduce the time it takes to analyse and classify what we find, and further developing our understanding of how ecological communities connect.

It’s been encouraging to see projects that aim to collate and standardise mapping of Australia’s benthic ecosystems, like Seamap Australia, as well as ongoing development of state-based marine habitat mapping. Some jurisdictions, including Victoria, have progressed to ranking the value of mapped benthic habitats (or biotopes). This work is important as it provides a means through which scientists can consistently describe, map and monitor benthic habitats, and assess and mitigate impacts to them. Further engagement with industry and consultants will be important to ensure these tools gain broad acceptance.

Standard tools, guidelines and technologies will be key. But novel and customised approaches to surveys and monitoring will also be vital – no two sites are the same. At the scale of individual offshore wind projects, we can take advantage of our own investigation activity to complete small-scale tests of how benthic communities could develop around offshore wind sites. The equipment we deploy for feasibility studies (such as floating LiDAR buoys and other monitoring equipment) can give us a unique insight into how local benthic species utilise and interact with man-made infrastructure affixed to the seafloor.

Artificial reef, shellfish hatchery, marine conservation zone, other?

We need to do the research when it comes to marine impacts from offshore wind farms. But we also need to set clear goals about what outcomes we are trying to achieve for the environment. Turbines have a key role to play in helping us decarbonise the energy system – that’s why we’re building them. But they also hold potential for achieving other marine environmental goals.  

The role that offshore infrastructure plays as high biodiversity artificial reef habitat is well-documented. The offshore oil and gas industry is now grappling with this phenomenon when seeking approval for decommissioning – what is the right balance between removal and abandonment of infrastructure, when 30-40 years of marine biodiversity has grown up around it? The offshore wind industry will have to deal with this question also.

In offshore wind farms, turbine foundations will be colonised by a wide range of marine life, including algae, invertebrates and fish. This is likely to attract pelagic species to feed, which can generate benefits further up the food chain. For example, in places like the Gippsland Declared Area, wind turbines will likely provide good foraging habitat for fur seals (Arctocephalus pusillus doriferus) – a protected species that was hunted to near extinction, but whose population is now rebounding. Fish-eating seabirds such as cormorants could also benefit. It’s not just the turbine foundations that could be beneficial, either. The rock rubble used to prevent scour around turbines and to protect cables could result in shellfish repopulation in a similar manner to shellfish reef restoration projects already underway in southern Australia.

While our nation has one of the world’s largest representative systems of marine protected areas, the Federal Government has committed to take this even further, setting a ‘30 by 30’ target that will see 30% of our landmass and 30% of our marine areas conserved by 2030. If offshore wind zones are already acting as biodiversity multipliers, perhaps portions of these areas could be added to this 30%, and set aside as no-take zones, where marine life can live with minimal interference from human activity, allowing us to study how the community develops.  

From baseline to benthic benefits

When it comes to offshore wind, there’s plenty of environmental investigation still to do. But based on observations from other marine uses and research projects, we know that marine infrastructure can generate benefits for the marine environment.

In the case of the benthic zone, most of the positives will come after construction is complete. There are range of impacts we will need to manage carefully before we to get to that point. But with our oceans under so much environmental pressure generally, it’s exciting to consider a future where the structures we’re planning for tomorrow yield benefits not just for humans and our economy, but for marine ecology, too.