Seasonal changes in growth rate and carrageenan yield of Kappaphycus alvarezii and Kappaphycus striatum (Rhodophyta, Gigartinales) cultivated in Kolambugan, Lanao del Norte

The seasonal changes in growth and carrageenan yield of Kappaphycus alvarezii (var. wayway) and Kappaphycus striatum (var. sacol) cultivated in Barangay Manga, Kolambugan, Lanao del Norte was determined during the southwest and northeast monsoon. Some environmental parameters were also determined: water temperature, salinity, water flow and inorganic phosphate and nitrate. The growth rate and carrageenan content varied significantly with sampling periods; highest growth rate and carrageenan content occurred during the northeast monsoon from November to January while the lowest growth and carrageenan yield obtained during the southwest monsoon from June to August. K. alvarezii had higher growth rate and carrageenan yield compared to K. striatum in both seasons. A positive relationship between growth rate and carrageenan yield was detected in both species. Multiple stepwise regression analysis showed that water flow was the only environmental factor that affects the growth and carrageenan yield of K. alvarezii and K. striatum. The results show that the highest growth rate and carrageenan yield of K. alvarezii and K. striatum can be obtained during the northeast monsoon when water movement was strong.