Why is Seagrass Important? With marine biologist Dr Jean-Luc Solandt

Why is Seagrass Important? With marine biologist Dr Jean-Luc Solandt

Ahead of World Seagrass Day on the 1st March we spoke with Dr Jean-Luc Solandt, a marine biologist with over 1,000 dives, to find out firsthand the vital importance of seagrass to the marine environment and how plastic pollution has put the marine ecosystem at unprecedented risk. 

Jean-Luc has worked with partners in four continents to deliver positive change to marine ecosystem management. He is currently working on seagrass restoration projects in UK coastal waters, coordinates coral reef research and surveys in the Maldives, and is lobbying for a greener economic model post-COVID that seeks to base decision making on carbon-friendly technologies. He has been most successful in applying environmental legislation to properly protect marine habitats in UK seas.

What is seagrass and where would you find it?

Seagrass is one of the world's only flowering plants, growing in shallow waters, and intertidal (where the tide comes in and out) waters of the world. It grows down to about 10m in most tropical or Mediterranean seas where the water is clear, but about 6m in UK waters where the water is less clear. Unlike algal plants, the seagrass has 'rhizomes' - or a root structure. this means that those roots need to be buried in sands and muds (they cannot grow on/around rocks). They can grow really long (over a metre), and fast - rapidly reaching great densities. That is very useful for binding carbon in day-to-day growth, and more significantly - securely locking down carbon between the blades over hundreds of years. It's estimated that we've lost upwards of 80% of UK seagrass area since the 1920s, largely due to pollution, and industrialisation of our coastal fringe.

Photo credit: Alex Mustard

Why is seagrass important to the marine environment?

The binding of the soils, sands and muds around the base of the seagrass shoots is the amazing thing that locks in carbon. Although seagrasses only cover 0.1% of the ocean, they sequester 10% of the total carbon in the ocean - an incredibly efficient store of organic carbon. https://phys.org/news/2012-05-seagrasses-carbon-forests.html

Amazingly, some beds have been known to have root systems going about 5m below the sands. So they are a bit like peat bogs - where almost ALL the carbon is being stored out of sight, BELOW the surface. Nevertheless, the habitat above the seafloor (i.e. the blades themselves) also provide an incredibly important function. The blades are food for dugongs, sea cows and green turtles (and other species) in the tropics, and houses habitat, food and shelter for seahorses and other fish (bass/cod/mullet/plaice) in the UK. Cuttlefish lay their eggs around the blades, as do some species of shark. The sheer amount of life protected within the blades of the forests creates amazing protection of codling and other juvenile species as well (black-tipped sharks, rays, and cute critters like stalked anenomes). It is a world within a (marine) world.

It is affected by climate change by a number of direct and indirect effects. Increased seawater temperature isn't good for the thermal tolerance of the blades. Increased temperatures also mean less oxygen in surface waters, and these - like all plants - need oxygen to respire. Increased temperature can lead to increased fouling of the blades of the seagrass as more plants and animals are able to colonise the blades. Also, increased sea surface temperature is leading to sea level rise, meaning that the light is moving further away from the blades, decreasing the photosynthetic rate, and thus reducing the power of seagrass to sequester more carbon. Increased acidification associated with increased CO2 concentration in the water column is not only stressful to seagrass, but particularly to the 'bony' and 'calcified' parts of other organisms such as fish, crustaceans (shrimp) and molluscs (whelk and cockles) that live in amongst seagrass blades. Perhaps most insidious and worrying of all is that increased seawater acidification is also reducing the breeding potential of fish and other marine organisms. Also, the increased severity and frequency of storms associated and driven by increased surface ocean temperatures can erode seagrass beds.

How does plastic waste impact seagrass?

Plastic becomes tangled up in seagrass beds and can rip off blades which could impact the seagrass habitat as a nursery, food source and breeding ground. Plastic will also be a threat to the creatures residing in seagrass habitats including entanglement and ingestion. 

But seagrass beds also turn plastic 'bundles' or 'neptune balls' into perhaps more benign objects: https://www.theguardian.com/environment/2021/jan/15/seagrass-neptune-balls-sieve-millions-of-plastic-particles-from-water-study-finds 

An interesting observation, but certainly not a benefit of plastic pollution! The negative impact of plastics more widely in the marine environment cannot be overstated. 

What is the solution to helping seagrass to recover?

Stop the pollution, stop inappropriate farming techniques (fertilizer, pesticides, run off, storm sewage overflow pipes, poor land management), increase residual water retention in uplands. Increase the use of 'advanced mooring systems' to replace traditional moorings in marinas (that erode the seabed of seagrass blades); increase the amount of seagrass restoration by planting out germinated seedlings as is being carried out in West Wales (by WWF), and southern England (by Natural England and Ocean Conservation Trust). We also perhaps most importantly, need to educate the public (and boating public) about these 'ecosystem services' of seagrass, and convince the boating public to avoid anchoring in seagrass beds, and for harbour authorities throughout the UK to switch to 'Advanced Mooring Techniques' – eco-moorings which keep the damaging chains off the seabed. Overseas, we need to prevent inappropriate hotel / city and marina /docking infrastructure that can remove seagrass beds with huge consequences for this habitat - the lungs of the ocean.

What happens to the donation made by Bower customers with every purchase?

We will educate more, help others to implement advanced mooring systems, have our divers (through Seasearch) monitor the beds. With partners, we will undertake remedial action to replant and protect them with advanced mooring systems, and hopefully increase awareness of their locations, and make the wider maritime community avoid dropping anchors on such areas. With partners, we will achieve much greater protection and respect for these habitats over decades and generations.

For every purchase you make with Bower Collective, we will make a donation to help protect 1m2 of endangered seagrass. Thank you for helping us to protect the marine environment - the 'lungs of the ocean'!

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