Invasive Alien Algae in the Main Hawaiian Islands

Cecile Walsh, a DLNR Aquatic Invasive Species Research Associate was the guest speaker at the July 9^th Hilo Bay Watershed Advisory Group (http://www.hilobaywatershed.org/) meeting.

Ms. Walsh explained that an invasive algae commonly known as gorilla ogo (scientific name Gracilaria salicornia) is threatening coral reefs throughout the Hawaiian islands and can be found on Oahu, Molokai, Maui, and the Big Island. At areas such as Kaunakakai Harbor, Keawanui, Ualapue and Kaloko`eli, gorilla ogo could smother coral reef habitats on Molokai if its growth is not stopped, according to Walsh so she is spending this summer working with Molokai’s concerned community members to educate the public and make efforts to eradicate these invasive alien species. See also The Molokai Dispatch’s June 23^rd article entitled Stinging Intruders http://www.themolokaidispatch.com/?q=node/3193 .

Ms. Walsh explained that the gorilla ogo is a brittle seaweed with cylindrical branches and that when a branch breaks it can grow into another plant. Studies have even shown that the smaller the piece the more rapid the re-growth. The problem is that gorilla ogo grows on the reef forming thick intertwining mats overgrowing and killing coral and other seaweeds. (See http://www.hawaiiinvasivespecies.org/pests/gorillaogo.html )

As a result Ms. Walsh and her colleagues use a “super sucker” which is an underwater vacuum to literally suck the gorilla ogo off the reefs which is more efficient that hand removal as the vacuum sucks all the small broken pieces of the ogo up too thus not making the problem worse. Once vacuumed off the reef and removed from the ocean the gorilla ogo makes for some good compost which farmers gladly use on their crops.

While the Big Island does not presently suffer from the invasion as severely as Molokai and parts of Oahu, the gorilla ogo has made its presences known and can be found in Queen Liliuokalani Gardens and around Coconut Island and Pohioki on the East side and off the Kona coast on the West side of Hawaii. It is thought that the gorilla ogo “escaped” from open aquaculture facilities in Kaneohe Bay on Oahu and spread. There was a similar “escape” from an aquaculture facility in Kona Ms. Walsh explained. These “escapes” were met with unspecified fines but the damage is done.

While it is not completely known why the ogo is a slow grow in East Hawaii compared to the neighboring islands, it is thought because of the large amounts of fresh water and the wave action – non the less the Big Island is grateful for the “slower” growth as it seeks ways to prevent it from suffering from the ogo to the magnitude of our neighbor isles.