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1.
Matthias Koschorreck 《Biogeochemistry》2000,50(2):195-206
In the Amazon floodplain large areas of unvegetatedlake sediments are exposed to air during low water. Imeasured methane fluxes from exposed sediments of anAmazonian floodplain lake and assessed the regulatingfactors. Methane emission decreased from values between 10 and 40 mol CH4 mminus 2 hminus 1to zero when the sediments were exposed to air. Meanfluxes were about 3.7 mol CH4mminus 2 hminus 1. Fluxes were low compared tomeasurements taken from flooded habitats makingexposed lake sediments a negligible source ofatmospheric CH4. This was mainly due to the lackof ebullition which governs methane flux in theflooded phase. Methane oxidation at the sedimentsurface consumed up to 75% of the methane enteringthe oxidised zone. Compared with CO2 emissionmethane turnover was of minor importance for thecarbon budget of the sediments. 相似文献
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Planktonic regeneration and uptake of ammonium was measuredin Lake Calado on the floodplain of the Amazon River (Brazil).In the epilimnion of the lake, regeneration and uptake averaged0.86 ± 0.15 and 1.9 ± 0.4 µmol NH411h1 respectively. Uptake exceeded regeneration under theammonium-enriched conditions of our experimental incubations,but uptake and regeneration are in near-balance at in situ ammoniumconcentrations of <1 µM. In experiments that simulatedlake overturn, samples from the meta- and hypolimnion had higherrates of regeneration (1.4 ± 0.6) and lower rates ofuptake (0.89 ± 0.53) than epilimnetic samples. Duringinflow of water from the Amazon River and a local stream, ammoniumregeneration rates were similar to those measured in the epilimnion(0.84 ± 0.22), but the uptake rates were lower (0.49± 0.13). Although regeneration always exceeded uptakein the overturn and inflow experiments, ammonium did not accumulate.Rapid isotope dilution of the ammonium pool occurred in theincubations, and the effect of not accounting for isotope dilutioncould result in underestimating uptake rates by a factor of25 in the epilimnion of this tropical lake. 相似文献
3.
Fisher T.R.; Morrissey K.M.; Carlson P.R.; Alves L.F.; Melack J.M. 《Journal of plankton research》1988,10(1):7-29
Uptake of ammonium and nitrate by plankton was measured in tropicalLake Calado, Brazil. Nitrate uptake was strongly influencedby light and was light saturated at {small tilde}340 µEm2 s1. In contrast, uptake of ammonium was lessinfluenced by light, and saturated at {small tilde}250 µEm2 s1. Uptake rates of both forms of nitrogenwere inhibited by up to 80% at light intensities higher thanthose required for saturation. Concentrations of ammonium andnitrate also had a strong influence on uptake rates. Half-saturationconstants (0.35 µM) were usually greater than ambientconcentrations (0.10.6 µM), indicating that uptakerates at ambient concentrations were less than one-half of thesaturated rates. Ammonium is the more important type of inorganicnitrogen for plankton of Lake Calado because nitrate concentrationsremain low to undetectable except during periodic inputs ofnitrate-rich water from the Amazon River. Using the observeddependence of uptake on concentration and light, maximum uptakerates per unit chlorophyll were computed to be in reasonableagreement with rates derived from PBm values for carbon uptake.
1 Present address: Florida Department of Natural Resources,Marine Research Laboratory, St Petersburg, FL 33701, USA 相似文献
4.
Diurnal distribution and behavioral responses of fishes to extreme hypoxia in an Amazon floodplain lake 总被引:1,自引:0,他引:1
Synopsis Because of the need for surface access for aquatic surface respiration (ASR), fish density increases were demonstrated for the open water of a floodplain lake during severe hypoxia. This indicates an O2-induced diurnal pattern of horizontal migrations between the zone of macrophyte cover and open water. Supplemental experimental investigations seem to suggest that species such as characoids,Colossoma macropomum andSchizodon fasciatum, deviate from this pattern. During long periods of oxygen depletion, they return to the region of macrophyte growth and survive there without displaying the usual kind of ASR. Mortality studies in net cages exposed in natural water bodies confirmed that only these two species are able to survive severe hypoxia beneath macrophyte cover. The possibility of an O2-input through the root system of plants is discussed. The O2-concentration has a significant influence on the locomotory behavior and the frequency of opercular movement in characoids. There is significantly less locomotory activity beneath the macrophytes during periods of oxygen depletion among those species not forced to migrate than among those in the open water regions, where normal ASR behavior is possible. 相似文献
5.
Carlos I. Molina François-Marie Gibon Thierry Oberdorff Eduardo Dominguez Julio Pinto Rubén Marín Marc Roulet 《Hydrobiologia》2011,663(1):135-153
Two stable isotopes δ13C and δ15N were used to identify the energy sources and trophic relationships of the main freshwater macroinvertebrates in a floodplain
lake of the Beni River (Bolivian Amazonia). Four energy sources (seston, bottom sediment, periphyton, and aquatic macrophytes)
and macroinvertebrate communities were collected during three periods of the river hydrological cycle. Macroinvertebrates
showed greater temporal variation in isotope values than their food sources. Six trophic chains were identified: four were
based on seston, periphyton, C3 macrophytes, and bottom sediments, and the last two chains on a combination of two carbon sources. One mixed seston and periphyton
sources during the wet season while the other mixed periphyton and macrophytes sources during the wet and dry seasons. Periphyton
was the most important energy source supporting the highest number of trophic levels and consumers. The macrophytic contribution
was only significant during the dry season. Bottom sediments constituted a marginal energy source. As each season is associated
with different physical and chemical conditions, processes organizing macroinvertebrate food web structure in the Beni floodplain
seem strongly linked to hydrological seasonality. 相似文献
6.
Albert JS 《Current biology : CB》2002,12(13):R442-R443
Deep and puzzling evolutionary questions are still being raised by the unfashionable work of systematic biologists. James S. Albert describes some such work and argues why we need much more of it in the face of unprecedented loss of species through human activity. 相似文献
7.
SUMMARY. 1. Quantities and the chemical composition of epiphyton on the roots of floating aquatic macrophytes were measured in Lake Calado, an Amazon floodplain lake. Growth of epiphytic algae following physical disturbance and losses of epiphyton due to grazing and storms were investigated.
2. Deposition of silt from invading river water decreased chlorophyll and nutrient content (%C, %N, %P) of epiphyton during rising water. N:P ratios of epiphyton indicated that proximity to the river increased supplies of phosphorus. Attached algal biomass per unit root tissue was higher overall during the falling water period, when light was greater, storms less frequent, and new host plant tissue produced more slowly.
3. Epiphytic algal biomass at the margins of floating meadows exceeded that of the phytoplankton in the open water on a per unit area basis. Increases in attached algal chlorophyll ranged from two- to ten-fold over 1 week. Artificial denudation of roots was followed by rapid regrowth of attached algae, leading, after I week, to four-fold increases in chlorophyll over the pre-denuded state.
4. Wind-blown macrophytes experienced an episodic loss of 70% of epiphytic material in less than 1 h. Particulate material lost from roots grazed by snails included root tissue and contained significantly more carbon than material lost from ungrazed roots. 相似文献
2. Deposition of silt from invading river water decreased chlorophyll and nutrient content (%C, %N, %P) of epiphyton during rising water. N:P ratios of epiphyton indicated that proximity to the river increased supplies of phosphorus. Attached algal biomass per unit root tissue was higher overall during the falling water period, when light was greater, storms less frequent, and new host plant tissue produced more slowly.
3. Epiphytic algal biomass at the margins of floating meadows exceeded that of the phytoplankton in the open water on a per unit area basis. Increases in attached algal chlorophyll ranged from two- to ten-fold over 1 week. Artificial denudation of roots was followed by rapid regrowth of attached algae, leading, after I week, to four-fold increases in chlorophyll over the pre-denuded state.
4. Wind-blown macrophytes experienced an episodic loss of 70% of epiphytic material in less than 1 h. Particulate material lost from roots grazed by snails included root tissue and contained significantly more carbon than material lost from ungrazed roots. 相似文献
8.
Methane emissions from an Amazon floodplain lake: Enhanced release during episodic mixing and during falling water 总被引:72,自引:7,他引:72
Soil respiration rates vary significantly among major plant biomes, suggesting that vegetation type influences the rate of soil respiration. However, correlations among climatic factors, vegetation distributions, and soil respiration rates make cause-effect arguments difficult. Vegetation may affect soil respiration by influencing soil microclimate and structure, the quantity of detritus supplied to the soil, the quality of that detritus, and the overall rate of root respiration. At the global scale, soil respiration rates correlate positively with litterfall rates in forests, as previously reported, and with aboveground net primary productivity in grasslands, providing evidence of the importance of detritus supply. To determine the direction and magnitude of the effect of vegetation type on soil respiration, we collated data from published studies where soil respiration rates were measured simultaneously in two or more plant communities. We found no predictable differences in soil respiration between cropped and vegetation-free soils, between forested and cropped soils, or between grassland and cropped soils, possibly due to the diversity of crops and cropping systems included. Factors such as temperature, moisture availability, and substrate properties that simultaneously influence the production and consumption of organic matter are more important in controlling the overall rate of soil respiration than is vegetation type in most cases. However, coniferous forests had 10% lower rates of soil respiration than did adjacent broad-leaved forests growing on the same soil type, and grasslands had, on average, 20% higher soil respiration rates than did comparable forest stands, demonstrating that vegetation type does in some cases significantly affect rates of soil respiration. 相似文献
9.
Autotrophic carbon sources for heterotrophic bacterioplankton in a floodplain lake of central Amazon 总被引:1,自引:1,他引:1
Andrea Viviana Waichman 《Hydrobiologia》1996,341(1):27-36
The relative contribution of autotrophic carbon sources (aquatic macrophytes, flooded forest, phytoplankton) for heterotrophic bacterioplankton was evaluated in a floodplain lake of the Central Amazon. Stable carbon isotopes (13C) were used as tracers. Values of 13C of different autotrophic sources were compared to those of dissolved organic carbon (DOC) and those of bacterially produced CO2.The percentage of carbon derived from C4 macrophytes for bacterially produced CO2 was the highest, on average 89%. The average 13C value of CO2 from bacterial respiration was –18.5 ± 3.3. Considering a fractionation of CO2 of 3 by bacterial respiration, 13C value was –15.5, near C4 macrophyte 13C value (–13.1).The average value of total DOC 13C was –26.8 ± 2.4. The percentage of C4 macrophytes carbon for total DOC was on average 17%. Considering that bacteria consume mainly carbon from macrophytes, the dominance of C3 plants for total DOC probably reflects a faster consumption of the former source, rather than a major contribution of the latter source.Heterotrophic bacterioplankton in the floodplain may be an important link in the aquatic food web, transferring the carbon from C4 macrophytes to the consumers. 相似文献
10.
Sustainable management for existing Amazonian forests requires an extensive knowledge about the limits of ecosystem nutrient
cycles. Therefore, symbiotic nitrogen (N2) fixation of legumes was investigated in a periodically flooded forest of the central Amazon floodplain (Várzea) over two
hydrological cycles (20 months) using the 15N natural abundance method. No seasonal variation in 15N abundance (δ
15N values) in trees which would suggest differences in N2 fixation rates between the terrestrial and the aquatic phase was found. Estimations of the percentage of N derived from atmosphere
(%Ndfa) for the nodulated legumes with Neptunia oleracea on the one side and Teramnus volubilis on the other resulted in mean %Ndfa values between 9 and 66%, respectively. More than half of the nodulated legume species
had %Ndfa values above 45%. These relatively high N gains are important for the nodulated legumes during the whole hydrological
cycle. With a %Ndfa of 4–5% for the entire Várzea forest, N2 fixation is important for the ecosystem and therefore, has to be taken into consideration for new sustainable land-use strategies
in this area. 相似文献
11.
de Souza Dilailson Arajo Kraus Cleber Nunes Burliga Ana Luiza de Melo Srgio Couceiro Sheyla Dias-Silva Karina Simes Nadson Ressye Braga Tony Bonnet Marie Paule da Motta Marques David 《Limnology》2022,23(2):275-286
Limnology - The Amazon floodplains are complex systems influenced by the annual hydrological regime with an effect on the structuring of physical, chemical and biological processes. Thus, we... 相似文献
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Silva Ide G Moura Ado N Dantas EW Bittencourt-Oliveira Mdo C 《Revista de biología tropical》2010,58(4):1421-1436
Natural lake systems represent important reservoirs for residential water supply, fish production, recreational activities and enjoyment of their natural beauty. Nevertheless, human impacts may affect their health status resulting in degradation and loss of biodiversity. The aim of the present study was to obtain data on the health status of a natural lake located in an indigenous reservation in the Brazilian Amazon, using the phytoplankton community changes along the rainy (June) and dry (November) seasons of 2006. We collected water (temperature, pH, Secchi depth and conductivity) and phytoplankton samples from the subsurface, middle of the water column, and approximately 30 cm above the bottom, over 24-hour sampling periods, from a central station in the lake. Samples taken from biotic and abiotic variables were correlated using canonical correspondence analysis (CCA). Results showed that the lake exhibited high temperatures in both seasons, and showed thermal stratification only during the rainy season. Dissolved oxygen exhibited a clinograde pattern in the rainy season and high oxygen in the hypolimnion in the dry season. In the rainy season, the water near the bottom was acidic, turbid and had a greater concentration of phosphorus. Dissolved oxygen, conductivity, pH, nitrite, total phosphorus and total dissolved phosphorus exhibited diel variations in the rainy season, whereas water temperature, dissolved oxygen, total nitrogen and total dissolved phosphorus exhibited significant differences between hours of the day in the dry season. The phytoplankton was represented by 39 taxa, and Chlorophyta showed the greatest species richness, totaling 25 taxa. Among Chlorophyta, desmids were the most diverse, accounting 52%. Bacillariophyta (nine species) was the second most diverse group. Cyanophyta was represented by three species, including Merismopedia tenuissima, the most abundant taxon. Despite the occurrence of taxa that indicate organic pollution, their biomass and frequency indicate that the system is not currently threatened. Lake Caracaran? is an oligotrophic system, with low algal density and isolated blooming episodes due to its shallow depth. 相似文献
15.
A. E. Dobrynin 《Inland Water Biology》2009,2(2):162-170
The diurnal dynamics of the vertical distribution of zooplankton was studied in an oligotrophic lake with a high water transparency.
Those sedentary species which occupy the upper water layers in waterbodies with low water transparency shift to a border between
epy- and metalimnion and stay there during most of the day in Koskovskoye Lake, which has a high water transparency. Active
diurnal vertical migrations are characteristic of large organisms. Increased water transparency weakly affects large zooplankters
that occupy metalimnial layers in mesotrophic waterbodies. The relationship between the zooplankton’s vertical distribution
and the distribution of phytoplankton and fish is analyzed. 相似文献
16.
Salome Jones Renzo Perissinotto Nicola Kim Carrasco Andre Vosloo 《Marine Biology Research》2016,12(2):158-167
Shallow coastal lakes are prone to large fluctuations in physico-chemical variables such as salinity and turbidity. This is now escalating in response to global change. A flood event in March 2014 resulted in a silt plume spreading through part of Lake St Lucia (South Africa). To determine the impact of this event on zooplankton, the Narrows region of St Lucia was sampled on a monthly basis from March to September 2014. For comparative purposes, data from samples collected prior to the flood event were included in the analyses. Analysis of similarity (ANOSIM) revealed dissimilarities in zooplankton community structure among the sampling occasions. The March 2014–May 2014 period was characterized by the highest abundance of freshwater species. Conversely, the abundance of the resident St Lucia copepods Acartiella natalensis and Oithona brevicornis was lowest during this time, and highest in September 2014. The other dominant copepod Pseudodiaptomus stuhlmanni prevailed in March 2014, but declined markedly in April. As of September 2014, P. stuhlmanni had yet to regain its pre-flood densities. The BIOENV procedure, which relates biological and environmental data, revealed that turbidity, salinity and dissolved oxygen were responsible for the observed changes in zooplankton community structure during the study period. Careful management of turbidity and salinity is stressed, as both factors are major drivers of the biota of St Lucia and similar systems worldwide. 相似文献
17.
Biomass and primary-production of herbaceous plant communities in the Amazon floodplain 总被引:3,自引:3,他引:0
The increase in biomass of different aquatic and terrestrial herbaceous plant communities was measured during various growth periods in the Amazon floodplain near Manaus. Maximum biomass varied from 4–11.2 t ha–1 dry weight in mixed annual terrestrial communities to 6–23 t ha–1 in aquatic annual species (Paspalum repens, Oryza perennis, Luziola spruceana and Hymenachne amplexicaulis) and 15.6–57.6 t ha–1 in communities of the perennial species Paspalum fasciculatum. Cumulative biomass of 3 successively growing annual species reached 30 t ha–1 a–1. Net primary production is considerably higher than maximum biomass. Paspalum fasciculatum reached 70 t during a growth period of 8 months. If one considers for annual species a monthly loss of 10–25% of the biomass, then net primary production in areas with three successive macrophyte communities and a cumulative maximum biomass of 30 t ha–1 is estimated to reach up to 50 t ha–1 a–1. Annual P/B ratio may reach about 3. 相似文献
18.
Impacts of nutrients and zooplankton on the microbial food web of an ultra-oligotrophic lake 总被引:3,自引:0,他引:3
In ultra-oligotrophic lakes and the sea, calanoid copepods arethe dominant mesozoo-plankton and cladocerans are generallysparse or absent. To determine the effects of predation andnutrient enrichment on the pelagic microbial food web of anultra-oligotrophic lake, we added copepods and cladocerans atlow biomasses (<60 µg l1 to in situ enclosuresin Lake Wakatipu, New Zealand, in the presence and absence ofadded nutrients (nitrogen and phosphorus). In response to nutrientfertilization, the concentrations of phototrophs >3 µmand heterotrophic bacteria increased by 50 and 15%, respectively,over 4 days, but those of cyanobacterial picoplankton decreasedby 68%. The presence of calanoid copepods (Boeckella dilatata)at ambient densities (1 and 4 l1) rapidly and severelysuppressed ciliate population growth over 4 days and also loweredthat of flagellates >3 µm, even when microbial growthwas enhanced by added nutrients. The presence of a small cladoceran,Ceriodaphnia dubia, at double the densities, but similar biomasses,to those of copepods, depressed the net growth rates of ciliatesand flagellates to a lesser degree. The net growth rate of heterotrophicbacteria after 4 days declined with flagellate abundance, consistentwith the possibility of regulation by flagellates. Althoughbacteria and algae increased in response to nutrient fertilization(bottom-up control), predation (top-down control) appeared toplay an important role in structuring the microbial food webof this ultra-oligotrophic lake in summer. 相似文献
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David G. McGrath Fabio de Castro Celia Futemma Benedito Domingues de Amaral Juliana Calabria 《Human ecology: an interdisciplinary journal》1993,21(2):167-195
Traditionally, the ribeirinhoeconomy has been based on strategies of multiple resource use including agriculture, fishing, and small-scale stock raising. In the last two decades though, ribeirinhostrategies of resource management have undergone major changes due to the decline of jute production (the principal cash crop), and the intensification of the commercial fisheries. As a result of these trends, there has been a shift of ribeirinholabor from agriculture to commercial fishing. Today, the diversity which once characterized ribeirinhosubsistence strategies is disappearing, and fishing has become the primary economic activity for the great majority of varzeafamilies. As pressure on varzeafisheries has increased, ribeirinhocommunities have attempted to assert control over local varzealakes and exclude fishermen from outside the community. In a number of cases, ribeirinhocommunities have closed lakes to outsiders and established informal lake reserves under local community management. These lake reserves are a promising strategy for managing lake fisheries on a sustainable basis. 相似文献