Autotrophic carbon sources for heterotrophic bacterioplankton in a floodplain lake of central Amazon

Abstract

The relative contribution of autotrophic carbon sources (aquatic macrophytes, flooded forest, phytoplankton) for heterotrophic bacterioplankton was evaluated in a floodplain lake of the Central Amazon. Stable carbon isotopes (61 3 C) were used as tracers. Values of 6 13 C of different autotrophic sources were compared to those of dissolved organic carbon (DOC) and those of bacterially produced CO 2 .The percentage of carbon derived from C 4 macrophytes for bacterially produced CO 2 was the highest, on average 89%. The average 6 13 C value of CO 2 from bacterial respiration was -18.5 ± 3.3%o. Considering a fractionation of CO 2 of 3%o by bacterial respiration, 6 13 C value was -15.5%o, near C 4 macrophyte 61 3 C value (-13.1%0).The average value of total DOC 6 13 C was -26.8 ± 2.4%o. The percentage of C 4 macrophytes carbon for total DOC was on average 17%. Considering that bacteria consume mainly carbon from macrophytes, the dominance of C 3 plants for total DOC probably reflects a faster consumption of the former source, rather than a major contribution of the latter source.Heterotrophic bacterioplankton in the floodplain may be an important link in the aquatic food web, transferring the carbon from C 4 macrophytes to the consumers.

Multiple tracers demonstrate distinct sources of dissolved organic matter to lakes of the Mackenzie Delta, western Canadian Arctic

“…Second, our results indicate that these distinct DOM sources have very different effects on within-lake biological, chemical, and physical processes. For example, preferential uptake of macrophytic DOM has clear implications for microbial food web structure, particularly given the high growth efficiency of bacteria on this substrate (Findlay et al 1986;Mann and Wetzel 1996;Tank 2009): once it enters the DOM pool, macrophytic organic matter could provide an important subsidy to higher trophic levels via a bacterial shunt (Waichman 1996). In macrophyte-rich Delta lakes, this could be particularly important, because algal photosynthesis is low (Squires et al 2009).…”

Autochthonous versus allochthonous carbon sources of bacteria: Results from whole‐lake 13C addition experiments

“…Bacterial incubations-Bacterial 13 C values in aquatic environments have been determined through analyses of bacterial cells or CO 2 respired from bacteria grown in bioassay experiments (Coffin et al 1989;Hullar et al 1996;Waichman 1996). Alternative methods for estimating bacterial 13 C include extractions of bacterial biomarkers such as nucleic acids (Coffin et al 1990), amino acids from the bacterial peptidoglycan cell wall (Pelz et al 1998), or polar lipidderived fatty acids (Boschker et al 1999).…”

Uso Dos Isótopos Estáveis De Carbono, Nitrogênio E Enxofre Em Estudos De Ecologia Costeira

“…Para o nitrogênio inorgânico, as seguintes referências podem ser úteis: Holmes et al (1998, Sigman et al (2001 e Teece & Fogel (2004). No caso do carbono orgânico, alguns métodos têm sido recentemente apresentados para a medição direta (Beaupré et al 2007, Osburn & St-Jean 2007, ou então ele tem sido medido indiretamente: faz-se a medição isotópica do CO 2 respirado por bactérias se alimentando do carbono orgânico (Waichman 1996, McCallister et al 2006.…”