Some observations on the green planktonic alga, Botryococcus braunii and its bloom form

The cells and colonies of Botryococcus braunii laboratory cultureswere examined by interference and scanning electron microcopyand compared with cells isolated from a bloom in Lake Kinneret,Israel. The green cells were located in cups representing theparental cell wall; the cell walls of successive daughter cellsappeared to be fused to the parent and daughter cells wherethey were contiguous. The arrangement of green cells in laboratorycultures was consistent; groups of 2 or 4 cells formed a unitand these units appeared joined together at their bases to formclusters. Green cells from the lake bloom appeared in irregularclusters of units of 2, 3 or more cells. Red bloom cells appearedto be dead with each cup compressed and empty with a hole showingat the cell surface. A hypothesis describing the role of senescenceand nitrogen depletion, based on cytological, ecological, andchemical data, is invoked to explain the change of the bloomcells from green relatively low lipid to orange (or red) highlipid cells.