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  • 1
    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
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  • 2
    Electronic Resource
    Electronic Resource
    Primary producer dynamics associated with evaporative concentration in a shallow, equatorial soda lake (Lake Elmenteita, Kenya) (1988)
    Springer
    Hydrobiologia 158 (1988), S. 1-14 
    Details
    ISSN: 1573-5117
    Keywords: Saline lakes ; phytoplankton ; benthic and planktonic photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Elmenteita (0°27′S, 36°15′E) lies on the floor of the rift valley at 1776 m above sea level in Kenya. As a consequence of lower than average rainfall, the mean depth decreased from 1.1 to 0.65 m during the study period (February 1973 to August 1974). The initiation of major biological changes coincided with a period of rapid evaporative concentration in 1973 (February to April) when the conductivity increased from 19.1 to 27.0 mmhmos cm-1. Spirulina platensis, Spirulina laxissima and Anabaenopsis arnoldii decreased in abundance precipitously in parallel with large declines in chlorophyll a concentration and phytoplankton photosynthetic rates. Once the overall abundance of phytoplankton had declined and the transparency had increased, primary productivity by benthic algae increased significantly. Paradiaptomus africanus, the only copepod living in the lake, was abundant in February and March 1973, but was gone by May. Eight hypotheses to explain these changes are evaluated and converge on the suggestion that a rate of change of salinity greater than 5 mmhmos cm-1 per month and a salinity exceeding 25 mmhmos cm-1 cannot be tolerated by P. africanus and adversely effects the nitrogen fixer, A. arnoldii. Furthermore, the loss of P. africanus and oxygenation of the sediments by benthic algae reduce the rate of recyling of nutrients which alters phytoplankton abundance and species composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026264
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  • 3
    Electronic Resource
    Electronic Resource
    Photosynthetic activity of phytoplankton and its relation to environmental factors in hypersaline Mono Lake, California (1988)
    Springer
    Hydrobiologia 158 (1988), S. 69-88 
    Details
    ISSN: 1573-5117
    Keywords: Mono Lake ; photosynthesis ; salt lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic activity of phytoplankton in hypersaline Mono Lake, California was measured over the three year period, 1983–1985. The maximum chlorophyll-specific rate of carbon uptake (Pm B) and the light-limited slope (alpha) were derived from laboratory measurements of photosynthesis vs. irradiance (P-I) relationships. Annual estimates of primary production were 340–540 g C m-2 yr-1. Production was two to three times higher during the spring of 1983 than in the springs of 1984 and 1985; higher standing biomass of algae occurred in 1983. While Pm B rates followed water temperatures and varied over 40-fold over the year, integral primary production varied less since periods of high Pm B occurred when algal biomass was low. Sixty-eight percent of the seasonal variation in the Pm B was explained by a regression on temperature (53%), chlorophyll a (12%), and the carbon:chlorophyll a ratio (3%). Light-saturated and light-limited rates of photosynthesis generally covaried, evidenced by the strong seasonal correlation between Pm B and alpha. Sixty-one percent of variation in alpha was explained by a regression on Pm B, temperature, grazing, water column stability, and self-shading. There was no correlation of carbon uptake with ambient levels of inorganic nitrogen. The regression coefficient of the dependence of Pm B on the seasonal temperature trend was much larger than that determined from individual samples incubated at several different temperatures; this indicates that uptake is limited by more than low temperatures in the spring. Regression equations including only temperature, chlorophyll and depth were sufficient to estimate patterns of seasonal and year to year variation in integral primary productivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026267
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  • 4
    Electronic Resource
    Electronic Resource
    In situ hatching of Artemia monica cysts in hypersaline Mono Lake, California (1988)
    Springer
    Hydrobiologia 158 (1988), S. 183-190 
    Details
    ISSN: 1573-5117
    Keywords: Artemia monica ; cyst hatching ; emergence traps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two emergence trap designs were tested in Mono Lake, California, to measure in situ hatching of Artemia monica cysts on the lake bottom. One design incorporated a removable sample bottle; the other had a catch tube which was pumped from the surface. Both traps rested on the bottom and had a narrow gap between the collecting funnel and bottom flange to allow the chemical conditions within the trap to be similar to those outside. This gap was open during April and May but, because some animals entered from outside the area enclosed by the trap, the gap was covered with 400 µm or 800 µm screen during June and July. The two trap types without screens sampled a station in oxic water 7 m deep similarly in April and May 1985. Mean daily hatching rates from April to May 1985 ranged from 720 to 25 340 shrimp m-2 day-1. In contrast, mean daily hatching rates during the same period at a station in anoxic water 21 m deep were from 3 to 138 shrimp m-2 day-1. June and July hatching rates in the shallow station were lower than in the spring, usually less than 1000 shrimp m-2 day-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026276
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  • 5
    Electronic Resource
    Electronic Resource
    Chlorophyll differences in Mono Lake (California) observable on Landsat imagery (1985)
    Springer
    Hydrobiologia 122 (1985), S. 13-17 
    Details
    ISSN: 1573-5117
    Keywords: spatial heterogeneity ; seasonality ; remote sensing ; salt lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Mono Lake (California), a large saline lake, chlorophyll concentrations in the euphotic zone increased from 4 to 45 µg l−1 between July and October 1979. These seasonal changes in chlorophyll are detectable on imagery obtained with the multispectral scanner on Landsat. Computer-compatible tapes of Landsat images were normalized for solar zenith and corrected for atmospheric scatter and absorption to obtain Landsat band 4 emittances (W m−2 str−1) of 13.4 ± 0.5 when chlorophyll was 4 µg l−1 and 4.6 ± 0.3 when chlorophyll was 45 µg l−1. Lake wide, spatial heterogeneity of chlorophyll of 2 µg l−1 in July and 8 µg l−1 in October was not detectable on the Landsat imagery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018955
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  • 6
    Electronic Resource
    Electronic Resource
    Interactions of detrital particulates and plankton (1985)
    Springer
    Hydrobiologia 125 (1985), S. 209-220 
    Details
    ISSN: 1573-5117
    Keywords: limnology ; aggregation ; adsorption ; bacteria ; zooplankton ; phytoplankton ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Detrital particulates, i.e. inorganic and non-living organic material of colloidal size and larger, span ten orders of magnitude in size and are ubiquitous in inland waters. Interactions between plankton and detrital particulates are reciprocal. Release of dissolved organics by living organisms enter the particulate size fraction by flocculation on bubbles or adsorption to inorganic particles. Bacteria benefit from attachment to particles and are agents in the aggregation of particulates. Nutrients released by decaying plankton can support phytoplankton growth. Potentially toxic compounds adsorb to particulates and then can enter pelagic food webs or sediment. Material egested by zooplankton contributes to the detrital pool which in turn is a food source for zooplankton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00045936
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  • 7
    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
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  • 8
    Electronic Resource
    Electronic Resource
    7. Photosynthetic activity of phytoplankton in tropical African soda lakes (1981)
    Springer
    Hydrobiologia 81-82 (1981), S. 71-85 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048707
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  • 9
    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
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  • 10
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    7. Photosynthetic activity of phytoplankton in tropical African soda lakes (1981)
    Springer
    Details
    Publication Date: 1981-06-01
    Print ISSN: 0018-8158
    Electronic ISSN: 1573-5117
    Topics: Biology
    Published by Springer
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