Find out more about the 14 species of seaweed we ask you to look for on the Big Seaweed Search, and what they can tell us about our oceans.

Sea temperature rise

We have seen a 2°C increase in sea surface temperature around Britain over the past 40 years. Evidence suggests that as a result the distribution of cold-water seaweeds is moving further north and that the distribution of warm water seaweeds is expanding. The eight seaweeds below may be affected by sea temperature rise – recording them helps us to monitor any change.

Non-native species

Non-native species of seaweed, ones that historically are not found in our waters but that have arrived due to human activity or environmental change, have been living around the British Isles for well over a century. But in recent years there has been an increase in the rate of their arrival. We need you to record the four non-native seaweeds below, to help us understand more about their impact on British coasts. 

Ocean acidification

Over the past few decades, there has been a significant increase in the amount of carbon dioxide in the atmosphere. Around half of this is absorbed by the sea, which makes the water more acidic. This may corrode the chalky skeletons of some seaweeds such as those shown below, and result in changes to their abundance and distribution.