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What is seagrass?
Seagrass is a marine flowering plant which forms dense underwater meadows in the shallow, sheltered areas of our coast.
Unlike seaweed, seagrass has roots, flowers, and leaves, just like a terrestrial plant. Individual seagrass plants spread through the seabed to create a seagrass meadow, a productive habitat with a number of benefits to people and planet.
There are two species of seagrass in Wales (and the rest of the UK). One species Zostera marina generally grows subtidally (always covered by water) and the other species Nanozostera noltei is smaller and grows intertidally (not always covered by water, where the tide comes in and out).
Healthy seagrass meadows support high biodiversity, provide nursery grounds for fish, capture and store carbon, protect our coasts from erosion, and filter pollutants.
They are a vital tool in the fight against the climate, biodiversity, and food crises that humanity currently faces.
The Value of Welsh Seagrass
Seagrass meadows play a critical role in keeping our oceans healthy and stocked with food.
Research in Wales has found that seagrass habitats harbour four times the number of fish of unvegetated habitats, providing spawning, nursery, and feeding grounds to support important commercial fisheries. One hectare of seagrass can support as many as 4,700 more fish and 28 million more invertebrates than unvegetated habitats.
Seagrass meadows also provide a suite of other valuable ecosystem services such as protecting property and beaches from coastal erosion and shifting sediments, as well as improving coastal defenses by dampening wave action. As a result of climate change, the frequency and intensity of storms around the Welsh coast is predicted to increase; the loss of seagrass meadows has potentially resulted in exposure of coastal areas to storm damage.
Seagrasses can also buffer ocean acidification, contributing to the resilience of vulnerable species and ecosystems (e.g. cockles, dogwhelks).
Seagrass meadows improve water quality (removing pollutants and bacteria from the water column, including nitrogen) thereby benefiting local people and visitors. The ecosystem services provided by seagrasses are therefore an important support to marine-based economic sectors, such as tourism and fisheries.
Why is seagrass important in Wales?
- Provides a nursery ground for fish, including commercial species.
- Provides habitat and shelter for a wealth of species, supporting biodiversity.
- Improves water quality, supports wildlife and tourism.
- Protects property and beaches from coastal erosion and shifting sediments.
- Improves coastal defences by dampening wave action.
- Stores carbon.
The Protection Of Seagrass In Wales
In recognition of their ecological and economic importance, seagrass meadows are protected through a variety of conservation legislation and policies.
They are included within Special Areas of Conservation (SAC) across Wales, and specified as Section 7 species within the Environment Act. They are also included within the features of some Sites of Special Scientific Interest (SSSI) within Wales.
Although legally well protected, threats from stressors such as poor water quality, boat anchoring, and bait digging remain unmanaged and pose a significant threat to our remaining Welsh seagrass.
Over the last 100 years, the UK has lost up to 92% of seagrass habitat due to coastal development,
pollution, fishing and water-based activities, with extensive loss within Wales.
