Exogenous organic matters are the important energy and materials source for Yellow River estuary ecosystem. And the contribution of exogenous organic matters to the system was analyzed by IsoSource Model using δ~(13)C and δ~(15)N in summer. The model ranked the contribution importance as follows: marine phytoplankton > terrestrial organic matter > freshwater phytoplankton. Nearly 20%-60% of the energy and materials were provided by the exogenous organic matters. Terrestrial organic matter played a second important role in the ecosystem, which provided 11%-36% of energy and materials to coastal organisms. And 8.5%-25% of energy and materials in organisms were supported by freshwater phytoplankton. Although the possible contribution of exogenous organic matters may be overestimated and fluctuated widely in summer, that sustained the energy flow and materials recycle in the system cannot be ignored.
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