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Diurnal variations in the auto‐ and heterotrophic activity of cyanobacterial phycospheres ( Gloeotrichia echinulata ) and the identity of attached bacteria
Author(s) -
EILER ALEXANDER,
OLSSON JAN A.,
BERTILSSON STEFAN
Publication year - 2006
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.2005.01493.x
Subject(s) - biology , planctomycetes , acidobacteria , water column , firmicutes , cyanobacteria , actinobacteria , proteobacteria , pelagic zone , ecology , pistia , bacteria , botany , verrucomicrobia , 16s ribosomal rna , aquatic plant , genetics , macrophyte
Summary 1. We assessed the role of cyanobacterial–bacterial consortia ( Gloeotrichia echinulata phycospheres) for net changes in inorganic carbon, primary production (PP) and secondary production in Lake Erken (Sweden). 2. At the time of sampling, large colonies of G. echinulata formed a massive bloom with abundances ranging from 102 colonies L −1 in the pelagic zone to 5000 colonies L −1 in shallow bays. These colonies and their surrounding phycospheres contributed between 17 and 92% of total PP, and phycosphere‐associated bacteria contributed between 8.5 and 82% of total bacterial secondary production. PP followed a diurnal cycle, whereas bacterial production showed no such pattern. Over a 24 h period, carbon dioxide measurements showed that the phycospheres were net autotrophic in the top layer of the water column, whereas they were net heterotrophic below 2 m depth. 3. Sequencing and phylogenetic analysis of 16S rRNA genes of attached bacteria revealed a diverse bacterial community that included populations affiliated with Proteobacteria, Bacteriodetes, Acidobacteria, Fusobacteria, Firmicutes, Verrucomicrobia, and other Cyanobacteria. 4. Compared with their planktonic counterparts, bacteria associated with cyanobacterial phycospheres had lower affinity for arginine, used as a model compound to assess uptake of organic compounds. 5. Extrapolation of our data to the water column of lake Erken suggests that microorganisms that were not associated with cyanobacteria dominated CO 2 production at the ecosystem scale during our experiments, as CO 2 fixation balanced CO 2 production in the cyanobacterial phycospheres.