Blue Solutions: Ecosystem engineering with optimised reef morphology

Much of the effort for SDG14 Life Underwater is rightly focused on overfishing. However, marine habitat loss is also one of the key drivers of fisheries identified by both the UN and NOAA along with coastal development, pollution and climate change. Efforts to restore habitats make a positive contribution by supporting and increasing fish stocks.

Subcon's team of Australian and Dutch scientists and engineers has been developing Blue Solutions for habitat restoration and enhancement. We call it ‘Ecosystem Engineering’.  

Our innovative approach melds engineering, marine biology, material science, art and economics to deliver scalable, nature-based solutions for coastal erosion control and fisheries decline. We’ve focussed our efforts on creating impact with scale after finding large scale reef morphology as the key driver of recruitment and production through our extensive research, experimentation and analysis.

 When we fuse reef science, art and engineering, we deliver the most impactful outcome.

Through the deployment of carefully engineered industrial-scale reef structures at over 26 sites, we have experimented with and refined engineered, reef morphologies to maximise the benefits provided to marine communities.

Whilst many reef experiments have focussed on mimicking substrate surface finishes and settlement ques, chemical composition, pH and material, historically these have only delivered short term, localised gains with methods that are difficult and expensive to scale. These expensive treatments typically deliver small gains targetting specific species, and provide negligible benefit in terms of overall abundance and diversity, yet they have a huge negative impact on the durability of the substrate. For example, biogenic substrates will collapse and degrade into the ocean within years whereas high-quality substrates will last millennia.

What these small scale experiments do demonstrate is that nature is great at recruiting and building the small, fine-scale topography of a reef, but it’s the underlying reef structure that takes thousands of years to establish. The successful initial recruitment of flora and fauna depends almost entirely on reef morphology – reef shape, surface area and volume. Maximise this and you maximise reef abundance! Then it comes down to natural factors like seasonal timing of the deployment, competition for space and metocean conditions at the site to ensure the long-term viability of the reef.

Our Blue Solutions team has focussed its efforts on designing structures that restore the macro morphology. These structures mimic nature by providing essential ecosystem services and hard substrates that are crucial to the restoration of aquatic ecosystems. Aspects such as complex habitat, current upwelling, vertical relief, surface area, stability, material selection and reef field layout are all carefully combined to maximise benefits.

Ecosystem Engineering success backed by independent research

Scientists from UNSW, Murdoch, Curtin, UWA have been measuring these benefits that our large-scale habitat enhancement projects provide. 

Dr Dianne McLean from the Australian Institute of Marine Science (AIMS) studies marine communities associated with artificial structures (e.g. pipelines, platforms, wells and purpose-built engineered reefs) to understand how they compare with natural marine communities and contribute to ecological processes. She said, “AIMS works with industry to deliver the environmental knowledge required to rigorously assess the benefits and risks of artificial structures in our oceans, to inform sound decision-making. Our research shows certain structures can provide habitat for important fishery species.”

 An example of this is the Shoalhaven Reef which was deployed off the NSW coast in 2015 and marked the start of large-scale deployments in the region. Dr Alistair Becker from NSW DPI co-authored research investigating the Distribution of pelagic and epi-benthic fish around a multi-module artificial reef field. Subcon’s 20 x 24Te concrete Reef Pyramids were deployed in 25m water depth and 4km offshore. The physical footprint of the modules was 320m2 whereas the total biological footprint of the reef was found to be 17,500m2.

As well as studying the biology of our engineered reef ecosystems, we've conducted parallel investigations into the engineering properties of the reef. Justin Geldard from UWA's Coastal and Offshore Engineering Lab has recently completed flume testing of engineered reefs with coral canopies which we'll discuss in the next issue. The key finding is that when we combine marine engineering with marine science we produce astounding outcomes that enable coastal communities to thrive, above and below the water line!

Engineered reefs provide critical ecosystem services such as refuge, habitat complexity, shade, upwelling and food abundance

Fish assemblages on the reef were assessed using camera drops to create a heat map of the population density and demonstrate that the reef's biological footprint is far greater than its physical footprint. Careful module spacing creates habitat zones within which fish abundance is greatly increased. The impact on the fish assemblage is clearly observed right through the water column from the seafloor to the surface and radiating out approximately 50m in all directions from the cluster. We then see an overlap of these assemblages between the clusters creating a diverse, productive and sustainable ecosystem. The whole, quite literally, is greater than the sum of the parts!

Recfishwest Marine Scientist and habitat enhancement advocate James Florisson has researched the impacts of engineered habitats at 6 sites, including Esperance, Dunsborough, Bunbury, Mandurah, Rottnest Island and most recently Exmouth. They’ve used a combination of university researchers and local fishers through Reef Vision, a citizen science program, to economically collect and analyse large amounts of data of fish assemblages on artificial reefs. 

 “The real surprise for us has been the rapid growth and colonisation we’ve seen on the modules and in between them. We’ve observed increases in the benthic habitat and associated species such as seagrasses, invertebrates, sponges and bottom-dwelling fishes as well as increases in epibenthic and pelagic populations of key species. A big factor for us has been the increase in juvenile fish populations which ultimately will increase the adult population. This demonstrates that properly engineered ecosystems can deliver a sustainable long term environmental outcome”, says Mr Florisson. "Our aim is to make fish stocks abundant, not just sustainable. The rapid colonisation of these artificial reefs has shown that they are a viable tool to make fishing better".

Observed marine abundance as a result of Ecosystem Engineering

Exmouth’s King Reef recorded over 90 species in the first 12 months following its installation. It involved a unique approach of integrating re-engineered structures with purpose-built concrete modules. One of the species identified was juvenile Red Emperor, which had not been commonly observed in the Exmouth Gulf in recent memory. The study found juvenile Red Emperor in various stages and in large amounts. They also identified a diverse array of recreational species on the reef, including Coral Trout, Spangled Emperor, Spanish Mackerel and Tuna. 

We are continuing to expand our knowledge of these unique productive marine ecosystems. We’re also using this information to fuel continual improvement in the module design and overall reef architecture as our artificial reef network expands along the coast. With increased scalability and the stewardship of the recreational fishing community, we can provide larger-scale social, economic and environmental benefits to these coastal communities. 

When we combine marine engineering with marine science we produce astounding outcomes that enable coastal communities to thrive!

Shoalhaven Offshore Artificial Reef was installed in 2015 and surveyed in 2018. The results speak for themselves. Salmon, King Fish and Taylor can be observed feasting on newly formed kelp gardens growing on the 20 Reef Pyramids.

Reef engineering pioneer Jack Francis is proudly philosophical about his role in helping restore biodiversity and abundance to our oceans. 

“Sustainability really should be our lowest benchmark. Promoting abundance should be the goal of all maritime developments! To this end we’re enabling scientists to leverage engineering methods, artists to communicate stories and coastal and maritime engineers to leverage the science around integrating marine habitat features that support productive ecosystems. We have created a unique fusion of reef science, art and engineering to deliver the most impact."

I’m always interested in discussing ways to optimise reef morphology - feel free to reach out to me or join the discussion in the comments below. 

This is the first of a three-part Reef Engineering series. In part two I’ll explore how integrating reefs into existing infrastructure can deliver large scale habitat and provide a civil benefit. And, in the final instalment, I’ll delve into reef economics and funding scenarios for investment in marine habitats. If you’re interested, click the follow button to make sure you don’t miss the updates.