Stable isotope analysis is a universally recognized and efficient method
of indicating trophic relationships that is widely applied in research.
However, variations in natural isotopic abundance may lead to
inaccuracies due to the effects of complex environmental conditions.
This research compared the carbon and nitrogen isotopic niches of fish
communities between diverse biotopes around the Yellow River estuary and
adjacent sea areas, with the aim of revealing distinctions in stable
isotopic niche metrics, trophic positions, and feeding preferences.
Stable isotopic niche results indicated that the communities of
estuarine habitants were compatible in most study biotopes, and may
provide a corridor for energy and material transportation between
Laizhou Bay and the open water. Local biocoenosis was embodied in the
wider isotopic niche corresponding to frequent environmental changes and
abiotic gradients. This implied that they used various food sources to
adapt to the fickle environment, including marine-terrestrial boundaries
and the estuary. Our analysis of the food source contribution indicated
that allochthonous sources were considered major energy sources in
estuarine areas directly affected by Yellow River-diluted water, while
autochthonous benthic and pelagic producers dominated carbon input into
the food web in Laizhou Bay and the open water. A significant variation
in the fish δN characteristic was found within
estuarine adjacent regions, so, together with the results from previous
studies, we deemed the local high concentration of dissolved inorganic
nitrogen as the original trigger of the abnormal δN
characteristic in fishes via a transport process along food chains.
These results provide a new perspective on the natural distinction of
carbon and nitrogen isotopic niches. The detailed data reported here
enhance our understanding of variations in fish communities in estuarine
ecosystems.
Riverine input of organic carbon and nitrogen in water-sediment system from the Yellow River estuary reach to the coastal zone of Bohai Sea, China
