This is a typical filament that was resuspended from the sediments not long before sampling. Its linking spines are of different lengths, possibly indicative of the filament having been broken at this place. In contrast, spines of equal length as in the other photo of this species are indicative of active growth. The chloroplasts here are partly compacted and do not fill the entire cell volume, indicative of the origin of this particular filament from the sediments. The other photo of this species shows actively growing, planktonic cells with chloroplasts filling the entire cell.
Aulacoseira granulata is a widespread centric diatom in the phytoplankton of lakes, reservoirs and rivers world-wide but particularly in African lakes and rivers, including the Nile River, L Naivasha, Kenya. It is typical of carbonate-rich, moderately eutrophic to eutrophic waters. It is used as indicator species of water with relatively low concentrations of salts, pH less than 9, and high silica concentrations.
aalster and tzohary
A Alster & T Zohary, Kinneret Limnological Laboratory, IOLR