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Ultrahigh bacterial production in a eutrophic subtropical Australian river: Does viral lysis short‐circuit the microbial loop?
Author(s) -
Pollard Peter C.,
Ducklow Hugh
Publication year - 2011
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2011.56.3.1115
Subject(s) - microbial loop , eutrophication , environmental science , aquatic ecosystem , ecosystem , freshwater ecosystem , trophic level , dissolved organic carbon , microbial food web , carbon cycle , plankton , bacterioplankton , heterotroph , subtropics , phytoplankton , ecology , environmental chemistry , biology , food web , nutrient , bacteria , chemistry , genetics
We studied trophic dynamics in a warm eutrophic subtropical river (Bremer River, Australia) to determine potential sources of dissolved organic carbon (DOC) and the fate of heterotrophic bacterial production. Sustained high rates of bacterial production suggested that the exogenous DOC was accessible (labile). Bacterial specific growth rates (0.2 h −1 to 1.8 h −1 ) were some of the highest measured for natural aquatic ecosystems, which is consistent with high respiration rates. Bacteria consumed 10 times more organic carbon than that supplied by the daily algal production, a result that implies that terrestrial sources of organic carbon were driving the high rates of bacterial production. Viruses (10 11 L −1 ) were 10 times more abundant than bacteria; the viral to bacterial ratio ranged from 3.5 to 12 in the wet summer and 11 to 35 in the dry spring weather typical of eutrophic environments. Through a combination of high bacterial respiration and phage lysis, a continuous supply of terrestrial DOC was lost from the aquatic ecosystem in a CO 2 ‐vented bacterial–viral loop. Bacterial processing of DOC in subtropical rivers may be contributing disproportionately large amounts of CO 2 to the global carbon cycle compared to temperate freshwater ecosystems.