Marina and Yard Sustainability
Monday, 21 March 2022
Kim Hollamby

Marinas to the rescue of wild oysters

A collaborative sustainability project involving the pontoons of coastal marinas, marine industry organisations and conservation bodies is seeking to restore wild oyster populations in England, Scotland and Wales.

Photo credit: The Wild Oysters Project

Oysters represent a delicacy for some or thoughts of pearls for others. However, they serve as a much more critical jewel in the coastal ecosystem of many global regions. Healthy oyster reefs lead to significant environmental benefits.

The sad reality is that 85-95 per cent of all native oysters have been lost globally since the 1800s due to human activity. It is only recently that the need to restore oyster reef habitats has come to prominence with projects emerging in the US, Australia and Europe. A particularly innovative example is happening in the UK where ZSL (Zoological Society of London), the Blue Marine Foundation charity (last year’s DAME Awards grant recipient) and marine industry association British Marine have combined to tackle the issue.

The Wild Oysters Project

The Wild Oysters Project owes its origins to pioneering work undertaken by Blue Marine Foundation and the University of Portsmouth in the Solent on England’s south coast since 2015.

In 1978, around 450 vessels caught 15 million oysters annually in this region until the fishery collapsed by 2013. The partners took inspiration from oyster gardening schemes in the USA and used marina pontoons to house adult broodstock oysters, enabling them to spawn and settle on the seabed. The Wild Oysters Project represented the logical next step, applying lessons learned to sites across the UK. The project’s strong industry-conservation partnership secured £1.18 million from The Dream Fund, run by the UK’s Postcode Dream Trust.

The Wild Oysters Project spans three regions and six locations. Sunderland Marina and the Port of Blyth in England with local delivery partner Groundwork North East & Cumbria; Conwy Marina and Deganwy Marina on the River Conwy in Wales with the School of Ocean Sciences at Bangor University, and Largs Yacht Haven and Fairlie Quay Marina on Scotland’s Firth of Clyde with Clyde Porpoise CIC, assisted by the Fairlie Coastal Trust.

Marine industry and conservation stakeholders

Wild Oysters Project Manager ZSL, Céline Gamble, says this project is notable for its geographical spread, scale and stakeholders: “ZSL and Blue Marine Foundation are international conservation charities with the scientific know-how. British Marine has deep knowledge of the marine industry and introduced us to marina partners who offered the use of their pontoons without payment.

“Having oysters suspended underneath a walkway is a neat way of making space for nature without getting in the way of its original purpose, which is exciting. We worked with local partners to fit the access hatches in the pontoon that lie flush when closed and with Walcon Marine to create the structure to hook the nurseries on. British Marine also engaged with apprentices at South Devon College and Princess Yachts in Devon to design and build a custom hoist for the Scottish installation. The method of housing the oysters was analysed by a three-year PhD student."

“We hope this project will inspire other marine businesses to do the same, whether for oysters or to commit to other marine conservation projects. Working together, we can also develop communications for those who use the sea for recreation or work. We want to evolve a progressive narrative outlining things that anyone can do to lessen the impact on the ocean without assigning blame for previous practice.”

How it works

The oysters used in the project start life at the Loch Ryan Oyster Fishery in Scotland. They are nurtured to the point of reproductive maturity, then placed in the marinas’ nurseries, where their expected lifespan is up to 15-20 years. The nurseries are monitored monthly, providing a great opportunity to get volunteers, schools and youth-focused groups involved.

“We want to inspire the next generation of marine stewards to help care for the ocean,” Céline states. “We’re holding education sessions over the three years of the project to reach 12,000 school students and teach them about the ocean habitat and ecosystem. The oysters are great as we can pull them out from under the pontoon as a talking point.”

Why restore oysters in a marina or on other structures?

A marina may not be the first place you think of when looking to restore oyster reefs. They are relatively harsh environments that can suffer from the effects of pollution. However, floating pontoons in marinas allow restoration projects, as well as boat users, direct access to the water.

Benefits of oyster restoration

As the important role marine and coastal habitats play in regulating our environment has become clearer, oysters have been recognised as more than just a food source. They form reefs that provide a home for other marine life, such as European eels, sea bass and sea horses, making them ‘biodiversity hotspots’.

The ability of oysters to enhance the marine environment does not stop here, as the native oyster can play the role of the kidneys of the ocean. As they feed, the surrounding water is filtered, removing tiny algae (phytoplankton), animals (zooplankton) and particles of suspended organic material. It is estimated that an individual oyster can filter between 100 - 200 litres of water a day.

Some of the benefits of oyster nurseries, next to the cultural value, in marinas are:

  • Increased water clarity
    Can benefit recovery of seagrass and other coastal aquatic plants
  • Biodiversity enhancement
    Form a complex structure that provides shelter and food for a diversity of species
  • Improved water quality
    Removes pollutants from the water column
  • Stabilisation of sediments
    Reduces the resuspension of fine sediment, improving water clarity
  • Denitrification
    Removes excess nutrients

Suitability of a marina or other floating structure

There are a few key environmental considerations before installing nurseries in marinas. Main considerations are:

  • Water temperature
    Native oysters can tolerate a wide range of water temperatures. Ideally sea surface temperature must be between arange of 25C in the summer and 5C in the winter.
  • Salinity
    Native oysters can be found in both fully marine and estuarine environments, where fresh and saltwater mix. However, if the water gets too fresh this can shock (and even kill) native oysters.
  • Depth
    It is recommended that the top of any oyster nursery sits at least 30 cm below the surface of the water. Therefore, ensuring that the depth of water at low tide is sufficient for the bottom of any nursery to remain off the seabed.

Other factors that can affect the success of oyster nurseries, include the flow rate of the water, food availability, shading, pollution and dissolved oxygen. Read more about this in the How To Guide to Oyster Nurseries.

Results so far

The Wild Oysters Project currently reports 1bn oyster larvae have been released so far with an impact of 22m litres of water filtered. The results should support 42 different marine species and 70 different volunteers are engaged in the work.

“It’s been important to show the marine industry that you can incorporate an environmental project like this without affecting day-to-day operations,” a British Marine spokesperson said. “The Wild Oysters Project has been attracting political and press interest locally. It addresses the growing demand from industry customers for social governance and an environmental commitment.

“It also demonstrates close collaboration and support from the industry. In addition to the involvement of the marinas, Princess Yachts and South Devon College, the project is also supported by METSTRADE exhibitors Ecoworks Marine and Halyard Marine and Wavestream bilge filters. This all fits with our National Environmental Roadmap, to proactively tackle problems and work with delivery partners.”

Read more about the Wild Oysters Project How To Guide to Oyster Nurseries.

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