Flocculated microalgae concentrates as diets for larvae of the tiger prawn Penaeus monodon Fabricius

Abstract

Fresh algal culture is a major bottleneck in the aquaculture industry. Substitutes that are cost-effective and simplify hatchery procedures, such as algae concentrates need to be evaluated. Four species of alga -Chaetoceros muelleri, C. calcitrans, a tropical Skeletonema sp. and Thalassiosira pseudonana -were concentrated by flocculation, stored for 6 weeks at 4°C and then compared with their fresh counterparts as feeds for Penaeus monodon larvae. The algae were fed at either high or low cell densities with no supplements. Fresh C. muelleri promoted the highest survival, greatest weight gain and fastest development to mysis 1. Larvae fed this diet were twice as heavy as those fed most of the other diets. Concentrated C. muelleri or T. pseudonana promoted similar survival rates to that of larvae fed fresh C. muelleri although development rates were slower. Larvae fed fresh C. calcitrans had high survival and intermediate development, but those fed the concentrate had very poor survival and development. Skeletonema sp., whether in the fresh or concentrated form, was a poor diet for prawn larvae: it resulted in high mortality and slow development. Cell density did not affect survival or dry weight of larvae but did affect development in some cases. Flocculated algal concentrates show promise as replacement feeds for fresh algae. KEY WORDS

The released polysaccharide of the cyanobacterium Aphanothece halophytica inhibits flocculation of the alga with ferric chloride

“…To harvest microalgal biomass, flocculation is a simple, gentle and cost-effective method and can be used to aggregate microalgal cells to increase the effective "particle" size and hence ease harvesting by centrifugation, filtration or gravity sedimentation. Furthermore, flocculated microalgal concentrates have been directly used as aquaculture feeds (D'Souza et al 2002;Knuckey et al 2006).…”

Use of Natural pH Variation to Increase the Flocculation of the Marine Microalgae Nannochloropsis oculata

“…However, a recent study has demonstrated that flocculants can interfere in the fatty acid profile of lipids produced by N. oculata, changing the amounts of saturated and unsaturated fatty acids [26]. However, [8,27] obtained good results growing mollusks and crustaceans fed on stored flocculated microalgae biomass.…”

Microalgal cell immobilization for the long-term storage of the marine diatom Haslea ostrearia

“…Chen (2001Chen ( , 2003 suggested that entrapped cells of S. quadricauda and I. galbana remained alive probably by consuming their reserve of pyrenoids during storage. It was shown that after concentration by floculation the algal cells not only retained their viability and growth-up to 14 days with Chaetoceros calcitrans (McCaustand et al, 1999)-but also their appetence for larvae as above mentioned with the example of C. muelleri or T. pseudonana (D'Souza et al, 2002). Nell and O'Connor (1991) showed also that a combination of P. Pavlova lutheri and C. calcitrans concentrated to a paste and stored up to 14 days at 4 • C produced greater length increases of larvae of Sydney rock oyster than any other fresh or stored, single or combined diet tested.…”