A Seaweed for the Climate

Published by Shannon Leigh Miller on 08/28/2024 08/28/2024

In the ocean garden, rockweed is really common. There are close to 70 species worldwide, and in the Pacific it’s one of the most commonly known seaweeds. Called rockweed, fucus, or bladderwrack, or more aptly pop weed by Indigenous nations, our local species is Fucus distichus. The profusely branched seaweed produces two nearly equal branches, directly opposite each other, looking much like the letter Y. It’s distinguishable by its inflated branch tips which buoy the seaweed upright in water.

Rockweed thrives in high to mid-intertidal zones and is prevalent on rocky shores, causing caution for any human moving on rocks in the tidal zones. The plant’s holdfast keeps it secured to the rock, the human slipping on it, not so much.

As our average global temperatures increase, both on land and in the ocean, and we look for resilience in Earth’s climate system, consider this common seaweed as an ecosystem engineer. Despite constant drying and wetting, desiccation and rehydration, individual rockweed survive and thrive for 10-15 years.

If you are curious about the age of the Rockweed that caused you to fall to your knees, first look at its colour. The younger ones are light green and grow darker green as they age. The youngest among the Fucus distichus don’t have bladders on branch tips. The exact age can be determined by counting the bladders it has produced: one per year (plus two for the first two bladder-less years of growth).

In a rapidly changing climate, a species that can withstand exposure to heat is notable. As Fucus is exposed to high levels of solar radiation it produces UV-absorbing compounds to protect itself. Researchers have taken note and are investigating the potential of utilizing the seaweed’s compounds as UVB and UVA-absorbing filters in sunscreen.

Researchers at The University of Washington Friday Harbour Marine Biology Field Station studied the effects of increasing temperature on the ability of rockweed to photosynthesize. Their results suggest that as seawater temperatures increase, rockweed will undergo a net increase in photosynthesis.

Should you need sunscreen in a tidal zone, pop a full rockweed bladder and apply the gel to your nose. It’s clear and odourless and will protect your exposed skin from being burnt. The thick gel in the rockweed bladder is also moisturizing. Skincare companies wax poetic about the brown algae’s abilities and mineral rich serum. One containing Fucus suggests it “is your express ticket to a glowing, flawless complexion and powerful lift. “If prepared to try Fucus distichus on your skin, harvest it without tearing away the holdfast, so it can regrow. Try a few branches and bladders in a mesh bag in your bath. They will turn bright green in hot water and release beneficial minerals and mucilaginous alginates to soothe any wounds from your slip on the seaweed rocks.

N.B.: A note on scientific names: The Pacific Fucus distichus is far more common on our coast than previously thought due to modern DNA barcode work on the species. Fucus gardneri and Fucus distichus once thought to be distinct species now appear to be the same species. F. distichus was thought to be the common Atlantic species while F. gardneri was applied to the common Pacific species; now they are usually used as synonyms, though F. distichus is preferred.