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1.
Following the extreme low ice year of 2007, primary production and the sinking export of particulate and gel-like organic
material, using short-term particle interceptor traps deployed at 100 m, were measured in the southeastern Beaufort Sea during
summer 2008. The combined influence of early ice retreat and coastal upwelling contributed to exceptionally high primary production
(500 ± 312 mg C m−2 day−1, n = 7), dominated by large cells (>5 μm, 73% ± 15%, n = 7). However, except for one station located north of Cape Bathurst, the sinking export of particulate organic carbon (POC)
was relatively low (range: 38–104 mg C m−2 day−1, n = 12) compared to other productive Arctic shelves. Estimates indicate that 80% ± 20% of the primary production was cycled
through large copepods or the microbial food web. Exopolymeric substances were abundant in the sinking material but did not
appear to accelerate POC sinking export. The use of isotopic signatures (δ13C, δ15N) and carbon/nitrogen ratios to identify sources of the sinking material was successful only at two stations with a strong
marine or terrestrial signature, indicating the limitations of this approach in hydrographically and biologically complex
Arctic coastal waters such as in the Beaufort Sea. At these two stations influenced by either coastal upwelling or erosion,
the composition and magnitude of particulate sinking fluxes were markedly different from other stations visited during the
study. These observations underscore the fundamental role of mesoscale circulation patterns and hydrodynamic singularities
on the export of particulate organic material on Arctic shelves. 相似文献
2.
Makoto Sampei Hiroshi Sasaki Ryosuke Makabe Alexandre Forest Hiroshi Hattori Jean-��ric Tremblay Yves Gratton Mitsuo Fukuchi Louis Fortier 《Polar Biology》2011,34(4):501-511
Regional variability in the annual fluxes of particulate organic carbon (POC) and biogenic silica (Si) at the periphery of
the Mackenzie Shelf (Beaufort Sea) was investigated using eight long-term sediment traps moored at ~100-m depth. Relatively
high autochthonous POC and Si fluxes were recorded in the Mackenzie Trough (4.1 and 8.9 g m−2 year−1 respectively) and off Cape Bathurst (6.6 and 79 g m−2 year−1), two areas where upwelling events are frequently observed. Diatomaceous new production was minimum on the mid-slope of the
Mackenzie Shelf (2.8 g C m−2 year−1), moderate in the Mackenzie Trough (14.5 g C m−2 year−1), and highest off Cape Bathurst (128.7 g C m−2 year−1). High annual autochthonous POC flux corresponded to high diatom production. Among sites, the vertical attenuation of the
POC flux increased with diatomaceous new production. Hence, the retention of autochthonous POC in the surface layer (<100 m)
was highest (95%) at the highly productive site off Cape Bathurst, intermediate (72%) in the moderately productive Mackenzie
Trough, and low (4%) at the unproductive mid-slope of the shelf. Our results indicate that, on Arctic shelves, upwelling and
the production of diatoms increase the fraction of the POC which is retained in the surface layer and diverted to the pelagic
food web. In the relatively unproductive waters of the Arctic Ocean, biological hot spots such as the one identified off Cape
Bathurst where the food web promotes retention rather than vertical export could be disproportionately important as feeding
grounds for higher trophic levels. 相似文献
3.
Rubén J. Lara Sucharit B. Neogi Mohammad S. Islam Zahid H. Mahmud Shafiqul Islam Debasish Paul Biniam B. Demoz Shinji Yamasaki Gopinath B. Nair Gerhard Kattner 《Wetlands Ecology and Management》2011,19(1):109-119
Wetland dynamics are probably linked to cholera endemicity in South Asia. We focus on links between Vibrio cholerae abundance, chitin content and suspended particle load in size fractions of suspended particulate matter (SPM) along the salinity
gradient of Sunderban mangrove waters. SPM decreased downstream, while salinity increased from 0.2 to 4. Particulate organic
carbon (90 ± 25 μM) and nitrogen (9.1 ± 3.3 μM) highly correlated with SPM and turbidity, suggesting a significant contribution
of fine particles to organic matter. Total chitin ranged 1–2 mg/l and decreased downstream. The distribution among size fractions
of SPM, chitin and V. cholerae O1 (the bacterial serogroup mainly associated with cholera epidemics) was similar, with ~98% of the total in the fraction
<20 μm. In comparison, the number of V. cholerae O1 attached to zooplankton and microplankton size classes >20 μm was almost negligible, in contrast to usual assumptions.
Thus, microdetritus, nanoplankton and fungal cells in size classes <20 μm represent a chitinaceous substrate on which V. cholerae can grow and survive. Total bacteria, cultivable vibrios and V. cholera O1 increased 5–10 times downstream, together with salinity and nitrite concentration. Overall, nitrate and silicate concentrations
were relatively constant (>22 μM N and 100 μM Si). However, nitrite increased ~9 times in the outer sector, reaching ~1.2 μM
N, probably as a result of increased abundance of nitrate-reducing vibrios. A characterization of Vibrio habitats that takes account of the presence of nitrate-reducing bacteria could improve the understanding of both mangrove
nitrogen cycling and cholera seasonality. 相似文献
4.
Effect of ice melting on bacterial carbon fluxes channelled by viruses and protists in the Arctic Ocean 总被引:1,自引:0,他引:1
Julia A. Boras M. Montserrat Sala Jesus M. Arrieta Elisabet L. Sà Jorge Felipe Susana Agustí Carlos M. Duarte Dolors Vaqué 《Polar Biology》2010,33(12):1695-1707
During the last few years, extensive sea ice melting in the Arctic due to climate change has been detected, which could potentially
modify the organic carbon fluxes in these waters. In this study, the effect of sea ice melting on bacterial carbon channelling
by phages and protists has been evaluated in the northern Greenland Sea and Arctic Ocean. Grazing on bacteria by protists
was evaluated using the FLB disappearance method. Lysis of bacteria due to viral infections was measured using the virus reduction
approach. Losses of bacterial production caused by protists (PMMBP) dominated losses caused by viruses (VMMBP) throughout the study. Lysogenic viral production was detected in 7 out of 21 measurements and constituted from 33.9 to 100.0%
of the total viral production. Significantly higher PMMBP and lower VMMBP were detected in waters affected by ice melting compared with unaffected waters. Consequently, significantly more bacterial
carbon was channelled to the higher trophic levels in affected waters (13.05 ± 5.98 μgC l−1 day−1) than in unaffected waters (8.91 ± 8.33 μgC l−1 day−1). Viruses channelled 2.63 ± 2.45 μgC l−1 day−1 in affected waters and 4.27 ± 5.54 μgC l−1 day−1 in unaffected waters. We conclude that sea ice melting in the Arctic could modify the carbon flow through the microbial food
web. This process may be especially important in the case of massive sea ice melting due to climate change. 相似文献
5.
I. Dumont V. Schoemann D. Lannuzel L. Chou J.-L. Tison S. Becquevort 《Polar Biology》2009,32(5):733-750
Distribution and composition of organic matter were investigated in Antarctic pack ice in early spring and summer. Accumulation
of organic compounds was observed with dissolved organic carbon (DOC) and particulate organic carbon (POC) reaching 717 and
470 μM C, respectively and transparent exopolymeric particles (TEP) up to 3,071 μg Xanthan gum equivalent l−1. POC and TEP seemed to be influenced mainly by algae. Particulate saccharides accounted for 0.2–24.1% (mean, 7.8%) of POC.
Dissolved total saccharides represented 0.4–29.6% (mean, 9.7%) of DOC, while dissolved free amino acids (DFAA) accounted for
only 1% of DOC. Concentrations of TEP were positively correlated with those of saccharides. Monosaccharides (d-MCHO) dominated
during winter–early spring, whereas dissolved polysaccharides did in spring–summer. DFAA were strongly correlated with d-MCHO,
suggesting a similar pathway of production. The accumulation of monomers in winter is thought to result from limitation of
bacterial activities rather than from the nature of the substrates. 相似文献
6.
Y. Satoh M. Sasaki Y. Miyamori K. Sugawara T. Nishi M. Nishizuka K. Inamura Y. Yamagami 《Limnology》2001,2(1):11-18
The perturbations of a water column at the deepest part of Lake Onogawa by a local heavy rainfall were analyzed. Mixing throughout
the water column (18.8-m deep) was indicated by changes in the distribution of water temperature. This mixing perturbed the
hypolimnetic seasonal distributions of dissolved components. All partic-ulate components peaked at 10 m, suggesting a center
of inflowing water. Compared with background levels, particulate nitrogen (PN), particulate carbon (PC), particulate phosphorus
(PP), and suspended solids (SS) increased from 16-fold for PN to 100-fold for SS. Soluble reactive phosphorus was the only
dissolved component that formed a clear maximum at 10 m, as did the particulate components. Assuming that SS consists mainly
of mineral particles, SS can be classified into three categories: (1) A rapidly sinking fraction, the main body of the loaded
SS, with a sinking rate exceeding 1 m day−1 and radii exceeding 2–3 μm. (2) A slowly sinking fraction with a sinking speed of about 10 cm day−1 and radii of 0.7–0.9 μm; this fraction is calculated to be about 4% of the total loaded SS at most. (3) A fraction that was
essentially retained in the water column. The maximum estimate of this fraction was 0.5% of the total.
Received: January 1, 2000 / Accepted: August 10, 2000 相似文献
7.
Land-use and land-cover strongly influence soil properties such as the amount of soil organic carbon (SOC), aggregate structure and SOC turnover processes. We studied the effects of a vegetation shift from forest to grassland 90 years ago in soils derived from andesite material on Barro Colorado Island (BCI), Panama. We quantified the amount of carbon (C) and nitrogen (N) and determined the turnover of C in bulk soil, water stable aggregates (WSA) of different size classes (<53 μm, 53–250 μm, 250–2000 μm and 2000–8000 μm) and density fractions (free light fraction, intra-aggregate particulate organic matter and mineral associated soil organic C). Total SOC stocks (0–50 cm) under forest (84 Mg C ha−1) and grassland (64 Mg C ha−1) did not differ significantly. Our results revealed that vegetation type did not have an effect on aggregate structure and stability. The investigated soils at BCI did not show higher C and N concentrations in larger aggregates, indicating that organic material is not the major binding agent in these soils to form aggregates. Based on δ13C values and treating bulk soil as a single, homogenous C pool we estimated a mean residence time (MRT) of 69 years for the surface layer (0–5 cm). The MRT varied among the different SOC fractions and among depth. In 0–5 cm, MRT of intra-aggregate particulate organic matter (iPOM) was 29 years; whereas mineral associated soil organic C (mSOC) had a MRT of 124 years. These soils have substantial resilience to C and N losses because the >90% of C and N is associated with mSOC, which has a comparatively long MRT. 相似文献
8.
Chaetognaths are among the most abundant predators in the Southern Ocean and are potentially important components in the biological
carbon pump due to the production of large, fast-sinking fecal pellets. In situ S. gazellae abundance, fecal pellet production, sinking rates, carbon content, and vertical carbon fluxes were measured at the Lazarev Sea between
December 2005 and January 2006. Sagitta gazellae produce fecal pellets that sink at speeds of 33–600 m day−1 and have carbon contents of 0.01–0.8 mg C pellet−1. Vertical carbon flux was later compared with the total carbon flux measured at 360 m depth at the study area. Rough estimates
using published seasonal abundance of S. gazellae indicate that, at 360 m depth in the Lazarev Sea, this specie may contribute 12 and 5% of the total vertical carbon flux
in winter (ice-covered) and summer (ice-free), respectively. Thus, the role of chaetognaths in the downward transport of organic
matter may be far more important than previously thought. 相似文献
9.
L. Charpy M. Rodier A. Couté C. Perrette-Gallet C. Bley-Loëz 《Coral reefs (Online)》2010,29(3):771-783
Closure of the Clipperton Island atoll (10°17′ N 109°13′ W), now a meromictic lake, is estimated to have occurred between
1839 and 1849. It was still closed in 2005. Brackish waters in the upper layer (0–10 m) were oxygenated, while saline waters
in the deep layer (>20 m) were anoxic. Allowing for the methodological difficulties of earlier measurements, the physical
characteristics of the lagoon did not seem to have changed significantly since the last expedition (1980). The intermediate
layer between brackish and saline waters was characterized by a strong density gradient and a temperature inversion of up
to 1.6°C. Microbial activity, water exchange between the deep layer and surrounding oceanic waters and the geothermal flux
hypothesis are discussed. The low DIN and SRP concentrations observed in the upper layer, despite high nutrient input by seabird
droppings, reflect the high nutrient uptake by primary producers as attested by the elevated overall gross primary production
(6.6 g C m−2 day−1), and high suspended photosynthetic biomass (2.23 ± 0.23 μg Chl a l−1) and production (263 ± 27 μg C l−1 day−1). Phytoplankton composition changed in 67 years with the advent of new taxa and the disappearance of previously recorded
species. The freshwater phytoplanktonic community comprised 43 taxa: 37 newly identified during the expedition and 6 previously
noted; 16 species previously found were not seen in 2005. The closure of the lagoon, combined with the positive precipitation–evaporation
budget characteristic of the region, has induced drastic changes in lagoon functioning compared with other closed atolls. 相似文献
10.
Jennifer Lawson Knoepfle Peter T. Doran Fabien Kenig W. Berry Lyons V. F. Galchenko 《Hydrobiologia》2009,632(1):139-156
In perennially ice-covered lakes of Taylor Valley, Antarctica, “legacy”, a carryover of past ecosystem events, has primarily
been discussed in terms of nutrient and salinity concentrations and its effect on the current ecology of the lakes. In this
study, we determine how residual pools of ancient carbon affect the modern carbon abundance and character in the water columns
of Lakes Fryxell, Hoare, and Bonney. We measure the stable carbon isotopic compositions and concentrations of particulate
organic carbon (POC) and dissolved inorganic carbon (DIC) in the water column of these lakes over four seasons (1999–2002).
These data are presented and compared with all the previously published Taylor Valley lacustrine carbon stable isotopic data.
Our results show that the carbon concentrations and isotopic compositions of the upper water columns of those lakes are controlled
by modern processes, while the lower water columns are controlled to varying degrees by inherited carbon pools. The water
column of the west lobe of Lake Bonney is dominated by exceptionally high concentrations of DIC (55,000–75,000 μmol l−1) reflecting the long period of ice-cover on this lake. The east lobe of Lake Bonney has highly enriched δ13CDIC values resulting from paleo-brine evaporation effects in its bottom waters, while its high DIC concentrations provide geochemical
evidence that its middle depth waters are derived from West Lake Bonney during a hydrologically connected past. Although ancient
carbon is present in both Lake Hoare and Lake Fryxell, the δ13CDIC values in bottom waters suggest dominance by modern primary productivity-related processes. Anaerobic methanogenesis and
methanotrophy are also taking place in the lower water column of Lake Fryxell with enough methane, oxidized anaerobically,
to contribute to the DIC pool. We also show how stream proximity and high flood years are only a minor influence on the carbon
isotopic values of both POC and DIC. The Taylor Valley lake system is remarkably stable in both inter-lake and intra-lake
carbon dynamics.
Handling editor: K. Martens 相似文献
11.
Size-fractionated phytoplankton chlorophyll in an Eastern Mediterranean coastal system (Maliakos Gulf, Greece) 总被引:1,自引:0,他引:1
Konstantinos A. Kormas Vasiliki Garametsi Artemis Nicolaidou 《Helgoland Marine Research》2002,56(2):125-133
The dynamics of phytoplankton biomass were studied in an Eastern Mediterranean semi-enclosed coastal system (Maliakos Gulf,
Aegean Sea), over 1 year. In particular, chlorophyll a (chl a) was fractionated into four size classes: picoplankton (0.2–2 μm), nanoplankton (2–20 μm), microplankton (20–180 μm) and
net phytoplankton (>180 μm). The spatial and temporal variation in dissolved inorganic nutrients and particulate organic carbon
(POC) were also investigated. The water column was well mixed throughout the year, resulting in no differences between depths
for all the measured parameters. Total chl a was highest in the inner part of the gulf and peaked in winter (2.65 μg l–1). During the phytoplankton bloom, microplankton and net phytoplankton together dominated the autotrophic biomass (67.2–95.0%
of total chl a), while in the warmer months the contribution of pico- and nanoplankton was the most significant (77.5–93.4% of total chl a). The small fractions, although showing low chl a concentrations, were important contributors to the POC pool, especially in the outer gulf. No statistically significant correlations
were found between any chl a size fraction and inorganic nutrients. For most of the year, phytoplankton was not limited by inorganic nitrogen concentrations.
Electronic Publication 相似文献
12.
Yoko Nishimura Taisuke Ohtsuka Kohei Yoshiyama Daisuke Nakai Fujiyoshi Shibahara Masayoshi Maehata 《Ecological Research》2011,26(3):615-626
Effects of fish predation propagate through aquatic food webs, where the classical grazing food chain and microbial loop are
interwoven by trophic interactions. The overall impact on aquatic food webs is further complicated because fish may also exert
bottom-up controls through nutrient regeneration. Yet, we still have limited information about cascading effects among fish,
zooplankton, phytoplankton, and microbes. In this study, we performed a mesocosm experiment to evaluate effects of fish introduction
on plankton communities. Six plots were set in factorial combination with fish introduction and rice straw plowing in a paddy
field, and the experiment was continued for 4 weeks. Introduction of fish significantly increased chlorophyll a concentrations in smaller size fractions (<15 μm) and abundances of filamentous bacteria (>5 μm in length) and heterotrophic
nanoflagellates in 3–15 μm fraction. Microbes in 0.8–3 μm fraction showed increasing but not significant trends in response
to fish introduction. These results indicate cascading effects of fish predation operating via two pathways, one through grazing
food chain and the other through microbial food web. Phytoplankton community compositions shifted in similar fashion in all
plots until 1 week after fish introduction, and then diverged between plots with and without fish thereafter. Bottom-up effects
of fish introduction were suggested by increases of total chlorophyll a and inedible phytoplankton species in response to fish introduction. This study provides an example of how fish predation
regulates biomass and structure of phytoplankton and microbial communities. 相似文献
13.
Michaela Aschan Oleg V. Karamushko Ingvar Byrkjedal Rupert Wienerroither Igor V. Borkin Jørgen S. Christiansen 《Polar Biology》2009,32(7):963-970
The Arctogadus glacialis is endemic to the Arctic Ocean and its apparently disjunct circumpolar distribution range from the Siberian coast through
the Chukchi Sea and the Canadian Arctic to the shelf off NE Greenland. Records of A. glacialis are scarce in the European Arctic and here we present all available and reliable records of the species in the area. Altogether,
296 specimens of A. glacialis are reported from 53 positions in the European Arctic during the period 1976–2008. The specimens were registered off Iceland
and the Jan Mayen Island, northwest and northeast of Svalbard, northeast in the Barents Sea, and south and east off Franz
Josef Land. The additional records show that A. glacialis display a circumpolar and more continuous distribution than described before. In the European Arctic, A. glacialis has been caught at 155–741 m depth with the highest abundance at 300–400 m. We therefore suggest that A. glacialis is more associated to the continental shelves surrounding the Arctic Ocean than previously thought. The length–weight relation
of A. glacialis is similar across the European Arctic. 相似文献
14.
In January 2004 the microplankton community from the coastal waters of Terre Adélie and Georges V Land (139°E–145°E) was studied.
Results showed a diatom-dominated bloom with chlorophyll a levels averaging 0.64 μg l−1 at 5 m depth (range 0.21–1.57 μg l−1). Three geographic assemblages of diatoms were identified, based on principal diatom taxa abundances. The stratified waters
near the Mertz Glacier presented highest phytoplankton biomasses (0.28–1.57 μg Chl a l−1 at 5 m) and diatom abundances (6,507–70,274 cells l−1 at 5 m), but low diversity, dominated by Fragilariopsis spp. Lower biomasses (0.38–0.94 μg Chl a l−1 at 5 m) and abundances (394–9,058 cells l−1 at 5 m) were observed in the mixed waters around the Astrolabe Glacier with a diverse diatom community characterised by larger
species Corethron pennatum and Rhizosolenia spp. Finally an intermediate zone between them over the shallower shelf waters of the Adélie Bank represented by Chaetoceros criophilus, where biomasses (0.21–0.35 μg Chl a l−1 at 5 m) and abundances (1,190–5,431 cells l−1 at 5 m) were lowest, coinciding with the presence of abundant herbivorous zooplankton. 相似文献
15.
Carolina C. Lisboa Richard T. Conant Michelle L. Haddix Carlos Eduardo P. Cerri Carlos C. Cerri 《Ecosystems》2009,12(7):1212-1221
The effect of conversion from forest-to-pasture upon soil carbon stocks has been intensively discussed, but few studies focus
on how this land-use change affects carbon (C) distribution across soil fractions in the Amazon basin. We investigated this
in the 20 cm depth along a chronosequence of sites from native forest to three successively older pastures. We performed a
physicochemical fractionation of bulk soil samples to better understand the mechanisms by which soil C is stabilized and evaluate
the contribution of each C fraction to total soil C. Additionally, we used a two-pool model to estimate the mean residence
time (MRT) for the slow and active pool C in each fraction. Soil C increased with conversion from forest-to-pasture in the
particulate organic matter (>250 μm), microaggregate (53–250 μm), and d-clay (<2 μm) fractions. The microaggregate comprised
the highest soil C content after the conversion from forest-to-pasture. The C content of the d-silt fraction decreased with
time since conversion to pasture. Forest-derived C remained in all fractions with the highest concentration in the finest
fractions, with the largest proportion of forest-derived soil C associated with clay minerals. Results from this work indicate
that microaggregate formation is sensitive to changes in management and might serve as an indicator for management-induced
soil carbon changes, and the soil C changes in the fractions are dependent on soil texture. 相似文献
16.
The Deepwater Horizon oil spill triggered a complex cascade of microbial responses that reshaped the dynamics of heterotrophic carbon degradation and the turnover of dissolved organic carbon (DOC) in oil contaminated waters. Our results from 21-day laboratory incubations in rotating glass bottles (roller bottles) demonstrate that microbial dynamics and carbon flux in oil-contaminated surface water sampled near the spill site two weeks after the onset of the blowout were greatly affected by activities of microbes associated with macroscopic oil aggregates. Roller bottles with oil-amended water showed rapid formation of oil aggregates that were similar in size and appearance compared to oil aggregates observed in surface waters near the spill site. Oil aggregates that formed in roller bottles were densely colonized by heterotrophic bacteria, exhibiting high rates of enzymatic activity (lipase hydrolysis) indicative of oil degradation. Ambient waters surrounding aggregates also showed enhanced microbial activities not directly associated with primary oil-degradation (β-glucosidase; peptidase), as well as a twofold increase in DOC. Concurrent changes in fluorescence properties of colored dissolved organic matter (CDOM) suggest an increase in oil-derived, aromatic hydrocarbons in the DOC pool. Thus our data indicate that oil aggregates mediate, by two distinct mechanisms, the transfer of hydrocarbons to the deep sea: a microbially-derived flux of oil-derived DOC from sinking oil aggregates into the ambient water column, and rapid sedimentation of the oil aggregates themselves, serving as vehicles for oily particulate matter as well as oil aggregate-associated microbial communities. 相似文献
17.
Primary production by phytoplankton in the eutrophic Mikawa Bay, Japan, was studied by simultaneous measurements of natural
carbon isotope ratio (δ
13C) and short-term carbon uptake rates (13C tracer study) of size-fractionated nannoplankton (<10 μm) and net plankton (>10 μm) samples. Short-term photosynthetic rates,
which represent the physiological state of algae, were variable regardless of standing stock sizes. Theδ
13C values of particulate organic carbon (POC) in June and July displayed horizontal variations for both the net plankton fraction
(−19.8 to −12.7‰) and the nannoplankton fraction (−22.0 to −12.8‰). For both fractions, low concentrations of POC had more
negativeδ
13C values (−22 to −18‰). Highδ
13C values for the net plankton were found when POC concentrations were much higher, due to red tide. This suggests that the
increase in algal standing crop for the net plankton fraction resulted from accelerated photosynthetic activity. However the
nannoplankton fractions with higher POC values have relatively lowδ
13C values. 相似文献
18.
Green krill, the indicator of micro- and nano-size phytoplankton availability to krill 总被引:2,自引:0,他引:2
Size-fractionated chlorophyll-a concentrations of surface seawater were measured for pico-, nano-, and micro-size fractions
(<2 μm, 2–10 μm, and >10 μm respectively) during commercial krill fishery operations in the waters north of the South Shetland
Islands. The proportion of green krill (individuals discoloured due to active feeding on phytoplankton) had significant regressions
with chlorophyll-a concentrations in micro- and nano-size fractions. Between these two fractions, chlorophyll-a concentration
in the micro-size fraction showed the higher partial regression coefficient. This result shows the importance of phytoplankton
larger than nano-phytoplankton, especially micro-phytoplankton, in terms of a phytoplanktonic food source for Antarctic krill
in the natural environment.
Accepted: 6 February 1999 相似文献
19.
Nitrogen deposition effects on soil organic matter chemistry are linked to variation in enzymes,ecosystems and size fractions 总被引:2,自引:0,他引:2
A. Stuart Grandy Robert L. Sinsabaugh Jason C. Neff Martina Stursova Donald R. Zak 《Biogeochemistry》2008,91(1):37-49
Recent research has dramatically advanced our understanding of soil organic matter chemistry and the role of N in some organic
matter transformations, but the effects of N deposition on soil C dynamics remain difficult to anticipate. We examined soil
organic matter chemistry and enzyme kinetics in three size fractions (>250 μm, 63–250 μm, and <63 μm) following 6 years of
simulated atmospheric N deposition in two ecosystems with contrasting litter biochemistry (sugar maple, Acer saccharum—basswood, Tilia americana and black oak, Quercus velutina—white oak, Q. alba). Ambient and simulated (80-kg NO3
−–N ha−1 year−1) atmospheric N deposition were studied in three replicate stands in each ecosystem. We found striking, ecosystem-specific
effects of N deposition on soil organic matter chemistry using pyrolysis gas chromatography/mass spectrometry. First, furfural,
the dominant pyrolysis product of polysaccharides, was significantly decreased by simulated N deposition in the sugar maple–basswood
ecosystem (15.9 vs. 5.0%) but was increased by N deposition in the black oak–white oak ecosystem (8.8 vs. 24.0%). Second,
simulated atmospheric N deposition increased the ratio of total lignin derivatives to total polysaccharides in the >250 μm
fraction of the sugar maple–basswood ecosystem from 0.9 to 3.3 but there were no changes in other size classes or in the black
oak–white oak ecosystem. Third, simulated N deposition increased the ratio of lignin derivatives to N-bearing compounds in
the 63–250 and >250 μm fractions in both ecosystems but not in the <63 μm fraction. Relationships between enzyme kinetics
and organic matter chemistry were strongest in the particulate fractions (>63 μm) where there were multiple correlations between
oxidative enzyme activities and concentrations of lignin derivatives and between glycanolytic enzyme activities and concentrations
of carbohydrates. Within silt-clay fractions (<63 μm), these enzyme-substrate correlations were attenuated by interactions
with particle surfaces. Our results demonstrate that variation in enzyme activity resulting from atmospheric N deposition
is directly linked to changes in soil organic matter chemistry, particularly those that occur within coarse soil size fractions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
Particulate and Dissolved Organic Carbon Production by the Heterotrophic Nanoflagellate Pteridomonas danica Patterson and Fenchel 总被引:1,自引:0,他引:1
Abstract
We established a budget of organic carbon utilization of a starved heterotrophic nanoflagellate, Pteridomonas danica, incubated in batch cultures with Escherichia coli as model prey. The cultures were sampled periodically for biomass determinations and total organic carbon dynamics: total
organic carbon, total organic carbon <1 μm, and dissolved organic carbon (DOC, <0.2 μm). During the 22 h incubation period,
P. danica underwent biovolume variations of 3.2-fold. Gross growth efficiency was 22% and net growth efficiency 40%. P. danica respired 33% and egested 44% of the ingested E. coli carbon during lag and exponential growth phases. The form of the organic carbon egested varied. Of the total ingested carbon,
9% was egested in the form of DOC and occurred mainly during the exponential growth phase; 35% was egested in the form of
particulate organic carbon (POC), ranging in size from 0.2 to 1 μm, and took place during the lag phase. P. danica could have reingested as much of 58% of this previously produced POC during the exponential growth phase as food scarcity
increased. We concluded that POC egestion by flagellates could represent a significant source of submicrometric particles
and colloidal organic matter. In addition, flagellate reingestion of egested POC could play a nonnegligible role in the microbial
food web. Finally, the methodology reported in this study has proved to be a useful tool in the study of carbon metabolism
in aquatic microorganisms.
Received: 31 July 1998; Accepted: 2 March 1999 相似文献