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1.
Temperature affects the response of heterotrophic bacteria and mixotrophic algae to enhanced concentrations of soil extract 总被引:2,自引:0,他引:2
Norbert Kamjunke 《Hydrobiologia》2010,649(1):379-383
To investigate the consequences of increased temperature and enhanced input of dissolved organic matter (DOM) into lakes for
heterotrophicic bacteria and for mixotrophic algae which use DOM in addition to photosynthesis, the hypotheses were tested
whether (1) both bacteria and mixotrophic algae benefit from increased input of DOM, or (2) increased DOM input enhances bacterial
biomass and thereby decreases algal biomass. Growth experiments in batch cultures, exudation measurements, and competition
experiments in chemostats were performed at two temperature levels. Increased temperature stimulated the autotrophic growth
rate of Chlorella protothecoides. Bacteria and Chlorella increased their heterotrophic growth rates at higher DOM concentration at lower temperature whereas enhanced DOM concentration
hardly stimulated their growth at higher temperature. In chemostats, enhanced input of soil extract increased both bacterial
and algal biomass at lower temperature whereas bacterial biomass increased only slightly and algal biomass decreased at higher
temperature. Thus, the temperature determines the response of microorganisms to enhanced DOM concentration. 相似文献
2.
Malmstrom RR Cottrell MT Elifantz H Kirchman DL 《Applied and environmental microbiology》2005,71(6):2979-2986
Members of the SAR11 clade often dominate the composition of marine microbial communities, yet their contribution to biomass production and the flux of dissolved organic matter (DOM) is unclear. In addition, little is known about the specific components of the DOM pool utilized by SAR11 bacteria. To better understand the role of SAR11 bacteria in the flux of DOM, we examined the assimilation of leucine (a measure of biomass production), as well as free amino acids, protein, and glucose, by SAR11 bacteria in the Northwest Atlantic Ocean. We found that when SAR11 bacteria were >25% of total prokaryotes, they accounted for about 30 to 50% of leucine incorporation, suggesting that SAR11 bacteria were major contributors to bacterial biomass production and the DOM flux. Specific growth rates of SAR11 bacteria either equaled or exceeded growth rates for the total prokaryotic community. In addition, SAR11 bacteria were typically responsible for a greater portion of amino acid assimilation (34 to 61%) and glucose assimilation (45 to 57%) than of protein assimilation (< or = 34%). These data suggest that SAR11 bacteria do not utilize various components of the DOM pool equally and may be more important to the flux of low-molecular-weight monomers than to that of high-molecular-weight polymers. 相似文献
3.
Under closed laboratory conditions, at non-limiting nutrient levels, the biomass of Anabaena variabilis, Anacystis nidulans, Chlorella pyrenoidosa, and Selanastrum capricornutum increased with increasing levels of dissolved organic matter (DOM) as a result of bacterially produced carbon dioxide (CO2) and (or) cofactors. Oxygen (O2) produced as a result of algal photosynthesis was sufficient to supply the najority of O2 required by the bacterial community. The percentage of DOM utilized by bacteria which was subsequently incorporated into algal biomass varied with individual species indicating that the association between individual algal species and the bacterial microbiota varied. Under natural conditions bacteria could provide CO2 and (or) cofactors for algal photosynthesis which in turn supplies O2 for bacterial respiration. This mutualistic association in aquatic environments could result in an increase in planktonic and epiphytic algal biomass if other nutrients are available. 相似文献
4.
Biomass Production and Assimilation of Dissolved Organic Matter by SAR11 Bacteria in the Northwest Atlantic Ocean 总被引:5,自引:1,他引:4 下载免费PDF全文
Rex R. Malmstrom Matthew T. Cottrell Hila Elifantz David L. Kirchman 《Applied microbiology》2005,71(6):2979-2986
Members of the SAR11 clade often dominate the composition of marine microbial communities, yet their contribution to biomass production and the flux of dissolved organic matter (DOM) is unclear. In addition, little is known about the specific components of the DOM pool utilized by SAR11 bacteria. To better understand the role of SAR11 bacteria in the flux of DOM, we examined the assimilation of leucine (a measure of biomass production), as well as free amino acids, protein, and glucose, by SAR11 bacteria in the Northwest Atlantic Ocean. We found that when SAR11 bacteria were >25% of total prokaryotes, they accounted for about 30 to 50% of leucine incorporation, suggesting that SAR11 bacteria were major contributors to bacterial biomass production and the DOM flux. Specific growth rates of SAR11 bacteria either equaled or exceeded growth rates for the total prokaryotic community. In addition, SAR11 bacteria were typically responsible for a greater portion of amino acid assimilation (34 to 61%) and glucose assimilation (45 to 57%) than of protein assimilation (≤34%). These data suggest that SAR11 bacteria do not utilize various components of the DOM pool equally and may be more important to the flux of low-molecular-weight monomers than to that of high-molecular-weight polymers. 相似文献
5.
Shazia N. Aslam Graham J. C. Underwood Hermanni Kaartokallio Louiza Norman Riitta Autio Michael Fischer Harri Kuosa Gerhard S. Dieckmann David N. Thomas 《Polar Biology》2012,35(5):661-676
Extracellular polymeric substances (EPS) are known to help microorganisms to survive under extreme conditions in sea ice.
High concentrations of EPS are reported in sea ice from both poles; however, production and dynamics of EPS during sea ice
formation have been little studied to date. This investigation followed the production and partitioning of existing and newly
formed dissolved organic matter (DOM) including dissolved carbohydrates (dCHO), dissolved uronic acids (dUA) and dissolved
EPS (dEPS), along with bacterial abundances during early stages of ice formation. Sea ice was formed from North Sea water
with (A) ambient DOM (NSW) and (B) with additional algal-derived DOM (ADOM) in a 6d experiment in replicated mesocosms. In
ADOM seawater, total bacterial numbers (TBN) increased throughout the experiment, whereas bacterial growth occurred for 5d
only in the NSW seawater. TBN progressively decreased within developing sea ice but with a 2-fold greater decline in NSW compared
to ADOM ice. There were significant increases in the concentrations of dCHO in ice. Percentage contribution of dEPS was highest
(63%) in the colder, uppermost parts in ADOM ice suggesting the development of a cold-adapted community, producing dEPS possibly
for cryo-protection and/or protection from high salinity brines. We conclude that in the early stages of ice formation, allochthonous
organic matter was incorporated from parent seawater into sea ice and that once ice formation had established, there were
significant changes in the concentrations and composition of dissolved organic carbon pool, resulting mainly from the production
of autochthonous DOM by the bacteria. 相似文献
6.
Vertical distribution of bacteria in Arctic sea ice from the Barents and Laptev Seas 总被引:5,自引:0,他引:5
The vertical distribution of bacterial abundance and biomass was investigated in relation to algal biomass in ice cores taken
from drifting ice floes in two Arctic shelf areas: the Barents Sea and the Laptev Sea. Bacteria were not homogeneously distributed
throughout the cores but occurred in dense layers. Different types of distribution patterns were found: either a single maximum
occurred inside or at the bottom of the ice floe or maxima were found in different parts of the floes. Bacterial concentrations
ranged from 0.4 to 36.7 · 105 cells ml−1. The size spectra of sea-ice bacteria were determined by image analysis. Cell sizes showed considerable variation between
the ice floes. In multi-year sea ice, the largest bacteria were observed in the area of an internal chlorophyll a maximum. No specific vertical distribution patterns were found in first-year ice floes. Bacterial biomass for the ice cores
ranged from 19.2 to 79.2 mg C m−2, and the ratio of bacterial:ice algal biomass ranged from 0.43 to 10.42. A comparison with data collected from fast ice revealed
large differences in terms of cell size, abundance and biomass.
Received: 7 September 1995 / Accepted: 10 September 1996 相似文献
7.
Sea Ice Microbial Communities: Distribution, Abundance, and Diversity of Ice Bacteria in McMurdo Sound, Antarctica, in 1980 总被引:13,自引:5,他引:8 下载免费PDF全文
An abundant and diverse bacterial community was found within brine channels of annual sea ice and at the ice-seawater interface in McMurdo Sound, Antarctica, in 1980. The mean bacterial standing crop was 1.4 × 1011 cells m−2 (9.8 mg of C m−2); bacterial concentrations as high as 1.02 × 1012 cells m−3 were observed in ice core melt water. Vertical profiles of ice cores 1.3 to 2.5 m long showed that 47% of the bacterial numbers and 93% of the bacterial biomass were located in the bottom 20 cm of sea ice. Ice bacterial biomass concentration was more than 10 times higher than bacterioplankton from the water column. Scanning electron micrographs showed a variety of morphologically distinct cell types, including coccoid, rod, fusiform, filamentous, and prosthecate forms; dividing cells were commonly observed. Approximately 70% of the ice bacteria were free-living, whereas 30% were attached to either living algal cells or detritus. Interactions between ice bacteria and microalgae were suggested by a positive correlation between bacterial numbers and chlorophyll a content of the ice. Scanning and transmission electron microscopy revealed a close physical association between epibacteria and a dominant ice alga of the genus Amphiprora. We propose that sea ice microbial communities are not only sources of primary production but also sources of secondary microbial production in polar ecosystems. Furthermore, we propose that a detrital food web may be associated with polar sea ice. 相似文献
8.
Hermanni Kaartokallio Jaana Tuomainen Harri Kuosa Jorma Kuparinen Pertti J. Martikainen Kristina Servomaa 《Polar Biology》2008,31(7):783-793
Coastal fast ice and underlying water of the northern Baltic Sea were sampled throughout the entire ice winter from January
to late March in 2002 to study the succession of bacterial biomass, secondary production and community structure. Temperature
gradient gel electrophoresis (TGGE) and sequencing of TGGE fragments were applied in the community structure analysis. Chlorophyll-a and composition of autotrophic and heterotrophic assemblages were also examined. Overall succession of ice organism assemblages
consisted of a low-productive stage, the main algal bloom, and a heterotrophic post-bloom situation, as typical for the study
area. The most important groups of organisms in ice in terms of biomass were dinoflagellates, plasticidic flagellates, rotifers
and ciliates. Ice bacteria showed a specific succession not directly dependent on the overall succession events of ice organisms.
Sequenced 16S rDNA fragments were mainly affiliated to α-, β-, and γ-proteobacterial phyla and Cytophaga–Flavobacterium–Bacteroides-group, and related to sequences from cold environments, also from the Baltic Sea. Temporal clustering of the TGGE fingerprints
was stronger than spatial, although lower ice and underlying water communities always clustered together, pointing to the
importance of ice maturity and ice–water interactions in shaping the bacterial communities. 相似文献
9.
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
10.
Effects of different molecular size fractions (< 1000 MW, < 10 000 MW, < 100 000 MW and <0.1 μm) of dissolved organic matter
(DOM) on the growth of bacteria, algae and protozoa from a highly humic lake were investigated. DOM from catchment drainage
water as well as from the lake consisted mostly (59–63%) of high molecular weight (HMW) compounds (> 10 000 MW). With excess
inorganic nutrients, the growth rate and yield of bacteria were almost identical in all size fractions. However, in < 1000
MW fractions and with glucose added, a longer lag phase occurred. Without added nutrients both the growth rates and biomasses
of bacteria decreased towards the smaller size fractions and the percentage of dissolved organic carbon (DOC) used during
the experiment and the growth efficiency of bacteria were lower than with excess nutrients. The growth efficiency of bacteria
was estimated to vary between 3–66% in different MW fractions, largely depending on the nutrient concentrations, but the highest
growth efficiencies were observed in HMW fractions and with glucose. The growth of algae was clearly lowest in the < 1000
MW fraction. In dim light no net growth of algae could be found. In contrast, added nutrients substantially enhanced algal
growth and in deionized water with glucose, algae achieved almost the same growth rate and biomass as in higher MW fractions
of DOM. The results suggested that bacteria and some algae were favoured by DOM, but protozoans seemed to benefit only indirectly,
through bacterial grazing. The utilization of DOM by bacteria and algae was strongly affected by the availability of phosphorus
and nitrogen. 相似文献
11.
《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1997,320(9):747-758
To construct a budget of carbon transformations occurring during leaf decomposition, alder leaves were placed in a woodland stream, later retrieved at weekly intervals, and rates of fungal and bacterial production, microbial respiration, and release of dissolved organic matter (DOM) and fine particulate organic matter (FPOM) were determined during short laboratory incubations. Carbon dioxide was the major decomposition product, explaining 17% of the microbially mediated leaf mass loss. DOM and FPOM were also important products (5 and 3% of total mass loss, respectively), whereas carbon flow to microbial biomass was low (2%). Fungal biomass in leaves always exceeded bacterial biomass (95–99% of total microbial biomass), but production of bacteria and fungi was similar, indicating that both types of microorganisms need to be considered when examining leaf decomposition in streams. Comparison of leaf mass loss in coarse and fine mesh bags revealed, in addition, that the shredder, Gammarus pulex, had a major impact on leaf decomposition in this study. 相似文献
12.
Experimental Evidence on Nutrient and Substrate Limitation of Baltic Sea sea-ice Algae and Bacteria 总被引:1,自引:0,他引:1
The effect of nutrient limitation on Baltic Sea ice algae, and substrate and nutrient limitation on ice bacteria, was studied
in a series of in situ -experiments conducted during the winter of 2002 in northern Baltic Sea. Community level changes in algal biomass (chlorophyll
a) and productivity, and bacterial thymidine and leucine incorporation were followed for one week after the addition of nutrient
and/or organic carbon rich filtered seawater to the experimental units. The results showed the major contribution of snow
cover to the algal responses during the beginning of the ice-covered season. Algal communities were able to grow even in January
if no snow was present. Nutrient addition
did occasionally have an effect on algal biomass and productivity in the ice. Surprisingly,
seeding effect from the ice to the underlying water was negatively affected by the nutrient
availability in March. Bacterial limitation varied between nutrient (phosphorus) and substrate
limitations. The results showed, that limitation in both algal and bacterial communities changed periodically in the northern
Baltic Sea ice. 相似文献
13.
Effects of Microscale Water Level Fluctuations and Altered Ultraviolet Radiation on Periphytic Microbiota 总被引:1,自引:0,他引:1
Abstract
Microscale fluctuations in water level (1–20 mm) are common on a diurnal basis in shallow (<5–10 cm) wetlands, coupled to
evapotranspiration losses during the daytime in excess of groundwater resupply. These depth variations alter the intensity
of UV irradiance reaching attached periphytic algal and bacterial microbial communities. Effects of alterations of UV irradiance
by micro-changes in water level on periphytic microbiota were examined experimentally. Attached microbial communities, grown
on glass fiber filters in situ in a natural wetland, were exposed experimentally to near-natural levels of UV irradiance of differing spectral quality.
UV intensity was altered by varying the distance of the communities from the light source, changes in UV-attenuating natural
dissolved organic matter (DOM), and small changes in water level (2 or 4 mm). Algal productivity and photosynthetic oxygen
production were significantly reduced by small enhancements of UV-B radiation, by decreased water levels of only 2 mm, and
by reductions in concentrations of DOM. UV-B had only small short-term effects on chlorophyll a, although small increases in water depth and DOM concentration reduced pigment damage. Experimental removal of UV-B during
in situ growth indicated that algae could adapt to UV radiation during growth in natural environments. Microbial oxygen consumption
and bacterial productivity and biomass were also lowered significantly by UV-B exposure, and damage decreased with small (2
mm) increases in water depth or in DOM concentration. Selective inhibitors of algal photosynthesis and production of released
extracellular organic substrates caused a concomitant reduction in bacterial productivity and a significant increase in magnitude
of UV-B damage to bacterial biomass. These effects suggested that metabolic interactions between the periphytic autotrophs
and heterotrophs altered community responses to UV-B radiation. Microscale water level reductions, common on a diurnal basis
in shallow wetlands, and associated increased UV intensity can result in rapid alterations in periphytic metabolism.
Received: 27 January 1999; Accepted: 18 May 1999 相似文献
14.
A study of sea ice biota was carried out in the Gulf of Bothnia (northern Baltic Sea) during the winter of 1989–1990. Samples (ice cores) were taken at a coastal station at regular time intervals during the ice season. Chlorophyll a concentration, algal species distribution, bacterial numbers, and primary and bacterial production were measured. Colonization of the ice began in January when daylight was low. As the available light increased, the algae started to grow exponentially. The vertical chlorophyll a distribution changed and algal species composition and biomass changed during the season. During the initial and middle phase of colonization, ice-specific diatoms, Nitzschia frigida and Navicula pelagica, dominated the algal biomass. Nutrients (PO4
3– and NO3j) were found to be depleted during the time of algal exponential growth. The maximum algal biomass exceeded 800 g C 1–1. The primary production supplied food for heterotrophic organisms. The presence of heterotrophic organisms of different trophic levels (bacteria, flagellates, ciliates and rotifers) indicated an active microbial food web. 相似文献
15.
The spatial distribution of bacterial abundance and production were measured every 4 h in a recently flooded oligo-mesotrophic reservoir (the Sep Reservoir, Puy-De-Dôme, France), in relation to concentrations of dissolved carbohydrates and combined amino acids. The concentration of dissolved organic matter (DOM) components in the recently flooded Sep Reservoir were higher than those measured in other lakes of similar trophic status. Short-term variations in the bacterial production in this new reservoir appeared cyclical and endogenous to bacterial communities. These results highlight the need for the evaluation of diel changes in bacterial production, if estimation of the daily production rate of bacteria is to be done accurately for a reliable model of carbon flow through bacterioplankton and ultimately through aquatic microbial food webs. Bacterial growth, measured over time and space, did not appear exclusively governed by DOM components from phytoplankton primary production. 相似文献
16.
The seasonal development of bacterial abundance in first year bottom ice and underlying seawater were studied at Saroma-ko Lagoon in Hokkaido, Japan, and at Resolute Passage in the High Canadian Arctic during the algal bloom in spring 1992. The aim of this study was to evaluate whether the high algal concentrations reached during the bloom of ice algae have inhibitory effects on bacterial dynamics. Bacterial abundance (measured as total cell count and colony-forming units CFU) increased with the increase of the algal biomass up to 500 micrograms Chla.L-1 in both locations. Culturable fraction (measured as the percentage of CFU counts versus the total cell counts) was between 7% and 22% at Saroma-ko, and approximately 0.08% at Resolute Passage. When algal biomass exceeded 500 micrograms of Chla.L-1, both bacterial abundance and culturable fraction decreased significantly. There was a maximum threshold of algal biomass (between 500 and 800 micrograms of Chla.L-1) after which bacterial dynamics become negatively coupled to the algal biomass. These results suggest that bactericidal and/or bacteriostatic compounds from these extremely high algal concentrations could explain the decrease in bacterial abundance and culturability in bottom ice observed after the ice algae bloom. 相似文献
17.
The efficiency of physical concentration mechanisms for enrichment of algae and bacteria in newly formed sea-ice was investigated
under defined conditions in the laboratory. Sea-ice formation was simulated in a 3,000 l tank under different patterns of
water movement. When ice formed in an artificially generated current pattern, algal cells were substantially enriched within
the ice matrix. Enrichment factors for chlorophyll a calculated from the ratio between the concentrations in ice and underlying water reached values of up to 53. Repeated mixing
of ice crystals into the water column, as well as flow of water through the new ice layer, contributed to the enrichment of
algae in the ice. Wave action during ice formation revealed lower phytoplankton enrichment factors of up to 9. Mixing of floating
ice crystals with underlying water and pumping of water into the ice matrix by periodical expansion and compression of the
slush ice layer were responsible for the wave-induced enrichment of algal cells. Physical enrichment of bacteria within the
ice was negligible. Bacterial biomass within new ice was enhanced only when the concentration of algae was high. At low algal
biomass, bacteria experienced substantial losses in the ice, most likely due to brine drainage, which were not observed for
the microalgae. Bacterial cells are therefore not scavenged by ice crystals and the observed enrichment and sustainment of
bacterial biomass within newly formed ice depend on their attachment to cells or aggregates of algae. Division rates of bacteria
changed only slightly during ice formation.
Received: 21 October 1997 / Accepted: 9 April 1998 相似文献
18.
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
19.
Antonio Pusceddu Antonio Dell’Anno Luigi Vezzulli Mauro Fabiano Vincenzo Saggiomo Stefano Cozzi Giulio Catalano Letterio Guglielmo 《Polar Biology》2009,32(3):337-346
We investigated organic carbon quantity and biochemical composition, prokaryotic abundance, biomass and carbon production
in the annual and platelet sea ice of Terra Nova Bay (Antarctica), as well as the downward fluxes of organic matter released
by melting ice during early spring. Huge amounts of biopolymeric C accumulated in the bottom layer of the ice column concomitantly
with the early spring increase in sympagic algal biomass. Such organic material, mostly accounted for by autotrophic biomass,
was characterised by a high food quality and was rapidly exported to the sea bottom during sea ice melting. Prokaryote abundance
(up to 1.3 × 109 cells L−1) and extracellular enzymatic activities (up to 24.3 μM h−1 for amino-peptidase activity) were extremely high, indicating high rates of organic C degradation in the bottom sea ice.
Despite this, prokaryote C production values were very low (range 5–30 ng C L−1 h−1), suggesting that most of the degraded organic C was not channelled into prokaryote biomass. In the platelet ice, we found
similar organic C concentrations, prokaryote abundance and biomass values and even higher extracellular enzymatic activities,
but values of prokaryote C production (range 800–4,200 ng C L−1 h−1) were up to three orders of magnitude higher than in the intact bottom sea ice. Additional field and laboratory experiments
revealed that the dissolved organic material derived from algae accumulating in the bottom sea ice significantly reduced prokaryote
C production, suggesting the presence of a potential allopathic control of sympagic algae on prokaryote growth.
This article belongs to a special topic: Five articles on Sea-ice communities in Terra Nova Bay (Ross Sea), coordinated by
L. Guglielmo and V. Saggiomo, appear in this issue of Polar Biology. The studies were conducted in the frame of the National
Program of Research in Antarctica (PNRA) of Italy. 相似文献
20.
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