title: Size-balanced community reorganization in response to nutrients and warming.
abstract: It is widely accepted that global warming will adversely affect ecological communities. As ecosystems are simultaneously exposed to other anthropogenic influences, it is important to address the effects of climate change in the context of many stressors. Nutrient enrichment might offset some of the energy demands that warming can exert on organisms by stimulating growth at the base of the food web. It is important to know whether indirect effects of warming will be as ecologically significant as direct physiological effects. Declining body size is increasingly viewed as a universal response to warming, with the potential to alter trophic interactions. To address these issues, we used an outdoor array of marine mesocosms to examine the impacts of warming, nutrient enrichment and altered top-predator body size on a community comprised of the predator (shore crab Carcinus maenas), various grazing detritivores (amphipods) and algal resources. Warming increased mortality rates of crabs, but had no effect on their moulting rates. Nutrient enrichment and warming had near diametrically opposed effects on the assemblage, confirming that the ecological effects of these two stressors can cancel each other out. This suggests that nutrient-enriched systems might act as an energy refuge to populations of species under metabolic constraints due to warming. While there was a strong difference in assemblages between mesocosms containing crabs compared to mesocosms without crabs, decreasing crab size had no detectable effect on the amphipod or algal assemblages. This suggests that in allometrically balanced communities, the expected long-term effect of warming (declining body size) is not of similar ecological consequence to the direct physiological effects of warming, at least not over the six week duration of the experiment described here. More research is needed to determine the long-term effects of declining body size on the bioenergetic balance of natural communities.
authors.affiliation: Coastal & Marine Ecosystems Group, School of Biological Sciences, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: David J
authors.initials: DJ
authors.lastname: McElroy
authors.affiliation: Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK.
authors.forename: Eoin J
authors.initials: EJ
authors.lastname: O'Gorman
authors.affiliation: Institut des Sciences de l'Evolution, Université de Montpellier, CNRS, IRD, EPHE, CC065, Place Eugène Bataillon, 34095, Montpellier Cedex 05, France.
authors.forename: Florian D
authors.initials: FD
authors.lastname: Schneider
authors.affiliation: Department of Environmental Biology, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, Netherlands.
authors.forename: Hanne
authors.initials: H
authors.lastname: Hetjens
authors.affiliation: Université d'Avignon et des Pays du Vaucluse, IUT Génie Biologique Option Agronomie, Site Agroparc, BP 1207, 84911, Avignon Cedex 9, France.
authors.forename: Prune
authors.initials: P
authors.lastname: Le Merrer
authors.affiliation: Coastal & Marine Ecosystems Group, School of Biological Sciences, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Ross A
authors.initials: RA
authors.lastname: Coleman
authors.affiliation: Institute of Global Food Security, School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK.|Queen's University Marine Laboratory, 12-13, The Strand, Portaferry, BT22 1PF, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Emmerson
mesh_terms: D033304:Amphipoda / Q000502:physiology; D000818:Animals; D058448:Biota; D049628:Body Size; D003386:Brachyura / Q000254:growth & development / Q000502:physiology; D005068:Eutrophication; D020387:Food Chain; D009660:Northern Ireland; D011235:Predatory Behavior; D012624:Seaweed / Q000502:physiology; D013696:Temperature
keywords: allometry; body size; climate change; food web; intertidal; nutrient; over-fishing; temperature; trophic cascade