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Ecology of the Invasive Red Alga Gracilaria salicornia (Rhodophyta) on O'ahu, Hawai'i

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Title:Ecology of the Invasive Red Alga Gracilaria salicornia (Rhodophyta) on O'ahu, Hawai'i
Authors:Smith, Jennifer E.
Hunter, Cynthia L.
Conklin, Eric J.
Most, Rebecca
Sauvage, Thomas
show 2 moreSquair, Cheryl
Smith, Celia M.
show less
Date Issued:Apr 2004
Publisher:University of Hawai'i Press
Citation:Smith JE, Hunter CL, Conklin EJ, Most R, Sauvage T, Squair C, Smith CM. 2004. Ecology of the invasive red alga Gracilaria salicornia (Rhodophyta) on O'ahu, Hawai'i. Pac Sci 58(2): 325-343.
Abstract:The red alga Gracilaria salicornia (C. Agardh) E. Y. Dawson was introduced
intentionally to two reefs on O'ahu, Hawai'i, in the 1970s for experimental
aquaculture for the agar industry. Some 30 yr later, this species has
spread from the initial sites of introduction and is now competing with native
marine flora and fauna. The goals of this study were to quantify various aspects
of G. salicornia ecology in Hawai'i in an effort to develop control or eradication
tools. Experimental plots were established to determine cover and biomass of G.
salicornia per square meter and to determine the amount of time and person
hours needed to remove G. salicornia from these plots. Substantial amounts of G.
salicornia become dislodged from the reef during large wave events and periodically
become deposited onto the beach in front of the Waikiki Aquarium. Algal
beach wash biomass was quantified and positive relationships were established
between swell height and the amount of algae that washed up onto the beach in
this location. We then quantified the ability of G. salicornia vegetative fragments
to regrow after desiccation to determine if algal biomass stranded on shore survives
the tidal cycle until being washed back out on the reef at high tide. Gracilaria
salicornia was remarkably resistant to temperature, salinity, and chemical
treatments examined as possible in situ control options. Herbivore preference
tests showed that a native Gracilaria species is consumed far more frequently
than the alien congener. Finally, large-scale community volunteer efforts were
organized to remove drifting G. salicornia fragments from the reef area in front
of the Waikiki Aquarium. Over 20,000 kg of alien algal fragments were removed
from this location in five 4-hr cleanup events. However, based on G. salicornia
growth rates, ability to fragment, physical tolerance, and low herbivory, it is
clear that a large-scale dedicated effort will be needed to control this invasive
species on Waikiki's reefs.
Appears in Collections: Pacific Science Volume 58, Number 2, 2004

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