ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Simulation of the effect of methane bubble plumes on vertical mixing in Mono Lake (1996)
    Springer
    Aquatic sciences 58 (1996), S. 210-223 
    Details
    ISSN: 1420-9055
    Keywords: Methane ebullition ; vertical mixing ; hypolimnetic heating ; saline lake ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A one-dimensional vertical mixing model modified for application to hypersaline Mono Lake reproduced mixed layer dynamics well but hypolimnetic heating was underestimated. One possible source of increased hypolimnetic heating is vertical mixing caused by bubble plumes of methane rising from the sediments. Estimates of vertical mixing from methane seepage in Mono Lake were made with the inclusion of a bubble plume algorithm. A methane ebullition rate three hundred times greater than the maximum estimate for Mono Lake was required to simulate the observed hypolimnetic heating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877509
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Responses of phytoplankton to experimental fertilization with ammonium and phosphate in an African soda lake (1982)
    Springer
    Oecologia 52 (1982), S. 321-326 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Phytoplankton abundance in tropical lakes is more often judged to be limited by nitrogen than phosphorus, but seldom does the evidence include controlled enrichments of natural populations. In January 1980 we performed the first experimental fertilization in an equatorial African soda lake, Lake Sonachi, a small, meromictic volcanic crater lake in Kenya. During our study the natural phytoplankton abundance was ca. 80 μg chl a/l, and the euphotic zone PO4 and NH4 concentrations were less than 0.5 μM. In the monimolimnion PO4 reached 180 μM and NH4 reached 4,600 μM. Replicate polyethylene cylinders (5 m long, 1.2 m3) were enriched to attain 10 μM PO4 and 100 μM NH4. Phytoplankton responses were measured as chlorophyll, cell counts and particulate N, P and C. After two days, the chlorophyll increase in the P treatment was significantly higher than the control (P〈0.01) while the N treatment was not. After five days the molar N/P ratio of seston was the same in the N treatment and control (23) but only 6 in the P treatment. The molar N/P ratio of seston in an unenriched Lake Sonachi sample was 21 and in samples from Lakes Bogoria and Elmenteita, two shallow soda lakes in Kenya, the ratios were 12 and 70 respectively. We conclude that limitation of phytoplankton abundance by phosphorus can occur even in some tropical African soda lakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367954
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Temporal variability of phytoplankton in tropical lakes (1979)
    Springer
    Oecologia 44 (1979), S. 1-7 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Temporal variability of ecological systems continues to receive theoretical and empirical attention but remains inadequately documented at low latitudes. Results of my comparative investigation of photosynthetic rates of phytoplankton in 6 equatiorial African lakes and similar information from 20 South American, Asian and African lakes studied by others provide the data for an assessment of the range of seasonal variability (expressed as coefficients of variation, CV) among tropical lakes. Sampling intervals varied from 1 week to 3 months and usually spanned at least one year. Within Africa the coefficient of variation ranged from 15% to 61%, and among all the lakes the coefficient of variation ranged from 15% to 86%. The Spearman rank correlation coefficient of the CV's of photosynthesis versus latitude is 0.24 and is not significant at the 0.05 level. Coefficients of variation of photosynthetic rates of phytoplankton in a diverse set of 45 temperate and arctic lakes ranged from 29% to 155% and were significantly different from the set of 26 tropical lakes by the Mann-Whitney U test. When all 71 lakes are compared, the Spearman rank correlation coefficient of CV's of photosynthesis versus latitude is 0.71 and is significant at the 0.0005 level. Three temporal patterns were recognized among tropical lakes. Most tropical lakes exhibit pronounced seasonal fluctuations that usually correspond with variations in rainfall, river discharges or vertical mixing. A second pattern occurs in lakes with muted fluctuations (coefficient of variation less than 20%) in which diel changes often exceed month to month changes. A third pattern is distinguished by an abrupt change from one persistent algal assemblage (i.e., extant for at least 10 generations) and level of photosynthetic activity to another persistent condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346388
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Limnological conditions in Mono Lake: contrasting monomixis and meromixis in the 1990s (1998)
    Springer
    Hydrobiologia 384 (1998), S. 21-39 
    Details
    ISSN: 1573-5117
    Keywords: Mono Lake ; saline lake ; Artemia ; monomixis ; meromixis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mono Lake is a large, saline lake, located in the North American Great Basin and is subject to large variations in freshwater inflow as climatic conditions and diversion schemes have changed; consequently, major variations in chemical stratification occur. A transition from monomixis to meromixis occurred from 1994 to 1995. Lake-wide surveys of temperature, conductivity, dissolved oxygen, ammonium and chlorophyll profiles, Secchi depth and light attenuation, and Artemia monica abundances conducted throughout 1993, 1994, 1995, 1996 and 1997 document the contrasts between monomixis and meromixis. During the monomictic conditions in 1993 and 1994, the lake thermally stratified in March and mixed to the bottom by December, the hypolimnion became anoxic in late March and the water column was oxygenated to the bottom by December. During meromictic conditions in 1995, 1996 and 1997, the absence of holomixis during winter resulted in persistent anoxic conditions beneath the chemocline, an accumulation of ammonium in the monimolimnion and depletion in the mixolimnion, and low mixolimnetic chlorophyll concentrations in the spring and autumn. A comparison of the density differences between 2 and 28 m due to thermal versus chemical stratification indicated thermal stratification predominated in 1993 and 1994, while in 1995, 1996 and 1997 chemical stratification dominated the density differences. Ammonium, the limiting nutrient in Mono Lake, was lower in the upper mixed layer throughout 1996 and 1997 compared to the monomictic years, 1993 and 1994. During 1996 and 1997, the annual maxima in Secchi depths were among the deepest observed during the past 19 years, and reflected the lower phytoplankton abundance caused by decreased availability of nitrogen as a result of strong chemical stratification and the absence of a period of holomixis. In both 1996 and 1997, maturation of the spring generation of Artemia was slowed, peak abundance of the first generation of adult Artemia was a month later and percent ovigery, fecundity, and body size were reduced as compared to 1993 and 1994.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003352511328
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Large, deep salt lakes: a comparative limnological analysis (1983)
    Springer
    Hydrobiologia 105 (1983), S. 223-230 
    Details
    ISSN: 1573-5117
    Keywords: saline lakes ; Mono Lake ; Lake Qinghai Hu
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Among athalassic salt lakes of the world large, deep lakes are rare. A comparative analysis of Mono(USA), Walker (USA), Qinghai Hu (China), Shala (Ethiopia), Van (Turkey), Panggong Tso (Indian Tibet) and Karakul (USSR) (with emphasis on the two italicized lakes) reveals a number of ecological similarities. The criteria for selection were a mean depth greater than 15 m, an area greater than 100 km2 and a salinity greater than 10 g l−1 and less than 100 g l−1. The Aral and Caspian Seas were excluded because of the relict marine affinities of their biota. Large, deep salt lakes are located at moderate to high altitude in mountainous terrain: They stratify and mix at least once per year, and dissolved oxygen is depleted in the hypolimnia of most. The lakes contain alkaline, sodium rich waters with considerable chloride, sulfate and carbonate plus bicarbonate. Phosphate concentrations are usually high while inorganic nitrogen varies widely. Secchi disk transparency ranged from 〈 1 m to ca. 20 m. Supersaturation of dissolved oxygen, abundant animals and seasonally high algal populations indicate that some of the lakes are productive. All except Mono contain fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025190
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    An initial measurement of photosynthetic productivity in Lake Tanganyika (1980)
    Springer
    Hydrobiologia 72 (1980), S. 243-247 
    Details
    ISSN: 1573-5117
    Keywords: Primary productivity ; Lake Tanganyika ; African lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Measurements of 14C uptake and oxygen evolution by phytoplankton in Lake Tanganyika provide the first direct estimates of the lake's primary productivity. These measurements at the expected nadir of the annual range suggest that Lake Tanganyika is as productive as other large, deep tropical lakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00005627
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Solute dynamics in soil water and groundwater in a central Amazon catchment undergoing deforestation (1997)
    Springer
    Biogeochemistry 38 (1997), S. 303-335 
    Details
    ISSN: 1573-515X
    Keywords: Amazon ; deforestation ; hydrologic pathway ; groundwater ; nitrogen ; rain forest ; slash-and-burn agriculture ; solutes ; tropical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Hydrochemical changes caused by slash-and-burnagricultural practices in a small upland catchment inthe central Amazon were measured. Soluteconcentrations were analyzed in wet deposition,overland flow, shallow throughflow, groundwater andbank seepage in a forested plot (about 5 ha) and anadjacent plot (about 2 ha) which had been deforestedin July 1989 and planted to manioc, and in streamwater in partially deforested and forested catchments. Measurements were made from November 1988 to June1990. The effects of slash-and-burn agriculturalpractices observed in the experimental plot includedincreased overland flow, erosion, and large losses ofsolutes from the rooted zone. Concentrations ofNO3 -, Na+, K+, SO4 2-,Cl- and Mn in throughflow of the experimentalplot were higher than those of the control plot bymore than a factor of 10. Extensive leaching occurredafter cutting and burning, but solute transfers werediminished along pathway stages of throughflow togroundwater, and particularly within the riparian zoneof the catchment. High concentrations of N and P inoverland flow indicate the importance of usingforested riparian buffers to mitigate solute inputs toreceiving waters in tropical catchments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005801303639
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Composition and deposition of throughfall in a flooded forest archipelago (1999)
    Springer
    Biogeochemistry 45 (1999), S. 169-195 
    Details
    ISSN: 1573-515X
    Keywords: Amazon ; flooded forest ; Negro River ; rain ; solutes ; throughfall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The sources of spatial and temporal variation and rates of nutrient deposition via throughfall were studied for 9 months in the Anavilhanas archipelago of the Negro River, Brazil. A total of 30 events was sampled individually for rain and throughfall chemistry in a 1-ha plot of flooded forest. Throughfall samples were collected in 40 collectors distributed in five parallel transects in the study plot, while rain was collected in 4 collectors in an adjacent channel. Volume-weighted mean (VWM) concentrations of solutes in rain were consistently lower than in throughfall, except for H+, NO3- and NH4+. Ratios of VWM concentrations of rain to throughfall indicated that K+, followed by Mg2+ and PO43-, were the most enhanced solutes as rain passed through the forest canopy. The deposition of solutes varied significantly among transects, except for Na+ and Ca2+, and was significantly correlated with maximum flooding depth, foliar nutrient content soil fertility and canopy closure for most solutes. The concentrations of PO43- and most major ions were higher in throughfall compared to those in rain due to canopy exchange and dry deposition. In contrast, NO3-, NH4+ and H+ were retained due to immobilization by leafy canopy and ion exchange processes. Solute inputs via throughfall (not including stemflow) to a floodplain lake (Lake Prato) of the archipelago accounted for 30 to 64% of the total for most solutes in the lake at high water, which indicates that throughfall is an important source of nutrients to the aquatic ecosystem of the Anavilhanas archipelago.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006108618196
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Nitrogen yields from undisturbed watersheds in the Americas (1999)
    Springer
    Biogeochemistry 46 (1999), S. 149-162 
    Details
    ISSN: 1573-515X
    Keywords: dissolved organic nitrogen ; nitrogen concentrations ; nitrogen cycle ; nitrogen yields ; nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Yields of total fixed nitrogen and nitrogen fractions are summarized for thirty-one watersheds in which anthropogenic disturbance of the nitrogen cycle, either through land use or atmospheric deposition, is negligible or slight. These yields are taken as representative of background conditions over a broad range of watershed areas, elevations, and vegetation types. The data set focuses on watersheds of the American tropics, but also includes information on the Gambia River (Africa) and some small watersheds in the Sierra Nevada of California. For the tropical watersheds, total nitrogen yield averages 5.1 kg ha−1 y−1. On average, 30% of the total is particulate and 70% is dissolved. Of the dissolved fraction, an average of 50% is organic and 50% is inorganic, of which 20% is ammonium and 80% is nitrate. Yields are substantially lower than previously estimated for background conditions. Yields of all nitrogen fractions are strongly related to runoff, which also explains a large percentage of variance in yield of total nitrogen (r2=0.85). For total nitrogen and nitrogen fractions, yield increases at about two-thirds the rate of runoff; concentration decreases as runoff increases. There is a secondary but significant positive relationship between elevation and yield of DIN. Ratios DON/TDN and PN/TN both are related to watershed area rather than runoff; DON/TDN decreases and PN/TN increases toward higher stream orders. The analysis suggests for tropical watersheds the existence of mechanisms promoting strong homeostasis in the yield of N and its fractions for a given moisture regime, as well as predictable downstream change in proportionate representation N fractions. Yields and concentrations for small tropical watersheds are much larger than for the few temperate ones with which comparisons are possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007577
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Methane emissions from an Amazon floodplain lake: Enhanced release during episodic mixing and during falling water (2000)
    Springer
    Biogeochemistry 51 (2000), S. 71-90 
    Details
    ISSN: 1573-515X
    Keywords: Amazon floodplain ; episodic mixing ; lakes ; methane emission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Methane fluxes to the troposphere were measured inLake Calado, a dendritic floodplain lake located inthe central Amazon Basin. Methane concentrations inthe surface water of the lake were less than 0.5 µM during a period of high and rising water inApril and May, except when episodic, deep mixingoccurred and surficial concentrations reached as highas 4.8 µM. Diffusive fluxes ranged from ca.2–20 mg CH4 m−2d−1 (mean: 6.6 mg CH4 m−2d−1) normally, but increased up to 220 mg CH4 m−2d−1 during the passageof a rare cold front. During six weeks of risingwater, the volume-weighted methane content of the lakeincreased during periods of stable thermalstratification (accumulation rates ranging from16–1411 mg CH4 m−2d−1) and decreasedduring episodes of partial mixing (rates of decreaseranging from 63–1792 mg CH4 m−2d−1). Surface water methane concentrations during low andfalling water in September varied by more than anorder of magnitude (range, 0.3–9 µM), anddiffusive fluxes ranged from 3–158 mg CH4m−2d−1 (mean, 54 mg CH4 m−2d−1). During falling water in September, total methane flux from the lake to the troposphere measured with a floating chamber rangedfrom 53–328 mg CH4 m−2d−1 (mean, 163 mgCH4 m−2d−1). Ebullitive flux averaged 69% of total flux. Total methane flux was highest when thermal stratification was lost due to decreasing lake depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006389124823
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...