A seagrass meadow with fish swimming above it — Seagrass provides a habitat for marine life and fights climate change by storing carbon. © Damsea/ Shutterstock

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ANTHROPOCENE

Can seagrass sow hope for the planetary emergency?

By Roween Rawat

Seagrass meadows are ecological powerhouses that support marine life and store carbon.

In the UK, we’ve lost as much as 90% of our seagrass, but conservationists are working hard to restore these important ecosystems.

Beneath the shimmering surface of coastal waters lies an often-overlooked ecosystem: seagrass meadows. Swaying with the rhythm of the tides, their delicate blades safeguard shorelines, purify water and support marine life.

What is seagrass?

A seagrass flower growing underwater in a seagrass meadow — Seagrasses are the only flowering plants able to live in seawater. © Citrus deliciosa/ Shutterstock

Seagrass is a flowering plant that evolved from a land-living ancestor to live in the sea. Meadows of it grow in shallow coastal waters all around the world and support thousands of fish species, marine mammals and invertebrates.

“Seagrass is often referred to as a Swiss-army knife, as it has so many wonderful services that are so valuable not just to us, but to nature as a whole,” shares Sophie Pipe, seagrass conservationist at Cornwall Wildlife Trust.

“I think some people in the UK find seagrass underwhelming, but when you’re immersed in that world, it’s utterly breathtaking,” Sophie adds. “Especially when you get the opportunity to see the biodiversity that it holds within it.”

Seagrass breathes life into water

Sophie explains how globally these meadows are crucial for marine life at all stages. “They’re used as a spawning ground for fish and sharks, a food source for manatees and a training ground for young dolphins.”

In the UK, these habitats are important commercially, as they sustain our fisheries. They’re also key habitats for rare and endangered species, such as long- and short-snouted seahorses – our two native seahorse species.

A seahorse with its tail wrapped around a blade of seagrass — Seagrass meadows provide a safe habitat for animals like the short-nosed seahorse to hide from predators. © Oleg Kovtun Hydrobio/ Shutterstock

A climate change heavy hitter

Seagrass is small but mighty! It covers only 0.1% of the ocean floor, but accounts for 18% of the ocean’s carbon storage. So, how do these underwater meadows do it?

As seagrass grows, its roots combine together like a net, trapping sediment and reducing coastal erosion.

Stabilising the sediment in this way makes seagrass meadows great carbon stores. They slow down waves, which causes organic debris to build up. This then becomes compacted into the sediment in the meadow, where it’s then trapped and stored.

What’s mowing them down?

A bare seabed with a sole seagrass plant growing — Seagrasses are threatened by water pollution, climate change, fishing and boating activity. © Laura Dts/ Shutterstock

“In the UK, we’ve lost as much as 90% of our seagrass. A major driver is water pollution from agricultural run-off and sewage overflow, which causes algal blooms that then block sunlight. This prevents photosynthesis and deprives seagrass meadows of oxygen,” Sophie explains.

Seagrass has also been seen to die off rapidly during marine heatwaves, which doesn’t bode well for our warming ocean. Climate change is also increasing the intensity and frequency of storms, which can disturb and uproot seagrass meadows.

Sophie adds, “boating activity, like anchoring, and damaging fishing practices, like trawling, can cause big scour patches in our seagrass meadows, which you can actually see on Google Earth”.

Replanting meadows

Conservationists planting seagrass — Cornwall Wildlife Trust conservationists have been trialling different methods for replanting seagrass. One involves tying up bundles of mud with seagrass seeds in hessian sacks and planting them a metre or so apart. © Cornwall Wildlife Trust

Sophie is working on a seagrass restoration project in Cornwall focusing on a lesser-known species called Zostera noltei. It grows on mudflats in the intertidal zone, meaning it’s sometimes exposed when the tide is out.

“We only have two remaining seagrass beds in Cornwall. The project aims to see if we can restore these sites in a cost-effective way so that our techniques can be used in other places to replant meadows,” explains Sophie.

She adds, “community is at the heart of what we do so we wanted to go back to basics and take out the lab intervention and fancy technologies so that anyone can get involved in restoring these seagrass meadows”.

The team have been trialling different methods. They’ve tied up bundles of mud and seagrass seeds in hessian sacks and planted them a metre or so apart. They’ve also used caulk guns from the hardware store to inject this mud-seed mixture straight into the ground.