Contribution of potential organic matter sources to the macrobenthos nutrition in the Natori estuarine tidal flats, Japan

In this investigation, we used stable isotope and fatty acid biomarker analyses to estimate and compare the potential food sources that support macrobenthos (Nuttallia olivacea, Corbicula japonica, and Hediste sp.) in the Natori estuarine tidal flats of Japan. The δ¹³C and δ¹⁵N mean values for the sediment organic matter (SOM) were −23.6‰ and 6.1‰, respectively, which were due to the contribution of terrestrial and/or aquatic vascular plant particulate organic matter (POM) from upper stream river or surrounding areas. Furthermore, from the results of the IsoSource mixing model, the contributions of estuarine POM to the diets of Hediste sp., C. japonica, and N. olivacea were 85.1%, 74.9%, and 48.9%, respectively. Moreover, essential fatty acids such as 20:5ω3, 18:2ω6 and 18:3ω3 highly contributed to the diets of macrobenthos from benthic diatoms, terrestrial and/or aquatic vascular plants. The contents of fatty acid markers of terrestrial OM (e.g., long chain fatty acids [LCFAs]) in the 3 species of macrobenthos were low in comparison to those of other food sources. Overall, the marine POM dietary contribution was minimal, while terrestrial OM, bacteria, and benthic diatoms constituted a significant portion of the macrobenthos diet, although the contribution varied among the 3 species of macrobenthos.