Kelps is a facet of blue carbon that holds the key to mitigating climate change. Its ability to capture and store carbon at a shorter time scale than land forests and its potential to grow globally has scientists looking at ways to best utilise this brown alga.

What is Carbon Sequestration?

Carbon sequestration is the process of capturing and storing carbon dioxide from the atmosphere. Carbon can be captured and stored through nature-based and engineered processes. A nature-based process of carbon sequestration that has recently been under the lens is blue carbon, carbon captured by ocean and coastal ecosystems which function as carbon sinks

Blue carbon is becoming an essential process to offset human forcing of carbon emissions. Specifically, research has shown that kelp, a facet of blue carbon, is able to capture and sequester carbon at a faster rate than land forests. We have heard of land forests being a large carbon sink but research is discovering the potential of kelp forests in the ocean. 

If you want to learn more about blue carbon, check out this article next: Blue Carbon Projects Can Be Instrumental in Combating Climate Change

Kelp and Kelp Forests

Kelp is a type of seaweed that grows in the ocean. More specifically, it is a brown algae consisting of a blade, stipe, and holdfast. Some larger species of kelp contain gas bladders called pneumatocysts. Gas bladders, clear waters, and location are important for kelp to absorb sunlight from the ocean’s surface to conduct photosynthesis. During photosynthesis, kelp absorbs sunlight, carbon dioxide, and water to produce sugar and oxygen. Absorption of carbon dioxide and production of oxygen is important for living things and reducing the amount of carbon dioxide in our oceans and atmosphere. Similar to forests on land, kelp will grow in concentrated areas with other kelp resulting in a kelp forest. Kelp is seen along rocky shorelines in upwelling zones where the nutrients are high and ocean temperatures are cool. 

kelp distribution across the world

Figure 1: Global Kelp Distribution from Pearsons Education 2011

You might also like: Kelp Forest: Restoring a Lifeline for the Ocean

Kelp Growth and Role in Carbon Sequestration

Depending on the species, the lifespan of kelp can vary from up to a year to longer. During that time they can grow up to two to 30 metres (98 ft) tall during their life and up to 61 centimetres (2 ft) per day. This rate of growth means more photosynthesis potential, thus carbon dioxide being absorbed to help the kelp grow. When kelp dies, the most of the carbon dioxide it has absorbed is locked up in its tissues and transported to the ocean floor. Kelps ability to grow faster in relation to land forests gives it the advantage to sequester carbon at a faster rate. 

A study published in the scientific journal Nature reported kelp forests in Australia’s Great Southern Reef sequester 1.3–2.8 teragrams of carbon per year (Tg C year−1), amounting to more than 30% of total blue carbon stored and sequestered around the Australian continent, and ~ 3% of the total global blue carbon. There is great potential for kelp forests to help offset carbon emissions. 

According to a BBC report, globally, seaweeds (including kelp) are thought to sequester nearly 200 million tonnes of carbon dioxide every year – as much as New York State’s annual emissions. Moreover, the article suggests that 48 million square kilometres of the world’s oceans are suitable for seaweed cultivation. 

Innovative Design

A company called Running Tide has developed a technology to sequester carbon using kelp’s potential through innovative design. They create and distribute buoys made of forestry residue and limestone, and seaweed with kelp into the ocean. The limestone lessens ocean acidification, kelp captures carbon through photosynthesis, and after three months the buoy and kelp sinks then is buried deep in the ocean.

Want to Monitor Kelp Forests? is open source data that uses machine learning algorithms and remote sensing to quantify kelp forests and how they are changing over time.

You might also like: Blue Carbon Credits Emerge as Potential New Market for Global Sustainability