ABSTRACT
Mexican Pacific sea urchin studies have been focused mainly on species distribution, ecology and fisheries. Reef degradation by sea urchin bioerosion has not been studied previously en these reefs. We investigate the importance of Diadema mexicanum as a bioerosive agent of coral carbonate at Bahias de Huatulco, and the relative magnitude of coral accretion and bioerosion. At each of five localities in Bahias de Huatulco, sea urchin density, feeding and mechanical (spine) erosion was determined for three size class intervals. In general, D. mexicanum do not exert any significant role on coral reef community structure (live coral, dead coral or algal coverage) at the Huatulco area, probably because they are generally small (2.9-4 cm test size) and few in number (1.0-6.8 ind.m-2). Mean bioerosion rates are consistent with those measured for other diadematoids, as well as other urchin species in various eastern Pacific localities. However, the degree of bioerosive impact depends on species, test size, and population density of urchins. Coral carbonate removal by D. mexicanum erosion varies from 0.17 to 3.28 kgCaCO3m(-2)yr(-1). This represents a carbonate loss of < 5% of the annual coral carbonate production at Jicaral Chachacual, San Agustín and Isla Cacaluta, but 16 and 27% at Isla Montosa and La Entrega. On balance, coral accretion exceeds sea urchin erosion at all sites examined at Huatulco. At Bahias de Huatulco coral reef communities are actively growing, though in the coming years, it might be necessary to investigate the local effects of the interaction among erosion, and environmental and human induced perturbations
Subject(s)
Animals , Anthozoa/physiology , Conservation of Natural Resources , Carbonates/metabolism , Predatory Behavior/physiology , Sea Urchins/physiology , Seawater/microbiology , Ecosystem , Environmental Monitoring , Feeding Behavior/physiology , Mexico , Population Density , Population DynamicsABSTRACT
Foi estudado por meio da titulometria a perda do teor de cloro da soluçäo de Dakin quando estocada em vidro ambar, mantida à temperatura ambiente, exposta à luz solar e na geladeira (9-C). Verificou-se que a soluçäo de Dakin quando exposta à luz solar perdeu 79,11 por cento do teor de cloro ativo em 122 dias, à temperatura ambiente a perda teor de cloro foi de 62,69 por cento e quando armazenada na geladeira, ou seja, a 9 graus centígrados a perda foi somente de 22,39 por cento no mesmo período