I was recently strolling along the beach at Clam Bay and my attention kept shifting between the expansive ocean view and the seaweeds washed up along the shore. I counted at least a dozen different kinds, in a remarkable variety of colours, shapes and sizes.

Most striking was the kelp: long, broad ribbons of brown seaweed, some more than a metre in length and wide as my hand.

When we look closely, we discover kelp is an important food and medicine, habitat and ecological force in our coastal waters.

Ecology

Kelp is a large brown seaweed. Unlike flowering land plants, sea plants have no true roots, stems or leaves. Instead, a root-like holdfast anchors them firmly to rocks on the ocean floor, while a flexible stalk and broad blades extend upwar d into the water.

Imagine an underwater forest growing several metres below the surface. Kelp must withstand
waves and strong currents while capturing enough light to photosynthesize. Its golden-brown colour comes partly from pigments such as fucoxanthin, which help it make use of available light underwater.

Kelp is remarkably fast-growing. During its most vigorous growing periods, sugar kelp can add roughly a centimetre or more to its length in a single day. An individual may live only two to four years, yet in that short time can grow several metres long and produce an enormous amount of biomass.

Kelp beds provide shelter, feeding grounds and nursery habitat for fish and invertebrates, including cod, lobster and crab. They also absorb carbon and nutrients as they grow.

Nova Scotia is home to several species, including sugar kelp (Saccharina latissima), oarweed (Laminaria digitata), winged kelp (Alaria esculenta) and shotgun kelp (Agarum clathratum), among others.

Our Nova Scotian kelp forests are worth watching. Kelp abundance has changed along parts of our coast, influenced by warming waters, grazing species, invasive organisms and other ecological pressures.

Historical and cultural uses

Kelp has a long history of use by coastal peoples around the world as food, fertilizer and animal feed. Burning seaweed produces an alkaline “kelp ash,” used in making soap, glass and other products. Alginate, a gel-forming compound extracted from brown seaweeds, is used in food, cosmetics and industry. Chances are your summer ice cream treats were thickened and stabilized with kelp or other seaweed extracts. And that anti-aging lotion applied to your skin most likely contains seaweed extracts.

Availability

Washed-up kelp is not suitable for eating, so fresh kelp should be gathered from clean coastal waters. Dried kelp is widely available through health food stores, natural food shops and online.

Food

Kelp is nutrient-dense and low in calories, providing fibre, minerals and trace elements. It is particularly well known as a source of iodine, an essential nutrient needed for thyroid hormone production.

It has a salty, savoury flavour and can be added to soups, beans, broths and stews, contributing minerals and a rich umami quality.

More is not necessarily better. Iodine levels vary considerably, and concentrated kelp supplements can provide very large amounts. Excessive iodine can interfere with thyroid function. I think of kelp primarily as a mineral-rich sea vegetable rather than something to consume in large medicinal doses.

Medicine

One of kelp’s most interesting qualities is its slippery, gel-forming nature. When dried kelp is soaked in water, it becomes thick and viscous due to water-soluble polysaccharides such as alginates. This gives kelp its mucilaginous quality.

For topical use, I find this soothing and cooling for dry, irritated skin, and burns, much like aloe
vera gel. Rehydrated kelp can be applied directly to irritated skin, or the slippery infusion can be applied to the skin or added to a bath.

Internally, kelp’s fibre can contribute to healthy digestion and bowel regularity, while its slippery polysaccharides may have a soothing quality for irritated, inflamed digestive tissues.

Essential to land and sea

Seaweeds like kelp are also part of a much larger story of oxygen production: more than half of the oxygen we breathe originates in the ocean, generated by marine algae — kelp among them, alongside the vast, unseen fields of phytoplankton drifting near the surface.

My kelp contemplation makes me realize that what looks like a simple piece of seaweed washed onto the beach is actually a fragment of a vast underwater forest, and a reminder of how much life exists beneath our coastal waters.