Planktonic filament with linking spines

Description:

Aulacoseira (formerly Melosira) granulata (Bacillariophyta, Centrales) is one of the most common diatoms of Lake Kinneret, and certainly the major phytoplankton biomass contributor in winter (Dec – Feb), when the water column is homothermal. Typically, it occupies the entire 43 m water column. At the end of the winter bloom in early March the filaments sink and remain in the sediments in a dormant form with compressed chloroplasts till they are resuspended when the lake destratifies the following fall. It is a relatively large filamentous diatom, with cell diameter of 9 – 15 μm (median: 12.4 μm), cell height of 27-37 μm (median: 31 μm), and mean cell volume of 3700 μm3. The Kinneret Aulacoseira granulata filaments are straight, typically with 8 - 24 cells per filament. The picture shows the typical equal length marginal spines at the perimeter of the end-cell, these are “linking spines” which hold adjacent cells together. The chloroplasts fill the entire cells. This specimen was sampled from the shore of the lake in June 2006.   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.