A dead Central American coral reef tract: Possible link with the Little Ice Age

Abstract

Journal of Marine Research, 41, 605-637, A dead Central American coral reef tract: Possible link with the Little Ice Age by Peter W. Glynn', Ellen M. Druffel 2 and Robert B. Dunbar 3,4 ABSTRACT Radiocarbon analyses, stable i'sotopic measurements and extensive field observations were made of coral reefs off the Pacific coast of Costa Rica and Panama, These analyses showed that live coral reefs in the Gulf of Papagayo, Costa Rica, were severely depleted in number, size and variety of species, compared to reefs in the major upwelling zone of the Gulf of Panama, Coral growth in the Gulf of Papagayo consisted mainly of dead reefs that died from 150-300 years B.P, The 0 18 0 records revealed that most of the dead reefs were exposed to relatively cool water immediately preceding death, We propose that during the latter part of the Little Ice Age there was probably an equatorward shift of the Northern Trade Wind system, which caused an intensification of upwelling at lower latitudes, This increased upwelling was the likely cause of the demise of coral reefs in the Gulf of Papagayo, 1. Introduction The adverse effects of cool water (15-20°C) on reef-building corals are well known (Wells, 1957; Stoddart, 1969; Clausen, 1971; Jokiel and Coles, 1977), Studies conducted over the past two decades have demonstrated the critical influence of upwelling (with attendant low temperatures and high nutrient input) in limiting coral reef development in a variety of areas (e.g., in Venezuela: Antonius, 1980; in Panama: Glynn and Stewart, 1973; Dana, 1975; Birkeland, 1977; in the Galapagos: Glynn and Wellington, 1983). In Panama, coral reef formations are present in the seasonally upwelling Gulf of Panama, but are notably limited in development compared with reefs in the non upwelling Gulf of Chiriqui (Glynn et aI., 1972; Glynn and Stewart, 1973; Glynn, 1977), The chief motivation behind this study was to test the hypothesis that coral reefs in Costa Rica are well developed on the SE Pacific coast, a nonupwelling area in the lee of a high mountain range, and reef development is weak on the NW Pacific coast, an upwelling area bordering the Costa Rican-Nicaraguan isthmian gap (Fig. 1). 1, Smithsonian Tropical Research Institute, P,O, Box 2072, Balboa, Republic of Panama, 2, Department of Chemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, 02543, U.s.A. 3. Geological Research Division, Scripps Institution of Oceanography, La Jolla, California, 92093, U.S.A. 4, Present address: Department of Geology, Rice University, Houston, Texas, 77001, U.S.A.