Effect of nitrogen sources on the growth and bioaccumulation of nitrogen in marine red alga Kappaphycus striatum (Rhodophyta, Solieriaceae) in culture

Kappaphycus striatum (Schmitz) Doty (=Eucheuma striatum Schmitz) was cultur ed in the laboratory. The natural seawater was supplimented with 1, 3, 5, 7 and 9 mg N l(-1) from NaNO3, NH4NO3,, (NH4)(2)SO4 and urea separately. In these cultures 0.25 mg P l(-1) as superphosphate and micronutrients were ad ded except in control. Effects of different concentrations of nitrogen from different sources after 60 days showed significant increase in wet weight (at 1% level) in cultures supplied with 1 to 3 mg N l(-1) from (NH4)(2)SO4 and 3 to 5 mg N l(-1) from NH4NO3. However, (NH4)(2)SO4 was more effective than NH4NO3. Maximum wet weight was obtained in 1 mg N l(-1) from (NH4)(2)S O4. Percentage dry weight of the alga was maximum at 1 mg N l(-1) supplied from each of the nitrogen sources separately. Urea was found effective at h igher concentrations 5 to 9 mg N l(-1). The bioaccumulation of total nitrog en content of K. striatum increased with increasing concentration of each o f the nitrogen sources in the culture media. It was higher in the plants su pplied with NH4NO3 or (NH4)(2)SO4 than those supplied with NaNO3 or in cont rol. Bioaccumulation of nitrogen in K. striatum in different treatments ran ged from 0.57% to 4.99%. However, in cultures supplied with (NH4)(2)SO4, th e critical concentration of nitrogen varied from 1.91% to 2.53%, observed a t 1 to 3 mg N l(-1) respectively. In the cultures supplied with (NH4)(2)SO4 , maximum growth and uptake of PO4-P and NH4-N was observed.