Carbon flow and trophic structure of an Antarctic coastal benthic community as determined by delta 13C and delta 15N

Stable isotopes of carbon and nitrogen were used to determine the different carbon pathways and trophic assemblages amongst coastal benthic fauna of the Windmill Islands, East Antarctica. Macroalgae, pelagic POM, sediment POM and sea ice POM had well-separated delta 13C signatures, which ranged from -36.75ppt for the red alga Phyllophora antarctica, to -10.35ppt for sea ice POM. Consumers were also well separated by delta 13C, ranging from -21.42ppt for the holothurian Staurocucumis sp. up to -7.47ppt for the urchin Sterechinus neumayeri. Analysis of delta 13C and delta 15N revealed distinct groups for suspension feeders, grazer/herbivores and deposit feeders, whilst predators and predator/scavengers showed less grouping. Consumers spanned a delta 15N range of 8.71ppt, equivalent to four trophic levels, although delta 15N ratios amongst consumers were continuous, rather than grouped into discrete trophic levels. The study has built a trophic model for the Windmill Islands and summarises three main carbon pathways utilised by the benthos: (1) pelagic POM; (2) macroalgae/epiphytic/benthic diatoms and (3) sediment POM/benthic diatoms. The movement of carbon within the coastal benthic community of the Windmill Islands is considered complex, and stable isotopes of carbon and nitrogen were valuable tools in determining specific feeding guilds and in tracing carbon flow, particularly amongst lower-order consumers.