Abundant on UK shores, seaweed is rich in medicinal and nutritional benefits. Dawn Ireland shares how to harvest safely and sustainably and ensure fresh, quality forages.
Seaweed is a nourishing food and medicine, and whilst popular in some cultures, it is not commonly consumed in the UK.
It is truly a superfood, with higher levels of vitamins and minerals than most land plants. The medicinal benefits are wide reaching and research is beginning to highlight this (1,2).
Seaweeds in the UK
Around the UK waters there are no poisonous seaweeds. However, care needs to be taken to harvest carefully, as some can produce unpleasant byproducts as they degrade and die that could temporarily cause an upset stomach.
Generally speaking, in the UK, most beaches are owned by the landowner nearest to the beach, which is often the local council. However, the area between high and low tides belongs to the Crown. Foraging for personal use is not illegal, though a permit is required to farm or commercially harvest.
Some seaweeds grow seasonally, in a similar way to land plants. Some disappear in the winter months and regrow each spring. Some are like the evergreens on the land, remaining all winter but going dormant without much growth.
Seaweeds are categorised into three main groups:
- Brown: Phaeophyceae such as bladderwrack and serrated wrack
- Green: Chlorophyta such as sea lettuce and gutweed
- Red: Rhodophyta such as Irish moss and dulse
They have root-like structures called holdfasts, which they use to cling to rocks. Occasionally, smaller seaweeds grow on the stalks (termed stipes) of larger ones which can sometimes cause confusion with identification.
Harvesting seaweed safely
Foraging and harvesting is best done from Spring to Autumn and growth will depend on the weather conditions, temperature, and geographic location.
It is not advisable to pick seaweed lying on the beach for consumption or for medicinal uses. There is no way to tell how long it has been there, how degraded it is, and whether dogs have been around it.
Harvesting in clean waters requires some care and attention:
- Don’t harvest where there is a regular discharge of land run off near grazing or farmed animals.
- Check with organisations such as Safer Rivers and Seas for water quality monitoring and sewage treatment overflow activity.
- Check with the Environment Agency for water quality monitoring. This agency gives a useful description of identifying the difference between algae and sewage accumulation in sea water (see below).
- Avoid harvesting for a couple of days after storms and rough water where pollutants may have been churned up from the sea bed.
- Avoid harvesting near industrial areas in case of chemical discharges and pollutants.
It is worth noting that seaweed does not absorb bacteria or viruses as they are non-filter feeders, unlike shellfish. Pathogens can coat the surface of the seaweed but can be washed clean. Storage in the fridge temporarily, and rinsing in low PH water (i.e. a 10% vinegar to water solution), or drying also helps inhibit pathogenic growth. However, chemical toxins such as metals can be absorbed as the seaweed grows, hence the need for reliable research around water quality.
Harvesting seaweed sustainably
Use scissors or a sharp knife if possible, and never pull the holdfast off the rocks, to ensure to preserve the plant without killing it and allow for new growth. Take no more than is required, and cut about 5 cm from the holdfast and stalk, to allow regrowth. Rinse in the sea to ensure no wildlife is attached and take less than a third of the plant.
Ensuring quality
There are different flavours and textures from different seaweeds, and varying levels of vitamins and minerals. Brown ones tend to be higher up on the tidal areas, green ones are mid depth, and most red ones tend to be farther out in deeper waters. Any of them can be free floating if waves have broken them from their holdfast. Use your common sense to check for freshness if this is the case.
- Is it slightly elastic and stretchy, or drying out and brittle?
- Is the colour bright and shiny, or dull and faded?
- Is the seaweed ragged and torn, or full of holes?
- Does it smell like the sea with a mild seaweed scent or is it unpleasantly strong like a harbour with the tide out?
Culinary ideas: Seaweed recipes
There are several simple ways to incorporate seaweeds into the diet.
Dry any seaweed thoroughly until crispy. In sunny weather, spreading it outside works well, or hanging on a washing line. Otherwise a dehydrator is an effective piece of equipment, or, on trays in the oven with the door open after it has been switched off from cooking. Once dried, crumble into flakes and store in airtight containers.
- Use the thin and flexible green seaweed called sea lettuce as a sushi type wrap. This can be used fresh, or dried. Fill with freshly cooked rice, barley or wholegrain buckwheat and wholegrain mustard, slivers of cucumber, sweet peppers or tomato.
- Use a teaspoon or two in dishes such as curry, chilli and stews. The nutritional benefits will still have an effect, even if the taste is not apparent.
- Take the ribbons of thicker brown seaweeds when fresh (kelps), and cut them into square pieces about 4 cm long. Flash fry them in hot oil (carefully as the oil will spit a lot with the water). The kelp will blister, bubble and become crispy. Remove from the oil, drain and eat like crisps.
UK Environment Agency advice
How to tell the difference between algae and sewage when at the coast
Confusing algae for sewage is an easy mistake, but there are a few tips to help you tell the difference:
- Algal blooms generally occur between April and August.
- Long lines of algal foam can often be seen off headlands lying parallel to the coast.
- In rough conditions, thick mats of foam may be created on the shoreline by wave action.
- Stormwater overflows tend to cause a grey discolouration of the water and often have an origin such as a pipe or outfall, where the discolouration is strongest.
- Sewage discharges can contain fats and oils causing waves to flatten around it and sometimes attract seabird flocks. (5)
References
- Mathew S. Seaweeds as a Source of Micro and Macro Nutrients. Indian Council of Agricultural Research. Published online 2018. https://krishi.icar.gov.in/jspui/bitstream/123456789/20485/1/Seaweeds%20as%20a%20source%20of%20micro%20and%20macro%20nutrients.pdf
- Trigo JP, Palmnäs-Bédard M, Mar Vall-Llosera Juanola, Undeland I. Effects of whole seaweed consumption on humans: current evidence from randomized-controlled intervention trials, knowledge gaps, and limitations. Frontiers in Nutrition. 2023;10. doi:https://doi.org/10.3389/fnut.2023.1226168
- José Lucas Pérez-Lloréns, Critchley AT, M. Lynn Cornish, Mouritsen OG. Saved by seaweeds (II): Traditional knowledge, home remedies, medicine, surgery, and pharmacopoeia. Journal of Applied Phycology. 2023;35(2049–2068). doi:https://doi.org/10.1007/s10811-023-02965-6
- Løvdal T, Lunestad BT, Myrmel M, Rosnes JT, Skipnes D. Microbiological Food Safety of Seaweeds. Foods. 2021;10(11):2719. https://doi.org/10.3390/foods10112719
- Environment Agency. Telling the difference between an algal bloom and sewage – Creating a better place. Creating a better place. Published June 22, 2022. https://environmentagency.blog.gov.uk/2022/06/22/telling-the-difference-between-an-algal-bloom-and-sewage/
