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Fucus gardneri (Rockweed)
Copyright © 2006
Jan Holmes
One of the most abundant and easily recognized brown seaweeds, Fucus gardneri inhabits the high to mid intertidal and thrives in both exposed and protected areas. It can tolerate a wide salinity range and withstand desiccation during long periods of exposure. Individuals grow to 40-50 cm and live up to four years. The flattened dichotomously branching body has a prominent midrib running up the center of the branches. Healthy branches are ~ 15 mm wide.
The tips of mature individuals swell up and provide flotation for the plant as well as reproductive chambers for developing sperm and eggs. During low tide, the swollen tips dry up squeezing out sperm and eggs which unite into a zygote during the next flood tide and settle onto a substratum. Native Americans historically harvested the dried swollen tips of Fucus - sometimes referred to as “Indian pop corn”.
A closely related species, Fucus spiralis may occur in the same area as F. gardneri but tends to grow a bit higher in the intertidal. Its blades tend to twist especially when dried out. Another distinction is the presence of tufts of hairs growing in pits on the surface of the blades of F. spiralis.
Note: In the past Fucus gardneri was referred to as Fucus distichus. The 2006 seaweed key for our area suggests that the name may revert back to F. distichus in the near future.
This
page was created by Jan Holmes on 12/18/06.
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