Why we should care about: Seagrass
Much like spring meadows and the grassy fields we see on land, there are similar areas underwater made up of seagrasses.
Underwater gardens filled with these flowering plants are vital and highly diverse habitats; breeding grounds, nursery grounds and source of food for thousands of species such as shellfish, seahorses, manatees, and sea turtles and commercially important fish such as herring, pollock and plaice. Seagrass meadows are a key marine environment found on every continent, except Antarctica, and have been shown to support over 30 times the amount of marine life in comparison to adjacent sandy habitats.
Alongside supporting thousands of marine species, our lives and indeed all lives also depend on the marine powerhouse that are seagrass meadow as these meadows, combined with phytoplankton and macro-algae, produce more oxygen for us to breath than all of the rainforests and grasslands combined.
The power of seagrasses does not stop there. The knock-on effects of seagrass meadows support 20% of the world’s fisheries and vital nutrition for close to 3 billion people, that’s nearly half of our world population, plus provide 50% of animal protein to 400 million people in the Global South.
Despite only occupying 0.1% of the seafloor these areas are responsible for 11% of the organic carbon captured in the ocean. These grasses capture 35 times more carbon than typical rainforests, making them a vital tool in fighting the climate crisis and help to provide fundamental ecological services for the marine environment, such as providing nutrients (phosphate and nitrogen, two key nutrients for growth of all plants), coastal protection by slowing down incoming waves and swells, as well as keeping the seabed stable through their root structures. All of these amazing characteristics impact us locally and globally, and have a monetary value beyond recognition.
Unfortunately, as with many of our environments, seagrasses globally have been exposed to environmental changes and human pressure such as destructive fishing practises, climate change, coastal developments and pollution.
Sadly, over the last two decades alone, the loss of seagrass from direct and indirect human impacts amounts to 18% of the total documented seagrass area. The rate of loss is equivalent to two football pitches every hour!
What's threatening seagrasses?
Seagrasses are very sensitive to changes in water quality and are used to determine the overall health of coastal ecosystems. As flowering plants, seagrasses require a certain level of sunlight to grow and reproduce, which is why they are found in shallower coastal waters, closer to the light of the sun. The clarity of the water in which seagrasses grow impacts the light levels that reach the seagrass, the more suspended solids within the water, the less light that reaches the seagrass. Whether pollution in the water or heavy rains that dislodges soils causing run off into estuaries and out to sea, the growth of the seagrasses can be hindered in many ways, which in turn has many knock-on effects to all of the wonderful things’ seagrasses provide, mentioned above. The UK alone has been estimates to have lost up to 92% of its seagrass which is why this has become an area of concern.
Alongside this, seagrasses are being smothered in microplastics. Seagrass meadows have been shown to slow down the water flow, modify currents and waves. When the water slows, heavier particles such as sediment and nutrients settle on the seabed which is great for the local marine environment who rely on these nutrients to grow, in turn providing food for marine life who feed on these plants. However, with 5.25 trillion pieces of microplastic floating around in our oceans, it is sadly no surprise that seagrasses also trap and enhance deposition of plastic.
Microplastics have even been found on the surface of seagrass leaves and in surrounding seabed. This is worrying for the other marine mammals that rely on the seagrass meadows for food, to protect their young and survive and are unknowingly ingesting microplastics – another reason why we need to stop the tap of plastic entering our oceans.
And Sailors, did you know that we have an impact on the seagrasses whilst out on the water as well? Mooring, anchoring and using our propellers in these shallow waters are main drivers for the loss of our precious seagrass environments.
Seagrass meadows are found in coastal nearshore waters, normally shallow sheltered water such as inlets and bays along the coast which are also our favourite resting areas as we sail – often quiet, sheltered and beautiful spots which also get heavily used by for kayaking, swimming and boating.
“Careless boating activities may only take seconds to damage the seagrass, but recovery of these meadows takes years, resulting in environmental and economic losses”
- Project Seagrass
Anchoring up in a seagrass area has a direct impact on the roots and fronds of the seagrass and therefore their health and that of the wealth of other creatures relying on them. Anchors are very heavy objects (for a reason!) however, anchors dragging across the bed uproots the seagrasses all together. Anchor chains themselves can also degrade the seagrasses and have been shown to create circular scars on the seagrasses as our boats swing in changing weather and tides. These visible markings across the seabed and through seagrass meadows are called ‘chain scrape’.
How can we Sailors help?
We can see that seagrasses are one of the MOST important ecosystems on our planet and therefore well worth protecting!
So, Sailors – let’s keep our impact to a minimum:
- Learn about the surroundings before mooring up / anchoring
The first and most important step we can take is learning where sensitive habitats (such as seagrasses but also reefs, fine muds and shellfish beds) are within our local area or areas where we are sailing, wherever we are in the world. Some of these areas are shown on charts, but normally seagrass beds and often coral reefs aren’t, so it’s best and important to check local pilotage books and website for more information.
- Grab a buoy if there is one!
If there are existing moorings, we should use these instead of dropping our own anchors. These moorings come in many different forms, and more recently Advanced Mooring Systems have been introduced which protect seagrass meadows even more by lifting the chain off the seabed so that even at low tide there is no scouring from the chains.
These moorings are particular important as even with dedicated anchorages, continuous anchor dropping, dragging and propeller blades put stress and strain on seagrass beds and drastically slow any recovery. Habitat fragmentation of seagrasses works the same as cutting down areas of the rainforest, the areas closest to the areas cut down become vulnerable and cause other areas to reduce in size. This is called ‘edging effects’ and can cause habitats and species to get cut off from one another which in turn causes issues for the health of these complex ecosystems.
- If we have to sling our hook…
If you are using your own anchor, it is good practice to avoid drag and further disruption to the seabed when you pivot by using the right anchor as well putting out the correct amount of chain for the water depth in order to reduce the disruption your chain and anchor will cause in these precious areas.
- Propeller blades are harmful – stay deep
Propellers blades are things we all want to stay away from – seagrasses included! Propellers can cut, scar and severely damage seagrass meadows, so know your draught and stay deep when using a propeller (and remember changing tides means changes of depth!) If you notice you are leaving a muddy trial behind your boat, you are disturbing the bottom and probably cutting the seagrass, so go back the way you came, using a pole or paddles instead of an engine. Stick in marked channels – going off piste we are more likely to risk damage to shallow and sensitive ecosystems.
- Help map the meadows!
Alongside us being more aware of seagrasses, and of how best to moor our boats we can continue learning, and become citizen scientists by visiting Seagrass Spotter (via the website and app). From this platform brought to us by Project Seagrass we can upload seagrass areas that we come across around the world, where we are or want to visit, helping us plan and sail more mindfully. There is a handy map that really highlights the global scale of where seagrasses are located, and therefore the real importance for us to conserve these vital marine habitats.
"Boating activities in the sea can be conducted in a sustainable manner and at Project Seagrass we’re trying to find ways to work with Sailors to improve the health of the worlds seagrass.”
- Richard J.Lilley, Director and Co-founder, Project Seagrass
With thanks to the Project Seagrass team!