By Sophie Coxon
The coastline of Scotland is known for its raw and rugged beauty, dramatic cliffs and merciless waves. But hidden beneath the waves is a whole other world, unknown to most of us. Meadows of seagrass fringe sandy shorelines, transcending into cobbled shellfish reefs and sweeping mudflat plains. Once vibrant and thriving with life, these subaquatic kingdoms have been ravaged by humans, and are now a rare oasis in an otherwise barren seascape.
On the rolling blue shores of Loch Craignish, on the West coast of Scotland, a huge change is happening. After decades of exploitation and abuse by humans, Scotland’s waters are devoid of their former riches, polluted by fish farms, plastic, and sewage, and are in dire need of improvement. Seagrass meadows once fringed the shores for kilometres, cushioning the coastline from storm surges and aggressive wave erosion. Shellfish reefs, such as mussels and oysters, are a lost habitat from Scotland’s shallows. Richly abundant in the past, oysters were commonplace on the dinner table of the working class and eaten by the poor throughout the 19th century. However, both habitats have been degraded and destroyed by exploitative human habits, to the point where there is only a third of historic seagrass cover and no natural oyster reefs remaining around the UK.
Both seagrass meadows and oyster reefs are essential habitats in the marine ecosystem. Juvenile fish live between the grass shards, feeding and growing until they are large enough to emerge and venture into the pelagic ocean. Reefs of oyster shells, studded with clams and scallops, form in the peripheries, harbouring crabs and eels and further buffering the wave energy that battles the coast. Oysters naturally filter and purify the water as they feed, reducing sedimentation and improving the water quality, making it crystal clear; this boosts photosynthesis rates in neighbouring seagrass meadows, which oxygenates the water column creating a positive feedback loop which enhances the ecosystem’s overall health.
A recent increase in awareness around seagrass, driven by NGOs such as Project Seagrass, has kick-started a national effort to restore and protect this vital ecosystem at locations up and down the UK. Seawilding, a Scottish community-led charity, is working at the forefront of marine habitat restoration in Scotland, and has combined both seagrass and oyster reef restoration in the waters of Loch Craignish. Focusing on growing and planting both native oysters (Ostrea edulis) and eelgrass (Zostera marina), the Seawilding team have played a huge role in improving the biodiversity of the sea loch, as well as incorporating the community into their work.
The charity works year-round, growing oysters in an offshore floating nursery, then planting them at suitable sites around the loch to allow natural breeding and proliferation of the reefs – oyster spat, or juveniles, are grown to the size of a small biscuit before being released. This increases their survival chance as the shell is large and thick enough to resist predation by crabs and seabirds, and the oyster is better able to cope with changing environmental conditions. The team also carry out seagrass seed harvesting, and subsequent planting of rhizomes in nursery beds across the loch to increase seagrass cover. Biodiversity is also monitored using baited remote underwater video surveys (BRUVs), allowing population trends of different species to be identified.
Another aim of the charity is to produce a framework of guidelines which inexperienced communities across Scotland can use to start their own restoration projects, enabling greater impact and success in the rewilding of the country’s seascape. This will include methods of best practice, tips and examples of what does and doesn’t work. Seawilding is a prime example of a marine restoration project powered by locals, their passion for native wildlife, and their determination to prevent further damage.
Over the summer months of 2023, the west coast region of Scotland experienced a heatwave, with the water temperature in Loch Craignish reaching 22°C. This is unusually high and subsequently puts a large amount of stress on the oysters in the nursery. Water temperature affects metabolic rate, as well as food availability, disease susceptibility and ability to cope with other stressors. As marine heatwaves increase in both frequency and intensity, brought about by climate change, the methods used in shellfish nursery management may have to change to maintain optimal health for the organisms. Nurseries may need to be relocated deeper in the water column, or on the seabed, to avoid the risk of overheating in the surface layers of the water which receive the most intense sunlight and the largest temperature fluctuations.
However this presents its own problems; will oysters on the seabed be more prone to algal overgrowth, sedimentation, or predation by crabs? How will the team access the cages day-to-day to carry out health checks and maintenance? Will the change alter the growth rate of the oysters? Across all sciences, a solution to one question often creates multiple more questions, in a never-ending quest to define, understand, and improve – and Seawilding is at the bow, riding out each wave and striving for better seas.
About The Author
Sophie is currently finishing her degree in Ecological & Environmental Sciences at the University of Edinburgh. An avid scuba diver, snorkeller, and sea kayaker, she spends her spare time either reading about the ocean or swimming in it. Sophie has experience working on coral restoration projects, oyster reef rehabilitation and seagrass meadow re-planting, and has conducted her own research focussing on the biodiversity these habitats provide. She regularly writes marine science articles for a variety of sources and hopes to make a larger impact through research and science communication after university.
This piece was prepared online by Panuruji Kenta, Publisher, SEVENSEAS Media