Nutritional contribution of terrestrial organic carbon to four fish species in the Yellow River Estuary and adjacent coastal waters

Abstract

Only a small amount of terrestrial organic carbon was found in the ocean organic carbon pool, though 0.40 Gt terrestrial organic carbon was transported to ocean via estuaries each year. This finding indicated that large quantity of terrestrial organic carbon was depleted in the estuaries and coasts, which provided additional materials and energy for the ecosystem. To investigate the material and energy supplement of terrestrial organic carbon transported by the Yellow River to the estuary and coastal system, the nutritional contribution of terrestrial organic carbon to four fish species: <italic>Acanthogobius ommaturus</italic>, <italic>Cynoglossus joyneri</italic>, <italic>Chaeturichthys stigmatias</italic>, <italic>Sardinella zunasi</italic>, was studied using multivariate analysis of similarity (MANOSIM) and stable isotope analysis in R (SIAR). In MANOSIM, the similarity carbon and nitrogen stable isotope in the temporal level was studied by the factors of species and seasons, and that in the spatial level was studied by the factors of species and stations. The similarity was judged by <italic>R</italic>. <italic>R</italic><0.25, similarity was high. 0.25≤<italic>R</italic>≤0.50, similarity was in the middle level. <italic>R</italic>>0.50, similarity was in the low level. In the study of SIAR, the nutritional sources of four fish species were considered as riverine, terrestrial and marine sources. The carbon stable isotope of riverine, terrestrial and marine source was (-30.0±0.4) ‰, (-26.0±0.4) ‰, and (-18.1±0.9) ‰ respectively. And the nitrogen stable isotope of riverine, terrestrial and marine source was (9.0±0.7) ‰, (1.0±0.7) ‰, and (6.0±1.2) ‰ respectively. Trophic enrichment factors (TEF) of carbon and nitrogen stable isotope was (1.1±1.3) ‰ and (2.8±1.4) ‰ respectively. We found that carbon and nitrogen stable isotope of four species showed no significant difference either in temporal level (<italic>R</italic>=0.08, <italic>P</italic><0.01) or in spatial level (<italic>R</italic>=0.19, <italic>P</italic><0.01) by MANOSIM. However, temporal and spatial variations of nutritional contribution of terrestrial organic carbon to four species were obvious. The nutritional contribution of terrestrial organic carbon was 8.7%, 7.3%, 4.3% and 32.0% higher in summer than that in autumn for <italic>Acanthogobius ommaturus</italic>, <italic>Cynoglossus joyneri</italic>, <italic>Chaeturichthys stigmatias</italic> and <italic>Sardinella zunasi</italic> respectively. And nutritional contribution of terrestrial organic carbon was 19.8%, 12.4%, 14.1% and 13.2% higher in estuary than that in coast for <italic>Acanthogobius ommaturus</italic>, <italic>Cynoglossus joyneri</italic>, <italic>Chaeturichthys stigmatias</italic> and <italic>Sardinella zunasi</italic> respectively. Temporal and spatial variations of Yellow River transporting terrestrial organic carbon may lead to variations.