Kondasinghe, K.P.R.S.2021-10-152021-10-152014UWU/AQT/14/0045http://www.erepo.lib.uwu.ac.lk/bitstream/handle/123456789/7305/AQT%2014%20045-19022021101803.pdf?sequence=1&isAllowed=yNannochloropsis sp. and Chaetoceros sp. are marine micro alga immensely valuable for aquaculture and food industry as they are rich sources of essential fatty acids, pigments, amino acids and vitamins. Present study was conducted to identify the effect of nitrogen sources on their growth and nutrient content in the cells. For the study, F/2 culture media was used as media in control culture which contains NaNO3 as the source of nitrogen. The F/2 culture media was prepared by using KNO3 (9 g 11), CH4N2O (Urea) (27 g 1') and NH4C1 (47.3 g I-1) as the sources of nitrogen in the culture media. Algae cultures were prepared in triplicates for all treatments in Nannochloropsis sp. and two replicates were prepared for Chaetoceros sp. and cultivated under indoor condition, maintaining the 27 °C of constant temperature and 25ppt of salinity with a continuous aeration. The results of ten days culture revealed that there was no significant difference for cell density with the time for all treatments (Two-way ANOVA: p>0.05). For the Chaetoceros sp. there was significant difference with the treatments. However, significant difference was found for chlorophyll-a nitrate and nitrite content which are produced by both species. (p<0.05). The significantly highest chlorophyll-a and cell density recorded with lower nitrogen assimilation level in the F/2 culture media with urea than that of other culture media treated with potassium nitrate and ammonium chloride. The Urea can be recommended as a more effective source of nitrogen for F/2 culture media to obtain high chlorophyll-a for Nannochloropsis sp. culture and to have higher cell density and chlorophyll-a content in Chaetoceros sp. This study provides baseline information about the appropriate nitrogem,sources which can elevate the higher productivity of Nannochloropsis sp. and Chaetoceros sp. Keywords Nannochloropsis sp, Chaetoceros sp.,Nitrogen sources, Cell density, Marine micro algaeenAquatic Resources Technology Degree Programme ( AQT)Thesis