title: Rainfall and hydrological stability alter the impact of top predators on food web structure and function.
abstract: Climate change will alter the distribution of rainfall, with potential consequences for the hydrological dynamics of aquatic habitats. Hydrological stability can be an important determinant of diversity in temporary aquatic habitats, affecting species persistence and the importance of predation on community dynamics. As such, prey are not only affected by drought-induced mortality but also the risk of predation [a non-consumptive effect (NCE)] and actual consumption by predators [a consumptive effect (CE)]. Climate-induced changes in rainfall may directly, or via altered hydrological stability, affect predator-prey interactions and their cascading effects on the food web, but this has rarely been explored, especially in natural food webs. To address this question, we performed a field experiment using tank bromeliads and their aquatic food web, composed of predatory damselfly larvae, macroinvertebrate prey and bacteria. We manipulated the presence and consumption ability of damselfly larvae under three rainfall scenarios (ambient, few large rainfall events and several small rainfall events), recorded the hydrological dynamics within bromeliads and examined the effects on macroinvertebrate colonization, nutrient cycling and bacterial biomass and turnover. Despite our large perturbations of rainfall, rainfall scenario had no effect on the hydrological dynamics of bromeliads. As a result, macroinvertebrate colonization and nutrient cycling depended on the hydrological stability of bromeliads, with no direct effect of rainfall or predation. In contrast, rainfall scenario determined the direction of the indirect effects of predators on bacteria, driven by both predator CEs and NCEs. These results suggest that rainfall and the hydrological stability of bromeliads had indirect effects on the food web through changes in the CEs and NCEs of predators. We suggest that future studies should consider the importance of the variability in hydrological dynamics among habitats as well as the biological mechanisms underlying the ecological responses to climate change.
authors.affiliation: Laboratório de Limnologia, Departamento de Ecologia, Instituto de Biologia, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, PO Box 68020, Rio de Janeiro, RJ, Brazil.
authors.forename: Nicholas A C
authors.initials: NA
authors.lastname: Marino
authors.affiliation: Department of Zoology and Biodiversity Research Centre, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Diane S
authors.initials: DS
authors.lastname: Srivastava
authors.affiliation: Department of Zoology and Biodiversity Research Centre, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: A Andrew M
authors.initials: AA
authors.lastname: MacDonald
authors.affiliation: Laboratório de Limnologia, Departamento de Ecologia, Instituto de Biologia, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, PO Box 68020, Rio de Janeiro, RJ, Brazil.
authors.forename: Juliana S
authors.initials: JS
authors.lastname: Leal
authors.affiliation: Laboratório de Limnologia, Departamento de Ecologia, Instituto de Biologia, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, PO Box 68020, Rio de Janeiro, RJ, Brazil.
authors.forename: Alice B A
authors.initials: AB
authors.lastname: Campos
authors.affiliation: Laboratório de Limnologia, Departamento de Ecologia, Instituto de Biologia, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, PO Box 68020, Rio de Janeiro, RJ, Brazil.|Laboratorio Internacional en Cambio Global (LINCGlobal).
authors.forename: Vinicius F
authors.initials: VF
authors.lastname: Farjalla
mesh_terms: D000818:Animals; D001419:Bacteria; D031229:Bromeliaceae; D057231:Climate Change; D004463:Ecology; D017753:Ecosystem; D020387:Food Chain; D007313:Insecta; D011235:Predatory Behavior
keywords: climate change; consumptive effect; food web; predation risk; rainfall; tank bromeliad