Volumen 44 - Número 1: 109-122 | 2009
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Carbon productivity and flux in the marine ecosystems of the Galapagos Marine Reserve based on cetacean abundances and trophic indices
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Juan José Alava1,2*
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1School of Resource & Environmental Management (Environmental Toxicology Research Group); Faculty of Environment, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
2Fundación Ecuatoriana para el Estudio de Mamíferos Marinos (FEMM) PO Box 09-01-11905, Guayaquil, Ecuador
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The role of cetaceans in marine ecosystems and food webs is scarcely known in the southeastern Pacific. Estimates of secondary and tertiary (carbon) production and daily food intake were deduced for five species of representative cetaceans for different marine habitats of the Galapagos by using associated calculations of annual primary production and carbon flux, as well as estimations of relative abundance, biomass, absolute density and trophic levels (TL) reported elsewhere. Under these premises, sperm (Physeter macrocephalus) and carnivore-generalist killer whales (Orcinus orca) for open ocean (i.e. no upwelling regions) had the lowest values of tertiary production at the top predator level (0.01-1.01 gC m-2 yr-1), while Bryde’s (Balaenoptera edeni) and blue (B. musculus) whales from upwelling zone located at southwest Galapagos Island yielded the highest cetacean production (13.7 and 35.4 gC m-2 yr-1, respectively). Significant positive correlations at a 15% of efficiency transfer were found between the estimated annual primary production and tertiary production of baleen whales, and between annual primary production and tertiary production of toothed cetaceans. When both groups of cetaceans were combined a no significant correlation was observed between cetacean production and annual primary productivity. This outcome was influenced by their different trophic positions in the food chain and different scenarios values of annual primary productivity of the marine ecosystems selected. More research is needed to determine abundance, prey selection, feeding rates, and fecal matter sinking rates from marine mammals in Galapagos waters, as well as their function in the vertical carbon flux.
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Key words: Baleen whales, sperm whale, bottlenose dolphin, killer whale, primary and tertiary production, trophic level
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