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Big seaweed search

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Join forces with the Natural History Museum and the Marine Conservation Society by helping them to monitor the effects of environmental change on Britain’s sealife.

Big Seaweed Search

All you have to do is explore the seashore and record the living seaweeds you find there.

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

Now they’re scaling 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 temperatures
  • 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 the Big Seaweed Search guide PDF by clicking on the image below.

The Big Seaweed Search guide

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. Record the seaweeds you find on the recording form and photograph them.

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.

You can find out more about the Big Seaweed Search on the Natural History Museum’s dedicated website page.

Alternatively get in touch with Justine Millard ( for more information.