AME 49:25-34 (2007)  -  DOI: https://doi.org/10.3354/ame01131

Contrasting interactions mediate dissolved organic matter decomposition in tropical aquatic ecosystems

André Megali Amado1,2,3,*, James Bryan Cotner2, Albert Luiz Suhett1,3, Francisco de Assis Esteves1,4, Reinaldo Luiz Bozelli1, Vinicius Fortes Farjalla1,4

1Universidade Federal do Rio de Janeiro (UFRJ), Inst. de Biologia, Depto. de Ecologia, Laboratório de Limnologia, PO Box 68020, Prédio CCS, Av. Carlos Chagas Filho 373, Ilha do Fundão, Rio de Janeiro 21941-902, Brazil
2University of Minnesota (UMN), Department of Ecology Evolution and Behavior, 100 Ecology Building, 1987 Upper Buford Circle, St. Paul, Minnesota 55108, USA
3Universidade Federal do Rio de Janeiro (UFRJ), Programa de Pós-Graduação em Ecologia (PPGE) Prédio CCS, Av. Carlos Chagas Filho 373, Ilha do Fundão, Rio de Janeiro 21941-902, Brazil
4Núcleo de Pesquisas Ecológicas de Macaé (NUPEM/UFRJ), PO Box 119331, Rua Rotary Club, s/n, São José do Barreto, Macaé, Rio de Janeiro 27901-000, Brazil

ABSTRACT: The interaction between photochemical and microbial degradation processes can have important effects on dissolved organic matter (DOM) decomposition in aquatic systems. Photochemical processes can stimulate or inhibit biological DOM degradation while biological processes often stimulate photochemical degradation. The aim of the present study was to evaluate whether these 2 degradation processes compete for the same organic substrates or use complementary components in 2 tropical systems with contrasting DOM sources (one dominated by humic, mostly terrigenous DOM and the other dominated by autochthonous phytoplankton production). We performed sequential exposures of DOM from both systems to photochemical or biological degradation. We then measured bacterial growth and respiration and photochemical oxygen consumption in addition to changes in DOM optical properties. In the humic lagoon, photochemical degradation stimulated bacterial degradation up to 500% with little complementary photochemical stimulation by bacterial degradation (an increase of only 13%). In the eutrophic lagoon, we found that photochemical degradation inhibited bacterial degradation 17%, suggesting competition with microbial substrates, while bacterial degradation had no effect on photochemical degradation. The net effect of these eutrophic lagoon interactions was a ca. 2% reduction in dissolved organic carbon degradation. Thus, we conclude that there was net complementary behavior between photochemical and bacterial processes in the humic lagoon in DOM degradation, while we observed little net competitive behavior in the eutrophic lagoon.


KEY WORDS: Dissolved organic matter · Photochemical degradation · Bacterial degradation · Dissolved organic carbon · Decomposition · Tropics


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Cite this article as: Megali Amado A, Cotner JB, Suhett AL, Assis Esteves Fd, Bozelli RL, Farjalla VF (2007) Contrasting interactions mediate dissolved organic matter decomposition in tropical aquatic ecosystems. Aquat Microb Ecol 49:25-34. https://doi.org/10.3354/ame01131

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