Heterotrophic Bacterial Production Research Articles

Drivers of phytoplankton production and community structure in nutrient-poor estuaries receiving terrestrial organic inflow

The influence of nutrient availability and light conditions on phytoplankton size-structure, nutritional strategy and production was studied in a phosphorus-poor estuary in the northern Baltic Sea receiving humic-rich river water. The relative biomass of mixotrophic nanophytoplankton peaked in spring when heterotrophic bacterial production was high, while autotrophic microphytoplankton had their maximum in summer when primary production displayed highest values. Limiting substance (phosphorus) only showed small temporal variations, and the day light was at saturating levels all through the study period. We also investigated if the phytoplankton taxonomic richness influences the production. Structural equation modelling indicated that an increase of the taxonomic richness during the warm summer combined with slightly higher phosphorus concentration lead to increased resource use efficiency, which in turn caused higher phytoplankton biomass and primary production. Our results suggest that climate warming would lead to higher primary production in northerly shallow coastal areas, which are influenced by humic-rich river run-off from un-disturbed terrestrial systems.

DOP Stimulates Heterotrophic Bacterial Production in the Oligotrophic Southeastern Mediterranean Coastal Waters.

Phytoplankton and heterotrophic bacteria rely on a suite of inorganic and organic macronutrients to satisfy their cellular needs. Here, we explored the effect of dissolved inorganic phosphate (PO4) and several dissolved organic molecules containing phosphorus [ATP, glucose-6-phosphate, 2-aminoethylphosphonic acid, collectively referred to as dissolved organic phosphorus (DOP)], on the activity and biomass of autotrophic and heterotrophic microbial populations in the coastal water of the southeastern Mediterranean Sea (SEMS) during summertime. To this end, surface waters were supplemented with PO4, one of the different organic molecules, or PO4 + ATP, and measured the PO4 turnover time (Tt), alkaline phosphatase activity (APA), heterotrophic bacterial production (BP), primary production (PP), and the abundance of the different microbial components. Our results show that PO4 alone does not stimulate any significant change in most of the autotrophic or heterotrophic bacterial variables tested. ATP addition (alone or with PO4) triggers the strongest increase in primary and bacterial productivity or biomass. Heterotrophic bacterial abundance and BP respond faster than phytoplankton (24 h post addition) to the various additions of DOP or PO4 + ATP, followed by a recovery of primary productivity (48 h post addition). These observations suggest that both autotrophic and heterotrophic microbial communities compete for labile organic molecules containing P, such as ATP, to satisfy their cellular needs. It also suggests that SEMS coastal water heterotrophic bacteria are likely C and P co-limited.

Gulf Stream Ring Water Intrusion on the Mid-Atlantic Bight Continental Shelf Break Affects Microbially Driven Carbon Cycling

Warm core, anticyclonic rings that spin off from the Gulf Stream circulate through the region directly offshore of the Mid-Atlantic Bight. If a warm core ring reaches the continental shelf break, its warm, highly saline water may subduct under cooler, fresher continental shelf surface water, resulting in subsurface waters at the shelf break and over the upper continental slope with high temperatures and salinities and distinct physical and chemical properties characteristic of Gulf Stream water. Such intruding water may also have microbial communities with distinct functional capacities, which may in turn affect the rate and nature of carbon cycling in this coastal/shelf environment. However, the functional capabilities of microbial communities within ring intrusion waters relative to surrounding continental shelf waters are largely unexplored. We investigated microbial community capacity to initiate organic matter remineralization by measuring hydrolysis of a suite of polysaccharide, peptide, and glucose substrates along a transect oriented across the Mid-Atlantic Bight shelf, shelf break, and upper slope. At the outermost sampling site, warm and salty water derived from a Gulf Stream warm core ring was present in the lower portion of the water column. This water exhibited hydrolytic capacities distinct from other sampling sites, and exhibited lower heterotrophic bacterial productivity overall. Warm core rings adjacent to the Mid-Atlantic Bight shelf have increased in frequency and duration in recent years. As the influence of warm core rings on the continental shelf and slope increases in the future, the rate and nature of organic matter remineralization on the continental shelf may also shift.

Winter Extratropical Cyclones as a Potential Driver of a Long‐Term Decline of Bacterial Production in the Sargasso Sea Near Bermuda

AbstractAnalysis of plankton data sets from the Bermuda Atlantic Time‐series Study site (31°40′N, 64°10′W) demonstrates a long‐term decreasing trend of marine heterotrophic bacterial production (BP) in winter (November–February) over the past 24 years (1989–2012). We propose winter extratropical cyclones (storms) as a potential driver of the observed BP trend. Stormy winters were characterized by significantly enhanced phytoplankton biomass and productivity as well as organic carbon pools, as storms induce deeper convective mixing and increased nitrate fluxes into upper mixed‐layer. Counter to expectation, BP was lower by 24% due to storm‐mediated entrainment of cold water into upper mixed‐layer. The frequency of storm‐impacted months has increased over time, driven by a decline of the North Atlantic Oscillation (NAO) index. Our findings suggest that a NAO‐induced southward shift of winter storm tracks contributes to the decreasing BP trend, via temperature‐dependent decoupling of bacteria from phytoplankton, ultimately impacting carbon fluxes and cycling near Bermuda.

High Frequency Multi-Year Variability in Baltic Sea Microbial Plankton Stocks and Activities.

Marine bacterioplankton are essential in global nutrient cycling and organic matter turnover. Time-series analyses, often at monthly sampling frequencies, have established the paramount role of abiotic and biotic variables in structuring bacterioplankton communities and productivities. However, fine-scale seasonal microbial activities, and underlying biological principles, are not fully understood. We report results from four consecutive years of high-frequency time-series sampling in the Baltic Proper. Pronounced temporal dynamics in most investigated microbial variables were observed, including bacterial heterotrophic production, plankton biomass, extracellular enzyme activities, substrate uptake rate constants of glucose, pyruvate, acetate, amino acids, and leucine, as well as nutrient limitation bioassays. Spring blooms consisting of diatoms and dinoflagellates were followed by elevated bacterial heterotrophic production and abundances. During summer, bacterial productivity estimates increased even further, coinciding with an initial cyanobacterial bloom in early July. However, bacterial abundances only increased following a second cyanobacterial bloom, peaking in August. Uptake rate constants for the different measured carbon compounds varied seasonally and inter-annually and were highly correlated to bacterial productivity estimates, temperature, and cyanobacterial abundances. Further, we detected nutrient limitation in response to environmental conditions in a multitude of microbial variables, such as elevated productivities in nutrient bioassays, changes in enzymatic activities, or substrate preferences. Variations among biotic variables often occurred on time scales of days to a few weeks, yet often spanning several sampling occasions. Such dynamics might not have been captured by sampling at monthly intervals, as compared to more predictable transitions in abiotic variables such as temperature or nutrient concentrations. Our study indicates that high resolution analyses of microbial biomass and productivity parameters can help out in the development of biogeochemical and food web models disentangling the microbial black box.

Heterotrophic bacterial production measured on soil microaggregates sampled using a Biological Laser Printer

Although routinely measured in aquatic systems over the last 30 years, heterotrophic bacterial production (3H-leucine method) has only more recently been measured in terrestrial ecosystems to elucidate the role of soil biogeochemical processes in global carbon cycles and climate change. Studying bacterial metabolism at the microaggregate scale (100–300 μm) may unmask important microscale biogeochemical relationships amongst bacterial processes and the surrounding soil. Biological laser printer technology was used to sample soil core sections (ca. one mm thick) into ca. 100–300 μm microaggregates. Bacterial production was measured on collections of five microaggregates each (180 samples over 5 cm depth profile) by suspending microaggregates into filtered rainwater with 3H-leucine and incubating for 4 h. Bacterial production varied by over two orders of magnitude amongst groups of five microaggregates collected over the same millimeter scale core slice. Range for all measurements along the core was below detection (0.005) to 897 fg C aggregate d−1. As expected, variability amongst adjacent (within 2 mm of each other) microaggregates groups generally decreased with depth along with the total magnitude of bacterial production rate. Variation in bacterial production at the microaggregate scale was greater than that seen at larger scale (ca. 50 mg; theoretical 3200 microaggregates) sampling of the same core. This is the first demonstration of using a biological laser printer for fine scale sampling of soil core slices and subsequent measurement of bacterial metabolism.

Potential role of oxygen and inorganic nutrients on microbial carbon turnover in the Baltic Sea

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 83:95-108 (2019) - DOI: https://doi.org/10.3354/ame01902 Potential role of oxygen and inorganic nutrients on microbial carbon turnover in the Baltic Sea Marie Maßmig1,*, Judith Piontek1,2, Frédéric A. C. Le Moigne1,3, Carolina Cisternas-Novoa1, Anja Engel1 1GEOMAR Helmholtz Centre for Ocean Research, 24105 Kiel, Germany 2Present address: Leibniz Institute for Baltic Sea Research Warnemünde, 18119 Rostock, Germany 3Present address: Mediterranean Institute of Oceanography, UM 110, Aix Marseille Univ., Université 6 de Toulon, CNRS, IRD, 13288, Marseille, France *Corresponding author: mmassmig@geomar.de ABSTRACT: Oxygen (O2) deficiency and nutrient concentrations in marine systems are impacting organisms from microbes to higher trophic levels. In coastal and enclosed seas, O2 deficiency is often related to eutrophication and high degradation rates of organic matter. To investigate the impact of O2 concentration on bacterial growth and the turnover of organic matter, we conducted multifactorial batch experiments with natural microbial communities of the central Baltic Sea. Water was collected from suboxic (<5 µmol l-1) depths in the Gotland Basin during June 2015. Samples were kept for 4 d under fully oxygenated and low O2 conditions (mean: 34 µmol l-1 O2), with or without nutrient (ammonium, phosphate and nitrate) and labile carbon (glucose) amendments. We measured bacterial abundance, bacterial heterotrophic production, extracellular enzyme rates (leucine-aminopeptidase) and changes in dissolved and particulate organic carbon concentrations. Our results show that the bacterial turnover of organic matter was limited by nutrients under both oxic and low O2 conditions. In nutrient- and glucose-replete treatments, low O2 concentrations significantly reduced the net uptake of dissolved organic carbon and led to greater accumulation of more labile dissolved organic matter. Our results therewith suggest that the combined effects of eutrophication and deoxygenation on heterotrophic bacterial activity might favor the accumulation of dissolved organic carbon in the Baltic Sea. KEY WORDS: Oxygen · Heterotrophic bacteria · Baltic Sea · Organic matter · Bacterial heterotrophic production · Extracellular enzymes · Leucine-aminopeptidase Full text in pdf format Supplementary material PreviousCite this article as: Maßmig M, Piontek J, Le Moigne FAC, Cisternas-Novoa C, Engel A (2019) Potential role of oxygen and inorganic nutrients on microbial carbon turnover in the Baltic Sea. Aquat Microb Ecol 83:95-108. https://doi.org/10.3354/ame01902 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 83, No. 1. Online publication date: June 06, 2019 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2019 Inter-Research.

Microbial metabolism of methanol and methylamine in the Gulf of Mexico: insight into marine carbon and nitrogen cycling.

One carbon (C1) metabolism plays an important role in marine carbon cycling but the dynamics and modes of C1 transformations are not fully understood. We made contemporaneous measurements of methylamine and methanol metabolism to elucidate the role of C1 compounds as sources of carbon, energy and nitrogen. Methanol and methylamine were predominantly used as an energy source in offshore waters (oxidation rate constant: kmethanol : 0.02-0.10 day-1 ; kmethylamine : 0.01-0.18 day-1 ), but were also important sources of biomass carbon in coastal waters (assimilation rate constant: kmethanol : 0.04-0.10 day-1 ; kmethylamine : 0.01-0.05 day-1 ). The relative extent of assimilation versus oxidation for these substrates correlated positively with chlorophyll, nutrients and heterotrophic bacterial production. Methanol oxidation and assimilation were stimulated significantly by nutrient addition. In contrast, methylamine metabolism was inhibited by ammonium or nitrate, suggesting that methylamine served as a nitrogen source. A preliminary metagenomic survey revealed a diverse population of putative C1-utilizing microorganisms. These results show that the remineralization of methylamine could provide both C and N sources for microbes. Both methanol and methylamine contribute to microbial energetic and carbon substrate demands with a distinctly different signature in nearshore versus offshore environments.

The effect of resource quality on the growth of Holothuria scabra during aquaculture waste bioremediation

Reducing dependency on environmentally unsustainable formulated feeds, most of which include limited reserves of fishmeal as a protein source, is a priority for the aquaculture industry, particularly for intensive culture systems. One approach is to increase nitrogen reuse within the system by feeding nitrogen-rich aquaculture effluent to deposit feeders, thereby closing the aquaculture nitrogen-loop. This study, for the first time and on a laboratory-scale, has reared juveniles of the sea cucumber Holothuria scabra at high densities solely on particulate organic waste from a commercial-scale land-based abalone recirculating aquaculture system. Furthermore, growth rates and biomass yields were increased significantly by adjusting the effluent C:N from 5:1 to 20:1 by adding exogenous organic carbon sources (glucose, starch and cellulose), so fuelling accelerated heterotrophic bacterial production within the redox-stratified tank sediment. Sea cucumber juveniles reared solely on effluent had a biomass density of 711 g m−2 after four months whereas animals reared on starch-amended effluent (the best performing treatment) had a final density of 1011 g m−2. Further optimisation of this approach could increase biomass yields and pave the way for the commercial cultivation of deposit feeding animals on waste streams, thus contributing to more environmentally sustainable aquaculture. Here, the nitrogen that originated from fishmeal is not lost through the discharge of aquaculture effluent; rather, it is immobilised into single cell biomass that is up-cycled into high-value secondary biomass. We demonstrate that sea cucumbers can be produced at high density through the manipulation of the C:N ratio of aquaculture effluent.

Basin-scale variability of microbial methanol uptake in the Atlantic Ocean

Abstract. Methanol is a climate-active gas and the most abundant oxygenated volatile organic compound (OVOC) in the atmosphere and seawater. Marine methylotrophs are aerobic bacteria that utilise methanol from seawater as a source of carbon (assimilation) and/or energy (dissimilation). A few spatially limited studies have previously reported methanol oxidation rates in seawater; however, the basin-wide ubiquity of marine microbial methanol utilisation remains unknown. This study uniquely combines seawater 14C labelled methanol tracer studies with 16S rRNA pyrosequencing to investigate variability in microbial methanol dissimilation and known methanol-utilising bacteria throughout a meridional transect of the Atlantic Ocean between 47° N to 39° S. Microbial methanol dissimilation varied between 0.05 and 1.68 nmol L−1 h−1 in the top 200 m of the Atlantic Ocean and showed significant variability between biogeochemical provinces. The highest rates of methanol dissimilation were found in the northern subtropical gyre (average 0.99±0.41 nmol L−1 h−1), which were up to 8 times greater than other Atlantic regions. Microbial methanol dissimilation rates displayed a significant inverse correlation with heterotrophic bacterial production (determined using 3H-leucine). Despite significant depth stratification of bacterial communities, methanol dissimilation rates showed much greater variability between oceanic provinces compared to depth. There were no significant differences in rates between samples collected under light and dark environmental conditions. The variability in the numbers of SAR11 (16S rRNA gene sequences) were estimated to explain approximately 50 % of the changes in microbial methanol dissimilation rates. We estimate that SAR11 cells in the Atlantic Ocean account for between 0.3 % and 59 % of the rates of methanol dissimilation in Atlantic waters, compared to &lt; 0.01 %–2.3 % for temperate coastal waters. These results make a substantial contribution to our current knowledge and understanding of the utilisation of methanol by marine microbial communities, but highlight the lack of understanding of in situ methanol production mechanisms.

Identifying labile DOM components in a coastal ocean through depleted bacterial transcripts and chemical signals.

Understanding which compounds comprising the complex and dynamic marine dissolved organic matter (DOM) pool are important in supporting heterotrophic bacterial production remains a major challenge. We eliminated sources of labile phytoplankton products, advected terrestrial material and photodegradation products to coastal microbial communities by enclosing water samples in situ for 24 h in the dark. Bacterial genes for which expression decreased between the beginning and end of the incubation and chemical formulae that were depleted over this same time frame were used as indicators of bioavailable compounds, an approach that avoids augmenting or modifying the natural DOM pool. Transport- and metabolism-related genes whose relative expression decreased implicated osmolytes, carboxylic acids, fatty acids, sugars and organic sulfur compounds as candidate bioreactive molecules. FT-ICR MS analysis of depleted molecular formulae implicated functional groups ~ 30-40 Da in size cleaved from semi-polar components of DOM as bioreactive components. Both gene expression and FT-ICR MS analyses indicated higher lability of compounds with sulfur and nitrogen heteroatoms. Untargeted methodologies able to integrate biological and chemical perspectives can be effective strategies for characterizing the labile microbial metabolites participating in carbon flux.

Influence of allochthonous dissolved organic matter on pelagic basal production in a northerly estuary

Phytoplankton and heterotrophic bacteria are key groups at the base of aquatic food webs. In estuaries receiving riverine water with a high content of coloured allochthonous dissolved organic matter (ADOM), phytoplankton primary production may be reduced, while bacterial production is favoured. We tested this hypothesis by performing a field study in a northerly estuary receiving nutrient-poor, ADOM-rich riverine water, and analyzing results using multivariate statistics. Throughout the productive season, and especially during the spring river flush, the production and growth rate of heterotrophic bacteria were stimulated by the riverine inflow of dissolved organic carbon (DOC). In contrast, primary production and photosynthetic efficiency (i.e. phytoplankton growth rate) were negatively affected by DOC. Primary production related positively to phosphorus, which is the limiting nutrient in the area. In the upper estuary where DOC concentrations were the highest, the heterotrophic bacterial production constituted almost 100% of the basal production (sum of primary and bacterial production) during spring, while during summer the primary and bacterial production were approximately equal. Our study shows that riverine DOC had a strong negative influence on coastal phytoplankton production, likely due to light attenuation. On the other hand DOC showed a positive influence on bacterial production since it represents a supplementary food source. Thus, in boreal regions where climate change will cause increased river inflow to coastal waters, the balance between phytoplankton and bacterial production is likely to be changed, favouring bacteria. The pelagic food web structure and overall productivity will in turn be altered.

Large Plankton Enhance Heterotrophy Under Experimental Warming in a Temperate Coastal Ecosystem

Microbes are key players in oceanic carbon fluxes. Temperate ecosystems are seasonally variable and thus suitable for testing the effect of warming on microbial carbon fluxes at contrasting oceanographic conditions. In four experiments conducted in February, April, August and October 2013 in coastal NE Atlantic waters, we monitored microbial plankton stocks and daily rates of primary production, bacterial heterotrophic production and respiration at in situ temperature and at 2 and 4°C over ambient values during 4-day incubations. Ambient total primary production (TPP) exceeded total community respiration (< 200 µm, TR) in winter and fall but not in spring and summer. The bacterial contribution to ecosystem carbon fluxes was low, with bacterial production representing on average 6.9 ± 3.2% of TPP and bacterial respiration (between 0.8 and 0.2 µm) contributing on average 35 ± 7% to TR. Warming did not result in a uniform increase in the variables considered, and most significant effects were found only for the 4°C increase. In the summer and fall experiments, under warm and nutrient-deficient conditions, the net TPP/TR ratio decreased by 39 and 34% in the 4°C treatment, mainly due to the increase in respiration of large organisms rather than bacteria. Our results indicate that the interaction of temperature and substrate availability in determining microbial carbon fluxes has a strong seasonal component in temperate planktonic ecosystems, with temperature having a more pronounced effect and generating a shift toward net heterotrophy under more oligotrophic conditions as found in summer and early fall.

Coastal Bacterioplankton Metabolism Is Stimulated Stronger by Anthropogenic Aerosols than Saharan Dust.

In oligotrophic regions, such as the Mediterranean Sea, atmospheric deposition has the potential to stimulate heterotrophic prokaryote growth and production in surface waters, especially during the summer stratification period. Previous studies focused on the role of leaching nutrients from mineral particles of Saharan (S) origin, and were restricted to single locations at given times of the year. In this study, we evaluate the effect of atmospheric particles from diverse sources and with a markedly different chemical composition [S dust and anthropogenic (A) aerosols] on marine planktonic communities from three locations of the northwestern Mediterranean with contrasted anthropogenic footprint. Experiments were also carried out at different times of the year, considering diverse initial conditions. We followed the dynamics of the heterotrophic community and a range of biogeochemical and physiological parameters in six experiments. While the effect of aerosols on bacterial abundance was overall low, bacterial heterotrophic production was up to 3.3 and 2.1 times higher in the samples amended with A and S aerosols, respectively, than in the controls. Extracellular enzymatic activities [leu-aminopeptidase (AMA) and β-glucosidase (β-Gl)] were also enhanced with aerosols, especially from A origin. AMA and β-Gl increased up to 7.1 in the samples amended with A aerosols, and up to 1.7 and 2.1 times, respectively, with S dust. The larger stimulation observed with A aerosols might be attributed to their higher content in nitrate. However, the response was variable depending the initial status of the seawater. In addition, we found that both A and S aerosols stimulated bacterial abundance and metabolism significantly more in the absence of competitors and predators.

Temporal Variability of Dark Carbon Fixation and Bacterial Production and Their Relation with Environmental Factors in a Tropical Estuarine System

Dark carbon fixation (DCF) is considered an important energy source in aquatic environments, although it has been neglected for a long time. DCF is known to be relevant in ecosystems associated with redoxclines, shallow-water sulfide-rich habitats, deep-sea vents, cold seeps, and even in coastal waters associated with upwelling events. The aim of this study was to evaluate the relative importance of DCF in relation to heterotrophic bacterial production (BP), as well as how these rates affect each other, and how they are influenced by the environmental factors. This study was conducted monthly during 2 years in a tropical eutrophic bay (Guanabara Bay), where two stations were sampled and compared. DCF and BP were measured by 14C-bicarbonate and 3H-leucine incorporation, respectively, and incubations in the dark. Our results showed that DCF is not a quantitatively relevant process in this estuarine system, when compared to heterotrophic BP, and possibly occurred via anaplerotic reactions. Relatively higher DCF rates were associated with less oxygenated waters at the more polluted station and during the wet summer-spring, when the water column is more stratified. BP rates presented clear spatial patterns, according to pollution and depth gradients, with higher rates in more polluted areas, and also at surface waters. The hydrodynamics combined with other environmental conditions (precipitation, temperature, dissolved organic carbon, and nutrients) may control the distribution of DCF and BP over space and time. The allochthonous inputs of organic matter are more important than DCF-derived organic carbon to bacterioplankton in this polluted and eutrophic bay, where the heterotrophic metabolism prevails.

Heterotrophic bacterial production, respiration, and growth efficiency associated with upwelling intensity in the Ulleung Basin, East Sea

We investigated bacterial production (BP) and respiration (BR), as well as the physico-chemical properties of the water column, to elucidate the effect of upwelling on heterotrophic bacterial metabolic activities and growth efficiency (BGE) in July 2012 and May 2013 in the Ulleung Basin (UB), East/Japan Sea. The upwelled conditions were characterized by higher chlorophyll-a (Chl-a) concentrations resulting from the upward shift of the nitracline compared to that of the non-upwelled condition. Analyses of the size fractions of Chl-a and pigment composition revealed that large size phytoplankton (> 20µm), mainly consisting of diatoms, appeared to be the major phytoplankton component. BP and BR were significantly correlated with Chl-a (P < 0.001), but the correlations with temperature were not significant (P > 0.05). These results suggest that bacterial metabolic activities are stimulated by the availability of organic resources enhanced by upwelling in the UB. Further statistical analysis showed that the difference in BP and BGE with variations in upwelling intensity were significant (P = 0.018 for BP, P = 0.035 for BGE), but the difference in BR was not significant (P = 0.321). These results suggest that metabolic energy is partitioned more for BP under a strong upwelling condition, i.e. high nutrient and Chl-a conditions. In contrast, the energy generated via respiration was partitioned more for maintaining metabolism rather than for biomass production under weakly or non-upwelled conditions, i.e. stratified and low Chl-a conditions. Overall, our results suggest that any changes in upwelling intensity would significantly affect the carbon cycle associated with the fate of primary production, and the role of the microbial loop in the UB where changes in the intensity and frequency of upwelling associated with climatic changes are in progress.

Epiphytic bacteria make an important contribution to heterotrophic bacterial production in a humic boreal lake

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 79:247-257 (2017) - DOI: https://doi.org/10.3354/ame01835 Epiphytic bacteria make an important contribution to heterotrophic bacterial production in a humic boreal lake Jussi Vesterinen1,*, Shawn P. Devlin1,2, Jari Syväranta1,3, Roger I. Jones1 1University of Jyväskylä, Department of Biological and Environmental Science, PO Box 35, 40014 University of Jyväskylä, Finland 2Flathead Lake Biological Station, University of Montana, Polson, MT 59860, USA 3University of Eastern Finland, Department of Environmental and Biological Sciences, PO Box 111, 80101 Joensuu, Finland *Corresponding author: jussi.p.vesterinen@jyu.fi ABSTRACT: Bacterial production (BP) in lakes has generally only been measured in the pelagic zone without accounting for littoral BP, and studies of BP at the whole-lake scale are very scarce. In the dystrophic humic lakes, which are common throughout the boreal region, low light penetration through water has been assumed to seriously limit available habitats for littoral organisms. However, many highly humic boreal lakes have extensive partly submerged vegetation around the lake perimeter which can provide well-lit substrata for highly productive epiphyton. We measured epiphytic BP on the littoral vegetation and pelagic BP in a small highly humic boreal lake in Finland during an open-water season and extrapolated the BP rates to the whole lake. Pelagic BP dominated the combined BP over the study period, but the epiphytic BP contributed an average of 24% to overall BP over the sampling period and was almost equal to pelagic BP in July. According to these results, a substantial component of BP has been previously overlooked in the lake when BP has been measured only from the pelagic. Our study demonstrates that the role of the littoral zone in BP in highly humic lakes has previously been understated, and needs to be taken into account in assessments of whole-lake carbon cycling and metabolism. KEY WORDS: Littoral · Periphyton · Pelagic · Autotrophic · Heterotrophic Full text in pdf format PreviousNextCite this article as: Vesterinen J, Devlin SP, Syväranta J, Jones RI (2017) Epiphytic bacteria make an important contribution to heterotrophic bacterial production in a humic boreal lake. Aquat Microb Ecol 79:247-257. https://doi.org/10.3354/ame01835 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 79, No. 3. Online publication date: July 05, 2017 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2017 Inter-Research.

Quantity and quality of particulate organic matter controls bacterial production in the Columbia River estuary

AbstractEstuaries function as “bioreactors” for fluvial materials in which microbial, biogeochemical, and ecological processes transform organic matter and nutrients prior to export to coastal oceans. The impact of estuarine bioreactors is linked to the bioavailability and residence time of fluvial material, and to rates of microbial activity. In the Columbia River estuary, water residence time is short (approximately 2 d), but particle residence time is extended by estuarine turbidity maxima (ETM). To investigate relationships between organic matter and microbial activity, samples were collected in spring and fall 2012 and summer 2013, and ETM particles were fractionated by settling velocity using an Owen‐style settling column. Data were also analyzed from 16 other sampling campaigns conducted in 1990–2009. The composition of suspended particulate matter shifted seasonally following the spring freshet and river phytoplankton bloom with decreasing organic content, increasing C/N ratio, and an increasing contribution of autochthonous particulate organic matter (POM) produced in four shallow lateral bays (based on del‐PO13C and pigment ratios). Heterotrophic bacterial production responded to seasonal changes in POM and correlated most strongly with estimates of labile particulate nitrogen during any particular season, and with the riverine flux of chlorophyll a (Chl a) across all seasons. Regression models suggest that labile particulate nitrogen and bacterial production can be predicted from sensor‐based measurements including turbidity, salinity, and temperature in the estuary and Chl a in the river. These results demonstrate that heterotrophic activity in the Columbia River estuary is controlled by POM lability, and by the degree to which ETM retain and concentrate POM.

Solar UVR sensitivity of phyto- and bacterioplankton communities from Patagonian coastal waters under increased nutrients and acidification

The effects of ultraviolet radiation (UVR) under future expected conditions of acidification and increase in nutrient inputs were studied on a post-bloom phytoplankton and bacterioplankton community of Patagonian coastal waters. We performed an experiment using microcosms where two environmental conditions were mimicked using a cluster approach: present (ambient nutrients and pH) and future (increased nutrients and acidification), and acclimating the samples for five days to two radiation treatments (full solar radiation [+UVR] and exclusion of UVR [–UVR]). We evaluated the short-term (hours) sensitivity of the community to solar UVR through chlorophyll a fluorescence parameters (e.g. the effective photochemical quantum yield of PSII [ΦPSII]) at the beginning, at the mid-point and at the end of the acclimation period. Primary production and heterotrophic bacterial production (HBP) were determined, and biological weighting functions were calculated, at the beginning and at the end of the acclimation period. Mid-term effects (days) were evaluated as changes in taxonomic composition, growth rates and size structure of the community. Although the UVR-induced inhibition on ΦPSII decreased in both clusters, samples remained sensitive to UVR after the 5 days of acclimation. Also, under the future conditions, there was, in general, an increase in the phytoplankton carbon incorporation rates along the experiment as compared to the present conditions. Bacterioplankton sensitivity to UVR changed along the experiment from inhibition to enhancement of HBP, and future environmental conditions stimulated bacterial growth, probably due to indirect effects caused by phytoplankton. Those changes in the microbial loop functioning and structure under future global change conditions might have important consequences for the carbon pump and thus for the carbon sequestration and trophodynamics of Patagonian coastal waters.

Coupled Response of Bacterial Production to a Wind-Induced Fall Phytoplankton Bloom and Sediment Resuspension in the Chukchi Sea Shelf, Western Arctic Ocean

Heterotrophic bacterial abundance and production, dissolved free amino acid (DFAA) and dissolved combined amino acid (DCAA) concentrations, and other microbial parameters were determined for seawater samples collected at a fixed station (maximum water depth, 56 m) deployed on the Chukchi Sea Shelf, in the western Arctic Ocean, during a 16-day period in September 2013. During the investigation period, the sampling station experienced strong winds and a subsequent phytoplankton bloom, which was thought to be triggered by enhanced vertical mixing and upward nutrient fluxes. In this study, we investigated whether bacterial and dissolved amino acid parameters changed in response to these physical and biogeochemical events. Bacterial abundance and production in the upper layer increased with increasing chlorophyll a concentration, despite a concomitant decrease in seawater temperature from 3.2°C to 1.5°C. The percentage of bacteria with high nucleic acid content during the bloom was significantly higher than that during the prebloom period. The ratio of the depth-integrated (0–20 m) bacterial production to primary production differed little between the prebloom and bloom period, with an overall average value of 0.14 ± 0.03 (± standard deviation, n = 8). DFAA and DCAA concentrations varied over a limited range throughout the investigation, indicating that the supply and consumption of labile dissolved amino acids were balanced. These results indicate that there was a tightly coupled, large flow of organic carbon from primary producers to heterotrophic bacteria during the fall bloom. Our data also revealed that bacterial production and abundance were high in the bottom nepheloid (low transmittance) layer during strong wind events, which was associated with sediment resuspension due to turbulence near the seafloor. The impacts of fall wind events, which are predicted to become more prominent with the extension of the ice-free period, on bacterial processes and the dynamics of organic matter in the Chukchi Sea Shelf could have far-reaching influences on biogeochemical cycles and ecosystem dynamics in broader regions of the Arctic Ocean.