DETERMINATION OF BIOMASS DRY-WEIGHT OF MARINE MICROALGAE

Total biomass dry weight (DW) and ash free dry weight (AFDW) of five s pecies of marine microalgae, Dunaliella sp., Isochrysis galbana, Nanno chloropsis sp., Nitzschia closterium and Porphyridium cruentum, retain ed on filter paper, were determined. Dunaliella and Isochrysis cells h ave no cell wall; Nannochloropsis, Nitzschia and Porphyridium possess a cell wall and Nitzschia and Porphyridium cells are covered by silica and mucilage coating, respectively. In all these algae, DW of non-was hed samples was at least 1.2 times higher than those washed by distill ed water, 0.9% sodium chloride, 0.5 M ammonium formate or 0.5 M ammoni um bicarbonate. DW of 0.9% sodium chloride washed samples was more tha n 0.8 times higher than the other three washed samples. In most of the cases, there was no significant difference between DW of samples wash ed by ammonium formate and ammonium bicarbonate solutions (p>0.05). Th e AFDW of the non-washed algal samples was about twice that of washed samples, and could be accounted for by a volatile component in the sea water medium. Isotonic solution of ammonium bicarbonate is a satisfac tory washing agent for algal cells for dry weight determination.