The Amazing and Humble Seagrass
Seagrass is the only flowering plant that can live and pollinate underwater. Its long green blades grow across our seabeds, forming sheltering meadows for a whole host of marine life, including the UK’s two native and endangered seahorses - Spiny and Short-snouted Seahorses. Because seagrass depends on high levels of light for growth its found in shallow waters - around the UK, usually in inlets, bays and harbours.
Seagrass has an important role in preventing coastal erosion. Its roots act as stabilisers in the seabed and its long blades help to counter ocean swell, reducing currents, which also allow nutrients to settle that draw more wildlife. As well as seahorses, seagrasses offer shelter and habitat to crabs, lobsters, starfish, sea snails, cuttlefish and octopuses, to name only a few. Two species of octopus can be found in seagrass around the UK - the Common Octopus (larger, with a double line of suckers) and the Curled Octopus (smaller, with a single line of suckers).
Scientists and conservationists estimate seagrass meadows are home to around 40 times more marine life than seabeds with no seagrass. They also calculate that seagrasses, which currently cover only around 0.2% of seabeds, are responsible for absorbing around 15% of the ocean’s intake of carbon dioxide, and are able to store it at a rate 35 times quicker than tropical rainforests!
However seagrasses are at great risk. Over the last 4 to 5 decades at least 35% of seagrasses around the world have been degraded or lost and in the UK seagrasses are now found in only around 20 of our 155 estuaries. There are several reasons behind its decline, including coastal development, increased pollution (from sewage discharge* and agriculture) and human disturbance, for example boating and damaging fishing practices. Figures released by the International Union for Conservation and Nature in 2014 and in a 2020 UN report suggest that it is perhaps the fastest disappearing habitat on Earth - about a football field worth of seagrass vanishing around every 30 minutes.
Scientists and conservationists are working though to change this, by altering traditional mooring practices, fishing practices and planting hundreds of thousands of seagrass seeds in large-scale restoration projects and working to create protected areas.
“Seagrass is the most amazing habitat that no one has ever heard of. If they are left undisturbed, seagrass soils will persist for thousands of years, and act as permanent carbon storage. Seagrass meadows can rebound, if allowed to, and it used to be everywhere, so there are limitless opportunities to build it back.”
- Alix Green, University College London, author of paper Historical Analysis Exposes Catastrophic Seagrass Loss for the United Kingdom
* As well as there being nutrients in sewage discharge that are toxic to seagrass, it also stimulates algae growth that hinders seagrasses’ exposure to sunlight
Further reading and resources
Planting Hope and How Seagrass Can Tackle Climate Change | WWF
Seagrass Restoration | National Marine Aquarium
Scientists Aim to Reverse the Trend of Seagrass Degradation | National Oceanography Centre