Effects of co-culture and salinity on the growth and agar yield ofGracilaria tenuistipitata varliui Zhanget Xia

Abstract

Gracilaria tenuistipitata varLiui were mono-cultivated and co-cultivated withPinctada martensii under high (33) and low (21) salinity conditions in laboratory. The daily growth rate of the alga was determined. Tissue carbon and nitrogen contents, the yield and fractional composition of agar were analyzed. Results showed that: 1.Gracilaria grew better under low salinity conditions, the daily growth rate was twice that under high salinity conditions. Co-cultivated algae grew faster than mono-cultivated algae under low salinity conditions, the daily growth rate was about 37.6% higher. 2. Compared with mono-cultivated algae, tissue nitrogen contents of co-cultivated algae were higher, while the C:N ratios were much lower. 3. The agar yields of co-cultivated algae were much lower than those of mono-cultivated algae. Agar yield was found to be negatively correlated to the tissue nitrogen contents, and positively correlated to the C:N ratios. 4. The highest fractional yields obtained from co-cultivated algae were extracted with 40% ethanol, while from mono-cultivated algae, the highest fractional yields obtained were extracted with distilled water at room temperature.