Miss Erin McCosker1, Dr Peter Steinberg1, Dr Mark Hay2, Dr Adriana Verges1
1University Of New South Wales, Sydney, Australia, 2Georgia Institute of Technology, Atlanta, USA
Food web studies have revealed stark differences in the movement of energy from producers to consumers on temperate vs tropical reefs. As oceans warm, climate-mediated shifts in species distributions and interactions are predicted to interrupt these patterns of production and consumption, with impacts on food webs and overall fish biomass. Here, we investigate potential changes in reef trophodynamics and fish productivity as temperate reefs undergo warming. We collected the dominant consumers spanning multiple trophic guilds and primary food sources from six sites at two distinct habitats, temperate inshore kelp-dominated and tropical offshore coral-dominated that represented a space-for-time substitution of how we expect temperate reefs in Australia to change in future decades. We use stable isotope analysis (15N and 13C) to estimate and compare the contribution of oceanic and reef-derived dietary material to fish biomass across kelp-dominated and coral-dominated habitats. We also examine differences in trophic niche width and dietary specialisation of fishes between these two habitats. We expect 13C:15N isotope ratios to indicate a greater reliance on locally produced energy sources such as turf algae and detritus by fishes at offshore sites, while oceanic plankton-derived energy primarily supports fish biomass at inshore sites. We also expect expansion of dietary niche widths for fishes occupying both inshore and offshore habitats, indicating greater dietary generalism by species in temperate habitats. This research will elucidate the effects of changes in energy flow and food webs for fish biomass on warming temperate reefs.
Presentation Slides – Erin McCosker
