Stable isotope data for plants and 35 fish species were used to identify autotrophic carbon sources for the central Amazon fish community. δ13C values for plants ranged from -39.4 to -11.9‰ with averages of -33.3, -28.8, -27.6, -26.2, and -12.8‰ for phytoplankton, flooded forest trees, C3 aquatic macrophytes, periphyton, and C4 macrophytes, respectively. The average for all C3 plants (phytoplankton, trees, C3 macrophytes, and periphyton) was -29.1‰, while the average for C4 plants (mainly C4 macrophytes) was -12.8‰. Mean δ13C calues for adult fish ranged from -37.0 to -19.8‰ with an average of -28.8‰. C4 macrophytes, which contributed over half of the primary production on the floodplain, accounted on average for only 2.5-17.6% of the carbon in fish. the C3 plants, as a group, were the primary carbon source for 34 fish species, and accounted for 82.4-97.5% of the carbon in all species. Phytoplankton, a minor C3 producer, accounted for a minimum of 36.6% of fish carbon on average, and was the principal carbon source for the commercially important characiform detritivores. -from Authors
|
