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Various biotic and abiotic measurements were made over a 48-h period in a small lava-lakelet on the sub-Antarctic Marion Island. Typical oligotrophic conditions prevailed, with low biomass values and rates of productivity for the phytoplankton and bacteria. The bacteria and phytoplankton were subject to heavy zooplankton grazing pressures, which in turn(More)
The incorporation of [methyl-H]thymidine into three macromolecular fractions, designated as DNA, RNA, and protein, by bacteria from Hartbeespoort Dam, South Africa, was measured over 1 year by acid-base hydrolysis procedures. Samples were collected at 10 m, which was at least 5 m beneath the euphotic zone. On four occasions, samples were concurrently(More)
The study provides a 2.5 year record of Rhenosterkop Dam (KwaNdebele, South Africa) plankton population dynamics and production in relation to physical and chemical changes which occurred during the trophic depression and stabilization phases of the reservoir. The mean volume of the reservoir was 4% of full storage capacity. Water temperatures ranged from(More)
The number of metabolically active bacteria was measured with nalidixic acid over two annual cycles at three depths in the epilimnion of hypertrophic Hartbeespoort Dam, South Africa. Concurrent measurements were made of water temperature, DOC, phytoplankton production of dissolved (EDOC) and particulate organic carbon, chlorophyll a and the uptake of(More)
The objectives of the 3 year study were to determine the relationship between bacterial numbers and phytoplankton standing crops (chlorophyll a) in sub-antarctic Marion Island lakes (33) and to determine the relative importance of labile dissolved organic carbon and water temperature as regulators of heterotrophic bacterial activity and production.(More)
The spatial and temporal changes in phytoplankton (predominantly Microcystis aeruginosa) production of particulate organic carbon (primary production) and extracellular dissolved organic carbon (EDOC) were measured in hypertrophic Hartbeespoort Dam, South Africa, for 5 years. The study objectives were to determine the significance of EDOC production to(More)
A major decrease in air temperature with an increase in wind stress created thermal instability resulting in overturn. Surface oxygen values decreased from 12.6 (170% saturation) prior to overturn to 0.4 mg · l−1 (5.7%) after overturn. Recovery of surface oxygen concentrations to supersaturation took approximately three months. Changes in the nitrogen(More)
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