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1.
Periphyton production in Fort River, Massachusetts 总被引:4,自引:0,他引:4
SUMMARY. The primary production and general ecology of a periphyton community of a New England, lowland stream were studied over a seventeen-month period. Temperature, light, periphyton chlorophyll-α, and community structure were monitored regularly. Seasonally distinct chlorophyll peaks coincided with the light maximum in early May, just prior to the appearance of leaves of riparian trees, and again in autumn after terrestrial leaf fall. During midwinter, despite low light and temperature levels and high stream discharge, mean chlorophyll concentrations remained similar to summer values.
A mathematical expression relating periphyton photosynthesis per unit chlorophyll-α to temperature, light and periphyton density was established with submersible light-dark chambers in situ . Survey data collected over the study period were employed in the empirical equation to estimate seasonal variations in periphyton primary production. Weekly mean daily estimates of periphyton gross production ranged from < 0.1 g O2 m−2 , during midwinter, to 6.5 g O2 m−2 during early May. Estimated annual periphyton gross production and respiration were 0.58 and 1.27 kg O2 m−2 , respectively. Factors influencing seasonal variations of Fort River periphyton standing crop are discussed. 相似文献
A mathematical expression relating periphyton photosynthesis per unit chlorophyll-α to temperature, light and periphyton density was established with submersible light-dark chambers in situ . Survey data collected over the study period were employed in the empirical equation to estimate seasonal variations in periphyton primary production. Weekly mean daily estimates of periphyton gross production ranged from < 0.1 g O
2.
Gross primary production, community respiration and reaeration coefficient were determined during an annual cycle on the Viroin
River (South Belgium), based on the daily variations of dissolved oxygen concentration.
Reaeration coefficient remains remarkably constant (0.26 h−1) during the year in spite of discharge variations. The autotrophic community is dominated by ‘Ranunculus fluitans’. Primary production parallels the variations of total solar radiations. It ranges from 0 in winter to 8 g O2 m−2 d−1 in summer. In spring and summer, respiration variations parallel those of primary production (average value: 10 g O2 m−2 d−1); in the dry autumn, decomposition of dying macrophytes considerably enhances the community respiration (15 g O2 m−2 d−1).
A P/R diagram is used to characterize the trophic state of the Viroin. 相似文献
3.
Stuart G. Fisher 《International Review of Hydrobiology》1977,62(6):701-727
An annual organic matter budget for a 1700 m segment of Fort River (Massachusetts, USA) is presented. Primary production in this fourth order stream exceeds litter input annually, however ecosystem P/R is 0.5. Respiration in excess of gross primary production is supported by allochthonous organic matter imported from upstream reaches. The relative contribution of organic matter size fractions to stream consumers depends upon biologic lability, rate of input, and residence time in the ecosystem. Particles of seston size (1 μm to 1 mm) are most heavily used by consumers, however dissolved organic matter represents the largest input component. Microorganisms are the predominant consumers in this soft-water, nutrient-poor stream ecosystem. A conceptual model for assessing the processing efficiency of stream ecosystems is presented and discussed in terms of several headwater to estuary gradients. 相似文献
4.
V. I. Kolmakov O. V. Anishchenko E. A. Ivanova M. I. Gladyshev N. N. Sushchik 《Journal of applied phycology》2008,20(3):289-297
Periphyton (epilithon) gross primary production (GPP) was estimated using the DCMU-fluorescence method in the Yenisei River.
In the unshaded littoral zone, chlorophyll a concentration (Chl a) and GPP value varied from 0.83 to 973.74 mg m−2and 2–304,425 O2 m−2 day−1 (0.64–95 133 mg C m−2 day−1), respectively. Positive significant correlation (r = 0.8) between daily GPP and periphyton Chl a was found. Average ratio GPP:Chl a for periphyton was 36.36 mg C mg Chl a m−2 day−1. The obtained GPP values for the Yenisei River have a high significant correlation with values predicted by a conventional
empirical model for stream periphyton. We concluded that the DCMU-fluorescence method can be successfully used for measuring
of gross primary production of stream phytoperiphyton at least as another useful tool for such studies. 相似文献
5.
The Pantanal Mato-grossense is an extensive floodplain system located in the center of South America with important macrophytic primary producers. This study describes the dynamics of net primary production and the biomass of the aquatic macrophyte Pontederia lanceolata, the dominant species in some floodplain fields near Poconé. Productivity was determined from a combination of demographic and growth methods. Biomass was determined using squares of known area, periodically distributed at random. The average productivity during the period was 3.11 g dry weight m-2 day-1. The minimum and maximum values (0.04 g dry weight m-2 day-1 and 8.59 g dry weight m-2 day-1, respectively) occurred during the drought and the flood period, respectively. The standing stock varied between 12.7 and 235.9 g dry weight m-2, determined at the beginning of the flood and at its peak, respectively. The dynamics of the productivity and the standing stock of the species are associated with the flood patterns of the area and with life cycle of the plant. 相似文献
6.
GABRIEL YVON‐DUROCHER JOSÉ M. MONTOYA GUY WOODWARD J. IWAN JONES MARK TRIMMER 《Global Change Biology》2011,17(2):1225-1234
Methane (CH4) and carbon dioxide (CO2) are the dominant gaseous end products of the remineralization of organic carbon and also the two largest contributors to the anthropogenic greenhouse effect. We investigated whether warming altered the balance of CH4 efflux relative to gross primary production (GPP) and ecosystem respiration (ER) in a freshwater mesocosm experiment. Whole ecosystem CH4 efflux was strongly related to temperature with an apparent activation energy of 0.85 eV. Furthermore, CH4 efflux increased faster than ER or GPP with temperature, with all three processes having sequentially lower activation energies. Warming of 4 °C increased the fraction of GPP effluxing as CH4 by 20% and the fraction of ER as CH4 by 9%, in line with the offset in their respective activation energies. Because CH4 is 21 times more potent as a greenhouse gas, relative to CO2, these results suggest freshwater ecosystems could drive a previously unknown positive feedback between warming and the carbon cycle. 相似文献
7.
Ecosystem measures of river health and their response to riparian and catchment degradation 总被引:16,自引:3,他引:16
1. Measurements of ecological patterns are often used as primary biological indicators of river health. However, these patterns provide little information about important stream ecosystem processes (e.g. the sources and fate of energy and nutrients). The direct measurement of these processes is considered fundamental to the determination of the health of stream and river ecosystems. 2. In this paper we used two basic approaches to assess stream ecosystem response to catchment disturbance and, particularly, to the loss of riparian vegetation in different forested biomes across Australia. Benthic gross primary production (GPP) and respiration (R24) provided measures of the amounts of organic carbon produced and consumed within the system, respectively. Stable isotope analysis was used to trace the fate of terrestrial and instream sources of organic matter in the aquatic food web. In a focal catchment in SE Queensland, additional measurements were taken of riparian attributes, catchment features and water quality. 3. Baseline measurements of GPP and R24 from undisturbed forest streams provided reference values for healthy streams for comparison with sites where the catchment or riparian vegetation had been disturbed. These values of metabolism were low by world standards in all biomes examined. Preliminary data from the Mary River catchment in SE Queensland indicated that these parameters were sensitive to variations in riparian canopy cover and, to a lesser extent, catchment clearing, and predictive models were developed. The ratio P : R (GPP : R24) was used to determine whether sites were net consumers (P < R) or producers (P > R) of carbon but this was not considered a reliable indicator of stream health on its own. 4. Although forest streams were typically net consumers of carbon (P < < R), stable isotope analysis of metazoan food webs indicated a high dependence on inconspicuous epilithic algae in some biomes. 5. A dramatic decline in the health of forest streams was observed when GPP substantially exceeded R24, especially when instream primary producers shifted from palatable unicellular algae to prolific filamentous green algae and macrophytes. These sources of instream production do not appear to enter aquatic food webs, either directly through grazing or indirectly through a detrital loop. Accumulation of these plants has led to changes in channel morphology, loss of aquatic habitat and often a major decline in water quality in some of the streams studied. 相似文献
8.
Simulation and scaling of temporal variation in gross primary production for coniferous and deciduous temperate forests 总被引:1,自引:0,他引:1
Q. Wang J. Tenhunen E. Falge Ch. Bernhofer A. Granier‡ T. Vesala§ 《Global Change Biology》2004,10(1):37-51
Observations of ecosystem net carbon dioxide exchange obtained with eddy covariance techniques over a 4‐year period at spruce, beech and pine forest sites were used to derive time series data for gross primary production (GPP) and ecosystem respiration (Reco). A detailed canopy gas exchange model (PROXELNEE) was inverted at half‐hour time step to estimate seasonal changes in carboxylation capacity and light utilization efficiency of the forest canopies. The parameter estimates were then used further to develop a time‐dependent modifier of physiological activity in the daily time step gas exchange model of Chen et al. (1999) , previously used for regional simulations in BOREAS. The daily model was run under a variety of assumptions and the results emphasize the need in future analyses: (1) to focus on time‐dependent seasonal changes in canopy physiology as well as in leaf area index, (2) to compare time courses of physiological change in different habitats in terms of recognizable cardinal points in the seasonal course, and (3) to develop methods for utilizing information on seasonal changes in physiology in regional and continental carbon budget simulations. The results suggest that the daily model with appropriate seasonal adjustments for physiological process regulation should be an efficient tool for use in conjunction with remote sensing for regional evaluation of global change scenarios. 相似文献
9.
Site-level evaluation of satellite-based global terrestrial gross primary production and net primary production monitoring 总被引:6,自引:0,他引:6
David P. Turner William D. Ritts Warren B. Cohen† Thomas K. Maeirsperger Stith T. Gower‡ Al A. Kirschbaum‡ Steve W. Running§ Maosheng Zhao§ Steven C. Wofsy¶ Allison L. Dunn¶ Beverly E. Law John L. Campbell Walter C. Oechel Hyo Jung Kwon Tilden P. Meyers Eric E. Small†† Shirley A. Kurc†† John A. Gamon‡‡ 《Global Change Biology》2005,11(4):666-684
Operational monitoring of global terrestrial gross primary production (GPP) and net primary production (NPP) is now underway using imagery from the satellite‐borne Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Evaluation of MODIS GPP and NPP products will require site‐level studies across a range of biomes, with close attention to numerous scaling issues that must be addressed to link ground measurements to the satellite‐based carbon flux estimates. Here, we report results of a study aimed at evaluating MODIS NPP/GPP products at six sites varying widely in climate, land use, and vegetation physiognomy. Comparisons were made for twenty‐five 1 km2 cells at each site, with 8‐day averages for GPP and an annual value for NPP. The validation data layers were made with a combination of ground measurements, relatively high resolution satellite data (Landsat Enhanced Thematic Mapper Plus at ~30 m resolution), and process‐based modeling. There was strong seasonality in the MODIS GPP at all sites, and mean NPP ranged from 80 g C m?2 yr?1 at an arctic tundra site to 550 g C m?2 yr?1 at a temperate deciduous forest site. There was not a consistent over‐ or underprediction of NPP across sites relative to the validation estimates. The closest agreements in NPP and GPP were at the temperate deciduous forest, arctic tundra, and boreal forest sites. There was moderate underestimation in the MODIS products at the agricultural field site, and strong overestimation at the desert grassland and at the dry coniferous forest sites. Analyses of specific inputs to the MODIS NPP/GPP algorithm – notably the fraction of photosynthetically active radiation absorbed by the vegetation canopy, the maximum light use efficiency (LUE), and the climate data – revealed the causes of the over‐ and underestimates. Suggestions for algorithm improvement include selectively altering values for maximum LUE (based on observations at eddy covariance flux towers) and parameters regulating autotrophic respiration. 相似文献
10.
Microcommunities and microgradients: Linking nutrient regeneration,microbial mutualism,and high sustained aquatic primary production 总被引:4,自引:0,他引:4
Robert G. Wetzel 《Aquatic Ecology》1993,27(1):3-9
Nutrient regeneration is essential to sustained primary production in the aquatic environment because of coupled physical
and metabolic gradients. The commonly evaluated ecosystem perspective of nutrient regeneration, as is illustrated among planktonic
paradigms of lake ecosystems, functions only at macrotemporal and spatial scales.
Most inland waters are small and shallow. Consequently, most organic matter of these waters is derived from photosynthesis
of emergent, floating-leaved, and submersed higher plants and microflora associated with living substrata and detritus, including
sediments, as well as terrestrial sources. The dominant primary productivity of inland aquatic ecosystems is not planktonic,
but rather is associated with surfaces. The high sustained rates of primary production among sessile communities are possible
because of the intensive internal recycling of nutrients, including carbon.
Steep gradients exist within these attached microbial communities that (a) require rapid, intensive recycling of carbon, phosphorus,
nitrogen, and other nutrients between producers, particulate and dissolved detritus, and bacteria and protists: (b) augment
internal community recycling and losses with small external inputs of carbon and nutrients from the overlying water or from
the supporting substrata; and (c) encourage maximal conservation of nutrients. Examples of microenvironmental recycling of
carbon, phosphorus, and oxygen among epiphytic, epipelic, and epilithic communities are explained. Recalcitrant dissolved
organic compounds from decomposition can serve both as carbon and energy substrates as well as be selectively inhibitory to
microbial metabolism and nutrient recycling. Rapid recycling of nutrient and organic carbon within micro-environments operates
at all levels, planktonic as well as attached, and is mandatory for high sustained productivity. 相似文献
11.
The literature and original data on the primary production of phytoplankton in the White Sea are analyzed. By this parameter, the White Sea is significantly inferior only to the Chukchi Sea; it is similar to the Barents Sea, and exceeds other Russian Arctic seas by two to three times (the Kara Sea, Laptev Sea, and East Siberian Sea). 相似文献
12.
河流生态系统服务功能及水坝对其影响 总被引:6,自引:0,他引:6
河流生态系统服务功能是指河流生态系统与河流生态过程所形成及所维持的人类赖以生存的自然环境条件与效用,包括河流生态系统产品与河流生态系统服务两个方面。文中分析了河流生态系统的15项服务功能,其中包括供水、水产品生产、内陆航运、水力发电、休闲娱乐和文化美学等6项河流生态系统产品与调蓄洪水、河流输送、蓄积水分、土壤持留、净化环境、固定CO2、养分循环、提供生境和维持生物多样性等9项河流生态系统服务;同时又分析了修建水坝对这此服务功能的影响。研究表明,使河流生态系统服务功能得到正常发挥,是水坝建设决策中应考虑的必要因素。 相似文献
13.
Ecological risk assessment (ERA) is a scientific tool used to support ecosystem-based management (EBM), but most current ERA methods consider only a few indices of particular species or components. Such limitations restrict the scope of results so that they are insufficient to reflect the integrated risk characterization of an ecosystem, thereby inhibiting the application of ERA in EBM. We incorporate the concept of ecosystem services into ERA and develop an improved ERA framework to create a comprehensive risk map of an ecosystem, accounting for multiple human activities and ecosystem services. Using the Yellow River as a case study, we show how this framework enables the implementation of integrated risk characterization and prioritization of the most important ecological risk issues in the ecosystem-based river management of the Yellow River. This framework can help practitioners facilitate better implementation of ERA within EBM in rivers or any target ecosystem. 相似文献
14.
Ryszard Staniszewski Krzysztof Szoszkiewicz Janina Zbierska Jacek Lesny Szymon Jusik Ralph T. Clarke 《Hydrobiologia》2006,566(1):235-246
The application of macrophytes in freshwater monitoring is still relatively limited and studies on their intercalibration
and sources of variation are required. Therefore, the aim of the study was to compare selected indices and metrics based on
macrophytes and to quantify their variability. During the STAR project, several aspects influencing uncertainty in estimation
of the ecological quality of river were assessed. Results showed that several metrics based on the indicative value of plant
species can be used in evaluation of the ecological status of rivers. Among estimated sources of variance in metric values
the inter-surveyor differences had the lowest effect and slightly stronger were the influences of temporal variation (years
and seasons) and shading. The impact of habitat modification was the most important factor. Analysis showed that some of macrophyte-based
metrics (notably MTR and IBMR) are of sufficient precision in terms of sampling uncertainty, that they could be useful for
estimating the ecological status of rivers in accordance with the aims of the Water Framework Directive. 相似文献
15.
Forest carbon use efficiency: is respiration a constant fraction of gross primary production? 总被引:1,自引:0,他引:1
EVAN H. DeLUCIA JOHN E. DRAKE† RICHARD B. THOMAS‡ MIQUEL GONZALEZ-MELER§ 《Global Change Biology》2007,13(6):1157-1167
Carbon‐use efficiency (CUE), the ratio of net primary production (NPP) to gross primary production (GPP), describes the capacity of forests to transfer carbon (C) from the atmosphere to terrestrial biomass. It is widely assumed in many landscape‐scale carbon‐cycling models that CUE for forests is a constant value of ∼0.5. To achieve a constant CUE, tree respiration must be a constant fraction of canopy photosynthesis. We conducted a literature survey to test the hypothesis that CUE is constant and universal among forest ecosystems. Of the 60 data points obtained from 26 papers published since 1975, more than half reported values of GPP that were not estimated independently from NPP; values of CUE calculated from independent estimates of GPP were greater than those calculated from estimates of GPP derived from NPP. The slope of the relationship between NPP and GPP for all forests was 0.53, but values of CUE varied from 0.23 to 0.83 for different forest types. CUE decreased with increasing age, and a substantial portion of the variation among forest types was caused by differences in stand age. When corrected for age the mean value of CUE was greatest for temperate deciduous forests and lowest for boreal forests. CUE also increased as the ratio of leaf mass‐to‐total mass increased. Contrary to the assumption of constancy, substantial variation in CUE has been reported in the literature. It may be inappropriate to assume that respiration is a constant fraction of GPP as adhering to this assumption may contribute to incorrect estimates of C cycles. A 20% error in current estimates of CUE used in landscape models (i.e. ranging from 0.4 to 0.6) could misrepresent an amount of C equal to total anthropogenic emissions of CO2 when scaled to the terrestrial biosphere. 相似文献
16.
Small intermittent rivers play an important role in the limnology of African lakes. The Mwenda River occurs on the southern shore of Lake Kariba. Its flow is governed by the incidence of tropical thunderstorms. During the dry period the river is reduced to a series of turbid pools. Physicochemically the river behaves similarly to a sheltered region of the lake. One river station deviates from the normal pattern because of the insulating effect of a Salvinia mat, and because of its permanent connection with the lake. River flooding flushes both nutrients and major ions into the lake. River phytoplankton populations peak prior to the flushing out of the river. Diatom populations are composed of cosmopolitan tropical taxa. 相似文献
17.
Most of the tested water quality factors increase downstream coinciding with changes in the aquatic vegetation, from typical species of fast-flowing oligotrophic waters to those of slower-flowing eutrophic waters. Several statistic analyses were carried out to relate physical and chemical parameters with plant distribution. Five vegetation types are found in a longitudinal distribution along the river system. They are dominated by bryophytes in the initial parts before the reservoirs and by higher plants in the final parts after the reservoirs. 相似文献
18.
Quantitative data on primary production of picoplankton are presented for three different Brazilian marine ecosystems: estuarine,
coastal and oceanic.
The size fraction from 0.45 μm to 1.0 μm was responsible for 3.0% to 28.5% of 14C uptake in estuarine waters; 18.5% to 40.4% in coastal waters, and 6.7% to 100.0% in oceanic waters, respectively.
These results establish the importance of picoplankton as primary producers in different marine environments along the Brazilian
waters. 相似文献
19.
Reconciling Carbon-cycle Concepts, Terminology, and Methods 总被引:4,自引:1,他引:4
F. S. Chapin III G. M. Woodwell J. T. Randerson E. B. Rastetter G. M. Lovett D. D. Baldocchi D. A. Clark M. E. Harmon D. S. Schimel R. Valentini C. Wirth J. D. Aber J. J. Cole M. L. Goulden J. W. Harden M. Heimann R. W. Howarth P. A. Matson A. D. McGuire J. M. Melillo H. A. Mooney J. C. Neff R. A. Houghton M. L. Pace M. G. Ryan S. W. Running O. E. Sala W. H. Schlesinger E.-D. Schulze 《Ecosystems》2006,9(7):1041-1050
Recent projections of climatic change have focused a great deal of scientific and public attention on patterns of carbon (C)
cycling as well as its controls, particularly the factors that determine whether an ecosystem is a net source or sink of atmospheric
carbon dioxide (CO2). Net ecosystem production (NEP), a central concept in C-cycling research, has been used by scientists to represent two different
concepts. We propose that NEP be restricted to just one of its two original definitions—the imbalance between gross primary
production (GPP) and ecosystem respiration (ER). We further propose that a new term—net ecosystem carbon balance (NECB)—be
applied to the net rate of C accumulation in (or loss from [negative sign]) ecosystems. Net ecosystem carbon balance differs
from NEP when C fluxes other than C fixation and respiration occur, or when inorganic C enters or leaves in dissolved form.
These fluxes include the leaching loss or lateral transfer of C from the ecosystem; the emission of volatile organic C, methane,
and carbon monoxide; and the release of soot and CO2 from fire. Carbon fluxes in addition to NEP are particularly important determinants of NECB over long time scales. However,
even over short time scales, they are important in ecosystems such as streams, estuaries, wetlands, and cities. Recent technological
advances have led to a diversity of approaches to the measurement of C fluxes at different temporal and spatial scales. These
approaches frequently capture different components of NEP or NECB and can therefore be compared across scales only by carefully
specifying the fluxes included in the measurements. By explicitly identifying the fluxes that comprise NECB and other components
of the C cycle, such as net ecosystem exchange (NEE) and net biome production (NBP), we can provide a less ambiguous framework
for understanding and communicating recent changes in the global C cycle. 相似文献
20.
T. Penczak 《Hydrobiologia》1992,237(2):117-129
The total mean biomass and production of fish populations were estimated at 80–116 kg ha–1 and 135–164 kg ha–1 yr–1, respectively, at two sites of a large alluvial river (the Warta River, Poland). In comparison with data for two large, temperate zone rivers (Thames, Pilica) the present values are intermediate, as is the degree of eutrophication in the rivers' water. 相似文献