TY - JOUR T1 - Production of microalgal concentrates by flocculation and their assessment as aquaculture feeds A1 - Knuckey,R A1 - Brown,M A1 - Robert,Rene A1 - Frampton,D AD - Northern Fisheries Ctr, Dept Primary Ind & Fisheries, Cairns, Qld 4870, Australia. AD - CSIRO, Marine Res, Hobart, Tas 7001, Australia. AD - IFREMER, UMR Physiol & Ecophysiol Mollusques Marins Stn Ex, F-29840 Argenton en Landunvez, France. UR - https://archimer.ifremer.fr/doc/00000/1820/ DO - 10.1016/j.aquaeng.2006.04.001 KW - Chaetoceros KW - Thalassiosira KW - Flocculation KW - Concentrate KW - Bivalve KW - Algal paste N2 - A novel technique was developed for the flocculation of marine microalgae commonly used in aquaculture. The process entailed an adjustment of pH of culture to between 10 and 10.6 using NaOH, followed by addition of a non-ionic polymer Magnafloc LT-25 to a final concentration of 0.5 mg L−1. The ensuing flocculate was harvested, and neutralised giving a final concentration factor of between 200- and 800-fold. This process was successfully applied to harvest cells of Chaetoceros calcitrans, C. muelleri, Thalassiosira pseudonana, Attheya septentrionalis, Nitzschia closterium, Skeletonema sp., Tetraselmis suecica and Rhodomonas salina, with efficiencies ≥80%. The process was rapid, simple and inexpensive, and relatively cost neutral with increasing volume (cf. concentration by centrifugation). Harvested material was readily disaggregated to single cell suspensions by dilution in seawater and mild agitation. Microscopic examination of the cells showed them to be indistinguishable from corresponding non-flocculated cells. Chlorophyll analysis of concentrates prepared from cultures of ≤130 L showed minimal degradation after 2 weeks storage. Concentrates of T. pseudonana prepared using pH-induced flocculation gave better growth of juvenile Pacific oysters (Crassostrea gigas) than concentrates prepared by ferric flocculation, or centrifuged concentrates using a cream separator or laboratory centrifuge. In follow up experiments, concentrates prepared from 1000 L Chaetoceros muelleri cultures were effective as supplementary diets to improve the growth of juvenile C. gigas and the scallop Pecten fumatus reared under commercial conditions, though not as effective as the corresponding live algae. The experiments demonstrated a proof-of-concept for a commercial application of concentrates prepared by flocculation, especially for use at a remote nursery without on-site mass-algal culture facilities. Y1 - 2006/10 PB - Elsevier JF - Aquacultural Engineering SN - 0144-8609 VL - 35 IS - 3 SP - 300 EP - 313 ID - 1820 ER -