GROWTH PERFORMANCE OF Kappaphycus alvarezii IN VARYING SALINITY LEVELS UNDER LABORATORY CONDITION

Salinity is an important abiotic factor in the cultivation of seaweed since it is responsible for the distribution of seaweeds. In coastal areas, salinity changes with prevailing winds, precipitation and intertidal conditions which could affect the growth of seaweeds. An experiment was conducted to evaluate the effects of salinity on the growth performance of Kappaphycus alvarezii under laboratory condition. Kappaphycus alvarezii was cultured under varying salinities ranging from 15 to 30 ppt where Treatment I (15 ppt), Treatment II (20 ppt), Treatment III (25 ppt) and Treatment IV (30 ppt). Each treatment was replicated three times and seaweed were cultured for a period of 28 days. A Complete Randomized Design (CRD) was used in the study and difference in treatment means were subjected to Duncan’s Multiple Range Test (DMRT). Kappaphycus alvarezii were surface sterilize and then excised into 2 cm length explants with a total of 2 g per 500 ml autoclaved seawater. Kappaphycus alvarezii was cultured in an enclosed cabinet-like storage to control the environment condition. Sampling was done every 7 days to get the final weight, weight gain and specific growth rate of the samples. Plants kept in Treatment 1 with 15 ppt presented loss of pigmentation and progressive deterioration during the 3rd day of culture and eventually found dead after 6 days. Seaweeds cultured in 20, 25 and 30 showed steady growth. The highest mean weight gain was attained in Treatment IV with 2.01 g followed by Treatment III with 1.70 g then Treatment II with 0.50 g. Highest specific growth rate was obtained by Treatment IV with 2.48 %/day followed by Treatment III with 2.20%/day and Treatment II with 0.80%/day. Analysis on the differences among treatments were statistically significant (P<0.05). Results indicated that Treatment IV (30ppt) obtained highest growth compared to other treatments. The growth and survival of Kappaphycus alvarezii was significantly affected by changes in salinity. Culturing of Kappaphycus alvarezii in 30 ppt is recommended to attain faster growth rate.