Seagrass is a somewhat mysterious plant, but it is essential for a healthy marine environment. Seagrass can play an important role in capturing carbon, purifying water, and promoting biodiversity.
Although estimated to cover up to 267,000 square kilometers (about 65.9 million acres) across the world, the exact extent is not fully understood, because large areas have not been mapped. What is known is that the plant can be found across 163 countries and territories, and there are 70 species, with the greatest diversity found in the Indo-Pacific Ocean.
Project Seagrass, a charity based in the UK, is on a mission to fill in the knowledge gaps. It carries out scientific research to discover more about this valuable ecosystem while promoting seagrass conservation and restoration efforts around the world.
What is Seagrass?
Unlike seaweed, seagrasses have long blade-like leaves as well as roots, shoots, and flowers, creating dense underwater meadows in shallow, sheltered coastal areas. They grow on soft sediments like sand and rely on roots and rhizomes to keep them in place, notes the University of Western Australia.
According to the Smithsonian National Museum of Natural History, the oldest known seagrass species— which could be up to 200,000 years old—is a “clone” of the Mediterranean Posidonia oceanica. The Thalassia testudinum, found in the Caribbean Sea and Gulf of Mexico, attracts amphipods and marine worms, which feed on its pollen. Further afield in Japan, the tallest seagrass species Zostera caulescens can grow up to 35 feet.
Biodiversity and Healthy Fish Stocks
Project Seagrass reveals that the plant plays an important role in supporting 20% of the world’s largest commercial fisheries, and communities around the globe depend on the fish found in its meadows. A whole host of marine species thrive in these areas—everything from shellfish and seahorses to sea turtles and manatees.
A study undertaken by scientists, including Leanne Cullen-Unsworth, Ben Jones, and Richard Unsworth, who lead Project Seagrass, showed seagrass meadows were increasingly being used as fishing habitat across Cambodia, Tanzania, Sri Lanka, and Indonesia.
Ben Jones said: “Seagrass was the most common habitat used for fishing. Nearly half of all households we talked to preferred fishing in seagrass over other habitats, such as coral, mangroves, open ocean, mud, and rock, for example. This was surprising because most people think of reef fisheries as the key tropical small-scale fishery, but we show that it’s actually engagement in seagrass fisheries that are much more characteristic of households.”
“Seagrass was the most common habitat used for fishing. … This was surprising because most people think of reef fisheries as the key tropical small-scale fishery.”
The research also found that 3 in 20 people across the region relied solely on seagrass meadows to provide them with their fishing ground. Coastal communities’ livelihoods are secured because of the reliability of fish stocks and invertebrates in seagrass meadows.
Meanwhile, in the UK, seagrasses are not only home to numerous species of fish, they also help stabilize sandy beaches, and their roots can reduce coastal erosion. And, overall, the plants filter bacteria, pathogens, and pollutants to improve the quality of seawater.
Carbon Storage
Seagrass has a carbon capture function too. Its leaves, which are covered in a porous cuticle layer, are ideal for sequestering carbon dioxide. An estimated 27.4 teragrams (over 30.2 million tons) of carbon are absorbed every year, globally amounting to as much as 19.9 billion metric tons (21.9 billion tons). Although lower compared with seaweed, which is thought to retain some 153 teragrams (over 168.6 million tons) annually, seagrass nonetheless stores about 35 times more carbon than rainforests and accounts for approximately 20% of the carbon buried in the sea every year. This means the plant can help alleviate local acidification by an estimated 30%.
Although lower compared with seaweed … seagrass nonetheless stores about 35 times more carbon than rainforests and accounts for approximately 20% of the carbon buried in the sea every year.
Seagrass At Risk
About one-fifth of the world’s seagrass meadows have disappeared over the past 100 years or so. In a review into seagrass ecosystems, Unsworth and Jones claimed: “[…] Bold steps are needed through improved legal instruments to halt damaging factors such as bottom trawling, prevent use of damaging boating activities, and to apportion responsibility for poor water quality that is causing the slow death of seagrass globally.”
In the UK, for example, seagrass is now in a state of decline as a result of nutrient pollution from sewage and livestock waste, based on a study by Project Seagrass.
Unsworth commented: “The world needs to rethink the management of our coastal environment that includes realistic compensation and mitigation schemes that not only prevent damage, but also drive the restoration, enhancement, and creation of seagrass habitat. We also need a major shift in how we perceive the status of our marine environment by examining historical information, not just recent ecological baselines.”
Conservation and Restoration
Project Seagrass’s scientific research informs the organization’s global program work—10 projects across 14 countries have been carried out involving more than 1,000 volunteers. Among them are an initiative to assess seagrass meadows and biodiversity in the Myeik Archipelago in Myanmar, a pilot nursery in south Wales to establish whether seagrass can be grown at scale to assist in restoration efforts, an examination of how a change in land use affects the coast in Quintana Roo in Mexico, and community action to help conserve seagrass in southeast Asia.
Education, Volunteering, and Citizen Scientists
Apart from raising awareness through education programs for school children, toolkits for researchers and student internships, Project Seagrass is keen to see people getting involved in practical restoration work.
Mike Furness volunteered to help plant seagrass seeds along the Pembrokeshire coast in Wales as part of a group of some 30 to 40 people over four days.
He said: “We were going to help to sow a seagrass meadow, not just a small patch but a whole ‘field.’ The logistics are daunting to think about—everything from feeding and accommodating the team to previously organizing hundreds of school children to fill and tie 20,000 small bags on to 20 km [12.4 miles] of ropes. Not to mention the harvesting and preparation of three-fourths of a million seeds. An astounding effort.”
He explained: “The seeds had been harvested in late summer and needed to spend several months rotting out of the harvested grass before being sown. By late February, they were ripe for planting and being kept in their own dedicated fridge. If you’ve ever walked through a geothermal area amidst the steam of fumaroles [volcanic vents], you will know the smell that hits you when that fridge door is opened! It’s pungent. It’s sulfurous. It’s clinging. But, you know what, by the end of the day it virtually disappears. And on the morning of day two, when it hits you again, you begin to realize—that’s the smell of success, bring it on.”
Since [SeagrassSpotter’s] launch in 2016, more than 3,500 users across 105 countries have recorded over 7,000 sightings and 45 different species of seagrass. A new version allows people to record data on where seagrass may once have been present.
The organization’s website and mobile app SeagrassSpotter, used to record seagrass sightings and absences, encourages people to act as “citizen scientists.” Since its launch in 2016, more than 3,500 users across 105 countries have recorded over 7,000 sightings and 45 different species of seagrass. A new version allows people to record data on where seagrass may once have been present.
Cullen-Unsworth, chief executive officer at Project Seagrass, said: “Over the last 10 years, we have successfully raised awareness of the importance of seagrass and the role it plays in tackling the biodiversity and climate crises. Now we must accelerate efforts to protect and restore this vital habitat. Everyone can have a part to play in securing a future for seagrass, and SeagrassSpotter is a great tool to engage and connect people in seagrass science and mapping all over the world.”
*Yasmin Prabhudas is a freelance journalist working mainly for non-profit organizations, labor unions, the education sector, and government agencies.
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