Oysters are possibly the most glamorous of all shellfish, known for their aphrodisiac qualities (rich in amino acids and zinc, they trigger increased levels of sex hormones when eaten) and for the production of pearls used in costume jewellery.
The latter, albeit a rare natural phenomenon, happens when an oyster secretes a special chemical called nacre (made of layers of calcium carbonate and proteins) to cover an irritant or parasite in the interior of the shell. Nowadays, though, most pearls are cultivated in waters across Australia, India, the Philippines and Indonesia by implanting tiny beads into oyster shells.
But oysters are also increasingly being called upon for reasons other than oyster and pearl farming. Earlier this month, Minister for Nature, Heritage and Biodiversity, Christopher O’Sullivan announced €7.9 million in funding over five years for the Tralee Bay Marine Biodiversity Restoration project, in which oysters will play a key role.
Ireland has a long history of oyster farming, with archaeological findings showing how coastal communities from the late Mesolithic period picked and ate oysters. Cultivation of oysters dates back to the 13th century, according to a report by the Centre for Environmental Humanities at Trinity College Dublin. Artificial oyster beds in Clontarf, Howth and Sutton in the 18th century were replenished by naturally occurring beds in counties Wexford, Wicklow and Down. Overharvesting, pollution and harsh winters all contributed to their decline.
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But commercial oyster farming of Pacific oysters (easier and faster to cultivate and available all year round) began again in the 1980s and 1990s and there are now about 130 oyster farms around the Irish coast, many of which export these larger oysters to the European mainland.
But it is the native Irish oyster (smaller and round compared to the oval-shaped Pacific oyster), which spawns in the summer months, that will now play a big part in a nature-based solution to help clean water, increase the growth of sea grass and provide shelter and spawning grounds for fish species along our coastline.
Scientists have high hopes for the Tralee Bay Marine Biodiversity Restoration project, for which work is due to start in the Tralee Bay Nature Reserve this month.
The initiative represents a “unique opportunity to restore two of Ireland’s most important marine habitats: native oyster reefs and eelgrass meadows, within one of the country’s most ecologically significant coastal systems”, says Prof Sarah Culloty, a marine biologist and professor at University College Cork.
The living laboratory will bring together researchers, fishermen, conservation agencies and local communities to restore the marine habitat for the benefit of biodiversity, water quality, climate resilience and coastal livelihoods.
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Starting life as tiny free-floating larvae, they take about three years to mature and attach themselves to an adult oyster or another substrate, such as a pier, rock or harbour wall. An adult oyster can then live for up to 20 years.
The adult oyster filters water in search for nutrients and deposits what it does not need on the sediment base where bacteria can break down any pollutants. The removal of pollutants by this water-filtration system reduces algae blooms, increasing the light penetration to the seafloor, which allows seagrasses such as eelgrass to grow. And, with this provision of food and shelter, fish can develop a nursery for their young.
Oyster reefs also protect against storm surges and coastal erosion, and their associated seagrass meadows are renowned for sequestering carbon at twice the rate of land-based trees. Coastwatch Ireland is calling for their protection, following mapping of 100 sites around the Irish coastline by citizen scientists in 2026.
Back on the east coast, the Green Ocean Foundation has been installing oyster gardens in six locations, including in Malahide, Howth, Dún Laoghaire and Greystones. Local volunteers help look after these oyster baskets submerged just below the surface along marina walkways.
In November 2025, the organisation brought 18,000 oysters to Dún Laoghaire from the Tralee Oyster Co-operative to establish a broodstock in the Dublin harbour.
Working with private and public funding, as well as technical support from scientists from the Water Institute in Dublin City University (DCU), the long-term aim is to promote self-seeding reefs along the east coast.
The Green Ocean Foundation is conducting a “disruptive and innovative natural biological solution to clean the water”, says Prof Fiona Regan, director of DCU’s Water Institute. Researchers there collect and analyse water and oyster samples to monitor water quality and biodiversity in Dublin Bay.
David Lawlor, a scuba diver and founder of Green Ocean Foundation, says it will take 15 to 20 years for oyster reefs to reform in Dublin Bay. “Nature needs all the help it can get and there is great personal satisfaction from doing this work,” says Lawlor.
Ella McSweeney returns at the end of the month.
