Bathed in sunlight, Brian Gennaco, owner of the Virgin Oyster Company, stoops to secure his waders. But today, rather than harvesting oysters for his seafood business, Gennaco is releasing thousands into the estuarine waters of the Great Bay in Durham, New Hampshire, USA. He’s part of a project, initiated by the Nature Conservancy, to use oysters that would otherwise be wasted to restore damaged reefs.
The pandemic provided the impetus for the project. ‘When the restaurants closed, our sales went to basically zero,’ says Gennaco. Suppliers were left with oysters that were rapidly growing too large (restaurants want oysters around 7.5 cm in length). This accumulating supply threatened a collapse in oyster prices and jeopardised 3,000 local jobs.
In response, The Nature Conservancy – in collaboration with Pew Charitable Trusts – initiated the Supporting Oyster Aquaculture and Restoration (SOAR) programme, purchasing more than five million surplus oysters from local farmers, thereby preserving some 220 jobs. The rescued oysters are now being deployed across 20 reefs, where they will breed and build up oyster populations in seven northern US states. This isn’t being done with seafood in mind, but rather to help bolster important ecosystems.
Oyster reefs are one of the most severely impacted marine habitats on Earth. Led by The Nature Conservancy, a study found that 85 per cent of oyster reefs globally have been lost due to overharvesting, hurricanes, disease and changes in freshwater flows. This is important because declines have serious consequences for marine and estuarine ecosystems. Along the northeast US coast, 60 per cent of bays and estuaries are plagued by eutrophication – a side-effect of the overuse of nitrogen-based fertilisers. The abundant nutrients trigger dense phytoplankton blooms that occlude sunlight and create anoxic conditions. So-called ‘dead zones’, which can’t sustain life, lurk beneath. Oyster reefs can help reverse this eutrophication and consequent habitat loss.
‘Shellfish are the biggest removers of excess nitrogen. They incorporate it into their shells and soft tissues,’ says Boze Hancock, a marine biologist at The Nature Conservancy. A single adult oyster can filter more than 200 litres of water a day, removing excess nutrients, toxins and other pollutants. ‘Oysters also remove small particles, making the water clearer and helping seagrasses to grow; they increase nutrient bioavailability for marine species such as crustaceans and worms. With nutrients unlocked, reefs can act as nursery areas, the number of baby fi sh explodes.’ In non-tropical waters, shellfish reefs perform similar ecological functions to coral reefs, Hancock adds.
He and others at The Nature Conservancy advocate ‘restorative aquaculture’, a practice that pairs extraction with restoration; that the sea cannot be neatly portioned, and that overextraction can collapse ecosystems. Many marine biologists believe that restorative aquaculture can create a positive feedback loop, increasing the productivity of marine ecosystems and benefitting the seafood industry in result.
The world's biggest reef-restoration project is in Chesapeake Bay, where The Nature Conservancy and Pew Charitable Trusts, along with multiple other partners, have pooled $53 million of philanthropic and federal funds to create 144 hectares of oyster reef. The restored reefs filter out $3 million worth of nitrogen annually, add $23 million worth of fish production to the waters, and boost returns from blue crabs by $11 million per year. Restorative aquaculture isn’t just good for the environment: ‘It’s actually a wise investment,’ says Hancock.
For the benefit of restorative aquaculture to be truly realised, the method will have to wash itself clean of the tarry reputation left by other, more depletive methods. ‘There’s a distinction between restorative aquaculture and other forms,’ says Hancock, pointing to shrimp aquaculture and caged salmon farming, charged with degrading the security of wild populations. With the right support, he says, the shellfish industry can safeguard marine habitats – a responsibility that conservation bodies, alone, cannot uphold.