title: Climate-driven disparities among ecological interactions threaten kelp forest persistence.
abstract: The combination of ocean warming and acidification brings an uncertain future to kelp forests that occupy the warmest parts of their range. These forests are not only subject to the direct negative effects of ocean climate change, but also to a combination of unknown indirect effects associated with changing ecological landscapes. Here, we used mesocosm experiments to test the direct effects of ocean warming and acidification on kelp biomass and photosynthetic health, as well as climate-driven disparities in indirect effects involving key consumers (urchins and rock lobsters) and competitors (algal turf). Elevated water temperature directly reduced kelp biomass, while their turf-forming competitors expanded in response to ocean acidification and declining kelp canopy. Elevated temperatures also increased growth of urchins and, concurrently, the rate at which they thinned kelp canopy. Rock lobsters, which are renowned for keeping urchin populations in check, indirectly intensified negative pressures on kelp by reducing their consumption of urchins in response to elevated temperature. Overall, these results suggest that kelp forests situated towards the low-latitude margins of their distribution will need to adapt to ocean warming in order to persist in the future. What is less certain is how such adaptation in kelps can occur in the face of intensifying consumptive (via ocean warming) and competitive (via ocean acidification) pressures that affect key ecological interactions associated with their persistence. If such indirect effects counter adaptation to changing climate, they may erode the stability of kelp forests and increase the probability of regime shifts from complex habitat-forming species to more simple habitats dominated by algal turfs.
authors.affiliation: National Marine Science Centre & Centre for Coastal Biogeochemistry Research, School of Environment, Science and Engineering, Southern Cross University, Coffs Harbour, NSW, Australia.
authors.forename: Euan J
authors.initials: EJ
authors.lastname: Provost
authors.affiliation: National Marine Science Centre & Centre for Coastal Biogeochemistry Research, School of Environment, Science and Engineering, Southern Cross University, Coffs Harbour, NSW, Australia.
authors.forename: Brendan P
authors.initials: BP
authors.lastname: Kelaher
authors.affiliation: National Marine Science Centre & Centre for Coastal Biogeochemistry Research, School of Environment, Science and Engineering, Southern Cross University, Coffs Harbour, NSW, Australia.
authors.forename: Symon A
authors.initials: SA
authors.lastname: Dworjanyn
authors.affiliation: The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Hong Kong, Hong Kong SAR.|Southern Seas Ecology Laboratories, School of Biological Sciences & Environment Institute, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Bayden D
authors.initials: BD
authors.lastname: Russell
authors.affiliation: Southern Seas Ecology Laboratories, School of Biological Sciences & Environment Institute, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Sean D
authors.initials: SD
authors.lastname: Connell
authors.affiliation: Southern Seas Ecology Laboratories, School of Biological Sciences & Environment Institute, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Giulia
authors.initials: G
authors.lastname: Ghedini
authors.affiliation: Southern Seas Ecology Laboratories, School of Biological Sciences & Environment Institute, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Bronwyn M
authors.initials: BM
authors.lastname: Gillanders
authors.affiliation: Marine Ecology Laboratories, School of Biological Sciences, University of Sydney, Sydney, NSW, Australia.
authors.forename: WillIAM
authors.initials: W
authors.lastname: Figueira
authors.affiliation: National Marine Science Centre & Centre for Coastal Biogeochemistry Research, School of Environment, Science and Engineering, Southern Cross University, Coffs Harbour, NSW, Australia.|Department of Primary Industries, New South Wales Fisheries, PO Box 4321, Coffs Harbour, NSW, Australia.
authors.forename: Melinda A
authors.initials: MA
authors.lastname: Coleman
mesh_terms: D000818:Animals; D018533:Biomass; D002980:Climate; D057231:Climate Change; D017753:Ecosystem; D020387:Food Chain; D065928:Forests; D044423:Kelp / Q000254:growth & development*; D008121:Nephropidae; D012617:Sea Urchins
keywords: acidification; kelp; kelp forests; ocean climate change; ocean warming; temperate reefs; trophic interactions