Planktonic Bacterial Production Research Articles

Differences in regulation of planktonic and epilithic biofilm bacterial production in the middle reaches of a temperate river

To clarify the governing factors of planktonic and epilithic bacterial production (BP) and to quantify their relative contributions to the carbon cycle, we investigated the seasonal variation and regulatory factors of planktonic and epilithic BP in the middle reaches of the Shinano River, Japan, ecosystem from February 2019 to May 2020. Sampling was conducted at 3 stations: upper stream riffle, upper stream pool, and lower stream riffle, where current velocity, water depth, and bed shear stress were distinct. Planktonic and biofilm BP ranged from 5.5 to 466 mgC m-3 d-1 and 2.9 to 132 mgC m-2 d-1, respectively, showing clear seasonal variation. Biofilm BP was higher in the upper stream riffle than at the other stations, where no spatial variation in planktonic BP was observed. Generalized linear models suggest that BP was primarily regulated by water temperature. Additionally, planktonic BP was significantly correlated with dissolved organic carbon, suggesting carbon limitation. Biofilm BP showed no evidence of resource limitation (nutrients and organic matter), but was significantly explained by current velocity and station. The results suggest that although seasonality is dominant in biofilm BP variation, spatial differences are significant within the seasonal variability. Moreover, current velocity and bottom shear stress related to local geomorphologies such as riffles and pools affect substrate supply rate and biofilm formation processes, regulating biofilm BP variation. This study demonstrated different regulatory factors of planktonic and biofilm BP in the middle reaches of a temperate river.

Disentangling multiple chemical and non-chemical stressors in a lotic ecosystem using a longitudinal approach

Meeting ecological and water quality standards in lotic ecosystems is often failed due to multiple stressors. However, disentangling stressor effects and identifying relevant stressor-effect-relationships in complex environmental settings remain major challenges. By combining state-of-the-art methods from ecotoxicology and aquatic ecosystem analysis, we aimed here to disentangle the effects of multiple chemical and non-chemical stressors along a longitudinal land use gradient in a third-order river in Germany. We distinguished and evaluated four dominant stressor categories along this gradient: (1) Hydromorphological alterations: Flow diversity and substrate diversity correlated with the EU-Water Framework Directive based indicators for the quality element macroinvertebrates, which deteriorated at the transition from near-natural reference sites to urban sites. (2) Elevated nutrient levels and eutrophication: Low to moderate nutrient concentrations together with complete canopy cover at the reference sites correlated with low densities of benthic algae (biofilms). We found no more systematic relation of algal density with nutrient concentrations at the downstream sites, suggesting that limiting concentrations are exceeded already at moderate nutrient concentrations and reduced shading by riparian vegetation. (3) Elevated organic matter levels: Wastewater treatment plants (WWTP) and stormwater drainage systems were the primary sources of bioavailable dissolved organic carbon. Consequently, planktonic bacterial production and especially extracellular enzyme activity increased downstream of those effluents showing local peaks. (4) Micropollutants and toxicity-related stress: WWTPs were the predominant source of toxic stress, resulting in a rapid increase of the toxicity for invertebrates and algae with only one order of magnitude below the acute toxic levels. This toxicity correlates negatively with the contribution of invertebrate species being sensitive towards pesticides (SPEARpesticides index), probably contributing to the loss of biodiversity recorded in response to WWTP effluents. Our longitudinal approach highlights the potential of coordinated community efforts in supplementing established monitoring methods to tackle the complex phenomenon of multiple stress.

Going with the flow: Planktonic processing of dissolved organic carbon in streams

A large part of the organic carbon in streams is transported by pulses of terrestrial dissolved organic carbon (tDOC) during hydrological events, which is more pronounced in agricultural catchments due to their hydrological flashiness. The majority of the literature considers stationary benthic biofilms and hyporheic biofilms to dominate uptake and processing of tDOC. Here, we argue for expanding this viewpoint to planktonic bacteria, which are transported downstream together with tDOC pulses, and thus perceive them as a less variable resource relative to stationary benthic bacteria. We show that pulse DOC can contribute significantly to the annual DOC export of streams and that planktonic bacteria take up considerable labile tDOC from such pulses in a short time frame, with the DOC uptake being as high as that of benthic biofilm bacteria. Furthermore, we show that planktonic bacteria efficiently take up labile tDOC which strongly increases planktonic bacterial production and abundance. We found that the response of planktonic bacteria to tDOC pulses was stronger in smaller streams than in larger streams, which may be related to bacterial metacommunity dynamics. Furthermore, the response of planktonic bacterial abundance was influenced by soluble reactive phosphorus concentration, pointing to phosphorus limitation. Our data suggest that planktonic bacteria can efficiently utilize tDOC pulses and likely determine tDOC fate during downstream transport, influencing aquatic food webs and related biochemical cycles.

Impacts of Tetracycline on Planktonic Bacterial Production in Prairie Aquatic Systems

In view of antibiotics being detected in surface waters, experiments were conducted to determine the impacts of tetracycline on planktonic bacteria in wetland and river waters. The minimum inhibitory concentration (MIC) method is often used to measure for resistance or susceptibility of microbes to antibiotics with typical concentrations of antibiotics being mg L(-1). Moreover, there is the belief that antibiotics in the lower microg L(-1) range are unlikely to affect bacteria. We examined this assumption by measuring the effects of a broad range of tetracycline concentrations on bacterial protein production by the incorporation of L-[4,5-3H]leucine method. Tetracycline significantly (P < 0.05) inhibited production in river water bacteria at a "free" concentration of 5 microg L(-1), but the inhibition was significant only at 1000 microg L(-1) in wetland water. The data indicate that planktonic bacteria can be very sensitive to tetracycline at extremely low concentrations and that microbial production is seriously affected.

Seasonal and interannual variation of bacterial production in lowland rivers of the Orinoco basin

Summary1. We examined the influence of hydrologic seasonality on temporal variation of planktonic bacterial production (BP) in relatively undisturbed lowland rivers of the middle Orinoco basin, Venezuela. We sampled two clearwater and two blackwater rivers over 2 years for dissolved organic carbon (DOC), chlorophyll, phosphorus and bacterial abundance to determine their relationship to temporal variation in BP.2. Dissolved organic carbon concentration was greater in blackwater (543–664 μm) than in clearwater rivers (184–240 μm), and was generally higher during periods of rising and high water compared with low water. Chlorophyll concentration peaked (3 μg L−1) during the first year of study when discharge was lowest, particularly in blackwater rivers. Soluble reactive phosphorus (SRP) was very low in the study rivers (&lt;3.8 μg L−1) and concentration increased during low water.3. Average BP was higher in clearwater (0.20–0.26 μg C L−1 h−1) than in blackwater rivers (0.14–0.17 μg C L−1 h−1), although mean bacterial abundance was similar among rivers (0.6–0.8 × 106 cells mL−1).4. Periods of higher chlorophyll a concentration (low water) or flushing of terrestrial organic material (rising water) were accompanied by higher BP, while low BP was observed during the period of high water.5. Interannual variation in BP was influenced by variations in discharge related to El Niño Southern Oscillation events.6. Seasonal variation in BP in the study rivers and other tropical systems was relatively small compared with seasonal variation in temperate rivers and lakes. In addition to the low seasonal variation of temperature in the tropics, low overall human disturbance could result in less variation in the inputs of nutrients and carbon to the study rivers compared with more disturbed temperate systems.

Control of bacterial production in cold waters. A theoretical analysis of mechanisms relating bacterial production and zooplankton biomass in Disko Bay, Western Greenland

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 228:15-24 (2002) - doi:10.3354/meps228015 Control of bacterial production in cold waters. A theoretical analysis of mechanisms relating bacterial production and zooplankton biomass in Disko Bay, Western Greenland T. Frede Thingstad1,*, Torkel Gissel Nielsen2, Anja Skjoldborg Hansen2, Henrik Levinsen2,** 1Department of Microbiology, University of Bergen, Jahnebakken 5, 5020 Bergen, Norway 2Department of Marine Ecology, National Environmental Research Institute, PO Box 358, 4000 Roskilde, Denmark *E-mail: frede.thingstad@im.uib.no **Present address: University of Copenhagen, Helsingørsgad 49-51, 3400 Hillerød, Denmark ABSTRACT: Data on planktonic bacterial production and biomass of copepods and heterotrophic dinoflagellates in Disko Bay, Greenland, are discussed within the framework of a theoretical model. The model is an extension of a previously published model that relates bacterial production and shifts between carbon and mineral nutrient limitation of bacteria to the structure of the planktonic food web. We suggest how dinoflagellates can be incorporated into this framework, and show how this affects bacterial production. With the parameters used, the model predicts the system mainly to be in, or close to, the state leading to carbon-limited bacterial growth, a prediction in accordance with results published for this environment. In the model, this is caused by a high combined biomass of copepods and heterotrophic dinoflagellates that keeps the biomass of phytoplankton competitors low and the regeneration rate high. In Disko Bay, high copepod biomass is not primarily the result of a succession from a high phytoplankton biomass to their predators, but is largely caused by migration of an over-wintering copepod population from deep waters into the photic zone prior to the spring bloom. The set of data thus comprises no situations combining high phytoplankton biomass with low combined biomass of heterotrophic dinoflagellates and copepods, a situation that in the model would lead to a state with pronounced mineral nutrient limitation of bacterial growth rate. Since such seasonal copepod migration is a feature common to many arctic ecosystems, the suggested relationship has strong potential implications for carbon cycling in the Arctic. KEY WORDS: Bacterial growth · Polar · Food web models · Copepods Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 228. Online publication date: March 06, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Bacterial Stimulation in Mixed Cultures of Bacteria and Organic Carbon from River and Lake Waters.

Abstract Interactions between natural bacterial assemblages and dissolved organic carbon (DOC) were investigated in two complementary batch experiments. In the first, a positive relationship was found between the proportion of electron transport system (ETS) active bacteria and the diversity of DOC in microcosms enriched with an increasing number of organic substrates. In a second experiment, bacterial and nutrient dynamics were measured in microcosms with natural bacterial populations and organic matter from rivers and lakes of different trophic levels. The interactions between the bacterial assemblages and DOC from different sources was investigated using source systems (rivers or lakes) and blended (different proportions of river and lake water) batch cultures. In each experiment, the number of total and ETS-active bacteria, the fluorescein diacetate (FDA)-hydrolytic activity, and the total (DOC), biodegradable (BDOC) and refractory (RDOC) dissolved organic carbon were measured four times during 5 days. The results suggested that the temperature, more than trophic level, controlled planktonic bacterial production. Furthermore, bacterial activity was stimulated in micrososms where river and lake waters were mixed. For the oligotrophic microcosms, this observation can be explained by a greater diversity of the organic nutrients ("qualitative" stimulation of bacteria), whereas for the meso-eutrophic microcosms, the production of new pools of dissolved organic carbon (both biodegradable and total) could account for the observed "quantitative" stimulation of the bacteria. These experiments suggest that the mixing of bacteria and organic matter from two different systems can give rise to novel nutrient and bacterial dynamics that are likely similar to those that occur in river-lake ecotones.http://link.springer-ny.com/link/service/journals/00248/bibs/38n3p285.html</hea

Original Articles: Sources of Dissolved Organic Carbon Supporting Planktonic Bacterial Production in the Tidal Freshwater Hudson River

Planktonic bacterial production in the tidal freshwater Hudson River is a major component of secondary productivity and is uncoupled from planktonic primary productivity. There are several major sources of allochthonous dissolved organic carbon (DOC) whose potential contribution to heterotrophic bacterial growth was examined with bioassays. Supply of DOC from the upper Hudson drainage basin and a large tributary in the mid-Hudson together comprise 70 kT DOC/year, which is the bulk of the DOC load to the tidal freshwater Hudson River. Two contrasting tidal wetlands contribute DOC to the main-stem river but were only a few percent of the tributary load even during summer low-flow conditions. The quantity of DOC released from fine sediments was intermediate to the other two loadings considered. Bacterial growth in bioassays receiving water from the sources varied, but differences in thymidine incorporation between reference and DOC sources were small, usually less than 2 nmol/L/h. Similarity in thymidine incorporation suggests that all sources of DOC were capable of supporting bacterial growth at approximately equal rates. Seasonal shifts in carbon availability were clear in several cases, for example, greater growth on wetland-derived DOC at times of peak plant productivity. Seasonal differences in tributary DOC bioavailability were not large despite the well-known seasonality of tributary inputs. Activities of a suite of extracellular enzymes were used as a biologically based characterization of DOC from the various sources. Shifts in allocation among enzymes were apparent, indicating that there are biologically relevant differences in composition among the sources. Fluorescence characteristics and absorbance per unit carbon also varied among sources, providing an independent confirmation of compositional differences among sources. The absence of large differences in bacterial productivity among sources suggests that growth is supported by a wide range of DOC, and the relative importance of the sources is probably related to the quantitative differences in inputs. Efforts to classify carbon supplies to ecosystems must recognize that organism plasticity in carbon use and physical mixing processes will both act to homogenize what might initially appear to be quite distinctive carbon inputs.

Influence of the benthos on growth of planktonic estuarine bacteria

Estuarine planktonic bacteria were incubated (bacterial bioassays) in water previously held in close contact with benthic sediments to assess the potential importance of benthic dissolved organic matter for planktonic bacterial production. The study was conducted using water and sediments collected from along a fresh to salt water gradient in the Parker River and Plum Island Sound Estuary in northern Massachusetts, USA. Initial concentrations of dissolved inorganic nutrients were elevated relative to ambient estuarine water while initial concentrations of dissolved organic carbon were higher during a June bioassay and lower during a December bioassay relative to ambient water. Specific growth rates of planktonic bacteria were calculated from changes in cell numbers during the exponential growth phase. Growth rates were very high, ranging from about 3.6 to 6.5 d-'. Rates at individual sites were generally higher in June than in December and higher in low salinity waters than in high salinity waters. These rates are substantially higher than bacterial growth rates typically found in the water column of Plum Island Sound (1.5 to 65x, depending on method) but had the same spatial pattern as is commonly found in the estuary. Growth rates were comparable to those observed during experimental additions of marsh macrophyte leachate to incubations. Growth rates were linearly related to initial dissolved organic carbon (DOC) concentration in the bioassays, suggesting that substrate may limit bacterial growth. Stable isotopic compositions (6I3C and 6I5N) of microbes grown in the bioassay indicated utilization of benthic derived DOC even during times when the net f l u of DOC was from overlying water into sediments. Further, the 6I5N of bioassay microbes suggested that microbes utilized benthic derived inorganic N to supplement an organic diet deficient in organic nitrogen. It appears that growth rates were elevated as a result of dissolved organic matter exchange with bottom sediments. These results suggest that there were gross fluxes of organic matter across the sedimentwater interface that were not apparent from net changes in DOC concentration in the overlying water pool. This study indicates that benthic systems must be seen not only as sites of inorganic nutrient remineralization important in support of planktonic primary producers, but also as sltes of dissolved organic matter generation and nutrient remineralization important in support of bacterioplankton production.

Fate of bacterial production in a heterotrophic ecosystem: grazing by protists and metazoans in the Hudson Estuary

The Hudson River Estuary IS a heterotrophic ecosystem with high rates of planktonic bacterial production. We measured grazing on bacteria in monthly experiments dunng 1990 to determine: ( l ) the prlmary consumers of bacteria; (2) whether absolute rates of grazing on bacteria were high relative to other systems; and (3) whether bacterla were a sufficient carbon resource for consumers. Fluorescent minicells were used to measure the Ingestion of bacteria by heterotrophic flagellates and ciliates. Using the abundances of bacteria, rotifers and cladocerans in the river, we also estimated zooplankton clearance rates. Total grazing of the plankton community was assessed by measuring the disappearance of fluorescent minicells over 24 and 48 h. Heterotrophic flagellates were the primary consumers of bacteria with ciliates and the cladoceran Bosmina longirostris also important seasonally. Ingestion of bacteria by heterotrophic flagellates, ciliates, and B. longirostris was sufficient at most times to satisfy estimated carbon requirements of these consumers. Large bacterial size and relatively low consumer populations in the Hudson account for the apparent sufficiency of bacteria as a carbon source We conclude that grazing on bacteria in the Hudson River is similar to the levels of grazlng observed in other systems. Nevertheless, bacteria are a potentially significant resource, because the domlnant planktonic consumers are capable of ~ngesting bacteria at rates sufficient to support carbon demands.

Planktonic community structure determines the fate of bacterial production in a temperate lake

We examined the fate of planktonic bacterial production and the balance between bacterial growth and grazing mortality in the surface waters of Upton Lake, New York. Growth rates were measured by the incorporation of t3H]thymidine into DNA. Grazing rates on bacteria were determined with small cells produced by a mutant strain ofEscherichia coli and made either fluorescent or radioactive to monitor feeding. Bacterial community turnover times calculated from either growth or grazing rates ranged from 1.5 to 16 d. On the basis of these data and results from 29 other studies, most bacterial communities appear to have turnover times substantially > 1 d. Our measurements of feeding rates on bacteria frequently exceeded estimates of growth. Limitations of precision and doubts about the accuracy of methods make attempts to balance measurements of bacterial growth and grazing with current techniques unrealistic. The fate of bacterial production depends on planktonic community structure. Flagellates were the primary consumers of bacteria in winter and fall. At other times, Daphnia galeata consumed most of the bacterial production. Ciliates and rotifers were never important bacterial grazers. In Upton Lake large populations of Daphnia effectively “break” the microbial loop and funnel bacterial production to higher consumers.

A simulation analysis of continental shelf food webs

Energy flow through continental shelf food webs was examined using a simulation model. The model structure expands the two traditional marine food chains of phytoplankton-zooplankton-pelagic fish and benthos-demersal fish into a complex web which includes detritus, dissolved organic matter (DOM), bacteria, protozoa, and mucus net feeders. Simulation of energy flux for different shelf systems using the expanded web revealed that heterotrophic microorganisms and their predators account for a significant component of the energy flux in the continental shelf ecosystem. Contrary to previous models, where all phytoplankton were considered to be grazed by zooplankton, our simulation results indicate that only slightly more than 50% of the annual net primary production is grazed. A substantial quantity of the phytoplankton production directly becomes detritus. Bacteria mineralize detritus and DOM produced by phytoplankton and other components of the food web, converting these to biomass with high efficiency. Consequently, the model predicts that planktonic bacterial production is equivalent to zooplankton production. Exclusion of the bacteria requires the assumption that all DOM is either exported from the system or consumed by another component of the food web. Neither of these assumptions can be supported by present knowledge of the dynamics of DOM in the sea. Model simulations were also employed to test the hypothesis that production exceeds consumption on continental shelves, resulting in exports of 50% of the annual primary production. Simulations of shelves with high rates of primary production resulted in a particulate export of 27% and realistic estimates of secondary production. Results of other simulations suggest that shelves with lower primary production cannot export production and still maintain the macrobenthos and their predators. General properties about continental shelves can also be inferred from the model. From simulations of shelves of differing primary production, nanoplankton are predicted to account for a greater proportion of the primary production in nutrient limited systems. Benthic production appears to be related to both the quantity of primary production and the sinking rates of the phytoplankton. The model indicates that zooplankton fecal inputs to the shelf benthos are only a small portion of the total detrital flux, leading to the prediction that fecal pellets are of little significance in determining benthic production. Finally, the model generates production efficiencies that are highly variable depending on the type of system and kind of populations involved. We argue that the assumed ecological efficiency of 10% should be abandoned for continental shelves and other ecosystems.

Measurement of planktonic bacterial production in an oligotrophic lake1

Planktonic heterotrophic bacterial production in Mirror Lake (New Hampshire) was estimated by several different methods. Production ranged between 3 and 8 g C·m−2 yr−1 based on organic C fluxes and the sum of bacterial losses. The close agreement with the estimate of 6.5 ± 1.8 (x̄ ± SE) obtained by the 35SO4 method (in which bacterial S uptake was multiplied by a C:S ratio of 50) supports the validity of using this method in aerobic freshwaters. Only 16% of the total SO4 uptake was due to bacteria as determined by differential filtration with Nuclepore filters. Production was overestimated (20 g C·m−2·yr−1) if bacterial dark CO2‐C uptake (58% of total dark CO2 C uptake) was taken as 6% of heterotrophic bacterial production. Doubling times for heterotrophic planktonic bacteria ranged from 1.2 days (September) to &gt;100 days (February). The annual C flux through planktonic bacteria, including respiration, represented 11–31% of the total autochthonous plus allochthonous organic C inputs to the lake.