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1.
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
2.
Malej Alenka; Mozetic Patricija; Turk Valentina; Terzic Senka; Ahel Marijan; Cauwet Gustave 《Journal of plankton research》2003,25(8):949-966
This study examined the partitioning of organic matter intoparticulate organic carbon (POC) and dissolved organic carbon(DOC) pools in nutrient-enriched enclosures containing naturalplankton from the Gulf of Trieste (northern Adriatic), an areaaffected by mucilage. The strategy of nutrient additions wasto introduce a pulse of new nutrients in concentrations thatmimic natural inputs and to survey community structure and organicmatter fluxes long enough so that plankton became nutrient-limited.Maximal bacterial biomass attained roughly double the initialvalue, while autotrophic carbon increased by nearly an orderof magnitude. The microflagellate-dominated community releasedmore DOC per unit biomass (5.5 ± 7.2 to 50.6 ±28.0 µg C µg Chl a-1 day-1 versus 3.4 ± 3.4to 10.8 ± 4.6 µg C µg Chl a-1 day-1 for diatom-dominatedphytoplankton), POC increase was modest (~300 µg C l-1)and there was little change in DOC. Organic carbon partitioningduring two experiments in which diatoms prevailed was dominatedby POC (>800 µg C l-1) in the exponential growth phasewith an increasing contribution of particulate carbohydratesthat paralleled gradual nutrient depletion. Transition to thestationary phase and the decay of autotrophic communities wereaccompanied by the net accumulation of a carbohydrate-rich DOC. 相似文献
3.
M. S. Naumann A. Haas U. Struck C. Mayr M. el-Zibdah C. Wild 《Coral reefs (Online)》2010,29(3):649-659
Particulate organic matter (POM) and dissolved organic carbon (DOC) release by six dominant hermatypic coral genera (Acropora, Fungia, Goniastrea, Millepora, Pocillopora and Stylophora) were measured under undisturbed conditions by laboratory incubations during four seasonal expeditions to the Northern Red
Sea. In addition, the influence of environmental factors (water temperature, light availability and ambient inorganic nutrient
concentrations) was evaluated. Particulate organic carbon (POC) and particulate nitrogen (PN) release were always detectable
and genus-specific, with Stylophora releasing most POM (6.5 mg POC and 0.5 mg PN m−2 coral surface area h−1) during all seasons. The fire coral Millepora released significantly less POM (0.3 mg POC and 0.04 mg PN m−2 coral surface area h−1) than all investigated anthozoan genera. The average POC:PN ratio of POM released by all coral genera was 12 ± 1, indicating
high carbon/low nitrogen content of coral-derived organic matter. POM release showed little seasonal variation, but average
values of POC and PN release rates correlated with water temperature, light availability and ambient nitrate concentrations.
DOC net release and elevated DOC:POC ratios were detectable for Acropora, Goniastrea and Millepora, revealing maximum values for Acropora (30.7 mg DOC m−2 coral surface area h−1), whilst predominant DOC uptake was observed for Pocillopora, Fungia and Stylophora. Depth-mediated light availability influenced DOC fluxes of Acropora and Fungia, while fluctuations in water temperature and ambient inorganic nutrient concentrations showed no correlation. These comprehensive
data provide an important basis for the understanding of coral reef organic matter dynamics and relevant environmental factors. 相似文献
4.
T. Yoshioka S. Ueda T. Khodzher N. Bashenkhaeva I. Korovyakova L. Sorokovikova L. Gorbunova 《Limnology》2002,3(3):0159-0168
Concentrations of dissolved organic carbon (DOC) in Lake Baikal ranged from 90 to 110 μM C, considerably higher than those
in oceanic environments. The DOC concentrations in the epilimnion were higher than those in the hypolimnion. Since particulate
organic carbon (POC) concentrations in the pelagic waters of Lake Baikal were <10–40 μM C in the epilimnion and 2–5 μM C in
the hypolimnion, DOC constitutes a major component of the organic carbon pool in Lake Baikal, especially in the deep layers.
The DOC concentrations downstream of the Barguzin and Selenga Rivers were quite high (400–500 μM C). Probably because of the
high concentrations of DOC in these rivers, the DOC levels in Barguzin Bay and offshore at the mouth of the Selenga River
were higher than those in the pelagic regions of the central and south basins of Lake Baikal. The relationship between DOC
and electric conductivity revealed the transport of DOC from rivers to the pelagic area in Lake Baikal. The spatial distribution
of DOC suggested that a major part of DOC in the lake was allochthonous (land-derived).
Received: July 26, 2002 / Accepted: September 16, 2002
Present address:Research Institute for Humanity and Nature, 335 Takashima-cho, Marutamachi Kawaramachi, Kamigyo-ku, Kyoto 602-0878, Japan
Tel. +81-75-229-6167; Fax +81-75-229-6150 e-mail: yos@chikyu.ac.jp
Acknowldgments The authors wish to thank Director Prof. M. Grachev and Dr. O. Timoshkin of the Limnological Institute, Siberian Branch,
Academy of Science, Russia, for arranging the cruise on Lake Baikal. We are also indebted to Drs. V. Sinyukovich, I. Khanaev,
and A. Zhdanov for their kind assistance during the expeditions. We wish to thank Ms. Y. Ito for measuring the DOC concentrations.
This work was supported and financed by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports,
Science and Technology (MEXT), Japan (No. 09041159) and for Scientific Research of Priority Area B (No. 11213101) and by the
International Geosphere-Biosphere Programme (IGBP) at Nagoya University.
Correspondence to:T. Yoshioka 相似文献
5.
Ryota Nakajima Teruaki Yoshida Bin Abdul Rahim Azman Kassim Zaleha Bin Haji Ross Othman Tatsuki Toda 《Aquatic Ecology》2009,43(4):815-823
In situ mucus release by Acropora nobilis and degradation of mucus from A. nobilis and Acropora formosa, by heterotrophic bacteria were investigated at Bidong and Tioman Island, Malaysia. Mucus release rate for A. nobilis was on average 38.7 ± 35.2 mg C m−2 h−1, of which ca. 70% consisted of dissolved organic carbon (DOC) and 30% particulate organic carbon (POC). In the mucus degradation
experiment, seawater-mucus mixtures were incubated and compared with control runs for 24 h. Bacterial abundance in the seawater-mucus
mixture increased significantly and coincided with a decline in DOC concentration. In controls, bacteria and DOC did not significantly
change. The coral mucus had a high content of inorganic phosphate. It is suggested that the coral mucus rich in DOC and phosphate
can induce the high bacterial growth. 相似文献
6.
湖泊湿地是地球上缓解全球变暖的巨大碳汇系统。在气候变化背景下,随着温度、降水等格局的改变,其碳汇功能存在高度的响应过程。基于135篇文献已发表的557项观测数据,运用meta分析的方法,分析全球尺度上气候及地理因素的相互作用对湖泊有机碳组分的影响,包括湖泊沉积物有机碳(Sediment Organic Carbon)、湖水中总有机碳(Total Organic Carbon)、湖水溶解有机碳(Dissolved Organic Carbon)和颗粒有机碳(Particulate Organic Carbon)。结果显示:1)在纬度3°49''N-76°24''N和海拔0-4500m范围内,SOC、TOC、POC和DOC的变化范围分别为0.25-15.6 g C/Kg、1.9-25.11 mg C/L、0.026-24 mg C/L、1-115.4 mg C/L;2)地理因素中,海拔与TOC呈显著的负相关(P < 0.05),每升高1m,TOC 增加0.0077 mg/L;纬度与POC呈显著负相关,与DOC呈显著正相关(P < 0.05),每增加1°,POC减少0.136 mg/L,DOC增加1.18 mg/L;3)气候因素中,年均温与SOC和POC呈显著的正相关,与DOC呈显著负相关(P < 0.05),每升高1℃,SOC和POC增加0.079 g/kg、0.36 mg/L,DOC下降1.52 mg/L;年均降水量与POC呈显著正相关,与DOC呈显著负相关(P < 0.05),每增加100mm,POC增加0.87 mg/L,DOC减少3 mg/L;4)气候和地理因素对SOC、TOC、POC、DOC综合影响的贡献度分别达到16.1%、14%、90%、61.6%;5)最热季度的降水对SOC的影响成正相关,其他季节性气候参数对湖水中TOC和SOC均无显著性影响;最冷季的降水因素是影响POC的主要因素,最潮湿月份、最潮湿季节的降水量和最冷季度的平均温度与POC呈显著正相关关系;最干燥月份、最干旱地区、最热季度和最冷季度的降水量对DOC的影响最显著。 相似文献
7.
Abstract
Sugar maple (Acer saccharum Marsh.)-dominated northern hardwood forests of the Great Lakes Region commonly receive elevated levels of atmospheric nitrate
(NO3−) deposition, which can alter belowground carbon (C) cycling. Past research has demonstrated that chronic experimental NO3− deposition (3 g N m−2 y−1 above ambient) elicits a threefold increase in the leaching loss of dissolved organic carbon (DOC). Here, we used DOC collected
from tension-cup lysimeters to test whether increased DOC export under experimental NO3− deposition originated from forest floor or mineral soil organic matter (SOM). We used DOC radiocarbon dating to quantify
C sources and colorimetric assays to measure DOC aromaticity and soluble polyphenolic content. Our results demonstrated that
DOC exports are primarily derived from new C (<50-years-old) in the forest floor under both ambient and experimental NO3− deposition. Experimental NO3− deposition increased soluble polyphenolic content from 25.03 ± 4.26 to 49.19 ± 4.23 μg phenolic C mg DOC−1, and increased total aromatic content as measured by specific UV absorbance. However, increased aromatic compounds represented
a small fraction (<10%) of the total observed increased DOC leaching. In combination, these findings suggest that experimental
NO3− deposition has altered the production or retention as well as phenolic content of DOC formed in forest floor, however exact
mechanisms are uncertain. Further elucidation of the mechanism(s) controlling enhanced DOC leaching is important for understanding
long-term responses of Great Lakes forests to anthropogenic N deposition and the consequences of those responses for aquatic
ecosystems. 相似文献
8.
Temporal and spatial distributions of dissolved organic carbon and nitrogen in two small lakes on the Southwestern China Plateau 总被引:6,自引:0,他引:6
Wen Li Fengchang Wu Congqiang Liu Pingqing Fu Jing Wang Yi Mei Liying Wang Jianyang Guo 《Limnology》2008,9(2):163-171
Temporal and spatial distributions of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), chlorophyll-a and inorganic nitrogen were investigated in two small mountainous lakes (Lake Hongfeng and Baihua), on the Southwestern China
Plateau, based on almost 2 years’ field observation. DOC concentrations ranged from 163 μM to 248 μM in Lake Hongfeng and
from 143 μM to 308 μM in Lake Baihua, respectively, during the study period. DON concentrations ranged from 7 μM to 26 μM
in Lake Hongfeng and from 14 μM to 47 μM in Lake Baihua. DOC showed vertical heterogeneity with higher concentrations in the
epilimnion than in the hypolimnion during the stratification period. The DON concentration profiles appeared to be more variable
than the DOC profiles. Apparent DON maxima occurred in the upper layer of water. In Lake Hongfeng, DOC concentration in the
surface water was highest at the end of spring and early summer. DON concentration was 2–5 μM higher in May 2003 and in June
2004 than in adjacent months. DOC and chlorophyll-a concentrations were significantly correlated (r = 0.79, P < 0.05). The period of highest concentrations of DOC in Lake Hongfeng was also the season of concentrated rainfall. Algae
activity and allochthonous input might result in an increase of DOC and DON concentrations together. In Lake Baihua, the maximum
concentrations of DOC and DON in the surface water occurred simultaneously in May 2003 and February 2004. DOC concentrations
were significantly correlated with DON (r = 0.90, P < 0.01), indicating the common sources. Allochthonous input, biological processes, stratification and mixing were the most
important factors controlling the distributions and cycling of dissolved organic matter (DOM) and inorganic nitrogen in these
two lakes. Inference from the corresponding vertical distributions of DOM and inorganic nitrogen indicated that DOM played
potential roles in the internal loading of nitrogen and metabolism in the water body in these small lakes. The carbon/nitrogen
(C/N) ratio showed a potential significance for tracing the source and biogeochemical processes of DOM in the lakes. These
results are of significance in the further understanding of biogeochemical cycling and environmental effects of DOM and nitrogen
in lake ecosystems. 相似文献
9.
Cristina Barrón Núria Marbà Carlos M. Duarte Morten F. Pedersen Cecilia Lindblad Kees Kersting Frithof Moy Tor Bokn 《Ecosystems》2003,6(2):0144-0153
We studied the effect of nutrient inputs on the carbon (C) budget of rocky shore communities using a set of eight large experimental
mesocosms. The mesocosms received a range of inorganic nitrogen (N) and phosphorus (P) additions, at an N:P ratio of 16. These
additions were designed to elevate the background concentration, relative to that in eutrophic Oslofjord (Norway) waters,
by 1, 2, 4, 8, 16, 32 μmol dissolved inorganic nitrogen (DIN)l−1 (and the corresponding P increase). Two unamended mesocosms were used as controls. The nutrients were added continuously
for 27 months before gross primary production (GPP), respiration (R), net community production (NCP), and dissolved organic
carbon (DOC) production were assessed for the dominant algal species (Fucus serratus) and for the whole experimental ecosystem. Inputs and outputs of DOC and particulate organic carbon (POC) from the mesocosms
were also quantified. The F. serratus communities were generally autotrophic (average P/R ratio = 1.33 ± 0.12), with the GPP independent of the nutrient inputs
to the mesocosms, and maintained a high net DOC production during both day (0.026 ± 0.008 g C m−2 h−1) and night (0.015 ± 0.004 g C m−2 h−1). All the experimental rocky shore ecosystems were autotrophic (P/R ratio = 2.04 ± 0.28), and neither macroalgal biomass
nor production varied significantly with increasing nutrient inputs. Most of the excess production from these autotrophic
ecosystems was exported from the systems as DOC, which accounted for 69% and 58% of the NCP of the dominant community and
the experimental ecosystem, respectively, the rest being lost as POC. High DOC release and subsequent export from the highly
energetic environments occupied by rocky shore communities may prevent the development of eutrophication symptoms and render
these communities resistant to eutrophication.
Received 10 October 2001; accepted 18 July 2002. 相似文献
10.
Céline Guéguen Laodong Guo Deli Wang Noriyuki Tanaka Chin-Chang Hung 《Biogeochemistry》2006,77(2):139-155
Monthly (or bi-weekly) water samples were collected from the Yukon River, one of the largest rivers in North America, at a
station near the US Geological Survey Stevens Village hydrological station, Alaska from May to September 2002, to examine
the quantity and quality of dissolved organic matter (DOM) and its seasonal variations. DOM was further size fractionated
into high molecular weight (HMW or colloidal, 1 kDa–0.45 μm) and low molecular weight (LMW, <1 kDa) fractions. Dissolved organic
carbon (DOC), colored dissolved organic matter (C-DOM) and total dissolved carbohydrate (TCHO) species were measured in the
size fractionated DOM samples. Concentrations of DOC were as high as 2830 μmol-C l−1 during the spring breakup in May and decreased significantly to 508–558 μmol-C l−1 during open-water season (June–September). Within the DOC pool, up to 85% was in the colloidal fraction (1 kDa–0.45 μm) in
early May. As DOC concentration decreased, this colloidal portion remained high (70–85% of the bulk DOC) throughout the sampling
season. Concentrations of TCHO, including monosaccharides (MCHO) and polysaccharides (PCHO), varied from 722 μmol-C l−1 in May to 129 μmol-C l−1 in September, which comprised a fairly constant portion of bulk DOC (24±2%). Within the TCHO pool, the MCHO/TCHO ratio consistently
increased from May to September. The C-DOM/DOM ratio and the size fractionated DOM increased from May to September, indicating
that DOM draining into the Yukon River contained increased amounts of humified materials, likely related to a greater soil
leaching efficiency in summer. The average composition of DOM was 76% pedogenic humic matter and 24% aquagenic CHO. Characteristics
of soil-derived humic substances and low chlorophyll-a concentrations support a dominance of terrestrial DOM in Yukon River waters. 相似文献
11.
Dynamics of dissolved and particulate organic carbon in a saline and semiarid stream of southeast Spain (Chicamo stream) 总被引:2,自引:1,他引:1
Vidal-Abarca M. R. Suárez M. L. Guerrero C. Velasco J. Moreno J. L. Millán A. Perán A. 《Hydrobiologia》2001,455(1-3):71-78
Annual variations in the concentration of dissolved (DOC) and particulate organic carbon (CPOC = Coarse; FPOC = Fine; UPOC = Ultrafine) were studied in a 100 m-reach of the Chicamo stream, an intermittent saline stream in southeast Spain. DOC represented the most important fraction of organic carbon flowing in the Chicamo stream (>98%), with concentrations of about 1.7 mgC l–1 during most of the year, reaching 2.5 mgC l–1 in summer. One high flow episode during a rain storm in winter was characterized by a considerably increased concentration of DOC (9.4 mgC l–1). CPOC was the dominant POC fraction. Positive and significant correlations were found for DOC and discharge, which support the idea of allochthonous inputs due to floods. There was no significant correlation between POC and discharge. No significant correlations were found for DOC or POC with the physico-chemical parameters measured, while a negative significant correlation was found between DOC and temperature. The export of total organic carbon from the drainage basin of the Chicamo stream was low (6.2 × 10–4 gC m–2 yr–1) and typical of streams in arid and semi-arid regions. The results of a Principal Component Analysis defined three different phases. The first consisted of short periods, during which floods provide pulses of allochthonous organic carbon and nutrients, the second a dry phase (summer), defined by biotic interactions, during which the stream could acts as a `sink' of organic matter, and the third and final phase which is characterised by hydrological stability. 相似文献
12.
V. S. Kuwahara R. Nakajima B. H. R. Othman M. R. M. Kushairi T. Toda 《Coral reefs (Online)》2010,29(3):693-704
Biologically diverse coral-reef ecosystems are both directly and indirectly susceptible to changes in the spectral ultraviolet
radiation (UVR) distribution. The purpose of this study was to (1) measure the variability of UVR and photosynthetically active
radiation (PAR) penetration in the water above coral reefs around the Malaysian peninsula, (2) measure the variability and
distribution of UVR-specific biogeochemical factors, and (3) determine the impact of biogeochemical variability as it affects
the UVR:PAR ratio. Downwelling UVR and PAR irradiance and bio-optically derived biogeochemical factors were measured at 14
coral survey stations around the Malaysian peninsula from August 10–29, 2007. The West Coast was characterized by relatively
shallow mean 10% UV-B (320 nm) penetration (1.68 ± 1.12 m), high chlorophyll (3.00 ± 4.72 μg l−1), high chromophoric dissolved organic matter (CDOM; 6.61 ± 3.31 ppb), high particulate organic carbon (POC; 190.65 ± 97.99 mg m−3), and low dissolved organic carbon (DOC; 1.34 ± 0.65 mg m−3). By contrast, the East Coast was characterized by relatively deep mean 10% UV-B penetration (5.03 ± 2.19 m), low chlorophyll
(0.34 ± 0.22 μg l−1), low CDOM (1.45 ± 0.44 ppb), low POC (103.21 ± 37.93 mg m−3), and relatively high DOC (1.91 ± 1.03 mg m−3). The UVR:PAR ratio was relatively higher on the East Coast relative to the West Coast, suggesting variable concentrations
of UVR-specific absorbing components. At all sites, UVR attenuation coefficients showed significant correlations with CDOM,
but were spatially dependent with regard to chlorophyll a, POC, and DOC. The results suggest that bio-optically significant CDOM and DOC factors are uncoupled in coral-reef communities
of Malaysia. Furthermore, the results support prior studies that show chromophorically active concentrations of DOM and POC
are significantly altering the amount of UVR penetration above coral reefs and may be notable factors in regulating intricate
biogeochemical cycles around benthic coral communities in Malaysia. 相似文献
13.
Fluxes of dissolved and nonfossil particulate organic carbon from an Oceania small river (Lanyang Hsi) in Taiwan 总被引:3,自引:0,他引:3
Concentrations of dissolved and particulate organic carbon (DOC & POC) in river waters were measuredduring 1993–1994 in the Lanyang Hsi watershed, which representsa typical small Oceania river. The DOC concentrations varied in the range of 0.5–4 mg/l during non-typhoon period, but rose to as highas 8 mg/l during Typhoon Tim in July, 1994. Based on the log-linearrelationship between the DOC load and the discharge rate, weestimated the DOC export to be 3.4 ± 0.6 ktC/yr,and the DOC yield to be 4.1 ± 0.7 gC/m2/yr,which is considerably higher than a former estimate (ca.0.1 gC/m2/yr) for the Oceania. On the other hand, the DOC yield is less than the concurrent POC yield (21.7 ± 4.7gC/m2/yr) by a factor of five, but most of theexported POC is fossil carbon. Under the assumption that the suspended sediments contain a mean fossil POC content of0.5%, the nonfossil POC yield was calculated to be 4.6± 3.0 gC/m2/yr, comparable to theDOC yield. Since DOC and nonfossil POC are directly related to theecosystem, their combined fluxes give a biogenic organic carbonyield of 8.7 ± 3.1 gC/m2/yr. 相似文献
14.
A set of three relatively pristine seasonally inundated limesink wetlands and one riparian wetland was studied over a 4–6 month
long inundation period in 2001. Patterns in organic matter properties and oxygen consumption in the water column followed
a previously documented ecological gradient based on soil composition, vegetation type, and canopy cover. The full canopy,
cypress-gum swamp had the highest mean concentrations of dissolved organic carbon (DOC; 26.2 mg/l) and dissolved lignin (sum
6; 299 μg/l) with lower concentrations observed in the partial canopy, cypress savanna (22.0 mg/l DOC; 252 μg/l sum 6) and the open marsh savanna (20.6 mg/l DOC; 135 μg/l sum 6), respectively. During the inundation period, DOC increased in concentration, dissolved lignin decreased, and δ13C shifted to more positive values which collectively indicate a large reduction in the percentage of aromatic carbon during
the inundation period. All wetlands had very high concentrations of organic matter, yet microbial oxygen consumption was almost
always stimulated by the addition of glucose rather than inorganic nutrients. Stimulation by glucose suggests that there were
very small pools of highly bioavailable forms of DOC in the wetlands. A larger pool of moderately bioavailable organic matter
had the capacity to sustain microbial oxygen consumption rates under dark conditions for at least 15 d. During the inundation
period, the cypress-gum swamp had the lowest average rates of whole water oxygen consumption (1.0 μM/h) with increasing rates observed in the cypress savanna (1.3 μM/h), marsh savanna (1.6 μM/h), and riparian wetland (1.9 μM/h), respectively. The lignin compositional fingerprint varied across the gradient of limesink wetlands, and was useful for
identifying different sources of vascular plant-derived DOM. Vascular plant production, algal production, microbial respiration,
and UV degradation are all important drivers of DOM cycling, and the consistencies observed in this initial assessment of
seasonally inundated limesink wetlands suggest they vary in predictable ways across the ecological gradient. 相似文献
15.
Concentrations of plankton, suspended particles 0.74–87 μm equivalent spherical diameter and dissolved organic carbon (DOC)
were measured from May to February at an Antarctic coastal site. Bacteria-sized particles 0.74–1 μm diameter, and bacterial
cells and heterotrophic protists all exhibited a seasonal minimum during winter and maxima in summer. Bacteria composed <10%
of the bacteria-sized particles. Release of autotrophic protists from the ice caused water column biomass of autotrophs to
reach maximum concentrations in October and November, but maximum cell concentration in the water column was reached in January.
Microheterotroph biomass weakly reflected the release of the ice algal community but reached maximum concentration during
the water column bloom in January. Total DOC concentrations varied from 0.36 mg C l−1 in July to 3.10 mg C l−1 in October, with a yearly average of 1.51 mg C l−1. Ultrafiltration of DOC revealed that the molecular weight composition of the DOC differed greatly through the year. DOC
<5 kDa molecular weight reached a maximum of 1.25 mg C l−1 in October and accounted for up to 60% of total DOC in July. Concentrations of high molecular weight DOC (>100 kDa) were
highest in July and November, with the DOC (100 kDa–0.5 μm) fraction reaching a maximum of 1.22 mg C l−1 in November and composing 82% of the total DOC in January. Wet chemical oxidation and high-temperature catalytic oxidation
organic carbon analyses were compared. Good correlation was observed between methods during summer but no significant correlation
existed in winter, indicating that winter DOC may be refractory.
Accepted: 21 March 2000 相似文献
16.
Colleen T. E. Kellogg Shelly D. Carpenter Alisha A. Renfro Am��lie Sallon Christine Michel J. Kirk Cochran Jody W. Deming 《Polar Biology》2011,34(12):2007-2023
Export of autochthonously produced particulate organic carbon (POC) is a globally important mechanism for sequestering carbon
in the deep sea. The role of microbial hydrolytic activity in attenuating POC flux is generally understudied, and particularly
complex on Arctic continental shelves influenced by other sources of POC. To evaluate this role, we used fluorogenic substrate
analogs to measure extracellular enzyme activity (EEA) associated with particle size fractions considered suspended (1–70 μm)
and sinking (>70 μm). Samples were collected by in situ filtration at depths of 25–100 m at ten stations (156–1,142 m deep)
in the Amundsen Gulf and Beaufort Sea in June–July, 2008, during the Circumpolar Flaw Lead project. Significant positive correlations
observed between EEA and both chlorophyll a and δ13CPOC suggest that EEA is elevated in waters dominated by marine-derived POC. No difference in bulk EEA was observed between size
fractions, but POC- and cell-specific EEA was significantly elevated on sinking aggregates. Calculations show that 2–44% of
carbon retention in surface waters could be attributed to mobilization by enzymes associated with sinking aggregates, and
up to 57% if enzymes associated with suspended particles are included. Model results suggest that microbial attenuation of
POC below the euphotic zone is a quantitatively important mechanism for carbon loss, especially when particles are sinking
slowly. The role of microbes in attenuating POC flux on Arctic shelves appears to have been underestimated previously and
may become increasingly important if climate warming brings increased marine productivity. 相似文献
17.
1. The carbon budgets and assimilation efficiencies (AEs) of adults and juveniles of Daphnia magna were quantified using 14C as a tracer. Animals were fed pure Chlamydomonas reinhardtii or Scenedesmus obliquus at different food concentrations. Carbon AEs (46–70%) were comparable at food concentrations of 0.03–0.30 mg C L?1 for both algal species, but decreased to 34–49% when the food concentration further increased by 10‐fold. The carbon AEs were significantly and negatively correlated with the food level. 2. During the postdigestive period, partitioning of ingested carbon into different compartments including excretion, respiration and egestion was not influenced by the food species and life stage. There was a negative correlation between respiration (as % of total loss) and food concentration and a positive correlation between egestion (as % of total loss) and food concentration. Dissolved organic carbon (DOC) and CO2 accounted for 55–72% and 9–37%, respectively, of the total carbon loss from juveniles fed both algal diets. For adults, DOC and CO2 contributed to 44–64% and 20–47% of the total carbon loss, respectively. Particulate organic carbon (POC) was a minor pathway for the overall carbon loss. 3. The turnover and release budget of structural carbon (as moults and neonate reproduction) were further evaluated in long‐term experiments at different algal concentrations. Food concentration did not affect the carbon efflux or the carbon allocation into different physiological compartments except for respiration. Juveniles had twofold lower carbon turnover rate (0.12–0.16 day?1) than those of the adults (0.32–0.35 day?1). In adults, comparable carbon was allocated into DOC (35–42%) and reproduction (27–35%), which were the dominant routes for carbon loss. For the juveniles, DOC accounted for 42–64% of the total carbon loss. 4. About 21–38% of the total DOC released by adults and juveniles was associated with the high molecular weight organic carbon fraction (>5 kDa). Our results show that carbon was mainly lost by D. magna in the form of DOC during assimilation process as well as from the structural materials. Reproduction or maternal transfer was another major drain of body carbon for adult D. magna. 相似文献
18.
Abstract
Freshwater ecosystems derive organic carbon from both allochthonous and autochthonous sources. We studied the relative contributions
of different carbon sources to zooplankton in a small, polyhumic, steeply stratified lake, using six replicate surface-to-sediment
enclosures established during summer and autumn 2004. We added 13C-enriched bicarbonate to the epilimnion of half the enclosures for three weeks during each season and monitored carbon stable
isotope ratios of DIC, DOC, POC and Daphnia, along with physical, chemical and biological variables. During summer, 13C-enriched DIC (δ13C up to 44 ± 7.2‰) was soon taken up by phytoplankton (δ13C up to −5.1 ± 13.6‰) and was transmitted to Daphnia (δ13C up to −1.7 ± 7.2‰), demonstrating consumption of phytoplankton. In contrast, during autumn, 13C-enriched DIC (δ13C up to 56.3 ± 9.8‰) was not transmitted to Daphnia, whose δ13C became progressively lower (δ13C down to −45.6 ± 3.3‰) concomitant with decreasing methane concentration. Outputs from a model suggested phytoplankton contributed
64–84% of Daphnia diet during summer, whereas a calculated pelagic carbon mass balance indicated only 30–40% could have come from phytoplankton.
Although autumn primary production was negligible, zooplankton biomass persisted at the summer level. The model suggested
methanotrophic bacteria contributed 64–87% of Daphnia diet during autumn, although the calculated carbon mass balance indicated a contribution of 37–112%. Thus methanotrophic
bacteria could supply virtually all the carbon requirement of Daphnia during autumn in this lake. The strongly 13C-depleted Daphnia values, together with the outputs from the models and the calculated carbon mass balance showed that methanotrophic bacteria
can be a greater carbon source for Daphnia in lakes than previously suspected. 相似文献
19.
揭示亚热带森林土壤有机碳流失规律是制定相应措施以巩固和维持森林生态系统碳汇的关键。然而已有研究存在的监测对象单一、频率过低、时间过短等问题,导致对这一规律的认识仍然不足。选择亚热带典型的常绿阔叶林和杉木人工林为研究对象,每次降雨过后监测其径流量、泥沙量,分析径流和泥沙中的可溶性有机碳(Dissolved organic carbon,DOC)含量以及颗粒有机碳(Particle organic carbon,POC)含量。旨在比较两种森林DOC和POC流失量的差异,并分析二者与降雨量、降雨强度、5 min最大雨强和降雨侵蚀力四个降雨特征值的关联。拟验证以下两个问题:(1)杉木人工林的DOC和POC流失量是否高于常绿阔叶林;(2)降雨侵蚀力对DOC和POC的解释是否优于降雨量、降雨强度和5 min最大雨强。研究结果发现常绿阔叶林径流量、泥沙量、径流水中DOC浓度和POC浓度、DOC和POC流失量均显著高于杉木人工林。回归分析表明常绿阔叶林和杉木人工林DOC和POC流失量与降雨量、降雨强度和降雨侵蚀力呈显著的线性或幂函数相关,其中降雨量与DOC和POC流失量之间的拟合关系最优。常绿阔叶林产流和产沙量高于杉木人工林可能与前者的林下植被生物量较低有关,前者径流水中DOC浓度和POC浓度较高可归因于其较高的总生物量和土壤有机碳含量。在未来森林经营过程中应合理管理林下植被,尽量减少和避免林下植被的抚育伐,从而能够降低有机碳的水土流失,达到巩固和维持森林碳汇的目的。在未来气候变暖导致降水变化背景下,利用降雨量作为预测指标能够较好评估我国亚热带森林有机碳流失的风险。 相似文献
20.
We studied the transport of particulate organic carbon (POC) and dissolved organic carbon (DOC) in two regulated rivers during minimum and increasing discharges. Mean annual concentrations of total POC, measured monthly during conditions of minimum discharge from the dams, were twice as high at a station below a dam with a selective withdrawal system on the Kootenai River (KR, 0.15 mg 1–1), as at station below a dam with hypolimnetic water releases on the Flathead River (FR, 0.07 mg 1–1). Annual mean concentrations of DOC were similar below both dams (1.62 mg 1–1 FR; 1.71 KR). The percentage of POC in four size fractions differed in regulated and unregulated reaches of each river system; the smallest size fraction (0.45–10 smm) constituted a larger percentage of the total POC at the stations below the dams (50–93%), because POC in large size classes had settled out in the reservoir. The three largest size fractions (10–1000 µm) comprised a larger percentage of the total POC when samples were taken during conditions of full discharge from the dam. We measured large increases in all size classes of POC in samples collected during increasing discharges in a regulated reach, reflecting the component of sloughed periphyton and resuspended organic matter that were added during periods of hydropower generation at the dam. Seston (355 µm to 1 cm) collected in nets increased dramatically during increasing flows; concentrations of particulate organic matter (POM) in samples collected two and three hours after water levels began to rise were 572 and 1440 times higher than those collected during minimum discharge at the dam. 相似文献