What are Seaweeds?
While the incredible potential for seaweed growing as an industry is inspiring and encouraging, it is common that a fundamental question arises for many looking to enter the sector as a producer or consumer - what are seaweeds?
Seaweeds are plants that grow in the ocean, right? Well, actually, not quite.
In the same way a mushroom is not a plant, seaweeds are not true plants either. While they share many similarities, like fungi they are completely different from the true plants we know on land. Plants are in the Kingdom ‘Plante’ and seaweeds are in the Kingdom ‘Protista’. Seaweeds are better known scientifically as “macro algae” and are genetically distinct from land plants, meaning that more than a billion years ago, the ancestors of modern day land plants and modern day algae diverged and began evolving differently. So differently that, genetically speaking, humans are more closely related to fungi than seaweeds are to land plants!
Like terrestrial plants, seaweeds require sunlight to create energy through photosynthesis and as such, many of them have developed leafy-looking structures called blades to catch sun filtering through the water. Unlike terrestrial, or “true” plants, seaweed is non-vascular, meaning it lacks the tissues required to transport water and nutrients around the body. Luckily, living submerged in nutrient-rich water, seaweeds thrive just fine. Seaweeds uptake nutrients from seawater via diffusion through their blades and stipes (stem) and not through soil and a root system. An amazing exchange happens along the body of seaweed where carbon, nitrogen and the many nutrients in seawater are taken in along the leafy blades. Because seaweeds don’t have the ability to transport nutrients via a vascular system, they have become incredibly efficient at photosynthesis as their whole body can photosynthesize! So as far as inputs go, seaweeds and algae really just need fresh seawater and sunlight to grow rapidly and efficiently, contributing over half the worlds oxygen production. Lastly, seaweeds do not have roots through which to pull in nutrients. However most species do have holdfasts: root-like structures that anchor seaweeds to a surface on which to grow such as rocks and lines. The many similarities between plants and algaes is an example of parallel evolution, where two different groups have evolved similar traits to thrive in similar conditions: large, leafy structures readily absorb sunlight and strong entwined anchoring systems hold the body in place.
A large holdfast from Giant Kelp! While very root-like in appearance, this structure is used to anchor the kelp to the bottom and does not absorb nutrients.
Seaweeds as a family are further split into three major groups - green seaweeds, red seaweeds, and brown seaweeds and each are separated by millions of years of evolution. While the names do often describe their colouration, it also describes their biology. Green and red seaweeds are somewhat similar and relatively more closely related to terrestrial plants while brown seaweeds are in a completely different group altogether. Kelps are a part of the brown seaweeds family where we see immense diversity in structures, from feather boa to bull kelp. Most brown seaweeds thrive in cold waters such as the north pacific and are known for their high mineral content, including iodine.
A common red seaweed - Gracilaria, known as Red Spaghetti. Many red seaweeds are used commercially to make thickeners like agar.
The northeastern pacific ocean has incredible biodiversity, especially within the seaweed family. There are over 650 species of seaweeds in the north pacific and many of them are still being studied to better understand their role in the ecosystems and possible human uses. We have a huge variety of green, red, and brown seaweeds and many variations of kelps. Kelps are the most popular seaweeds to grow given their rapid growth rate and impressive nutritional profiles. Species such as Macrocystis, Saccharina, Alaria, Nereocystis, and Laminaria are popular in the commercial space. Typically for use in food, cosmetics, fertilizers, and animal feed - though there is much potential for other uses!
Now we know the basics of what seaweeds really are: an organism all their own. We should be sure to expect the unexpected with seaweeds and keep our eyes out for an ever evolving understanding of what seaweeds are capable of. Seaweeds have a plethora of amazing qualities that can benefit the ocean, the earth, and humans. These strange and wonderful macro-algaes can mitigate climate change, protect ocean ecosystems, feed us, provide jobs, and grow a thriving blue economy. With people and the planet at the centre of a regenerative seaweed industry, we can have hope for a healthy ocean that provides for us all.
