Dictyota galapagensis is endemic to the Galápagos Islands, reported from: Isabela: Turtle Point (Farlow 1902: Type locality), Tagus Cove (Taylor 1945) and Caleta Iguana (Wellington 1975). San Cristóbal: Wreck Bay (1972 UC K.A. Miller pers. comm.). Floreana: Black Beach Anchorage (Taylor 1945, Mead et al. 1972) and Champion Island (Wellington 1975). Santa Cruz: Academy Bay (Wellington 1975).
Habitat and Ecology
Habitat and Ecology
D. galapagensis is a large (35 cm long), conspicuous and easy to identify seaweed (K.A. Miller and L. Garske pers. comms.). Found on rocky substrata in shallow waters, with records from the lower intertidal to 7 m depth (K.A. Miller and L. Garske pers. comms.).
IUCN Red List Assessment
Red List Category
Red List Criteria
Miller, K.A., Garske, L. & Edgar, G.
Stuart, S.N. & Carpenter, K.E. (Global Marine Species Assessment Coordinating Team)
A conspicuous, shallow water seaweed that was historically fairly common but which has not been found in recent surveys. Last recorded in 1974 (Wellington 1975). There is a presumed 100% decline in the population. However, shallow subitidal areas have not been thoroughly surveyed. This species is assessed as Critically Endangered (Possibly Extinct).
Historically, D. galapagensis was classified as fairly common. Additionally, Wellington (1975) listed this species as being abundant in the western archipelago. Nevertheless, recent surveys have failed to find this species (K.A Miller and L. Garske pers. comms.), and there have been no other records since 1974.
Presumably El Niño and climate change. Ecosystem interactions involving these two factors appear to have caused widespread decline in algal populations because of an increase in density of grazing sea urchins and other herbivores, following overexploitation of predators along with ENSO disturbances.
Based on historical distribution, G. galapagensis occurs inside the Galápagos Marine Reserve (IUCN category VI); Galápagos Archipelago Particularly Sensitive Sea Area (PSSA); Galápagos Island World Heritage Site (UNESCO N (i)(ii)(iii)(iv)), and Galápagos Island Man and Biosphere Reserve (UNESCO).