Scotland provides a home to a wide variety of seaweed species, with different species thriving in different coastal areas. One of the most abundant and widely harvested types of seaweed, and one which has a lot of potential as a sustainable material, is kelp. Kelp is a large brown seaweed that grows on rocks, from the low tide down to deeper waters. There are 5 species of kelp native to Scotland – Laminaria digitata, Laminaria hyperborea, Saccharina latissima, Saccorhiza polyschides, and Alaria esculenta.
Kelp grows on the rocky seabed – it has a structure called a holdfast which grips onto rocks on the seabed. The holdfast is visually similar to the roots of a plant, but doesn’t penetrate the seabed or draw nutrients from it in the same way as land plants. Instead of stems, kelp has a stiff stipe that holds them upwards towards the sunlight. They are topped with palm-like fronds which vary in shape depending on the species, from long and strap shaped to split into several lobes.
Kelp forests provide an important habitat for and support a wide range of other marine life including otters, fish, urchins, limpets, red seaweeds, and soft corals. Kelp forests are also thought to provide some coasts with a degree of protection from storms, by absorbing some of the energy of the waves. In many ways, kelp forests can be considered the Scottish equivalent of tropical coral reefs.
The two most abundant kelp species are Laminaria digitata and Laminaria hyperborea:
Laminaria digitata is the main kelp seen along the shores and coastline, growing in a narrow band around low water.
Laminaria hyperborea, also known as cuvie kelp,growsin deeper waters and can grow taller than the average human, it is the main forest-forming kelp in Scotland and only visible at the lowest tides.
Kelp can be found all around the coast of Scotland, but Laminaria hyperborea grows particularly well along the West Coast of Scotland, particularly around the islands of Skye, the Outer Hebrides, Orkney, and Shetland. Kelp lives on the rocky seabed and plants often grow together in large numbers to form dense forests, usually composed of a single kelp species.
Kelp, and other seaweeds, have a long history in Scotland of being harvested for commercial purposes, although it is an industry which has been dormant for many years. Historically, it was harvested to extract iodine, produce alginates, and used as a food source. It was also burned in deep pits to create soda ash – an important chemical in the glass and soap making industries, and used in ceramic glazes. It played an important role in sustaining communities on the west coast and islands including the Outer Hebrides and Orkney, but the industry collapsed in 1822 after the duty payable on cheaper imported help was removed.
The climate emergency that we are now facing globally has caused many people to look again at seaweed, and in particular the large Laminaria hyperborea as a crop which has the potential to be used in sustainable, environmentally friendly ways.
One Scottish business that is looking at ways to develop products from Kelp is Oceanium, a start-up based in Oban. They are developing a bio packaging material using kelp which could provide a biodegradable alternative to plastic on food packaging. Using an innovative biorefinery approach, they also intend to extract valuable nutritional resources from the seaweed to produce plant-based protein and nutraceuticals (foods which also have medicinal and health benefits). They aim to harvest kelp for sustainable farmed sources of kelp, not from wild harvested kelp from kelp forests.
Interestingly, one of the nutraceuticals that can be harvested from kelp – Fucoidan – has recently been the subject of studies that have shown it to be a promising Covid-19 antiviral in a laboratory setting. The Fucoidan acts as a decoy for the virus, causing it to bind to the anti-viral rather than the host’s cells. This disarms the virus and means that it cannot infect cells and replicate. While promising in theory, the research is still in the early stages and researchers need to trial and corroborate the findings in living human cells to see if the Fucoidan extracts from seaweed can form the basis of a new anti-viral drug.
On a smaller scale, kelp also has the potential to be used by makers as an alternative textile material. Jasmine Lingington is inspired by and uses seaweed in innovative ways. She experiments with a variety of seaweeds found on the beaches close to her home in Edinburgh, as well as working with a fibre called Seacell made from seaweed and eucalyptus. One of her recent developments has been a sequin made from kelp she harvests by hand on the south east coast of Scotland. They have a subtle, leather-like texture and can be used to create jewellery, textile art, and as embellishments in garments.
Seaweeds can also be used as a fertiliser or soil conditioner, and many island communities use beach-cast seaweed (including kelp species) gathered from the shore to spread on land.
Laminaria hyperborea is also a rich source of alginates which are used in a wide variety of products, especially within the food industry. They are added to beer to keep a foamy head, and as a thickener in ice cream and jelly.
In order to protect the kelp forests around Scotland, and the role they play in the marine ecosystem, it’s important to find sustainable ways to harvest and grow kelp for use as a commercial resource.
Currently there is no large scale harvesting of kelp or other seaweed species in the UK, but there are a number of businesses and individuals harvesting wild seaweed on a small scale in Scotland. Kelp along the shoreline, including Laminaria digitata which is accessible at low tide, can be harvested by hand using a sharp knife in ways that remove the fronds but leave the stipe intact to allow regrowth. Beach-cast kelp that has been washed up onto the shore after storms can also be harvested for use.
Laminaria hyperborea is significantly more difficult to harvest without disrupting the ecosystem that it provides. In some countries, such as Norway, it is harvested using a mechanical device called a kelp dredge that hovers around 0.5 meters above the seabed. The dredge is designed to catch mature kelp, and removes it entirely from the seabed, but leaves juvenile kelp intact. New kelp grows more quickly on the patches of bare rock more quickly than it would if the holdfasts were left in place to rot, but there is evidence that the plants which grow back in its place support a significantly smaller number of other marine species than the original plants. This, among other reasons, has led to wide opposition to harvesting Laminaria hyperborea from the wild kelp forests surrounding Scotland’s coast.
Some companies, including Oceanium, have been researching other more sustainable ways to grow kelp in Scotland that can be harvested without damaging these wild kelp forests. One way this could be done is by farming kelp using moors. AquaMoor is a Scottish company who design innovative aquaculture structures that can be used to farm kelp on a commercial scale. These are anchored into the seabed and use a system of ropes to grow kelp which can then be harvested when it is mature.
Farming kelp, and other seaweeds, in this way could help protect the wild kelp forests whilst also having a positive environmental impact. Seaweed farming doesn’t require land to be cleared, freshwater, or any insecticides or fertilisers. Seaweed farms can also play an important role in carbon capture, as seaweed has the ability to absorb up to 47kg per pet tonne. This equates to approximately one tonne of carbon per hectare annually. They can also encourage responsible coastal management and provide areas for sea life to thrive.
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