Approximately 145 species of marine macroalgae (or seaweeds) are consumed around the world. The consumption of seaweed dates back to before 700AD. The Pacific Northwest has many species, but I'll focus on 5: Bull Kelp, Bladderwack, Kombu, Brown Kelp and Wakame.
Seaweeds don't use roots as do land plants to take up nutrients, they can live for months drifting it they remain inside environmental parameters suitable to their growth. Whether they're found on the beach, or floating, they're perfectly good to eat as long as they are fresh and look good [K. Neumeyer, 1981].
Never take the first one you see. There is a chance that it might be the only one there, and it is better to harvest when there's an abundance.
Find a clean place to do your harvesting. Avoid inner urban areas, or those near cities or at the head of estuaries (near heavy industries). Seaweed take up heavy metals, as well as nutrients from inputs around it. Another important thing to remember, is that every place has different regulations. Find out what's allowable in your area.
When harvesting, with much care, cut 30 cm above the bulb to permit regrowth.
It forms dense 'kelp forests' in areas of fast currents usually in channels between islands. Its long strong stipes grow from attached holdfasts on rocky seafloors at depths of up to 100 feet. Its many 6-12 inch wide thick tender leaves grow out of a large hollow bulb at the top of each solitary stipe; these leaves can grow to 60 feet in length. The bulb is filled with Carbon Monoxide for flotation (R. Drum, 2020).
Nutrition:
Rich in Calcium, Magnesium, Sodium, Iodine, Potassium, Bromine, Phosphorus, Iron, Bulk fibre, Vitamin A B complex, C D E and K.
The plant reaches 16" (40 cm) in length, and consists of many branches with little spherical air bladders at their tips. They're usually paired, one on either side of the mid-rib, but these may be absent in young plants. These little buoys float the plant in an upright position, when surrounded by tidal water, enabling the plant to absorb the most nutrition and sunlight, while submerged. They're attached by a basal disc-shaped holdfast (R. Drum, 2020).
The bulbs also contain crevices, which house the reproductive structures, that bear both egg and sperm, once maturity is reached (BC Kelp, 2020).
Common Names:
Kelp, Seawrack/Sea-Wrack, Kelpware/Kelp-Ware, Black-tang, Bladder Fucus, Cutweed, Fucus, Quercus Marina, Bladder Wrack, Black Tang, Rockweed, Bladder Fucus, Sea Oak, Black Tany, Cut Weed, Dyers Fucus, Red Fucus, and Rock Wrack
Nutrition:
Rich in Iodine, Calcium, Potassium, Protein, Mannitol, Phosphorus, Alginate, Fucoidan, Phytohormones, Laminarin, Vitamins A, C, D, E, K and B complex
Has a wide blade with a 5–20” round stipe connected to root-like, branching holdfast. Blade may be smooth in the center and on the edges. Indentations tend to look like two rows. Blade may be torn or studded with blotchy coral encrustations (Breona Gutschmidt, 2020).
Common names: Horsetail kelp, tangle.
Nutrition:
High in Iodine, Calcium, Potassium, Magnesium, Iron, Sodium, Chromium, Protein, Mannitol, Phosphorus, Alginate, Fucoidan, Laminarin, Carotene, Phytohormones, Vitamin A, C, D, E, K and the B Complex Vitamins.
How to harvest:
Use scissors to cut the upper blade and leave the rest to keep growing.
Grows to about 6 metres long. Deep brown color on flattened rhizomes which are profusely dichotomously branched. Each is attached by branched root-like structures coming out of the sides of the rhizomes. Slender main stipes wide to 30 metres come from the rhizome which is up to 0.1 metres at the widest. Periodically 5 centimetres wide and 35 centimetres long flattened leaf-like branches derive from the stipe. They have furrowed surfaces and taper gradually, but then have an oval or rounded float where attached to the stipe. The blade-like branches have notched denticulate edges leading to the terminal blade at the tip of the stipe, which is separated by several smaller branches (Pearson College UWC, 2013).
Nutrition:
high in Algin, Mannitol, Potassium, Sodium, Calcium, Magnesium, Sulfur, Nitrogen, Iron, Zinc, Boron, Copper, Manganese, Chromium, Selenium, Bromine, Vanadium, Nickel; Vitamin A, B's, B12, C, D, E, and K as well as Essential fatty acids.
Large, thin blade with flat midrib, May be torn on edges or ends or appear ruffly. Stipe up to 24” long, often with groups of leaf-like sophorophls on each side (“wings”). Branched, root-like holdfast. Center rib. “Wings” (groups of leaf-like sophorophls on each side of the stipe.) One of many Alaria species that look similar. All are edible.
Common names:
Strap Kelp, Winged Kelp, Honey Ware
Nutrition: high in Calcium, Protein, Iron, Magnesium, Sodium, Phosphorus, Potassium, Chromium, Zinc, Iodine. Rich in B Complex Vitamins, Vitamin., A, C and K.
Harvesting:
Use scissors to cut off upper part of blade. Leave the leafy “wings” as these are the reproductive parts of the seaweed that will produce next years’ seaweed.
In late summer, bryozoans (round crusty white spots) grow on kelp. They're edible, being made up of calcium carbonate. White kelp salt crystals also appear on kelp. Bryozoans, or "moss animals," are aquatic organisms, living for the most part in colonies of interconnected individuals.
Clean seaweed with fresh water (or rainwater) to get the sand off. The salt over it's surface is fine, it can be used in your garden or for cooking. Salt content on seaweed is very small, doesn't affect garden soil.
Dry flat on baskets, trays or long lines. If there is no sunlight, set seaweed atop heater on a wire rack, or in the oven on a low-setting. Dry until crispy.
When drying kombu, a white powder will gather on its surface. This sweet white powder is predominately made up of sodium-based minerals known as mannite. It is umami, very agreeable in taste.
Store in airtight container such as glass jar with a screw on lid or food grade airtight hard container (plastic). Store away from light in a cool dry area. Seaweed will keep well up to 2 yrs.
"Based upon available findings, total number of deaths (14) and illnesses (73) attributed to the consumption of seaweeds is very small, and has occurred over a relatively short time period (1980–2003), as well as over a relatively small geographical part of the world (the Pacific Rim). Not only is the number of reports of harmful effects small, but the source of the toxin involved in most cases is questionable and may not be seaweed-produced, but instead produced by epiphytic cyanobacteria contaminants." (D. Cheney, 2016).
The most serious reports of illness and death come from reports of direct consumption of species of just three genera:
Sources:
David Cheney, 2016. Seaweed in Health and Disease Prevention.
Ryan Drum, 2020. The World's Tastiest and Easiest Kelp To Eat.