Seaweed – What Are They ?

The sea plants are the most ancient plants on earth. Their essence includes tenacity, flexibility, endurance, cyclical balance and environmental resilience – hence why they can carry the goodness of the sea to your blood!

Sea vegetables are edible plants from the sea, and are highly nutritious. I sometimes refer to them as ‘the other seafood’, as people mostly restrict the term ‘seafood’ only to the animal component.

Edible seaweed, also known as sea vegetables, refers to marine algae. While ‘weed’ is a misnomer for these valuable plants, ‘vegetable’ is not accurate either as the the algae do not have roots and do not flower. They are quite distinctive in their structure and chemistry.
Their physical structure is simple with no roots or internal tissues; instead they have a holdfast to anchor themselves to rock or soil,  blades instead of leaves with one or several fronds (part of a blade) to keep the plant afloat, and a stipe instead of a stalk.
Their chemistry is very different from the land vegetables’. They are very concentrated in nutrients, containing 10-20 times what would be found in the equivalent amount of land vegetables, and still have elements that are no longer found in the soils due of erosion or over-cultivation. They also contain exclusive compounds that are not found in any other living organism. Scientific research has begun to suggest that these special compounds may have a significant impact on the body’s ability to remain healthy.

Seaweed grow everywhere – in polar areas and in tropical seas – and usually near the coastline where they attach to undersea rock formations. The most highly nutritious sea vegetables come from the cooler waters. Temperature tends to have the opposite effects on sea vegetables and those raised in the soil. In cool waters, plants will grow into dense forest of luxuriant seaweed, averaging ten to twelve feet high and growing up to a meter a day; in tropical water, plants grow slowly and not very large.

There is great diversity among sea vegetables in appearance, texture, colour & flavour. Some are sweet while others have a more robust, salty flavour; some have a delicate cellophane-like texture while other are leathery.
Seaweed are classified by colour: Red, Brown & Green algae.
Here in New Zealand, we have a lot of red seaweeds. Examples include Karengo and the Agar seaweed. The physically largest seaweeds by far are the browns, such as kelps (including Bull kelp, North Island kelp and Macrocystis kelp). The green varieties (sea lettuce, for instance) are the most similar to the higher level plants (terrestrial) and are found closest to the shore.

All seaweed contain chlorophyll in order to perform photosynthesis, but red & brown varieties have additional pigments that cover the green. As a food component, chlorophyll is a great cleanser/purifier, and rids the body of the congestion, thereby acting as an anti-carcinogenic agent. The seaweed world offers a fantastic range of colours – as an example, the red seaweed can be pink, red, purple &  even black; the browns come in shades of yellow, kaki, golden & brown; and the greens cover all the possible variations on the green theme.

Generally, red & green seaweeds are primarily composed of carbohydrates, whereas the brown seaweed are high in soluble fiber and iodine. As with variation in land vegetables, it is a good practice to eat from all three seaweed groups.

Different seaweed grow in different micro-climates (currents, light, depth). With 15,000km of coastline around New Zealand and the wide variety of landscapes, there are a great many species of seaweed growing – 25,000 in NZ alone – yet we are familiar with only a few, with just a handful being used commercially in the food industry.


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