Allochthonous and autochthonous carbon sources for fish in floodplain lagoons of an Australian dryland river |
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Authors: | Elvio S F Medeiros Angela H Arthington |
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Institution: | 1.Australian Rivers Institute and eWater Cooperative Research Centre,Griffith University,Nathan,Australia;2.Centro de Ciências Biológicas e Sociais Aplicadas,Universidade Estadual da Paraíba—UEPB,Tambiá,Brazil |
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Abstract: | Dryland rivers associated with arid and semi-arid land areas offer an opportunity to explore food web concepts and models
of energy sources in systems that experience unpredictable flooding and long dry spells. This study investigated the sources
of energy supporting three species of fish feeding at different trophic levels within floodplain lagoons of the Macintyre
River in the headwaters of the Murray-Darling river system, Australia. Stable isotope analyses revealed that fish consumers
derived, on average, 46.9% of their biomass from zooplankton, 38.1% from Coarse Particulate Organic Matter (CPOM) and 24.0%
from algae. Ambassis agassizii derived on average 57.6% of its biomass carbon from zooplankton and 20.4–27.8% from algae or CPOM. Leiopotherapon unicolor derived most of its carbon from zooplankton and CPOM (38.3–39.5%), with relatively high contributions from algae compared
to the other species (33.3%). An average of 48.4% of the biomass of Nematalosa erebi was derived from zooplankton, with CPOM contributing another 38.1%. Zooplankton was the most important source of organic
carbon supporting all three fish species in floodplain lagoons. Phytoplankton, and possibly, particulate organic matter in
the seston, are the most likely energy sources for the planktonic suspension feeders (zooplankton) and, consequently, the
fish that feed on them. These results indicate a stronger dependence of consumers on autochthonous sources and on locally
produced organic matter from the riparian zone (i.e., the Riverine Productivity Model), than on other resources. |
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