Big Seaweed Search

At a glance

Identify and record seaweeds.

Type of activity: Outdoors

Who can take part? Everyone

When? All year round

Where? UK seashore

How long will it take? About one hour

Help us monitor the effects of environmental change on Britain's sealife by exploring the seashore and recording the living seaweeds you find there.

Spring 2020 update

Thanks for all your help so far with the survey. If you want to know what kind of data is being collected and the best ways to contribute more, please download this update (PDF 444KB).

Why we are doing the project

The Big Seaweed Search first launched in 2009. Hundreds of people took part and the data gathered, alongside other research, show that the distribution of seaweeds around the UK is changing.

Now we aim to scale up the survey to collect thousands of new observations and to focus on key environmental issues that need more research.

These issues are:

  • rising sea temperature
  • the arrival and spread of non-native species of seaweed
  • ocean acidification (the sea becoming more acidic as a result of absorbing carbon dioxide from the air)

Home to a particularly high diversity of species, the UK is a special place for seaweeds. Unfortunately, seaweeds are not as popular as flowers, butterflies or birds, so fewer people make and submit observations of them.

As a result, we know comparatively little about the abundance and distribution of seaweed species, and how this may change over time.

Understanding more about seaweeds is critical to protecting marine environments.

How to take part

1. Download and print the Big Seaweed Search guide PDF (3.3MB) and recording form PDF (73KB) or request a free copy by emailing your name and postal address to

If you are running a group survey, download our guide for group leaders PDF (4.93MB).

2. Visit the seashore and choose your survey plot. This should be a five-metre-wide strip that runs from the top of the shore right down to the sea.

3. Walk to the sea, then take a photo of your plot (with your back to the sea).

4. Walking away from the sea, thoroughly explore the whole of your five-metre-wide plot. Aim to cover the whole of your plot within an hour. When you find one of the 14 target seaweeds:

  • Tick it off on your recording form PDF (73KB)
  • Take a clear photo showing the identification features. There are tips on this in our guide for taking photos PDF (3.08MB) for the Big Seaweed Search. Don't forget to photograph each seaweed you record.
  • Record its abundance as band-forming, patchy or sparse:
    • Band-forming - the seaweed grows as an uninterrupted band right across the width of your five-metre plot. 
    • Patchy - the seaweed grows in large patches (greater than one metre across) but does not cover the whole width of your plot.
    • Sparse - the seaweed grows in small patches (less than one metre across)
  • If you later find a bigger patch, update the recording form.
  • Only record living seaweeds, not dead ones washed up on the beach.

5. Submit your results and photos using our online form, or post them with printed photos to:

Big Seaweed Search
Angela Marmont Centre for UK Biodiversity
The Natural History Museum
Cromwell Road

You can send in records at any time of the year and as many times as you like.

Project team

  • Prof Juliet Brodie, Life Sciences Research Chair
  • Lucy Robinson, Citizen Science Programme Manager
  • Justine Millard (Marine Conservation Society)
  • Peter Richardson (Marine Conservation Society)
  • Richard Harrington (Marine Conservation Society)
Big Seaweed Search logo

In partnership with:

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