Multiple-biomarkers show the importance of blue carbon to commercially important fishery species

Abstract

Coastal blue carbon ecosystems (BCE) support nearshore food webs and provide habitat for many commercially important fish and crustacean species. However, the complex links between catchment vegetation and the carbon food-base of estuarine systems are difficult to disern. We employed a multi-biomarker approach (stable isotope ratios - δ¹³C and δ¹⁵N, fatty acid trophic markers - FATMs and metabolomics - central carbon metabolism metabolites) to test links between estuarine vegetation and the food sources available to commercially important crabs and fish occurring within the river systems of the near-pristine eastern coastline of the Gulf of Carpentaria, Australia. Stable isotope analysis confirmed the dietary importance of fringing macrophytes to consumer diet, but showed that this is modulated by their dominance along the riverbank. FATMs indicative of specific food sources further confirmed the differences among upper intertidal macrophytes (driven by concentrations of 16: 1ω7, 18:1ω9, 18:2ω6, 18:3ω3 & 22.0) and seagrass (driven by 18:2ω6, 18:3ω3). These dietary patterns were also reflected in the concentration of central carbon metabolism metabolites. Overall, our study demonstrates the congruence of different biomarker approaches to resolve biochemical links between blue carbon ecosystems and important nekton species, and provides fresh insights into the pristine tropical estuaries of northern Australia.

Keywords: Blue carbon; Mangroves; Metabolomics; Saltmarsh; Seagrass; Stable isotopes.