Mazzaella (the iridescent seaweed)

By Judith Connor and Elizabeth Nelson

Common name: Iridescent seaweed

• Type: red alga
• Light: some grow in the intertidal zone and some deeper in the subtidal
• Substratum: rock

Greek myths describe Iris, the goddess of the rainbow, as a messenger for the Olympian deities. The characteristics of the seaweed Mazzaella (previously called  Iridaea) strikingly reflect its prior name. The same properties of light which produce a rainbow provide the plant’s  surface with its brilliant iridescence. Vibrant colors wash across the thallus surface due to the multilayered construction of its cuticle.

Blades that grow on high intertidal rocks have a liver-gold or greenish color, while those growing deeper in the intertidal zone are often a spectacular iridescent purple. You can find blades as large as 4 feet long that stretch out like abandoned spandex clothes in the beach wrack.
The gametophyte plants produce gametes (male or female reproductive cells). The term “phyte” means “plant”. A sporophyte is a plant that produces spores. Many seaweeds (including Mazzaella) have life histories that alternate between the gametophyte and sporophyte stages.

Mazzaella’s gametophytes and tetrasporophytes are smooth, rubbery blades that look similar (isomorphic), until they become reproductive. The female gametophytes start smooth but develop  bumps (called cystocarps) that hold the zygote after fertilization. When reproductive, the tetrasporophyte blades develop patches of small bumps that bear tetrads (clumps of four spores).

Both its iridescent cuticle and the differences in rubbery blade strength between its life phases provide insights into the adaptations of wave-swept algae to mechanical stress.

kingdom Plantae, phylum Rhodophyta, class Florideophyceae, order Gigartinales, genus Mazzaella