Search

Microautoradiography was used to screen natural phytoplankton populations from Lake Kinneret for their ability to take up radioactive organic substrates (glucose, acetic acid, amino acids, and glycollic acid. Several of the important Chlorophyta ( Pediastrum spp., Actinastrum hantzschii, Kirchncriella spp., Coelastrum spp., Scenedesmus spp., and Tetraëdron spp.) and Cyanophyta ( Microcystis spp., Merismopedia sp., Chroococcus spp., and Anabaena spp.) showed consistent organic uptake. However, the principal bloom former, the dinoflagellate Peridinium cinctum fa westii and most of the pelagic algae observed, never assimilated any of the above substrates. Autoradiographic surveys permit rapid screening of algal populations for species which are capable of taking up organic matter and can indicate potential facultative heterotrophs. [ABSTRACT FROM AUTHOR]

The article examines the components and seasonal variation in numbers and species of algal flora growing on two sediments in Yorkshire, England. The two sediments that were investigated were the black peaty nature sediment comprising the decayed fibrous remains of Angiosperms and Bryophytes and the grayish calcareous sediment containing sand grains. The majority of the groups making up the flora are the Bacillariophyceae, with highest growth in spring and autumn, the Cyanophyceae, reaching a maximum growth in spring, and the Chlorophyceae, with peak growth in May. The seasonal variation in numbers of these group is related to the nutrient absorption of the lake water and looks to be untouched by the sediments.

The invertebrate fauna of permanently alkaline and permanently acid small lakes in the western Cape Province is described. It is discussed from the point of view that the faunal associations present are related to the pH conditions. An important part of the fauna of permanently alkaline lakes consisted of species which appeared to be limited to alkaline conditions, whereas in acid, humic lakes there were few specialized, ‘acidobiontic’ species. [ABSTRACT FROM PUBLISHER]