3Department of Marine Sciences (Department of Marine Sciences, University of North Carolina, Chapel Hill, North Carolina 27599-3300, USA - United States)
5Division of Earth and Ecosystem Science (Division of Earth and Ecosystem Science, Desert Research Institute, 2215 Raggio Parkway, Reno, Nevada 89512, USA - United States)
Abstract : We monitored the dynamics of extracellular organic matter in 3 mesocosms: one dominated by a heterotrophic (microbial) community with negligible autotrophic activity (net heterotrophic system), a second where a small Phaeocystis bloom developed (production and loss almost balanced), and a third harboring a large diatom bloom (net autotrophic system). In all mesocosms, meso- and macroscopic heterotrophic organisms were excluded to primarily study extracellular organic matter production and turnover by specific algae and microbial loop organisms, respectively. Concentration and composition of dissolved organic matter (DOM), i.e. dissolved organic carbon (DOC), monosaccharides and total carbohydrates (MCHO and TCHO), free and combined neutral carbohydrates (DFCHO and DCCHO), as well as free and combined amino acids (DFAA and DCAA) were measured. In addition, net and gross community production rates were determined to calculate C-budgets. Whereas concentrations and composition of MCHO differed very little among the 3 mesocosms, dynamics of TCHO, DFCHO, and DCCHO differed significantly. Concentrations of DFAA were higher in both algal mesocosms compared to the heterotrophic system, and composition of DFAA was significantly different in the Phaeocystis and Diatom tanks. The composition and concentration of DCAA, however, were similar in all 3 mesocosms. Total dissolved carbohydrates and amino acids comprised a substantial fraction of the DOC pool. Dynamics of these DOC fractions, however, could only partly explain those of DOC, implying either that other dissolved compounds were important for overall C-cycling, or that microbial degradation of DOM affects the detection of carbohydrates and protein components.
https://hal.univ-brest.fr/hal-00467208 Contributor : Christina de la RochaConnect in order to contact the contributor Submitted on : Sunday, December 19, 2021 - 3:46:58 PM Last modification on : Tuesday, May 10, 2022 - 3:25:44 PM Long-term archiving on: : Sunday, March 20, 2022 - 6:38:45 PM
H.-P. Grossart, Anja Engel, Carol Arnosti, Christina de la Rocha, Alison E. Murray, et al.. Microbial dynamics in autotrophic and heterotrophic seawater mesocosms. III. Organic matter fluxes. Aquatic Microbial Ecology, Inter Research, 2007, 49 (2), pp.143-156. ⟨10.3354/ame01140⟩. ⟨hal-00467208⟩