2022 Early Hearing Detection & Intervention Virtual Conference

March 13 - 15, 2022

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6/08/2017  |   10:15 AM - 10:30 AM   |  SHADE AND GRAZING, NOT PHOSPHORUS, LIMIT ALGAL BIOMASS IN TROPICAL BRAZILIAN ATLANTIC FOREST (MG) STREAMS.   |  306B

SHADE AND GRAZING, NOT PHOSPHORUS, LIMIT ALGAL BIOMASS IN TROPICAL BRAZILIAN ATLANTIC FOREST (MG) STREAMS.

We manipulated nutrients grazers and predators in enclosures implanted in a shaded and a partially open site in an Atlantic Brazilian forest stream to address the question of whether these streams are top-down limited by grazers or bottom-up limited by light and nutrients. Algal biomass was low (56 to 162 µg chl-a /m 2). A 58% increase in light resulted in 2.2 fold increase in algal biomass (128 vs. 343 µg chl-a /m 2 ) and 4 fould increase in primary production (from 10 to 40 mg C m 2 day -1 ). Nutrient (P) addition did not stimulate algal standing crop. Helicopsyche grazing caused a 49 to 59% algal biomass reduction when compared with treatments with no grazers. The presence of Anacroneuria sp. (predator) did not reduce feeding by Helicopsyche. Substrates exposed to shade and semi-open sites differed in the dominance of some algal taxa. We conclude that (1) shade and herbivory control algal biomass and in these Atlantic forest streams; and (2) small changes in the light entering the streams can have profound implications in primary producers.

  • C22 Disturbance
  • S09 The importance of environmental gradients for the advance of tropical stream ecology
  • C25 Food Webs

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Presenters/Authors

Manuel Graça (), MARE, University of Coimbra, Portugal , mgraca@ci.uc.pt;


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José Barbosa (), Universidade Estadual da Paraíba, Campina Grande, PB, Brazil, ethambarbosa@hotmail.com;


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Kele Ferminiano (), Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, kelerocha@gmail.com;


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Juliana França (), Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, jsfranca@yahoo.com.br;


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José Júnior (), University of Brasíla, Brasília, DF, Brazil, jfjunior@unb.br;


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Marcos Callisto (), Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, callistom@ufmg.br ;


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Tatiany Chaves (), Universidade Estadual da Paraíba, Campina Grande, PB, Brazil, ethambarbosa@gmail.com;


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