Miss Paula Sgarlatta1, Camille Magneville2, Sébastien Villéger2, Hamish Malcolm3, Iain M. Suthers1,4, Adriana Vergés1,4
1Centre for Marine Science and Innovation; Ecology and Evolution Research Centre; School of Biological, Earth and Environmental Sciences, University of New South Wales, , Australia, 2MARBEC, Université de Montpellier, CNRS, IFREMER, IRD, , France, 3Fisheries Research, NSW Department of Primary Industries, , Australia, 4Sydney Institute of Marine Sciences, , Australia
The redistribution of species due to climate change challenges traditional management approaches focused on conserving species. While the impacts of ocean warming on the species composition of ecological communities have been explored, we know little about how to predict the impacts on functional composition. Here, we investigated temporal changes in taxonomic and functional diversity of fish assemblages on warming reefs experiencing tropicalization (i.e., increased dominance of tropical species) in the Solitary Islands, eastern Australia. We contrasted these changes with reefs across a spatial cross-shelf gradient of tropicalization in the same area. Temporal changes in fish functional diversity were derived from baited remote underwater videos collected over 17 years (2002-2018) from midshelf reefs where kelp forests have disappeared through time. Underwater visual censuses were used to characterize fish communities along a cross-shelf gradient including kelp-dominated inshore reefs, midshelf tropicalised reefs where kelp has declined and offshore reefs where warm-affinity corals have been dominant for decades. We found an increase in functional richness over time driven by increases in tropical herbivores and small invertivores species. We found similar patterns across space, with midshelf and offshore ‘tropicalized’ sites also characterized by more tropical faster-growing species when compared with inshore reefs. Our study suggests that the spatial changes observed along the cross-shelf communities of the Solitary Islands provide an effective space-for-time substitution of changes caused by warming. The observed changes in trophic structure and shift towards faster-growing species have important ecological implications, via impacts to overall fish productivity and restructuring of food webs.
Presentation Slides – Paula Sgarlatta
