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1.
Simultaneous consumption and production of fluorescent dissolved organic matter by lake bacterioplankton 总被引:1,自引:0,他引:1
Recent evidence suggests a key role of bacterioplankton in shaping the composition of the dissolved organic matter (DOM) pool in aquatic systems, not only through consumption but also through production of specific compounds, but the latter process is still not well understood. We used a bioassay approach to assess the patterns in bacterial production and consumption of five fluorescent DOM pools in seven lakes and two streams in Southeastern Québec, Canada, and the links these patterns may have with key aspects of bacterial metabolism, DOM origin and nutrients availability. Total dissolved organic C declined by 3-15% during these incubations, whereas the specific DOM pools had very different dynamics: Two humic-like fractions accumulated in all incubations, with rates of production increasing as a function of bacterial growth efficiency, which itself increased with phosphorus concentrations. In contrast, two protein-like fractions and a third humic-like fraction either increased or declined over the course of the experiments. The net production or consumption of these pools appeared to be a function of the contribution of terrestrial C to bulk DOM (derived from δ(13) C of the DOM) and of total bacterial activity. Our results suggest that lake bacterioplankton play a dual role in DOM dynamics, as consumers and also producers, and that the interplay between DOM origin and nutrient availability appears to determine the net outcome of bacterial DOM processing, thus influencing the bulk DOM composition and its fate in these aquatic systems. 相似文献
2.
Contrasting effects of solar UV radiation on dissolved organic sources for bacterial growth 总被引:11,自引:0,他引:11
The photochemical transformation of dissolved organic matter (DOM) in lakes and oceans has been shown to either reduce or enhance bacterial utilization. We compared the effects of UV radiation on the bacterial use of DOM in a wide range of lakes. Although complex DOM was converted in all irradiated samples into carboxylic acids that are readily utilized by bacteria, irradiation in several lakes resulted in a decreased ability of DOM to support bacterial growth. The effect of irradiation on the ability of DOM to promote bacterial growth was a positive function of the terrestrial humic matter, and a negative function of indigenous algal production. We suggest that the net effect of irradiation is a result of counteracting but concurrent processes rendering DOM either labile or recalcitrant. Humic DOM is predominantly transformed into forms of increased lability, whereas photochemical transformation into compounds of decreased bacterial substrate quality dominates in algal-derived DOM. Hence, solar-induced photochemical reactions interact with microbial degraders in different ways, depending on the origin and nature of the organic matter, affecting the transfer of energy within aquatic food webs, as well as the degradation and preservation of detrital organic matter, in different directions. 相似文献
3.
Farjalla VF Marinho CC Faria BM Amado AM Esteves Fde A Bozelli RL Giroldo D 《Microbial ecology》2009,57(4):657-666
The main goal of this research was to evaluate whether the mixture of fresh labile dissolved organic matter (DOM) and accumulated
refractory DOM influences bacterial production, respiration, and growth efficiency (BGE) in aquatic ecosystems. Bacterial
batch cultures were set up using DOM leached from aquatic macrophytes as the fresh DOM pool and DOM accumulated from a tropical
humic lagoon. Two sets of experiments were performed and bacterial growth was followed in cultures composed of each carbon
substrate (first experiment) and by carbon substrates combined (second experiment), with and without the addition of nitrogen
and phosphorus. In both experiments, bacterial production, respiration, and BGE were always higher in cultures with N and
P additions, indicating a consistent inorganic nutrient limitation. Bacterial production, respiration, and BGE were higher
in cultures set up with leachate DOM than in cultures set up with humic DOM, indicating that the quality of the organic matter
pool influenced the bacterial growth. Bacterial production and respiration were higher in the mixture of substrates (second
experiment) than expected by bacterial production and respiration in single substrate cultures (first experiment). We suggest
that the differences in the concentration of some compounds between DOM sources, the co-metabolism on carbon compound decomposition,
and the higher diversity of molecules possibly support a greater bacterial diversity which might explain the higher bacterial
growth observed. Finally, our results indicate that the mixture of fresh labile and accumulated refractory DOM that naturally
occurs in aquatic ecosystems could accelerate the bacterial growth and bacterial DOM removal. 相似文献
4.
Rafael D. Guariento Luciana S. Carneiro Adriano Caliman Reinaldo Luiz Bozelli Francisco A. Esteves 《Aquatic Ecology》2011,45(4):561-569
This study examines how nutrients and light affect the relationship between autotrophic biomass and non-autotrophic periphyton
organic matter in a tropical black water lake biofilm community. We hypothesized that there is no positive correlation between
autotrophic and non-autotrophic organic matter in the periphytic community of a black water humic lake, where non-algal components
of periphyton can rely on carbon sources external to the periphyton matrix and where nutrient availability is low. Second,
we sought to test our hypothesis that non-autotrophic periphyton organic matter will benefit from nutrient enhancement in
a lake where the availability of DOC is high. We performed a field experiment using in situ lake mesocosms to manipulate nutrient
concentrations and light availability in a 2 × 2 factorial design. Control treatments (no nutrient added) and nutrient treatments
(N + P) were compared in different light conditions: high light (near surface water) and low light (near bottom). No positive
correlation was found between autotrophic biomass and non-autotrophic periphyton organic matter, but a negative correlation
was observed in high nutrient and light conditions. The low C:P and N:P ratios revealed that the non-autotrophic organic matter
mostly comprised a heterotrophic microbial biofilm. High levels of light and nutrients together caused significant changes
in periphyton community properties. The non-autotrophic periphyton organic matter was negatively affected by nutrient addition,
whereas autotrophic biomass was positively affected, especially in high light conditions. Our results strongly suggest that
non-autotrophic periphyton organic matter in a humic lake is primarily comprised of a bacterial biofilm that directly competes
for nutrients with autotrophs in the periphytic community. We also observed no effect of nutrient addition on periphyton growing
in light-limited conditions. These results suggest that heterotrophic periphytic organisms might experience carbon limitation
despite the high availability, but usually low quality, of dissolved carbon in the water column of humic lakes. 相似文献
5.
1. Ultraviolet radiation (UV) is an important stressor for zooplankton in alpine lake ecosystems. Multiple environmental variables such as dissolved organic matter (DOM), temperature and nutrient availability may alter how UV affects zooplankton. 2. We conducted a week‐long experiment manipulating UV, nutrients and DOM in enclosures suspended at the surface of cold and warm alpine lakes to determine the interactive effects of these variables on ovigerous Leptodiaptomus ashlandi (Marsh, 1893), a calanoid copepod. 3. UV had a negative effect on nauplii and gravid females at the colder temperature and at low, ambient DOM levels, but had no effect at the warmer temperature or when DOM was added. At the warmer temperature, fewer nauplii were produced in the +nutrient compared to ?nutrient treatment. Adult survival was not affected by UV or any other experimental variable. 4. These results demonstrate that the extent of the impact of UV radiation on zooplankton in alpine systems is altered by other environmental variables, and that these effects may not be apparent from experiments that look only at the survival of adult organisms that are better defended against UV. 相似文献
6.
In high-nutrient low-chlorophyll areas, bacterial degradation of organic matter may be iron-limited. The response of heterotrophic
bacteria to Fe addition may be directly controlled by Fe availability and/or indirectly controlled through the effect of enhanced
phytoplankton productivity and the subsequent supply of organic matter suitable for bacteria. In the present study, the role
of Fe on bacterial carbon degradation was investigated through regrowth experiments by monitoring bacterial response to organic
substrates derived from Phaeocystis antarctica cultures set up in <1 nM Fe (LFe) and in Fe-amended (HFe) Antarctic seawater. Results showed an impact of Fe addition on
the morphotype dominance (colonies vs. single cells) of P. antarctica and on the quality of Phaeocystis-derived organic matter. Fe addition leaded to a decrease of C/N ratio of Phaeocystis material. The bacterial community composition was modified as observed from denaturing gradient gel electrophoresis (DGGE)
profiles in LFe as compared to HFe bioassays. The percentage of active bacteria as well as their specific metabolic activities
(ectoenzymatic hydrolysis, growth rates and bacterial growth efficiency) were enhanced in HFe bioassays. As a consequence,
the lability of Phaeocystis-derived organic matter was altered, i.e., after seven days more than 90% was degraded in HFe and only 9% (dissolved) and
55% (total) organic carbon were degraded in LFe bioassays. By inducing increased bacterial degradation and preventing the
accumulation of dissolved organic carbon, the positive effect of Fe supply on the carbon biological pump may partly be counteracted. 相似文献
7.
IVAN J. FERNANDEZ STEPHEN A. NORTON TSUTOMU OHNO H. MAURICE VALETT KEVIN S. SIMON 《Freshwater Biology》2013,58(2):248-260
1. Chronic nitrogen (N) deposition may alter the bioavailability of dissolved organic matter (DOM) in streams by multiple pathways. Elevated N deposition may alter the nutrient stoichiometry of DOM as well as nutrient availability in stream water. 2. We evaluated the influence of a decadal‐scale experimental N enrichment on the relative importance of DOM nutrient content and inorganic nutrient availability on the bioavailability of DOM. We measured the consumption of dissolved organic carbon (DOC) and changes in nutrient concentration, DOM components and enzyme activity in a bottle incubation assay with different DOM and nutrient treatments. To evaluate the effect of DOM stoichiometry, we used leaf leachates of different carbon/N/phosphorus (C : N :P) ratio, made from leaf litter sourced in the reference and N‐enriched catchments at the Bear Brook Watershed in Maine (BBWM). We also manipulated the concentration of inorganic N and P to compare the effect of nutrient enrichment with DOM stoichiometry. 3. DOC from the N‐enriched catchment was consumed 14% faster than that from the reference catchment. However, mean DOC consumption for both leachates was more than doubled by the simultaneous addition of N and P, compared to controls, while the addition of N or P alone increased consumption by 42 and 23%, respectively. The effect of N and/or P enrichment consistently had a greater effect than DOM source for all response variables considered. 4. We subsequently conducted DOC uptake measurements using leaf leachate addition under ambient and elevated N and P in the streams draining the reference and N‐enriched catchments at BBWM. In both streams, DOC uptake lengths were shorter when N and P were elevated. 5. Although both DOM stoichiometry and inorganic nutrient availability affect DOM bioavailability, N and P co‐limitation appears to be the dominant driver of reach‐scale processing of DOM. 相似文献
8.
Ziliang Li Weijie Xu Luyao Kang Yakov Kuzyakov Leiyi Chen Mei He Futing Liu Dianye Zhang Wei Zhou Xuning Liu Yuanhe Yang 《Global Change Biology》2023,29(22):6367-6382
Mineralization of dissolved organic matter (DOM) in thermokarst lakes plays a non-negligible role in the permafrost carbon (C) cycle, but remains poorly understood due to its complex interactions with external C and nutrient inputs (i.e., aquatic priming and nutrient effects). Based on large-scale lake sampling and laboratory incubations, in combination with 13C-stable-isotope labeling, optical spectroscopy, and high-throughput sequencing, we examined large-scale patterns and dominant drivers of priming and nutrient effects of DOM biodegradation across 30 thermokarst lakes along a 1100-km transect on the Tibetan Plateau. We observed that labile C and phosphorus (P) rather than nitrogen (N) inputs stimulated DOM biodegradation, with the priming and P effects being 172% and 451% over unamended control, respectively. We also detected significant interactive effects of labile C and nutrient supply on DOM biodegradation, with the combined labile C and nutrient additions inducing stronger microbial mineralization than C or nutrient treatment alone, illustrating that microbial activity in alpine thermokarst lakes is co-limited by both C and nutrients. We further found that the aquatic priming was mainly driven by DOM quality, with the priming intensity increasing with DOM recalcitrance, reflecting the limitation of external C as energy sources for microbial activity. Greater priming intensity was also associated with higher community-level ribosomal RNA gene operon (rrn) copy number and bacterial diversity as well as increased background soluble reactive P concentration. In contrast, the P effect decreased with DOM recalcitrance as well as with background soluble reactive P and ammonium concentrations, revealing the declining importance of P availability in mediating DOM biodegradation with enhanced C limitation but reduced nutrient limitation. Overall, the stimulation of external C and P inputs on DOM biodegradation in thermokarst lakes would amplify C-climate feedback in this alpine permafrost region. 相似文献
9.
Tadonléké RD 《FEMS microbiology ecology》2007,59(3):543-555
Dilution-regrowth experiments coupled to fluorescence in situ hybridization were conducted with samples from two humic reservoirs in order to examine how inorganic nutrients (N, P) affect free-living bacterioplankton phylogenetic groups and subsequently the quality of dissolved organic matter (DOM). The experiments were complemented by analyses of the empirical relationships between the targeted bacteria, nutrients, DOM and grazers. The ratio of absorbance of waters (A) at 250 and 365 nm (A(250 nm):A(365 nm)), which has been found to increase with the proportion of small molecules in the DOM pool in other humic waters, was used as an index of DOM quality. When nutrient stimulated bacteria, both the responses of bacterial groups (in the absence of grazers) and the ratio A(250 nm):A(365 nm) were generally different between treatments (+N, +P, +NP), suggesting that in nutrient-poor systems, differences in the type of inorganic nutrient supply will ultimately cause differences in DOM quality. The ratio A(250 nm),:A(365 nm) peaked in the +N treatments where members of the Planctomycetes (PLA) were the most stimulated group, and across treatments, PLA best explained (positive relationship) variations in this ratio. Consistent with this, the in situ data showed that the removal of the negative effects of flagellates on PLA yielded the highest R(2) in attempts to use bacterial groups to explain variations in A(250 nm):A(365 nm). These findings provide lines of evidence, not previously demonstrated in natural waters, that Planctomycetes may be an important factor changing the DOM quality, particularly in nutrient-poor systems when supplied with inorganic N. 相似文献
10.
Interactions of Photobleaching and Inorganic Nutrients in Determining Bacterial Growth on Colored Dissolved Organic Carbon 总被引:8,自引:0,他引:8
Abstract Bacteria are key organisms in the processing of dissolved organic carbon (DOC) in aquatic ecosystems. Their growth depends on both organic substrates and inorganic nutrients. The importance of allochthonous DOC, usually highly colored, as bacterial substrate can be modified by photobleaching. In this study, we examined how colored DOC (CDOC) photobleaching, and phosphorus (P) and nitrogen (N) availability, affect bacterial growth. Five experiments were conducted, manipulating nutrients (P and N) and sunlight exposure. In almost every case, nutrient additions had a significant, positive effect on bacterial abundance, production, and growth efficiency. Sunlight exposure (CDOC photobleaching) had a significant, positive effect on bacterial abundance and growth efficiency. We also found a significant, positive interaction between these two factors. Thus, bacterial use of CDOC was accelerated under sunlight exposure and enhanced P and N concentrations. In addition, the accumulation of cells in sunlight treatments was dependent on nutrient availability. More photobleached substrate was converted into bacterial cells in P- and N-enriched treatments. These results suggest nutrient availability may affect the biologically-mediated fate (new biomass vs respiration) of CDOC. 相似文献
11.
Organic carbon and mineral nutrient limitation of oxygen consumption, bacterial growth and efficiency in the Norwegian Sea 总被引:1,自引:0,他引:1
To evaluate the role of bacteria in the transformation of organic matter in subarctic waters, we investigated the effect of
mineral nutrients (ammonia and phosphate) and organic carbon (glucose) enrichment on heterotrophic bacterial processes and
community structure. Eight experiments were done in the Norwegian Sea during May and June 2008. The growth-limiting factor
(carbon or mineral nutrient) for heterotrophic bacteria was inferred from the combination of nutrient additions that stimulated
highest bacterial oxygen consumption, biomass, production, growth rate and bacterial efficiency. We conclude that heterotrophic
bacteria were limited by organic carbon and co-limited by mineral nutrients during the prevailing early nano-phytoplankton
(1–10 μm) bloom conditions. High nucleic acid (HNA) bacteria became dominant (>80%) only when labile carbon and mineral nutrient
sources were available. Changes in bacterial community structure were investigated using denaturing gradient gel electrophoresis
(DGGE) of polymerase chain reaction (PCR)-amplified 16S ribosomal RNA genes. The bacterial community structure changed during
incubation time, but neither carbon nor mineral nutrient amendment induced changes at the end of the experiments. The lack
of labile organic carbon and the availability of mineral nutrients are key factors controlling bacterial activity and the
role of the microbial food web in carbon sequestration. 相似文献
12.
In aquatic ecosystems, carbon (C) availability strongly influences nitrogen (N) dynamics. One manifestation of this linkage is the importance in the dissolved organic matter (DOM) pool of dissolved organic nitrogen (DON), which can serve as both a C and an N source, yet our knowledge of how specific properties of DOM influence N dynamics are limited. To empirically examine the impact of labile DOM on the responses of bacteria to DON and dissolved inorganic nitrogen (DIN), bacterial abundance and community composition were examined in controlled laboratory microcosms subjected to various combinations of dissolved organic carbon (DOC), DON, and DIN treatments. Bacterial communities that had colonized glass beads incubated in a stream were treated with various glucose concentrations and combinations of inorganic and organic N (derived from algal exudate, bacterial protein, and humic matter). The results revealed a strong influence of C availability on bacterial utilization of DON and DIN, with preferential uptake of DON under low C concentrations. Bacterial DON uptake was affected by the concentration and by its chemical nature (labile versus recalcitrant). Labile organic N sources (algal exudate and bacterial protein) were utilized equally well as DIN as an N source, but this was not the case for the recalcitrant humic matter DON treatment. Clear differences in bacterial community composition among treatments were observed based on terminal restriction fragment length polymorphisms (T-RFLP) of 16S rRNA genes. C, DIN, and DON treatments likely drove changes in bacterial community composition that in turn affected the rates of DON and DIN utilization under various C concentrations. 相似文献
13.
The role of dissolved organic matter bioavailability in promoting phytoplankton blooms in Florida Bay 总被引:3,自引:1,他引:3
Joseph N. Boyer Susan K. Dailey Patrick J. Gibson Matthew T. Rogers Danielle Mir-Gonzalez 《Hydrobiologia》2006,569(1):71-85
The clear, shallow, oligotrophic waters of Florida Bay are characterized by low phytoplankton biomass, yet periodic cyanobacteria
and diatom blooms do occur. We hypothesized that allochthonous dissolved organic matter (DOM) was providing a subsidy to the
system in the form of bound nutrients. Water from four bay sites was incubated under natural light and dark conditions with
enrichments of either DOM ( > 1 kD, 2×DOM) or inorganic nutrients (N+P). Samples were analyzed for bacterial numbers, bacterial
production, phytoplankton biomass, phytoplankton community structure, and production, nutrients, and alkaline phosphatase
(AP) activity. The influence of 2×DOM enrichment on phytoplankton biomass developed slowly during the incubations and was
relatively small compared to nutrient additions. Inorganic nutrient additions resulted in an ephemeral bloom characterized
initially as cyanobacterial and brown algae but which changed to dinoflagellate and/or brown algae by day six. The DIN:TP
ratio decreased 10-fold in the N+P treatments as the system progressed towards N limitation. This ratio did not change significantly
for 2×DOM treatments. In addition, these experiments indicated that both autotrophic and heterotrophic microbial populations
in Florida Bay may fluctuate in their limitation by organic and inorganic nutrient availability. Both N+P and 2×DOM enrichments
revealed significant and positive response in bioavailability of dissolved organic carbon (BDOC). Potential BDOC ranged from
1.1 to 35.5%, with the most labile forms occurring in Whipray Basin. BDOC at all sites was stimulated by the 2×DOM addition.
Except for Duck Key, BDOC at all sites was also stimulated by the addition of N+P. BDOC was lower in the dry season than in
the wet season (5.56% vs. 16.86%). This may be explained by the distinct chemical characteristics of the DOM produced at different
times of year. Thus, both the heterotrophic and autotrophic microbial communities in Florida Bay are modulated by bioavailability
of DOM. This has ramifications for the fate of DOM from the Everglades inputs, implicating DOM bioavailability as a contributing
factor in regulating the onset, persistence, and composition of phytoplankton blooms. 相似文献
14.
杉木人工林土壤可溶性有机质及其与土壤养分的关系 总被引:28,自引:5,他引:23
通过在福建省来舟林场对不同栽植代数杉木人工林土壤可溶性有机碳(DOC)和氮(DON)及土壤养分的研究,其结果表明,随着杉木栽植代数的增加林地土壤DOC和DON含量逐渐下降,在0~10cm土层内第3代杉木林土壤DOC和DON含量分别是第1代杉木林的83.9%和87.1%、第2代杉木林的90.6%和96.9%,在10~20cm土层内第3代杉木林土壤DOC和DON含量分别是第1代杉木林的80.2%和81.5%、第2代杉木林的81.8%和90.0%。在不同林地和土层内土壤DOC含量之间的差异性达到了显著或极显著水平,而DON含量之间的差异性不显著。不同栽植代数杉木林土壤养分的变化趋势与DOM一致,随着杉木连栽,土壤养分含量呈下降趋势。在0~10cm土层内第3代杉木林土壤全氮、全钾、铵态氮和速效钾含量分别是第1代杉木林的83.1%、60.4%、68.1%和44.3%,是第2代杉木林的84.6%、68.5%、74.4%和58.7%;在10~20cm土层内第3代杉木林土壤全氮、全钾、铵态氮和速效钾含量分别是第1代杉木林的74.0%、53.4%、57.6%和54.6%,是第2代杉木林的94.8%、59.5%、74.3%和65.5%。经相关性分析,在各土层内土壤DOC和DON含量与土壤全氮、全钾、铵态氮和速效钾等土壤养分含量存在着不同程度的相关性。 相似文献
15.
Abstract
The effect of dissolved organic matter (DOM) and temperature on bacterial production was examined in the equatorial Pacific
Ocean. Addition of glucose, glucose plus ammonium, or free amino acids stimulated bacterial production ([3H]thymidine incorporation), whereas changes in bacterial abundance were either negligible or much less than changes in bacterial
production. The average bacterial growth rate also greatly increased following DOM additions, whereas in contrast, addition
of ammonium alone never affected production, bacterial abundance, or growth rates. Since the large glucose effect was not
observed in previous studies of cold oceanic waters, several experiments were conducted to examine DOM-temperature interactions.
These experiments suggest that bacteria respond more quickly and to a greater extent to DOM additions at higher temperatures,
which may explain apparently conflicting results from previous studies. We also examined how temperate affects the kinetic
parameters of sugar uptake. Maximum uptake rates (Vmax) of glucose and mannose increased with temperature (Q10= 2.4), although the half-saturation constant (Km) was unaffected; Km+ S was roughly equal to glucose concentrations (S) measured by a high pressure liquid chromographic technique. Bacterial
production and growth rates appear to be limited by DOM in the equatorial Pacific, and thus bacterial production follows primary
production over large spatial and temporal scales in this oceanic regime, as has been observed in other aquatic systems. Although
temperature may not limit bacterial growth rates in the equatorial Pacific and similar warm waters, it could still affect
how bacteria respond to changes in DOM supply and help set steady-state DOM concentrations.
Received: 26 July 1995; Revised: 19 January 1996 相似文献
16.
Stream bacteria may be influenced by the composition and availability of dissolved organic matter (DOM) and inorganic nutrients, but knowledge about how individual phylogenetic groups in biofilm are affected is still limited. In this study, the influence of DOM and inorganic nutrients on stream biofilm bacteria was examined. Biofilms were developed on artificial substrates (unglazed ceramic tiles) for 21 days in a northeastern Ohio (USA) stream for five consecutive seasons. Then, the developed biofilm assemblages were exposed, in the laboratory, to DOM (glucose, leaf leachate, and algal exudates) and inorganic nutrients (nitrate, phosphate, and nitrate and phosphate in combination) amendments for 6 days. Bacterial numbers in the biofilms were generally higher in response to the DOM treatments than to the inorganic nutrient treatments. There were also apparent seasonal variations in the response patterns of the individual bacterial taxa to the nutrient treatments; an indication that limiting resources to bacteria in stream biofilms may change over time. Overall, in contrast to the other treatments, bacterial abundance was generally highest in response to the low-molecular-weight DOM (i.e., glucose) treatment. These results further suggest that there are interactions among the different bacterial groups in biofilms that are impacted by the associated nutrient dynamics among seasons in stream ecosystems. 相似文献
17.
The decomposition of dissolved organic matter (DOM) in pelagic ecosystems is mediated primarily by heterotrophic bacteria,
but transformation by short-wave solar radiation may play an important role in surface waters, in particular when humic substances
constitute a substantial fraction of the DOM pool. Most of the studies examining bacterial decomposition and photochemical
transformation of DOM stem from limnetic and coastal marine systems and much less information is available from oceanic environments.
To examine the bacterial decomposition of humic and non-humic DOM in the Southern Ocean we carried out microcosm experiments
in which we measured bacterial growth on isolated fractions of humic and non-humic DOM of the size classes <3 kDa and >3 kDa.
Experiments carried out at the Polar Front showed a preferential bacterial growth on non-humic DOM and in particular on the
size fraction <3 kDa. Bacterial growth, measured as bacterial biomass production, on non-humic DOM accounted for 74% to 88%
of the total growth on all four DOM fractions. In experiments in the Antarctic circumpolar current and the coastal current
under pack ice, bacterial growth was 6× lower than at the Polar Front, and humic and non-humic DOM was consumed to equal amounts.
The size fraction <3 kDa was always preferred. Experiments examining the effect of solar radiation on the release of dissolved
amino acids (DAA) and carbohydrates (DCHO) and their subsequent bacterial utilization showed a stimulating effect on glucose
uptake and the release of DAA at the Polar Front but an inhibition in the eastern Weddell Sea. Ultraviolet-B was the most
effective component of the solar radiation spectrum tested. Effects of UV-B on glucose uptake and release of DAA were positively
correlated with concentrations of humic-bound DAA. The data imply that at low concentrations, e.g., <100 nM (amino acid equivalent),
UV-irradiation reduces, whereas at concentrations >100 nM UV-irradiation stimulates glucose uptake and release of DAA as compared
to dark conditions. 相似文献
18.
Paul J. Mann William V. Sobczak Madeleine M. LaRue Ekaterina Bulygina Anna Davydova Jorien E. Vonk John Schade Sergei Davydov Nikita Zimov Robert M. Holmes Robert G. M. Spencer 《Global Change Biology》2014,20(4):1089-1100
Permafrost thaw in the Arctic driven by climate change is mobilizing ancient terrigenous organic carbon (OC) into fluvial networks. Understanding the controls on metabolism of this OC is imperative for assessing its role with respect to climate feedbacks. In this study, we examined the effect of inorganic nutrient supply and dissolved organic matter (DOM) composition on aquatic extracellular enzyme activities (EEAs) in waters draining the Kolyma River Basin (Siberia), including permafrost‐derived OC. Reducing the phenolic content of the DOM pool resulted in dramatic increases in hydrolase EEAs (e.g., phosphatase activity increased >28‐fold) supporting the idea that high concentrations of polyphenolic compounds in DOM (e.g., plant structural tissues) inhibit enzyme synthesis or activity, limiting OC degradation. EEAs were significantly more responsive to inorganic nutrient additions only after phenolic inhibition was experimentally removed. In controlled mixtures of modern OC and thawed permafrost endmember OC sources, respiration rates per unit dissolved OC were 1.3–1.6 times higher in waters containing ancient carbon, suggesting that permafrost‐derived OC was more available for microbial mineralization. In addition, waters containing ancient permafrost‐derived OC supported elevated phosphatase and glucosidase activities. Based on these combined results, we propose that both composition and nutrient availability regulate DOM metabolism in Arctic aquatic ecosystems. Our empirical findings are incorporated into a mechanistic conceptual model highlighting two key enzymatic processes in the mineralization of riverine OM: (i) the role of phenol oxidase activity in reducing inhibitory phenolic compounds and (ii) the role of phosphatase in mobilizing organic P. Permafrost‐derived DOM degradation was less constrained by this initial ‘phenolic‐OM’ inhibition; thus, informing reports of high biological availability of ancient, permafrost‐derived DOM with clear ramifications for its metabolism in fluvial networks and feedbacks to climate. 相似文献
19.
Eva Ortega-Retuerta Quentin Devresse Jocelyne Caparros Barbara Marie Olivier Crispi Philippe Catala Fabien Joux Ingrid Obernosterer 《Environmental microbiology》2021,23(3):1363-1378
Marine heterotrophic prokaryotes (HP) play a key role in organic matter processing in the ocean; however, the view of HP as dissolved organic matter (DOM) sources remains underexplored. In this study, we quantified and optically characterized the DOM produced by two single marine bacterial strains. We then tested the availability of these DOM sources to in situ Mediterranean Sea HP communities. Two bacterial strains were used: Photobacterium angustum (a copiotrophic gammaproteobacterium) and Sphingopyxis alaskensis (an oligotrophic alphaproteobacterium). When cultivated on glucose as the sole carbon source, the two strains released from 7% to 23% of initial glucose as bacterial derived DOM (B-DOM), the quality of which (as enrichment in humic or protein-like substances) differed between strains. B-DOM induced significant growth and carbon consumption of natural HP communities, suggesting that it was partly labile. However, B-DOM consistently promoted lower prokaryotic growth efficiencies than in situ DOM. In addition, B-DOM changed HP exoenzymatic activities, enhancing aminopeptidase activity when degrading P. angustum DOM, and alkaline phosphatase activity when using S. alaskensis DOM, and promoted differences in HP diversity and composition. DOM produced by HP affects in situ prokaryotic metabolism and diversity, thus changing the pathways for DOM cycling (e.g. respiration over biomass production) in the ocean. 相似文献
20.
Microbial films play a central role in mediating energy flux in groundwater ecosystems. The activity of these microbes is
likely to be influenced by the availability of resources, especially dissolved organic matter (DOM), and also by consumers,
such as invertebrates that feed on microbial films. We used microcosm experiments to examine how bacterial production and
extracellular enzyme activity on rocks and fine sediments from cave streams responded to amendments of DOM of varying form
and to cave amphipods (Gammarus minus) that feed on microbial films. Glucose and mixtures of DOM extracted from soils and leaves stimulated bacterial production
on rocks by 89–166% relative to unamended controls. In contrast, tannic acid amendment did not influence production. Microbial
films on fine sediment were not consistently responsive to DOM amendment. Glucose amendment led to increased activity of enzymes
associated with C acquisition, but other forms of DOM generally did not alter enzyme activity. DOM amendment led to removal
of nitrate and this was correlated with bacterial production, suggesting microbes can link carbon and nitrogen cycling in
groundwater as is the case in surface systems. Amphipods reduced bacterial production on rocks, but not fine sediments. The
reduction caused by amphipods offset the stimulatory effect of glucose amendment, but there was no interactive effect of DOM
and grazing on bacterial production or enzyme activity. Both resources and consumers play important roles in regulating microbial
activity in groundwater with important implications for higher trophic levels that use microbes for food. 相似文献