In situ variability of carrageenan content and biomass in the cultivated red macroalga Kappaphycus alvarezii with an estimation of its carrageenan stock at the scale of the Malasoro Bay (Indonesia) using satellite image processing

International audienceThe combination of in situ measurements, hydrodynamical modeling, and satellite imagery processing presents a complete tool to improve seaweed culture management. This study measured the evolution of carrageenan content during 1-year period and estimated the biomass of Kappaphycus alvarezii at a bay scale in Malasoro Bay, Indonesia. It allowed the determination of the carrageenan stock at the scale of the bay. The carrageenan content was assessed from different parts, i.e., basal and apical, of the thallus. The biomass from T (0) (beginning of the cultivation) to T (45) (harvesting time) was determined at two seasons. Satellite image processing was performed to estimate the biomass at bay scale using parcels resulting from a semi-automatic delineation process. As no long-term in situ environmental data existed in the study area, a 3D hydrodynamical model (Model for Application at Regional Scale 3D) was implemented to obtain high-frequency salinity, water temperature, and currents. The high carrageenan yield was obtained from April to September 2015 (54-63%) when temperature ranged from 25 to 30 A degrees C, salinity range from 33.8 to 34.8 psu, and precipitation below 0.5 mm. The biomass at bay scale was estimated at 2590 t with the highest carrageenan stock at 1.8 t ha(-1) in May 2015. The carrageenan yields and quality obtained in this study fulfilled the specification recommended for industry, and the cultivation of K. alvarezii can be carried out at optimal environmental conditions on April-September. The comprehensive approaches used in this study provide information for carrageenan stock and seaweed culture management as an important economic activity to support Indonesian coastal communities