Marine algae are crucial components of the tropical reef ecosystem, providing food for numerous herbivorous fishes and invertebrates, buttressing our coasts with living pavement and drawing down the nutrient levels in coastal waters – all steps to keeping our coasts healthy. In line with its geographical isolation, many of the marine algae found in the Hawaiian archipelago are endemic, occurring here and nowhere else, and have coevolved within an intricate and complex reef ecosystem. The high degree of endemicity of Hawaii’s coral reefs – over 25% of the fishes, invertebrates, and algae make them especially vulnerable to habitat changes with increasing seawater temperature, increasing acidity and introductions of alien species.
Unfortunately, several species of alien algae have become established on Hawaii’s reefs, and have contributed towards the decline of several areas. Acanthophora spicifera is an accidental introduction having carried attached to the hull of a military fuel barge in 1950 that arrived in Pearl Harbor. Three other alien algae, Gracilaria salicornia, Hypnea musciformis and Kappaphycus alvarezii, were intentionally introduced on Oahu in the 1970’s for experimental aquaculture for the agar and carrageenan gels that these algae make for their cell walls.
On some Oahu coastline, G. salicornia, K. alvarezii and Eucheuma striatum are dominant, outcompeting and excluding native algae. One such area is the reef fronting the Aquarium, and here efforts have been underway since 2002 to remove these alien species and to restore the reef to its natural condition. Driven by Dr. Celia Smith and her students at the University of Hawaii’s Department of Botany, this Aquarium/Botany Department collaboration is a community-oriented project that seeks to remove the alien algae from the reef ecosystem by picking them from the substrate and loading them onshore. Care is taken that any native species inadvertently collected by volunteers is returned to the ocean. The alien algae are weighed, to assess both the scale of the challenge and the effectiveness of the removal efforts, and transported to Honolulu Zoo. There the algae are added to the Zoo’s compost pile, which is used to fertilize the plants on the Zoo grounds and available for public use.
Initially, the removal teams consisted solely of university students and a few other individuals, but the interest and participation in this project have now grown and expanded to over 500 people in a year coming out to help. At each cleanup, volunteers range from 25 to 70 and represent individuals from throughout the community.
More recently, herbivorous collector urchins, bred especially for this purpose by the State’s Anuenue Fisheries Research Center, have been introduced onto the reef after removal efforts, to help graze down the alien algae and thereby control the rate of alien species recolonization.
Plan are also underway to breed a herbivorous fish, the Sailfin Tang, for eventual introduction onto affected reef areas. Research by Dr. Smith’s Manoa undergraduates at the Aquarium has revealed this species prefers to graze on alien algae over native species.
Educating the public, enabling them to understand more about Hawaii’s marine ecosystem, reaffirming their sense of ownership in Hawaii’s reefs, and empowering them to contribute directly to their well-being – this project touches all these areas, and taking part is also fun!
Interested? Please check out the calendar for the next algae clean up, and come and join us in rehabilitating this iconic Hawaiian landmark – Waikiki Beach!
Volunteers bring their own towels, sunblock, sun-shirt, hat, etc.
Location Skill Set Suggested Items to Bring Description of Work Open Water Swim/Snorkel Mask, Fins, Snorkels Snorkel overhead of the divers and take the filled burlap bags to the surface. (Divers sit on the bottom of the trench). Open Water Lift filled burlap bags onto paddle board/kayak. Can swim/tread water. Tabis Load up the paddle board or kayaks with the filled burlap bags of algae. Have paddle board ready out by where the divers are positioned. Open Water Shoreline Swim, paddle/swim paddle board back to shore Swim the paddle boards back to shore loaded with filled burlap bags. Return paddle board and empty bags back to where divers are positioned. Shoreline Carry burlap, push filled trashcans Tabis Once in shallow water, we unload algae from the burlap bags into big wheeled trash cans and use the ramp to bring algae up from the reef. Sidewalk by Banyan tree Sorting species of algae. Training and reference photos provided. Sort native algae and invasive algae. Invasive algae is put back into trash cans and native algae is separated and returned to the ocean. Sidewalk by Banyan tree Lift filled trash cans of/off scale Weigh invasive biomass and record weight with UH Botany staff. Sidewalk by Banyan tree Lift biomass onto truck Gloves Transport weighed biomass to the back of a truck parked at the cul de sac by the banyan tree. Shallow Water, Shoreline Identifying invasive algae species. Training and reference photos provided. Goggles, Gloves, Tabis Remove invasive algae from the shallow reef, more on the Ewa end of this region.
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