Autotrophic carbon sources for fish of the central Amazon

Abstract

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