The periphyton communities of Nyumba ya Mungu reservoir, Tanzania

The periphyton communities established in Nyumba ya Mungu were investigated between July and September 1974.
One hundred and ninety-two taxa were identified. One hundred and fifteen taxa were collected in the southern end of the lake, where 97 taxa were non-selectively distributed in the littorine epiphytic, epilithic, and epixylic environments. The offshore epixylon supported only 53 taxa. The epipelon and epipsammon were poorly developed at the southern end of the lake but were well developed in the northern inflow regions.
Diatoms and cyanophytes were the dominant phyla which contributed over 80% of the algal numbers. Chlorophytes were not common. Taxonomic compositions of periphyton on artificial and natural surfaces were similar, but artificial substrata accumulated greater proportional representations of diatoms.
The mean net production rates of periphyton on artificial substrata located at depths from 0-0.65 m for 28 days ranged from 140 mg organic dry weight m^-2 day^-1 on shoots in the macrophyte zone to 820 mg organic dry weight m^-2 day^-1 on glass surfaces on a rocky shore. The epiphytic environments produced the least standing crops of less than 250, 000 individuals cm^-2, but maximum densities of over 2,000,000 individuals cm^-2 were recorded in the epilithon.     

Polymixis of a shallow lake (Groβer Müggelsee,Berlin) and its influence on seasonal phytoplankton dynamics

The polymictic properties of Lake Müggelsee, a eutrophic shallow lake in Berlin, are described by the water column stability (N ²) and gradients in saturation of oxygen at the deepest site of the lake (7.5 m). Mixing and stratification changed irregularly up to 7 times during the vegetation season (April to September), as was indicated by all of the stratification parameters. Thermally stable conditions generally lasted 1–2 weeks. A maximum of 5 weeks stratification was observed in 1982.In order to investigate the response of algal development, the internal rates of change of the dominant algal species in the lake during the vegetation period were estimated from weekly measurements of phytoplankton biomass from 1980 to 1990. The necessity taking a mixed sample in a shallow lake is discussed. The polymictic properties favoured the development of specific blue-green algal species; there dominance was also favoured by the trophic conditions. Among the dominant blue-greens the growth of Limnothrix redekei was independent of polymixis whereas stratification supported the starting conditions for the summer blue-greens Aphanizomenon flos-aquae and Planktothrix agardhii. After these algae reached a distinct level of biomass, they grew under mixing as well as under stratified conditions.For the development of solitary centric diatoms during summer regulation by growth restriction through nutrient limitation, esp. dissolved silicon was more important. However, Melosira sp. developed well under stratified conditions but collapsed due to increased sinking losses when the water column became too stable.An attempt is made to apply Reynolds' possibility matrix of the most likely phytoplankton assemblages as a function of nutrients and mixing in the shallow Lake Müggelsee.     

云南石林碳酸盐岩表面气生蓝藻(蓝细菌)研究

云南石林的黑石头及其颜色会随着天气的变化而变化的自然景观,是由于其碳酸盐岩表面长满黑色气生蓝藻（蓝细菌）之故。经鉴定,气生蓝藻共４目,１１科,３１届,１８８种。种类十分丰富。其优势种主要为寄生微囊藻、红色星球藻、伯氏伪枝藻和皮壳伪枝藻等;寄生微囊藻和红色星球藻呈面状分布,相对均衡,伯氏伪枝藻和皮壳伪枝藻呈点状分布,相对集中。这些气生蓝藻的胶被色泽鲜艳,宽厚而坚硬,是适宜高山岩石表面生活的典型进化特征。在野外肉限观察时,气生蓝藻还表现出不同形态的微群落;发现气生蓝藻能溶解石灰石,形成钻孔,加速岩石的溶蚀与风化。这些现象表明,气生蓝藻与云南石林岩石表面的微形态及整个石林景观的形成都有着十分密切的关系。