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A window into the world of seaweeds

They may not look like much when washed up on the beach, but seaweeds provide a vital underwater habitat.

Professor Juliet Brodie is shedding light on the vast forests growing in our oceans.

There are many species of seaweed that call Britain's cold seas home.

The largest of these are kelps. These brown seaweeds grow from the shore down to 20-30 metres, or further if the water is clear. They form dense forests and provide a habitat for a diversity of marine life.

Juliet says, 'They can be nurseries for fish and provide services for many other different types of animals and seaweeds. The forest is full of all this amazing life.'

Even the holdfast - the structure that connects large brown seaweeds to rocky seafloors - sustains a huge amount of life.

Underwater forest of giant kelps

Some of the tallest kelps in the world are Macrocystis pyrifera, which grow up to 50 metres © Claire Fackler CINMS, NOAA/ Wikimedia Commons


'If you take it apart and have a look in, you can find worms, snails and other shelled animals, and maybe sponges - a whole variety of organisms.'

The kelps found along the British coastline reach up to three metres in height. But some of the tallest in the world are giant kelp (Macrocystis pyrifera), which can be found in places such as along the coast of California and grow up to 50 metres.

However, kelps in many areas in the world are in decline, particularly because of rising seawater temperatures.

Losing kelps on a large scale will damage the underwater ecosystem, displacing the marine creatures that live among them. Coasts around the world will also be exposed to damaging erosion where the seaweeds would have formed a protective barrier.

Recreating a forest

A new display in Hintze Hall, the Museum's central space, will feature three panels of seaweeds collected by Juliet and her team. They are organised to create an impression of the natural arrangement in the sea.

'We want to give people a sense of what it is like in the seaweed forests,' says Juliet.

To show this, the large kelps will be surrounded by a variety of other associated seaweed species. 

Sargassum muticum seaweed

Sargassum muticum is one of the seaweed species that have been pressed and dried for the display © Lamiot/ Wikimedia Commons


'There are lots of different types of seaweed and they grow at different levels on the shore and in the sea. So for the display we want to create a lovely array showing the diversity of species.'

The seaweeds have been set into three panels of acrylic and glass. 'It takes quite a bit of visualisation. We want to create the feeling of an underwater forest but also keep it simple,' Juliet explains.

Pressing seaweeds

Once collected, the seaweeds had to be pressed and dried. This method preserves them for their future in the Museum.

Some seaweeds were a challenge for the team, however. Juliet says, 'Some of the kelp specimens that the divers picked up were really big, so we struggled to get them to fit into even the largest press.'

Hintze Hall seaweeds close-up

Seaweeds collected by Juliet and her team will be displayed in acrylic and glass to replicate underwater kelp forests


Through the pressing process the seaweeds became translucent, but their original structures have been maintained.

Once the seaweeds had dried some became very delicate, so the team had to take great care when handling them.

'It was a very tricky stage in the process because the specimens were dried for quite a long time and they became very brittle. We had to be careful that bits didn't break off.'

Searching shore and sea

The seaweeds on display were collected from shores and the shallow subtidal in Pembrokeshire and Devon.

'Around the UK, kelps can be found wherever there is a rocky bottom,' explains Juliet. 

Hintze Hall seaweeds panel

A large variety of seaweeds, collected from Devon and Pembrokeshire, had to be pressed and dried for preservation


The Pembrokeshire coast in particular has played a significant part in the collection process, both for the project and for Juliet herself - despite the conditions not always being favourable.

'Pembrokeshire is a challenging coastline. It's very rocky and the weather can be very changeable,' she says.

'But it's where I built up my first love of these organisms, and that's really why I went back.

'It's a great adventure into the unknown, and I love it.'

Swim through the forest

Museum visitors can see the underwater kelp forest in Hintze Hall.