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

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

Since 2009, hundreds of people have taken part in the Big Seaweed Search. Alongside other research, the data you've gathered shows that the distribution of seaweeds around the UK is changing.

Why we are doing the project

Home to a particularly high diversity, the UK is a special place for seaweeds, with over 650 species.

Understanding more about them is critical to protecting marine environments. Seaweed creates habitat where fish, invertebrates, birds, and marine mammals find food and shelter.

We know comparatively little about the abundance and distribution of seaweed species. So it is important to record them and monitor how they change over time.  

Your observations will give us a better picture of how seaweeds are affected by:

  • 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)

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 (89KB)
  • 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 updates

Project team

  • Prof Juliet Brodie, Life Sciences Research Chair
  • Lucy Robinson, Citizen Science Programme Manager
  • Dr Jessica Wardlaw, Citizen Science Programme Developer
  • 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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