The Big Seaweed Search

The Big Seaweed Search is a joint project between the Marine Conservation Society and the Natural History Museum. The Big Seaweed Search asks volunteers to identify, photograph and record 14 key species of seaweed that can be found around the UK coastline.

Seaweed spotters are now wanted! Big Seaweed Search Week 2025 is running from 26th July to 3rd August 2025. Dive in and get exploring!

Why record seaweed?

Did you know? The UK coastline is home to an amazing variety of seaweeds. 650 different species live and grow around the UK!

It may be a bit slippery and slimy, but seaweed is a real ocean superhero. Studying seaweeds can tell us a lot about wider ocean and environmental conditions. By taking part in the Big Seaweed Search, you’ll be helping to gather vital evidence that can be used to map and document any changes to our coastal environments.

How to take part in the Big Seaweed Search

Whether you live by the sea or only visit every now and again, you can get involved in the Big Seaweed Search! It’s free, fun, and suitable for everyone – you don’t need to be a scientist to get involved.

Steps to become a seaweed citizen scientist

First, you'll need a seaweed guide and a recording form. You can download and print these below.

If you'd like a printed version of the identification guide or recording form, you can email the team at seaweeds@nhm.ac.uk including your name, address and the number of guides you would like.

If you need any further assistance to access our resources, please contact us.

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English
Big Seaweed Search guide

Big Seaweed Search recording form

Welsh

Llyfryn Chwiliad Gwymon Mawr

Ffurflen gofnodi

We want you to have fun at the beach, but it's always important to make sure you're staying safe. Check out the safety information in your Big Seaweed guide booklet before you start searching.

Try to start your survey an hour before low tide. This time is best for your safety and for seaweed spotting, too. You can check tide times for your chosen beach at www.tidetimes.co.uk

All shores are important for seaweed research, but you'll find more seaweeds on shores with hard structures like rocks, sea walls and piers, as many species anchor themselves to these.

Select a five metre wide plot that runs from the top of the shore down to the sea - five metres is around five adult paces. You can mark your survey area with a bucket, sticks, or using natural landmarks.

Stand with your back to the sea and take a picture of your survey area. This gives our scientists a good idea of the conditions on the shore where you've carried out your survey.

Walking away from the sea, explore the whole of your five metre wide plot - you might need to get your hands wet! Aim to cover your whole survey area in under an hour.

When you find one of the target seaweeds:

Tick it off as ‘present’ on your recording form
Take a clear picture of its identifying features - you need to do this for every species you find
Record it as band forming, patchy, or sparse - if you later find a larger patch afterwards, update your recording form.

Download our handy guide to taking photos

Remember, only record living species which are attached to the rocks. Ignore any seaweed which is washed up on the beach, as it could have been transported from anywhere around the coast in storms and big waves.

Now, the really important bit! Tell us what you have found. You can even do this on the beach using your phone.

There's a button to upload your pictures so our scientists can confirm what you've spotted. You can upload three images for each seaweed species you found.

The button below will direct you to an external site. For more information on how your data is used, please read the privacy policy on the Big Seaweed Search website.

Report your Big Seaweed Search findings!

Using the Big Seaweed Search data

Hundreds of volunteers have submitted data which shows how the distribution of seaweeds around the UK is changing. This information helps us to take action to protect our coastlines, seaweeds, and all the amazing wildlife that depend on them.

The Big Seaweed Search tracks and records these changes around the coast each year, so we can understand the impact of environmental change on our seas. This information supports real scientific research, which we can use to protect our ocean, and seaweeds, for the future.

Every year we share your findings, including our favourite pictures, interesting finds, and what we've done with the data.

2025 annual report coming soon!

Seaweed science

In 2022, our seaweed scientists released a scientific paper evaluating the citizen science project and 4 years of seaweed data, to highlight any findings and areas of development for the project. 

Find out more and read the full paper

The Big Seaweed team

Professor Juliet Brodie

This project is funded by the Government's Green Recovery Challenge Fund. The fund was developed by Defra and its Arm's-Length Bodies. It is being delivered by The National Lottery Heritage Fund in partnership with Natural England, the Environment Agency and Forestry Commission.