Effects of climate change on leaf breakdown by microorganisms and the shredder Phylloicus elektoros (Trichoptera: Calamoceratidae)
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Climate change may affect species diversity and, consequently, ecological processes such as leaf decomposition. We evaluated the effects of increased temperature and carbon dioxide (CO2) on fungal biomass, leaf breakdown, and on survival and growth of the shredder Phylloicus elektoros. We hypothesized that climatic changes would result in lower survival and growth of shredders and lower leaf consumption by these organisms. On the other hand, we predicted an increase in fungal biomass in response to climatic changes. We conducted an experiment in Manaus, Brazil, using four microcosms that simulate real-time air temperature and CO2 (control chamber), as well as three other chambers subjected to fixed increases in temperature and CO2 as compared to the control chamber. The “extreme” condition represented an increase of ~4.5°C in temperature and ~870 ppm in CO2 in relation to the control chamber. Total and shredder leaf-breakdown rates, fungal biomass, and shredder survival rates were significantly lower in warmer and CO2 concentrated atmospheres. Shredder growth rate and leaf breakdown by microorganisms were similar among all climatic conditions. With climatic changes, we found an increase in the relative importance of microorganisms on leaf-breakdown rates as compared to shredders. Thus, lower leaf breakdown and a change in the main decomposer due to future climatic conditions may result in major changes in the pathways of organic matter processing and, consequently, in aquatic food webs.
KeywordsAquatic insects Carbon dioxide and temperature increase Shredder consumption rate Fungal biomass Growth rate Survival rate
We thank Dr. Adalberto L. Val for microcosm use, Dr. Ana M.O. Pes for Phylloicus elektoros identification, Dr. Sérgio Nunomura for lyophilizer use, Dr. Manuel A.S. Graça for suggestions during data analysis, and Fernanda Dragan and Jéssica Oliveira for help during the experiment. We also thank Fernanda Dragan and collaborators who are finalizing a detailed description of the microcosms. ASM, JFGJr, and NH received research fellowships (procs. 307479/2011-0, 302957/2014-6 and 306328/2010-0, respectively) from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). RTM received a fellowship from Programa de Apoio à Fixação de Doutores no Amazonas—FIXAM/AM. CT-Amazônia/CNPq (Proc. 575875/2008-9), Pronex/CNPq/Fapeam—Aquatic insects, CT-Hidro/Climatic Changes/Water Resources/CNPq (Proc. 403949/2013-0) and INCT/ADAPTA (CNPq/FAPEAM)—Amazon projects supported the invertebrate sample collection, laboratory analyses, and microcosm experiments.
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