Seagrass meadows under water in the UK are ‘one of the most valuable and biodiverse habitats on Earth’

Seagrass meadows in the UK are important wildlife habitat and fundamental to the fight against climate change, but they are rapidly disappearing. Jack Watkins finds out more about the ongoing fight to save them.

A hidden world lies in the shallow waters around the UK coastline, but before many of us realize its extraordinary beauty and diversity, parts of it are gone.

Some 167 years ago, Charles Kingsley, author of the underwater classic Water baby (1863), he vented his fascination with the mysteries of underwater plants and animal life Gloux, or Wonders of the Coast (1855). He lamented the wealth of our coastal waters, which had to be seen, alas! Not by imagination not by eyes. …. Often, standing on the shore at low tide, one longs to walk on and under the waves…and see it all, but only for a moment’. It wasn’t until the second half of the 20th century that scuba diving gained a more complete understanding of what was going on below, allowing for a systematic investigation, although much remains to be discovered.

The potential contribution of ocean habitats to our response to the climate crisis remains underestimated. However, an increasingly important coastal underwater habitat is seagrass meadows or seabeds.

Seagrasses are the only salt-tolerant flowering plants, so they can live in seawater and pollinate even when submerged. The grass grows to 6 feet long in 12 feet of water, deep enough for the sun’s rays to penetrate it. Because they often form huge clusters, they look like large underwater meadows.

Spiny Seahorse (Hippocampus guttulatus) female in seagrass meadow. (Zostera marina) Studland Bay, Dorset.Credit: Nature Image Gallery

Amelia Newman, Seagrass Cultivation Officer at the Marine Conservation Trust, calls seagrass “one of the most valuable and biodiversity-rich habitats on Earth, and one of the few that provides multiple benefits to the environment.” In addition to their ability to store large amounts of carbon (which makes seagrass beds so important in the fight against climate change), they provide nurseries for commercially important fish, including cod and mullet, supporting thousands of small Invertebrates and provide habitat for rare and endangered species such as seahorses and stem jellyfish. Seagrass root systems also increase subsidence, which helps stabilize the seafloor and reduce coastal erosion.

About 45 known species of seagrasses are found in the world’s oceans, from northern Russia to Oceania, three of which are found in the UK – the common eelgrass (Banded Begonia), Dwarf Eelgrass (Z. noltii) and eelgrass (Z. angustifolia) — in ports, estuaries and lagoons. Globally, however, the total area of ​​seagrass is declining at a rate of about 7% per year, equivalent to two football fields per hour.A study published in a journal Frontiers in Plant Science Last year it was estimated that the UK had lost 39% of seagrass since the 1980s. The study acknowledges that knowledge of historical losses is limited, but it suggests that “losses over longer periods of time can be as high as 92 percent.” Collated data over the past 25 years confirms that there are only 32 square miles of remaining seagrass beds around the UK.

Miss Newman attributed the decline to a number of factors, including ill health, pollution and illness. ‘Seagrass wilt (caused by pathogens that limit plant growth) is considered the leading cause of losses in the mid-20th century. However, seagrass is also damaged by physical disturbances, including anchoring and launching of recreational boats, dredging and destructive fishing activities. Seagrasses also face the negative effects of poor water quality. Increased nutrients in local water sources can lead to nutrient enrichment and macroalgal growth that limits seagrass growth.

The snake anemone (Anemonia viridis) grows on the leaves of the common eelgrass (Zostera marina) meadow at the mouth of the Helford River in Cornwall.Credit: Nature Image Gallery

Compared to the destruction of rainforest or coral reefs, this loss is hardly as catastrophic, if not so public. Not only do seagrass meadows host 30 times more marine life than their surroundings are used to, they also absorb carbon 40 times faster than terrestrial forests. One of the main remaining areas around these islands is Cromarty Bay, which likely supports the largest combined area of ​​our surviving dwarf eelgrass and narrow-leaf eelgrass, according to the Joint Conservation Committee for the Conservation of Nature’s UK BAP Priority Habitat Description for seagrass beds. Other important surviving seagrass areas include the Isle of Scilly, the Estuary of Eck, Maplene Beach, Solent Marsh, Milford Harbour and Mofaneffin on the Lam Peninsula.

There is a silver lining. Seagrass is difficult to recover, but recovery measures are being taken. As part of the Life Recreation ReMEDIES partnership led by Natural England, the Marine Conservation Trust has worked with Natural England’s marine modelling team to find the best areas to recreate grasslands.

The goal is to plant 20 acres in five special reserves in the south of England. Miss Newman said the project started with divers collecting seeds: “These seeds are taken to our cultivation laboratory at the National Marine Aquarium in Plymouth, Devon, where we can replicate the sandy seabed, using burlap to set roots. We’ve also been able to replicate April’s water and environmental conditions with light, water temperature and salinity. As we learn more about seagrass germination, we’ve been able to increase seedling survival from 7% to 70%.

Large male spider crab / Cornish king crab (Maja brachydactyla) taking refuge in a common eelgrass (Zostera marina) meadow at the mouth of the Helford River in Cornwall.Credit: Nature Image Gallery

In spring 2021, volunteers manually transplanted more than 18,000 bags of seed from a barge in Jenneycliff Bay, Plymouth Bay, an effort that will be repeated this year, but increased to 40,000 bags across Plymouth and the Solent . The next stage of the plan is to transplant the seedlings into the Plymouth Sound and then assess which technique will work best.

The Ocean Conservation Trust has also launched Blue Meadows with the aim of working with recreational and commercial vessels to minimise seagrass disturbance. “For many boaters, it’s not clear where the seagrass meadows are, so they don’t know the damage caused by dropping anchors or fishing,” said Mark Parry, the trust’s development officer. In Falmouth, Cornwall Sri Lanka launched a pilot program where buoys were placed to mark 50 acres of seagrass, the equivalent of 20 football fields. Torbay in Devon is planning a similar move. The Marine Conservation Trust says it aims to protect 10% of UK seagrass in the next five years.


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