Ecology of the Imported Red Seaweed Eucheuma striatum Schmitz on Coconut Island, Oahu, Hawaii

Abstract

The introduced alga Eucheuma striatum Schmitz was studied regarding its spread, control, and ecology in Kaneohe Bay, Oahu, Hawaii. Its distribution in Kaneohe Bay during May 1976was nearly the same as when it was originally planted 2 yr earlier. It lacked the ability to disperse over shallow depressions both in the reef and in deep water , and it did not colonize neighboring reefs without the help of man. Depth was the single most important physical factor limiting its dispersal. A total fresh weight standing crop of from 21 to 24 metric ton s of E. striatum was recorded on a 500-m-long section of reef edge from December 1976 to June 1977. When protected from grazing its growth rate was about 5.0 percent/day. Data support the conclusion that the population on the reef edge was maintained only by a steady influx of thallus fragments that escaped from enclosed experimental plantings on the reef flat. When the experimental plantings were removed the population could not maintain itself and soon disappeared. Eucheuma striatum did not compete with native algal macrophytes and appeared to be the basis of a community richer in animal species than adjacent reefs. It provided 10-20 tons/me of food for grazing fish, shelter , and a substratum for numerous invertebrates. Eucheuma striatum did not attach to corals, but it did cause their death by shading.