Seaweed distribution and abundance around our coasts is changing. To investigate why this might be and what’s out there, the Marine Conservation Society has joined forces with the Natural History Museum to encourage people to take part in the Big Seaweed Search.
The aim of the project
The aim of this citizen science project is to encourage the public to record the presence, absence and abundance of 14 species of seaweed around the UK. The data will be utilised by research scientists to study the changes in distribution and abundance of these native and non-native species in relation to changes in sea surface temperature and ocean acidification.
Seaweed expert, Professor Juliet Brodie, from the Natural History Museum, explains what we know about seaweed and why it is so important we learn more…
Every time you visit the rocky seashore or take a dive in the shallow waters around Britain, you enter the realm of the seaweeds. Large brown wracks (fucoids) grow in bands across the rocky shore and kelps create the forests of the seas. Search under the wracks or in rock pools and you will find pink paint-like crusts and mini-forests of chalky (calcified) coralline algae.
Seaweeds are red, green and brown macroalgae but look more closely and you will encounter a unique myriad of colours, shapes and forms like no other. The brown seaweed Giant Kelp, Macrocystis pyrifera, found in the Pacific and Southern Oceans, is huge at up to 60 metres long. Other seaweeds might be just a few millimetres long or only one giant cell such as Codium species, the green sponge weeds. Others have structures that produce different colours. The red seaweed Irish Moss, Chondrus crispus, which is common on our shores, has frond tips that appear an iridescent blue. The brown Bushy Rainbow Wrack, Cystoseira tamariscifolia, which is frequent on south-western shores, appears turquoise-blue when under water.
Kelp forests are some of the most productive organisms on the planet. They also protect coasts by reducing wave action and storm damage. The kelps and wracks together around Britain are estimated to cover the equivalent area of British woodland.
Seaweeds have provided humans with a source of raw materials for millennia. A much loved food in Wales is laver bread which is made from the red Porphyra which is closely related to seaweeds that are used to make nori, the dark wrapping in sushi. Seaweeds are also a valuable source of phycocolloids (carbohydrates), fertilizers, bioactive compounds, biomedical compounds, functional foods, cosmetics and increasingly, biofuels.
Climate change has resulted in a 2°C increase in sea surface temperature around Britain over the last 40 years. Cool water-adapted kelps and wracks have been reported as disappearing from several regions of the northeast Atlantic.
The changes are complex, but for Britain, the distribution of some of the large brown seaweeds appears to be moving north.
Non-native species of seaweed, i.e. those that do not occur naturally in our waters, but that have arrived due to human activity or environmental change, have been recorded around the British Isles for well over a century. However, in recent years there has been an increase in the rate of their arrival.
Over the last few decades, there has been a significant increase in the amount of carbon dioxide in the atmosphere. When carbon dioxide is absorbed by the sea, the water becomes more acidic. As the seas around Britain become more acidic we may expect to see a change in the distribution and abundance of calcified red seaweeds whose skeletons are potentially vulnerable to the corrosive effect of the seawater.
The Big Seaweed Search was launched in June 2016 and focuses on 14 species of seaweed including 8 species of conspicuous wracks for the public to record. Many of these will probably be familiar, such as Bladder Wrack, Fucus vesiculosus, with its bladders resembling bubble-wrap that pop underfoot, and Knotted Wrack, Ascophyllum nodosum, which produces a single egg-like bladder once a year.
We’re also keen to study the non-natives to know more about their impact on British coasts. One of the most well-known of these listed in the study is Wireweed, Sargassum muticum, a brown seaweed that was first recorded on the south coast of England in 1973 and has spread very rapidly since then. Another conspicuous non-native seaweed and a favoured food in Japan, Wakame, Undaria pinnatifida, was first recorded in Britain in 1994 on pontoons but is now starting to colonise rocky shores. These ‘aliens’ are here to stay so we need to learn to love them.
The survey also asks volunteers to search for calcified coralline algae including the paint-like crusts and mini-forest Corallina species.
The seashores and shallow seas around Britain support over 650 species of seaweeds making them globally significant and an important component of British biodiversity. This project will enable the public to contribute to scientific research and will help track changes in the UK’s marine environment using the distribution of seaweed species as an indicator of what’s going on beneath the waves.
Taking part
Why not take part and request or download a copy of the identification guide and recording form
If you’d like more information or wish to discuss the project further then please get in touch with Justine Millard, Head of Volunteer and Community Engagement at MCS.