Seaweed: A Love Letter

So much more than a 'weed,' and your new sustainability crush

Flathead at Shelly Beach, NSW by Gergo RugliOriginal Source:

What is a seaweed?

Seaweed is a diverse group of photosynthetic, plant-like marine algae that provide essential habitats and food for many ocean creatures.

Seaweed Diversity and Southern Rock Lobster by Stefan AndrewsOriginal Source: @ocean_imaging

Did you know?

Australia's Great Southern Reef has the highest level of species richness and endemism of seaweed flora in the world.

Seaweed Diversity by Stefan AndrewsOriginal Source: @ocean_imaging

The colour of seaweed

Seaweeds are grouped into three main colours: red, green and brown.

Red Seaweed by Stefan AndrewsOriginal Source: @ocean_imaging


The most diverse of the seaweeds, there are more than 800 species of red seaweed in the world, and over 75% of them are found nowhere else but on Australia's Great Southern Reef.

Green Caulerpa Seaweed by Stefan AndrewsOriginal Source: @ocean_imaging


Green seaweed thrives in shallow water where they are able to absorb red light and reflect their green chlorophyll pigment.

Brown Seaweeds by Stefan AndrewsOriginal Source: @ocean_imaging


Brown seaweeds, like giant kelp (macrocystis) and golden kelp (ecklonia radiata) are canopy forming and are the backbone of the Great Southern Reef, the temperate reef system spanning over 8000km of Australia's southern coastline.

Kelp and Fish by Stefan AndrewsOriginal Source: @ocean_imaging

Kelp: A firm foundation

Scientists refer to kelp as a 'foundation' species because they create habitats that benefit other organisms.

Bull Kelp in Motion by Stefan AndrewsOriginal Source: @ocean_imaging

Bull Kelp

Attaching to rocky reefs by a large disc-shaped holdfast, the brown leathery branches of Bull Kelp (Durvillaea potatorum) can reach a lengths in excess of eight metres. Individual bull kelps can weigh up to 75kg!

Golden kelp (Ecklonia radiata) by Stefan AndrewsOriginal Source: @ocean_imaging

Golden Kelp

The golden kelp (ecklonia radiata) form the backbone of the Great Southern Reef.

With strong holdfasts gripping tightly to the shallow, rocky surfaces, these highly productive algae dance gracefully in the high swell conditions where they flourish.

Golden Kelp. Australia's Great Southern ReefGreat Southern Reef Foundation

Giant Kelp by Stefan AndrewsOriginal Source: @ocean_imaging

Giant Kelp

Giant kelp (macrocystis) is the iconic canopy forming seaweed that grows over 35 metres long and up to half a metre each day.

Like trees in a forest, giant kelp modifies the environment and the resulting conditions favour a huge diversity of other species.

Golden kelp washup on beach by Stefan AndrewsOriginal Source: @ocean_imaging

Seagrass vs. Seaweed

Do you know the difference?

Blue Swimmer Crab in seagrass by Stefan AndrewsOriginal Source: @ocean_imaging


Seagrasses are the only flowering plants that grow in marine environments.

Similar to plants on land, seagrasses have roots, stems and leaves, and produce flowers and seeds.

Kelp holdfast by Stefan AndrewsOriginal Source: @ocean_imaging


Seaweeds don't have leaves or roots – instead, every part of the seaweed can absorb nutrients and take in energy from the sun.

Instead of being rooted in the ground, they are anchored to rocky reefs or hard substrate with a root-like claw called a holdfast.

Credits: Story

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Imagery by Stefan Andrews and Gergo Rugli.

Credits: All media
The story featured may in some cases have been created by an independent third party and may not always represent the views of the institutions, listed below, who have supplied the content.
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