Spatio-temporal patterns of bacterioplankton production and community composition related to phytoplankton composition and protistan bacterivory in a dam reservoir

Abstract

Seasonal changes in the abundance and production of epilimnetic bacterioplankton, protistan abundance and bacterivory, and extracellular phytoplankton production (EPP) were studied at 3 sampling stations (DAM, MIDDLE and RIVER) located along the longitudinal axis of the canyon-shaped, meso-eutrophic Ř ímov reservoir (Czech Republic). We found that at the river inflow (RIVER) compared to lacustrine parts of the reservoir (MIDDLE and DAM), different sources of organic carbon and of bacterial mortality control bacterioplankton dynamics and community composition. At the RIVER site, EPP accounted for a negligible part of bacterial carbon demand, thus indicating the prominent role of allochthonous sources of organic substrates in the river inflow. In addition, protistan bacterivory removed there, on average, only 9% of bacterial production. In contrast, at the lacustrine MIDDLE and DAM stations, protistan bacterivory accounted for 47 and 78% of bacterial production, respectively. Moreover, at these stations EPP was an autochthonous source of organic carbon sufficient to meet bacterial carbon demand and EPP was tightly correlated with bacterial carbon demand (DAM, r 2 = 0.589, p < 0.005; MIDDLE, r 2 = 0.716, p < 0.001). At the DAM site, we analyzed changes in EPP in relationship to phytoplankton community dynamics and found that cryptophytes were associated with EPP. Only 2 algal groups, cryptophytes in a spring-early-summer period and diatoms in a summer-fall period, clearly dominated the phytoplankton. Changes in phytoplankton composition were related to changes in bacterial community composition studied by means of group-specific rRNA-targeted oligonucleotide probes. A trend of increased proportions of certain bacterial groups, mainly of the genus-like R-BT065 subcluster of Betaproteobacteria, was detected for the periods of high EPP levels, dominated by cryptophytes. More than 52% of the seasonal variability in the abundance of the R-BT065 cluster was explained by changing EPP levels that indicated a tight taxon-specific algal-bacterial relationship.KEY WORDS: Reservoir · Bacterioplankton composition and production · Protistan bacterivory · Phytoplankton community · Extracellular phytoplankton production · Algal-bacterial relationships · Betaproteobacterial groups Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 51: [249][250][251][252][253][254][255][256][257][258][259][260][261][262] 2008 nounced differences exist with regard to canyonshaped reservoirs, since they are spatially highly heterogeneous systems due to relatively short water retention times and often show pronounced longitudinal heterogeneity (Thornton et al. 1990). In reservoir systems, nutrient and organic matter loads in riverine input combined with morphology and hydraulic retention time of a reservoir are the major factors affecting downstream plankton succession, rates of biological processes and resulting water quality (Comerma et al. 2003, Ma$ín et al. 2003.In common with other aquatic...

Production of dissolved organic matter by phytoplankton and its uptake by heterotrophic prokaryotes in large tropical lakes

“…The high abundance and activity of members of the Betaproteobacteria group is not surprising; their abundance has been found to be positively related with the amount of algal-derived substrates (Simek et al 2008;Paver et al 2012), and they are usually ubiquitous in freshwaters. The relatively high abundance of Alphaproteobacteria and Bacteroidetes members is more difficult to interpret.…”

Repeated flood disturbance enhances rotifer dominance and diversity in a zooplankton community of a small dammed mountain pond

“…Additionally, DOC and POC were measured on April 22, 2014. vi) Bacterial and protozoan abundances and sizes were determined every 2-3 days (three times a week) from May 5 to June 27, 2014. For bacterial enumeration and sizing, duplicate formaldehyde-fixed subsamples of 1-2 mL were filtered onto black 0.2 µm pore-size membrane filters, stained with the DAPI fluorochrome and the bacterial abundance was determined via epifluorescence microscopy as described Simek et al (2008). Bacteria (> 300 cells per sample) were sized by using the semiautomatic image analysis systems (NIS-Elements 3.0, Laboratory Imaging, and Prague, Czech Republic).…”

Patterns of asynchrony for phytoplankton fluctuations from reservoir mainstream to a tributary bay in a giant dendritic reservoir (Three Gorges Reservoir, China)

“…Numerous physical (e.g., light availability, mixing regime) and chemical (nutrient concentrations) factors have shown pronounced longitudinal changes from the riverine zone to the lacustrine zone, which promote the occurrence of spatial heterogeneity of phytoplankton in reservoirs (Nogueira 2000;Mašín et al 2003;Sthapit et al 2008). On the other hand, reservoirs are subject to high temporal variability in habitat conditions, with frequent reorganization of phytoplankton abundance and species composition, as a result of the interactions between various physical, chemical and biological factors (Calijuri et al 2002;Simek et al 2008;Znachor et al 2008). Temporal fluctuations of phytoplankton have thus been regarded as one notable characteristic of the reservoir ecosystem.…”