Hawaii has four ‘bad guy’ algae

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In Hawaii, four "bad guy" alien invasive species of algae pose a clear threat to the reefs, marine life and native species of algae.

Hypnea musciformis - Maui's most problematical species - arrived in Hawaii in 1974, when it was introduced to Oahu's Kaneohe Bay as part of an unsuccessful aquaculture project. It is believed to have spread to other islands via boat traffic.

Hypnea grows in clumps and has intertwining branches with flattened tips and distinctive hooks at the end of them. When a clump is removed, the hooks remain behind to regrow, making it a difficult species to eradicate. Yellow-colored in sunlight and dark red in shade, hypnea attaches to flat rocks on the ocean bottom.

Kappaphycus spp. is another fast-growing species found on the windward side of Oahu in Kaneohe Bay but not yet on Maui or the other islands. It grows by fragmentation of its thick, spiny branches and has the capacity to turn a life-filled diverse reef into a seaweed-dominated habitat with far fewer life forms. It can appear green, red or yellowish-orange, depending on lighting.

Gracilaria salicornia can be yellow to brownish green in color with cylindrical, but often flattened, branches. Currently found only in Hilo Bay of the Big Island and in Kaneohe Bay, this species shows a preference for calm, protected waters and forms large mats that effectively outcompete native species.

The fourth alien species is Acanthopora spicifera. It arrived in the islands in 1950 via a barge from Guam. It invaded Oahu first then spread to all of the islands. This species thrives on the high nutrient content in our coastal waters and reproduces rapidly.

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