Relationship of the viscosity of carrageenan extracted from Kappaphycus alvarezii with seawater physical and chemical properties at different planting distances and depth

Abstract

The carrageenophyte seaweed Kappaphycus alvarezii is important both as an export commodity and for the livelihoods of coastal communities. Seawater physical and chemical properties can influence the viscosity of carrageenan produced by K. alvarezii. This study analysed the relationship between this viscosity and seawater physical and chemical properties. The study site was Laikang Bay in Jeneponto District, South Sulawesi, Indonesia. A nested factorial design was used. The two factor levels were seedling planting distance (10, 20 and 30 cm), and depth (2 and 5 m). Treatments were grouped by planting time (2 periods) with three replicate stations. A floating raft culture method was used. Seawater parameters measured were light intensity (in-situ), sediment, nitrate, orthophosphate, ammonia, calcium, and magnesium concentrations (ex situ). Carrageenan extraction and viscosity measurement were performed at the Hasanuddin University Industrial Engineering Laboratory in Makassar. There was a medium strong (64%) correlation between physical and chemical seawater parameters and viscosity. Viscosity range was 41-80 cP (mean 62.78±12.99 cP). The lowest viscosity was obtained with 30 cm planting distance at 5 m, and the highest with 10 cm planting distance at 2 m. We recommend planting distance and depth for seaweed farming in areas with coral substrate