Establishing a food web model for coastal Antarctic benthic communities: a case study from the Vestfold Hills

Shallow-water benthic communities throughout coastal Antarctica share many species and are governed by similar physico-oceanographic processes. This suggests community structure and function may be similar among communities despite being geographically separated by up to 15 degrees of latitude and 18 000 km of coastline. To test this theory, we developed a food web model using stable isotopes (delta C-13, delta N-15) for the high-latitude Vestfold Hills shallow-water benthic community and compared it to the isotopic food web model developed for the Windmill Islands, located over 1000 km away. For the Vestfold Hills food web, carbon sources were generally well separated by delta C-13, and lower-order consumers could be grouped according to their feeding guild and main dietary sources as determined by delta C-13 and delta N-15. Higher-order consumers occupied the full range of delta C-13 ratios and had similar delta N-15 values, although predators were weakly, but significantly, enriched in delta N-15 compared to scavenger/predators and omnivores. When comparing with the Windmill Islands food web, we found similar delta C-13 ratios for several co-occurring carbon sources and consumers, whilst the delta N-15 ratios in consumers from the Vestfold Hills were consistently enriched compared to those from the Windmill Islands by 1 to 2 parts per thousand. The relative positions of feeding guilds on the delta C-13 and delta N-15 planes were similar for both food webs. These results suggest there is considerable merit in developing a representative food web model for Antarctic shallow-water communities. Such a model would provide a trophic benchmark against which modification in these communities brought about by climate change or other human impacts could be compared.