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

Abstract

The cells and colonies of Botryococcus braunii laboratory cultures were examined by interference and scanning electron microcopy and compared with cells isolated from a bloom in Lake Kinneret, Israel. The green cells were located in cups representing the parental cell wall; the cell walls of successive daughter cells appeared to be fused to the parent and daughter cells where they were contiguous. The arrangement of green cells in laboratory cultures was consistent; groups of 2 or 4 cells formed a unit and these units appeared joined together at their bases to form clusters. Green cells from the lake bloom appeared in irregular clusters of units of 2, 3 or more cells. Red bloom cells appeared to be dead with each cup compressed and empty with a hole showing at the cell surface. A hypothesis describing the role of senescence and nitrogen depletion, based on cytological, ecological, and chemical data, is invoked to explain the change of the bloom cells from green relatively low lipid to orange (or red) high lipid cells.