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1.
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
2.
Shell size distribution patterns of marine gastropod populations may vary considerably across different environments. We investigated
the size and density structure of genetically continuous periwinkle populations (Littorina littorea) on an exposed rocky and a sheltered sedimentary environment on two nearby islands in the south-eastern North Sea (German
Bight). On the sedimentary shore, periwinkle density (917 ± 722 individuals m−2) was about three times higher than on the rocky shore (296 ± 168 individuals m−2). Mean (9.8 ± 3.9 mm) and maximum (22 mm) shell size of L. littorea on the sedimentary shore were smaller than on the rocky shore (21.5 ± 4.2 and 32 mm, respectively), where only few small
snails were found. Additionally, periwinkle shells were thicker and stronger on the rocky than on the sedimentary shore. To
ascertain mechanisms responsible for differences in population structures, we examined periwinkles in both environments for
growth rate, predation pressure, infection with a shell boring polychaete (Polydora ciliata) and parasitic infestation by trematodes. A crosswise transplantation experiment revealed better growth conditions on the
sedimentary than on the rocky shore. However, crab abundance and prevalence of parasites and P. ciliata in adult snails were higher on the sedimentary shore. Previous investigations showed that crabs prefer large periwinkles
infested with P. ciliata. Thus, we suggest that parasites and shell boring P. ciliata in conjunction with an increased crab predation pressure are responsible for low abundances of large periwinkles on the sedimentary
shore while high wave exposure may explain low densities of juvenile L. littorea on the rocky shore. We conclude that biotic factors may strongly contribute to observed differences in size structure of
the L. littorea populations studied on rocky and sedimentary shores. 相似文献
3.
Autochthonous origin of semi-labile dissolved organic carbon in a large monomictic lake (Lake Biwa): carbon stable isotopic evidence 总被引:1,自引:0,他引:1
Koh Maki Chulgoo Kim Chikage Yoshimizu Ichiro Tayasu Toshihiro Miyajima Toshi Nagata 《Limnology》2010,11(2):143-153
Semi-labile dissolved organic carbon (DOC) plays an important role in the transport and hypolimnetic remineralization of carbon
in large freshwater lakes. However, sources of semi-labile DOC in lakes remain unclear. This study used a carbon stable isotope
approach to examine relative contributions of autochthonous and allochthonous sources to semi-labile DOC. Vertical and seasonal
variations in the concentration and carbon stable isotope ratio (δ13C) of DOC were determined in large (surface area 674 km2; maximum depth 104 m), monomictic Lake Biwa. A sharp vertical gradient of δ13C of DOC (δ13C-DOC) during the stratification period [mean ± standard error (SE) −25.5 ± 0.1 and −26.0 ± 0.0‰ in the epi- and hypolimnion,
respectively] indicated the accumulation of 13C-rich DOC in the epilimnion. Vertical mixing explained the intermediate values of δ13C-DOC (−25.7 ± 0.0‰) measured throughout the water column during the overturn period. Both DOC concentration and δ13C-DOC decreased in the hypolimnion during stratification, indicating selective remineralization of 13C-rich DOC. Using a two-component mixing model, we estimated the δ13C value of semi-labile DOC to be −22.2 ± 0.3‰, which was close to the δ13C of particulate organic carbon collected in the epilimnion during productive seasons (−22.7 ± 0.7‰) but much higher than
the δ13C-DOC in river waters (−26.5 ± 0.1‰). Semi-labile DOC appeared to be mainly autochthonous in origin, produced by planktonic
communities during productive seasons. The spatiotemporal uncoupling between production and remineralization of semi-labile
DOC implies that hypolimnetic oxygen consumption may be affected by pelagic primary production during productive seasons of
the preceding year. 相似文献
4.
To identify the controls on dissolved organic carbon (DOC) production, we incubated soils from 18 sites, a mixture of 52 forest
floor and peats and 41 upper mineral soil samples, at three temperatures (3, 10, and 22°C) for over a year and measured DOC
concentration in the leachate and carbon dioxide (CO2) production from the samples. Concentrations of DOC in the leachate were in the range encountered in field soils (<2 to >50 mg l−1). There was a decline in DOC production during the incubation, with initial rates averaging 0.03–0.06 mg DOC g−1 soil C day−1, falling to averages of 0.01 mg g−1 soil C day−1; the rate of decline was not strongly related to temperature. Cumulative DOC production rates over the 395 days ranged from
less than 0.01 to 0.12 mg g−1 soil C day−1 (0.5–47.6 mg g−1 soil C), with an average of 0.021 mg g−1 soil C day−1 (8.2 mg g−1 soil C). DOC production rate was weakly related to temperature, equivalent to Q10 values of 0.9 to 1.2 for mineral samples and 1.2 to 1.9 for organic samples. Rates of DOC production in the organic samples
were correlated with cellulose (positively) and lignin (negatively) proportion in the organic matter, whereas in the mineral
samples C and nitrogen (N) provided positive correlations. The partitioning of C released into CO2–C and DOC showed a quotient (CO2–C:DOC) that varied widely among the samples, from 1 to 146. The regression coefficient of CO2–C:DOC production (log10 transformed) ranged from 0.3 to 0.7, all significantly less than 1. At high rates of DOC production, a smaller proportion
of CO2 is produced. The CO2–C:DOC quotient was dependent on incubation temperature: in the organic soil samples, the CO2–C:DOC quotient rose from an average of 6 at 3 to 16 at 22°C and in the mineral samples the rise was from 7 to 27. The CO2–C:DOC quotient was related to soil pH in the organic samples and C and N forms in the mineral samples. 相似文献
5.
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
6.
Mark S. Johnson Johannes Lehmann Eduardo Guimarães Couto João Paulo Novães Filho Susan J. Riha 《Biogeochemistry》2006,81(1):45-57
Organic and inorganic carbon (C) fluxes transported by water were evaluated for dominant hydrologic flowpaths on two adjacent headwater catchments in the Brazilian Amazon with distinct soils and hydrologic responses from September 2003 through April 2005. The Ultisol-dominated catchment produced 30% greater volume of storm-related quickflow (overland flow and shallow subsurface flow) compared to the Oxisol-dominated catchment. Quickflow fluxes were equivalent to 3.2 ± 0.2% of event precipitation for the Ultisol catchment, compared to 2.5 ± 0.3% for the Oxisol-dominated watershed (mean response ±1 SE, n = 27 storms for each watershed). Hydrologic responses were also faster on the Ultisol watershed, with time to peak flow occurring 10 min earlier on average as compared to the runoff response on the Oxisol watershed. These different hydrologic responses are attributed primarily to large differences in saturated hydraulic conductivity (K
s). Overland flow was found to be an important feature on both watersheds. This was evidenced by the response rates of overland flow detectors (OFDs) during the rainy season, with overland flow intercepted by 54 ± 0.5% and 65 ± 0.5% of OFDs for the Oxisol and Ultisol watersheds respectively during biweekly periods. Small volumes of quickflow correspond to large fluxes of dissolved organic C (DOC); DOC concentrations of the hydrologic flowpaths that comprise quickflow are an order of magnitude higher than groundwater flowpaths fueling base flow (19.6 ± 1.7 mg l−1 DOC for overland flow and 8.8 ± 0.7 mg l−1 DOC for shallow subsurface flow versus 0.50 ± 0.04,mg l−1 DOC in emergent groundwater). Concentrations of dissolved inorganic C (DIC, as dissolved CO2–C plus HCO3−–C) in groundwater were found to be an order of magnitude greater than quickflow DIC concentrations (21.5 mg l−1 DIC in emergent groundwater versus 1.1 mg l−1 DIC in overland flow). The importance of deeper flowpaths in the transport of inorganic C to streams is indicated by the 40:1 ratio of DIC:DOC for emergent groundwater. Dissolved CO2–C represented 92% of DIC in emergent groundwater. Results from this study illustrate a highly dynamic and tightly coupled linkage between the C cycle and the hydrologic cycle for both Ultisol and Oxisol landscapes: organic C fluxes strongly tied to flowpaths associated with quickflow, and inorganic C (particularly dissolved CO2) transported via deeper flowpaths. 相似文献
7.
The Long-term Effects of Disturbance on Organic and Inorganic Nitrogen Export in the White Mountains, New Hampshire 总被引:22,自引:8,他引:14
Traditional biogeochemical theories suggest that ecosystem nitrogen retention is controlled by biotic N limitation, that stream
N losses should increase with successional age, and that increasing N deposition will accelerate this process. These theories
ignore the role of dissolved organic nitrogen (DON) as a mechanism of N loss. We examined patterns of organic and inorganic
N export from sets of old-growth and historically (80–110 years ago) logged and burned watersheds in the northeastern US,
a region of moderate, elevated N deposition. Stream nitrate concentrations were strongly seasonal, and mean (± SD) nitrate
export from old-growth watersheds (1.4 ± 0.6 kg N ha−1 y−1) was four times greater than from disturbed watersheds (0.3 ± 0.3 kg N ha−1 y−1), suggesting that biotic control over nitrate loss can persist for a century. DON loss averaged 0.7 (± 0.2) kg N ha−1 y−1 and accounted for 28–87% of total dissolved N (TDN) export. DON concentrations did not vary seasonally or with successional
status, but correlated with dissolved organic carbon (DOC), which varied inversely with hardwood forest cover. The patterns
of DON loss did not follow expected differences in biotic N demand but instead were consistent with expected differences in
DOC production and sorption. Despite decades of moderate N deposition, TDN export was low, and even old-growth forests retained
at least 65% of N inputs. The reasons for this high N retention are unclear: if due to a large capacity for N storage or biological
removal, N saturation may require several decades to occur; if due to interannual climate variability, large losses of nitrate
may occur much sooner.
Received 27 April 1999; accepted 30 May 2000. 相似文献
8.
Effects of hydrologic and water quality drivers on periphyton dynamics in the southern Everglades 总被引:2,自引:2,他引:0
David M. Iwaniec Daniel L. Childers Damon Rondeau Christopher J. Madden Colin Saunders 《Hydrobiologia》2006,569(1):223-235
Everglades periphyton mats are tightly-coupled autotrophic (algae and cyanobacteria) and heterotrophic (eubacteria, fungi
and microinvertebrates) microbial assemblages. We investigated the effect of water column total phosphorus and nitrogen concentrations,
water depth and hydroperiod on periphyton of net production, respiration, nutrient content, and biomass. Our study sites were
located along four transects that extended southward with freshwater sheetflow through sawgrass-dominated marsh. The water
source for two of the transects were canal-driven and anchored at canal inputs. The two other transects were rain-driven (ombrotrophic)
and began in sawgrass-dominated marsh. Periphyton dynamics were examined for upstream and downstream effects within and across
the four transects. Although all study sites were characterized as short hydroperiod and phosphorus-limited oligotrophic,
they represent gradients of hydrologic regime, water source and water quality of the southern Everglades. Average periphyton
net production of 1.08 mg C AFDW−1 h−1 and periphyton whole system respiration of 0.38 mg C AFDW−1 h−1 rates were net autotrophic. Biomass was generally highest at ombrotrophic sites and sites downstream of canal inputs. Mean
biomass over all our study sites was high, 1517.30 g AFDW m−2. Periphyton was phosphorus-limited. Average periphyton total phosphorus content was 137.15 μg P g−1 and average periphyton total N:P ratio was 192:1. Periphyton N:P was a sensitive indicator of water source. Even at extremely
low mean water total phosphorus concentrations ( ≤ 0.21 μmol l−1), we found canal source effects on periphyton dynamics at sites adjacent to canal inputs, but not downstream of inflows.
These canal source effects were most pronounced at the onset of wet season with initial rewetting. Spatial and temporal variability
in periphyton dynamics could not solely be ascribed to water quality, but was often associated with both hydrology and water
source. 相似文献
9.
To determine the chemical and physicochemical characteristics of dissolved organic carbon in the Ado River and the Yasu River,
the main rivers flowing into Lake Biwa, the adsorption behavior onto hydrous iron oxide (HIO) and the reactivity to KMnO4 oxidant were investigated in parallel with measurement of the distribution profiles of dissolved organic carbon (DOC) along
the rivers. In one year of observation at the mouths of the two rivers, DOC concentrations were found to vary in the Ado over
the range 0.28–1.21 mg C l−1 and in the Yasu over the range 1.01–2.68 mg C l−1. Act-DOC, one of the fractions separated from the total DOC by its adsorption-active character onto HIO at pH 4, was thought
primarily to control the variation of total DOC, as in Lake Biwa. The int-DOC, another fraction separated by its adsorption-inert
or -inactive character onto HIO, remained at almost a steady value around 0.18 ± 0.07 mg C l−1 in the Ado, which was lower than that (0.35 ± 0.05 mg C l−1) in Lake Biwa. The act-DOC in river waters was reactive to KMnO4 oxidant, showing a linear relation with the amount of permanganate consumed for the reaction (chemical oxygen demand: COD).
In river waters, the relation can be approximated by a straight line expressed as COD (mg O2 l−1) = 0.64 × act-DOC (mg C l−1) − 0.02. In contrast, in the lake water the relation was COD (mg O2 l−1) = 0.97 × act-DOC (mg C l−1) − 0.50.
Received: March 3, 1999 / Accepted: December 2, 1999 相似文献
10.
The carbon cycle was quantified in the catchment of Doe House Gill, which drains high-relief moorland, with thin organic-rich
soils (leptosols and podzols) 10–25 cm deep, in northern England. The soil C pool of 8,300 g m-2 is due mainly to humic acid and older humin. If steady state is assumed, and a single soil C pool, the average 14C content of the whole soil (93% modern) yields a mean carbon residence time of 800 years, although this varied from 300 to
1,600 years in the four samples studied. Stream water fluxes of dissolved and particulate organic carbon (DOC, POC) were 2.5
and 0.4 g m−2 a−1 respectively in 2002–2003, lower than values for some other upland streams in the UK. The C pool, flux, and isotope data
were used, with the assumption of steady state, to calibrate DyDOC, a model that simulates the soil carbon cycle, including
the generation and transport of DOC. According to DyDOC, the litter pool (ca. 100 gC m−2) turns over quickly, and most (>90%) of the litter carbon is rapidly mineralised. The soil is calculated to gain only 16 gC m−2 a−1, and to lose the same amount, about 80% as CO2 and 20% as DOC. From the DO14C content of 107.5% modern (due to “bomb carbon”) the model could be calibrated by assuming all DOC to come directly from
litter, but DOC is more likely a mixture, derived from more than one soil C pool. The seasonal variability exhibited by stream
water DOC concentration (maximum in September, minimum in January) is attributed mainly to variations in rainfall and evapotranspiration,
rather than in the metabolic production rate of “potential DOC”. The model predicts that, for a Q
10 of 2, the total soil organic C pool would decrease by about 5% if subjected to warming over 200 years. DyDOC predicts higher
DOC fluxes in response to increased litter inputs or warming, and can simulate changes in DOC flux due to variations in sorption
to soil solids, that might occur due to acidification and its reversal. 相似文献
11.
Response of Oxidative Enzyme Activities to Nitrogen Deposition Affects Soil Concentrations of Dissolved Organic Carbon 总被引:10,自引:0,他引:10
Recent evidence suggests that atmospheric nitrate (NO
3
−
) deposition can alter soil carbon (C) storage by directly affecting the activity of lignin-degrading soil fungi. In a laboratory
experiment, we studied the direct influence of increasing soil NO
3
−
concentration on microbial C cycling in three different ecosystems: black oak–white oak (BOWO), sugar maple–red oak (SMRO),
and sugar maple–basswood (SMBW). These ecosystems span a broad range of litter biochemistry and recalcitrance; the BOWO ecosystem
contains the highest litter lignin content, SMRO had intermediate lignin content, and SMBW leaf litter has the lowest lignin
content. We hypothesized that increasing soil solution NO
3
−
would reduce lignolytic activity in the BOWO ecosystem, due to a high abundance of white-rot fungi and lignin-rich leaf litter.
Due to the low lignin content of litter in the SMBW, we further reasoned that the NO
3
−
repression of lignolytic activity would be less dramatic due to a lower relative abundance of white-rot basidiomycetes; the
response in the SMRO ecosystem should be intermediate. We increased soil solution NO
3
−
concentrations in a 73-day laboratory incubation and measured microbial respiration and soil solution dissolved organic carbon
(DOC) and phenolics concentrations. At the end of the incubation, we measured the activity of β-glucosidase, N-acetyl-glucosaminidase,
phenol oxidase, and peroxidase, which are extracellular enzymes involved with cellulose and lignin degradation. We quantified
the fungal biomass, and we also used fungal ribosomal intergenic spacer analysis (RISA) to gain insight into fungal community
composition. In the BOWO ecosystem, increasing NO
3
−
significantly decreased oxidative enzyme activities (−30% to −54%) and increased DOC (+32% upper limit) and phenolic (+77%
upper limit) concentrations. In the SMRO ecosystem, we observed a significant decrease in phenol oxidase activity (−73% lower
limit) and an increase in soluble phenolic concentrations (+57% upper limit) in response to increasing NO
3
−
in soil solution, but there was no significant change in DOC concentration. In contrast to these patterns, increasing soil
solution NO
3
−
in the SMBW soil resulted in significantly greater phenol oxidase activity (+700% upper limit) and a trend toward lower DOC
production (−52% lower limit). Nitrate concentration had no effect on microbial respiration or β-glucosidase or N-acetyl-glucosaminidase
activities. Fungal abundance and basidiomycete diversity tended to be highest in the BOWO soil and lowest in the SMBW, but
neither displayed a consistent response to NO
3
−
additions. Taken together, our results demonstrate that oxidative enzyme production by microbial communities responds directly
to NO
3
−
deposition, controlling extracellular enzyme activity and DOC flux. The regulation of oxidative enzymes by different microbial
communities in response to NO
3
−
deposition highlights the fact that the composition and function of soil microbial communities directly control ecosystem-level
responses to environmental change. 相似文献
12.
Coastal eutrophication may alter the dominance patterns of marine macroalgae, with potential consequences for the associated
fauna and the entire ecosystem. Benthic macroalgae and animals in control and nutrient-enriched mesocosms were monitored to
investigate eutrophication-induced changes in rocky shore communities. During a 3-year project, nutrient addition had only
minor effects on the community structure, such as increased cover and biomass of green Ulva spp. and increased abundance of certain animal species at high nutrient levels. This study is a 4-year extension of a previously
reported project, with 2 extra years of effect studies (altogether 5 years) and a subsequent 2 years for recovery. During
the 4th year of nutrient enrichment, the cover of Fucus vesiculosus and Fucus serratus started to decline. In the 5th year, these canopy species crashed and there was an evident take-over by green algae at high
nutrient addition levels. The previously observed abundance stimulation for fauna disappeared later in the time series, probably
due to the loss of the macroalgal canopy. After less than 2 years on regular seawater, the algal and animal communities had
returned to within the range of normal variability. The results indicate that established rocky shore communities of perennial
algae with associated fauna are able to persist for several years, even at very high nutrient levels, but that community shifts
may suddenly occur if eutrophication continues. They also indicate that rocky shore communities have the ability to return
rapidly to natural undisturbed conditions after the termination of nutrient enhancement. 相似文献
13.
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
14.
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
15.
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
16.
DeXiang Chen YiDe Li HePing Liu Han Xu WenFa Xiao TuShou Luo Zhang Zhou MingXian Lin 《中国科学:生命科学英文版》2010,53(7):798-810
Biometric inventories for 25 years, from 1983 to 2005, indicated that the Jianfengling tropical mountain rain forest in Hainan,
China, was either a source or a modest sink of carbon. Overall, this forest was a small carbon sink with an accumulation rate
of (0.56±0.22) Mg C ha−1yr−1, integrated from the long-term measurement data of two plots (P9201 and P8302). These findings were similar to those for
African and American rain forests ((0.62±0.23) Mg C ha−1yr−1). The carbon density varied between (201.43±29.38) Mg C ha−1 and (229.16±39.2) Mg C ha−1, and averaged (214.17±32.42) Mg C ha−1 for plot P9201. Plot P8302, however, varied between (223.95±45.92) Mg C ha−1 and (254.85±48.86) Mg C ha−1, and averaged (243.35±47.64) Mg C ha−1. Quadratic relationships were found between the strength of carbon sequestration and heavy rainstorms and dry months. Precipitation
and evapotranspiration are two major factors controlling carbon sequestration in the tropical mountain rain forest. 相似文献
17.
Effects of acid wastes from titanium dioxide production on biomass and species richness of benthic algae 总被引:1,自引:1,他引:0
Titanium dioxide wastes are suspected to be toxic to rocky shore communities in an estuary in southeast Norway. An experimental project lasting two years examined whether titanium dioxide wastes affected recolonization by rocky shore organisms. The experiments were performed in situ in six tanks (each with 9 m3 brackish water) at two different levels of salinity. Three different concentrations of industrial waste water were used. The growth season in 1986 was dry and sunny compared to 1987, causing reduction of growth on exposed granite chips compared to controls. At the two highest waste concentrations in the tanks, Fucus serratus was observed with necrotic tissue both years, and in 1986 benthic diatoms were scarce. 相似文献
18.
The Ferrous Wheel Hypothesis (Davidson et al. 2003) postulates the abiotic formation of dissolved organic N (DON) in forest floors, by the fast reaction of NO2
− with dissolved organic C (DOC). We investigated the abiotic reaction of NO2
− with dissolved organic matter extracted from six different forest floors under oxic conditions. Solutions differed in DOC
concentrations (15–60 mg L−1), NO2
− concentrations (0, 2, 20 mg NO2
−-N L−1) and DOC/DON ratio (13.4–25.4). Concentrations of added NO2
− never decreased within 60 min, therefore, no DON formation from added NO2
− took place in any of the samples. Our results suggest that the reaction of NO2
− with natural DOC in forest floors is rather unlikely. 相似文献
19.
Response of Periphytic Algae to Gradients in Nitrogen and Phosphorus in Streamside Mesocosms 总被引:2,自引:1,他引:1
In this study we manipulated both nitrogen and phosphorus concentrations in stream mesocosms to develop quantitative relationships
between periphytic algal growth rates and peak biomass with inorganic N and P concentrations. Stream water from Harts Run,
a 2nd order stream in a pristine catchment, was constantly added to 36 stream-side stream mesocosms in low volumes and then
recirculated to reduce nutrient concentrations. Clay tiles were colonized with periphyton in the mesocosms. Nutrients were
added to create P and N concentrations ranging from less than Harts Run concentrations to 128 μg SRP l−1 and 1024 μg NO3-N l−1. Algae and water were sampled every 3 days during colonization until periphyton communities reached peak biomass and then
sloughed. Nutrient depletion was substantial in the mesocosms. Algae accumulated in all streams, even streams in which no
nutrients were added. Nutrient limitation of algal growth and peak biomass accrual was observed in both low P and low N conditions.
The Monod model best explained relationships between P and N concentrations and algal growth and peak biomass. Algal growth
was 90% of maximum rates or higher in nutrient concentrations 16 μg SRP l−1 and 86 μg DIN l−1. These saturating concentrations for growth rates were 3–5 times lower than concentrations needed to produce maximum biomass.
Modified Monod models using both DIN and SRP were developed to explain algal growth rates and peak biomass, which respectively
explained 44 and 70% of the variance in algal response. 相似文献
20.
Algesten G Sobek S Bergström AK Jonsson A Tranvik LJ Jansson M 《Microbial ecology》2005,50(4):529-535
We measured sediment production of carbon dioxide (CO2) and methane (CH4) and the net flux of CO2 across the surfaces of 15 boreal and subarctic lakes of different humic contents. Sediment respiration measurements were
made in situ under ambient light conditions. The flux of CO2 between sediment and water varied between an uptake of 53 and an efflux of 182 mg C m−2 day−1 from the sediments. The mean respiration rate for sediments in contact with the upper mixed layer (SedR) was positively correlated
to dissolved organic carbon (DOC) concentration in the water (r2 = 0.61). The net flux of CO2 across the lake surface [net ecosystem exchange (NEE)] was also closely correlated to DOC concentration in the upper mixed
layer (r2 = 0.73). The respiration in the water column was generally 10-fold higher per unit lake area compared to sediment respiration.
Lakes with DOC concentrations <5.6 mg L−1 had net consumption of CO2 in the sediments, which we ascribe to benthic primary production. Only lakes with very low DOC concentrations were net autotrophic
(<2.6 mg L−1) due to the dominance of dissolved allochthonous organic carbon in the water as an energy source for aquatic organisms. In
addition to previous findings of allochthonous organic matter as an important driver of heterotrophic metabolism in the water
column of lakes, this study suggests that sediment metabolism is also highly dependent on allochthonous carbon sources. 相似文献