Hail the humble seaweed

By Julia Mahoney, class of 2020

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It’s slimy, smelly, slippery and disconcerting when it brushes against your leg while you’re swimming in the ocean. But there’s a lot more to the humble seaweed (aka marine macroalgae) than meets the eye.

From food to fertiliser, cosmetics to climate change – seaweed is all around us and it has the potential to change the world.

How big is the kingdom?
There are almost 10,000 different species of seaweed and they are usually categorised into three groups – Brown algae (Phaeophyceae), green algae (Chlorophyta) and red algae (Rhodophyta). You might think that these three groups of seaweed are closely related but that’s only party true. Red algae and brown algae for example, belong to different biological kingdoms and could be more strongly related to a jellyfish (in their respective kingdom’s) than to each other.

Fun fact: the largest brown algae can grow up to a couple of centimetres an hour!

A supreme superfood
Jamie Oliver once called seaweed “the most nutritious vegetable in the world”, and with good reason. While the exact composition varies between species, the mineral content of seaweed is said to be 10 times greater than plants grown in soil. Minerals that contribute to good health such as iodine, calcium, magnesium, iron, sodium and potassium can all be found in seaweed along with trace elements such as zinc, copper and manganese.

An 8g portion of dried kelp provides more calcium than a glass of milk, and as much fibre as a banana. Seaweeds also contain amino acids that help us digest our food – and are considered to be a better source of iron than foods like spinach and egg yolks. Add the presence of vitamins A, B (B1, B2, B3, B6, B12, and folate), C and E and you have the recipe for a superfood.

Unlike other forms of agriculture seaweed doesn’t need fertiliser or freshwater to grow, nor does it contribute to land erosion or deforestation. So there is huge potential for it to be cultivated as a sustainable, nutritious food source.

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Air to the throne
It has been estimated that algae alone produces 90% of the oxygen in the atmosphere. Thanks seaweed.

It also has the ability to reduce ocean acidification and absorb toxins like carbon dioxide, nitrogen and phosphorus.

One study proposes that cultivating mature seaweed, then harvesting and sinking it in the deep ocean where the carbon dioxide captured won’t be disturbed for hundreds or thousands of years – could help to offset our carbon emissions and prevent climate change.

Waging a war
Australian researchers at James Cook University and CSIRO have taken seaweed’s climate change fighting properties one step further. Their exciting research found that introducing a type of red algae called asparagopsis taxiformis to cow feed can reduce cattle methane production by up to 99% in the lab.

Methane is a greenhouse gas that cows emit when they burp and fart. It’s effect on global warming is 28 times greater than carbon dioxide. This potent gas makes livestock responsible for approximately 5% of human-produced greenhouse gases each year and a significant contributor to climate change.

Asparagopsis produces a compound called bromoform (CHBr₃), that prevents methane production in cows by disrupting the enzymes used by gut microbes to produce the gas. The researchers found that introducing just 2% of this special seaweed into a cow’s diet is enough to prevent methane production, and doesn’t have any negative health impacts on the animals.

The challenge now is to reproduce the asparagopsis feed at scale so that it can reach the 1.5 billion cows living on the planet at any one time.

So next time you encounter seaweed’s slimy surface at the beach, or while snacking on some sushi, take a moment to thank it for all of the benefits it brings to our human empire.