title: Long-term empirical evidence of ocean warming leading to tropicalization of fish communities, increased herbivory, and loss of kelp.
abstract: Some of the most profound effects of climate change on ecological communities are due to alterations in species interactions rather than direct physiological effects of changing environmental conditions. Empirical evidence of historical changes in species interactions within climate-impacted communities is, however, rare and difficult to obtain. Here, we demonstrate the recent disappearance of key habitat-forming kelp forests from a warming tropical-temperate transition zone in eastern Australia. Using a 10-y video dataset encompassing a 0.6 °C warming period, we show how herbivory increased as kelp gradually declined and then disappeared. Concurrently, fish communities from sites where kelp was originally abundant but subsequently disappeared became increasingly dominated by tropical herbivores. Feeding assays identified two key tropical/subtropical herbivores that consumed transplanted kelp within hours at these sites. There was also a distinct increase in the abundance of fishes that consume epilithic algae, and much higher bite rates by this group at sites without kelp, suggesting a key role for these fishes in maintaining reefs in kelp-free states by removing kelp recruits. Changes in kelp abundance showed no direct relationship to seawater temperatures over the decade and were also unrelated to other measured abiotic factors (nutrients and storms). Our results show that warming-mediated increases in fish herbivory pose a significant threat to kelp-dominated ecosystems in Australia and, potentially, globally.
authors.affiliation: Centre for Marine Bio-Innovation, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia; a.verges@unsw.edu.au.|Evolution and Ecology Research Centre, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.|Sydney Institute of Marine Science, Mosman, NSW 2088, Australia.
authors.forename: Adriana
authors.initials: A
authors.lastname: Vergés
authors.affiliation: Centre for Marine Bio-Innovation, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.|Commonwealth Scientific and Industrial Research Organization Oceans and Atmosphere, Dutton Park, QLD 4102, Australia.|Marine Spatial Ecology Lab, Australian Research Council Centre of Excellence for Coral Reef Studies, School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia.
authors.forename: Christopher
authors.initials: C
authors.lastname: Doropoulos
authors.affiliation: Marine Ecosystem Research, Fisheries NSW, Department of Primary Industries, Coffs Harbour, NSW 2450, Australia.
authors.forename: Hamish A
authors.initials: HA
authors.lastname: Malcolm
authors.affiliation: Centre for Marine Bio-Innovation, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.|Evolution and Ecology Research Centre, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Mathew
authors.initials: M
authors.lastname: Skye
authors.affiliation: Centre for Marine Bio-Innovation, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.|Evolution and Ecology Research Centre, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Marina
authors.initials: M
authors.lastname: Garcia-Pizá
authors.affiliation: Centre for Marine Bio-Innovation, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.|Evolution and Ecology Research Centre, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.|Sydney Institute of Marine Science, Mosman, NSW 2088, Australia.|Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technical University, Singapore 637551, Singapore.
authors.forename: Ezequiel M
authors.initials: EM
authors.lastname: Marzinelli
authors.affiliation: Centre for Marine Bio-Innovation, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.|Evolution and Ecology Research Centre, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.|Sydney Institute of Marine Science, Mosman, NSW 2088, Australia.
authors.forename: Alexandra H
authors.initials: AH
authors.lastname: Campbell
authors.affiliation: Centre d'Estudis Avançats de Blanes (Consejo Superior de Investigaciones Científicas), 17300 Blanes, Girona, Spain.
authors.forename: Enric
authors.initials: E
authors.lastname: Ballesteros
authors.affiliation: Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Hoey
authors.affiliation: Geocoastal Research Group, School of Geosciences, The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Ana
authors.initials: A
authors.lastname: Vila-Concejo
authors.affiliation: Marine Spatial Ecology Lab, Australian Research Council Centre of Excellence for Coral Reef Studies, School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia.|Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia.
authors.forename: Yves-Marie
authors.identifier: 0000-0002-7190-5187
authors.initials: YM
authors.lastname: Bozec
authors.affiliation: Centre for Marine Bio-Innovation, School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.|Sydney Institute of Marine Science, Mosman, NSW 2088, Australia.|Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technical University, Singapore 637551, Singapore.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Steinberg
mesh_terms: D000818:Animals; D001315:Australia; D057231:Climate Change; D017753:Ecosystem; D005399:Fishes / Q000502:physiology*; D020387:Food Chain; D060434:Herbivory / Q000502:physiology; D044423:Kelp / Q000254:growth & development*; D009792:Oceans and Seas; D013696:Temperature; D014329:Tropical Climate
keywords: climate change; macroalgae; plant–herbivore interactions; range shifts; tropicalization