![]() A microalgal diet rich in lipids has been shown to be particularly essential at the late larval stage of C. gigas, and a reliable supply of ‘good quality’ algae is paramount for optimal spat output ( Loosanoff and Davis, 1963 Walne and Spencer, 1974 Helm and Millican, 1977 Coutteau and Sorgeloos, 1992 Helm and Bourne, 2004).īivalve larvae fed ‘good quality’ algae display rapid growth, early settlement, and high metamorphic rates ( Holland and Spencer, 1973 Robert and Gérard, 1999 Powell et al., 2002 Robert et al., 2017). ![]() Marine microalgae produced by mass-culture are an essential food source for many bivalve species cultured in hatcheries, including C. Prophylactic measures to reduce such mortality events include enhanced biosecurity and hatchery hygiene, improved husbandry (e.g., reduction of stocking density, temperature, increase of water renewal), the use of antibiotics or probiotics and routine water monitoring ( Sindermann and Lightner, 1988 Prieur et al., 1990). These mortality events are generally linked to outbreaks of bacterial infections ( Tubiash et al., 1965 Elston and Leibovitz, 1980 Nicolas et al., 1996 Prado et al., 2005). gigas is currently the only sustainable way of reliably supplying this significant industry but the recurrence of mass mortality events in hatcheries is a major constraint to increasing spat supply and enabling sustained productivity. The Pacific oyster, Crassostrea gigas, is a major commercial species and the most cultivated oyster globally with a production value estimated at US$ 1.24 billion p.a. Our research demonstrated that metabarcoding can be effectively used to identify microbiota features associated with larval fitness. Several bacterial genera (e.g., Halomonas, Marinomonas) were strongly associated with impaired larval performance while the presence of genera in larvae including Vibrio was closely associated with overfeeding. These results suggest significant dysbiosis induced by compromised feed and/or increased feed ration. In larval tissue, bacterial richness was highest in stressed and high-feed treatments, and negatively correlated with larval fitness parameters. The rearing seawater showed the highest bacterial richness compared to the larval and the microalgal compartments, regardless of feeding regime. Bacterial profiling using 16S rRNA showed that most bacterial families characterized in larval tissue were also present in larval rearing seawater and in the microalgae feed (98%). The quantity of stressed algae supplied to oyster larvae also influenced overall larval performance, with high feeding rations generally causing greater impairment than low rations. 36% in control) and became spat (1.5% vs. Following the recovery period, fewer larvae reached pediveliger stage (2.7% vs. 20% in control), reduced feeding and swimming ability, and slowed development. Feeding stressed algae to oyster larvae for 96 h increased the occurrence of deformities (>70% vs. Bacterial communities associated with the microalgae feed, rearing seawater, and the oyster larvae, were characterized and correlated with effects on oyster fitness parameters. ![]() Biological endpoints of larval performance were measured following the 96 h exposure and subsequent recovery. Intentionally ‘stressed’ (high pH) or non-stressed microalgae were fed to 11 day-old oyster larvae at two feeding rations for 96 h, followed by a recovery period. This study assessed the effects of feeding compromised microalgae to developing oyster larvae. Outbreaks of bacterial infection via microalgal feed are frequently implicated in these mortalities. ![]() ![]() The Pacific oyster Crassostrea gigas is the world’s most cultivated oyster and seed supply is heavily reliant on hatchery production where recurring mass mortality events are a major constraint. 4Institute of Marine Science, The University of Auckland, Warkworth, New Zealand.3Moana New Zealand Ltd., Nelson, New Zealand.2Coastal and Freshwater Group, Cawthron Institute, Nelson, New Zealand.1Aquaculture Group, Cawthron Institute, Nelson, New Zealand.Julien Vignier 1*, Olivier Laroche 2, Anne Rolton 1, Pandora Wadsworth 3, Karthiga Kumanan 1, Branwen Trochel 2, Xavier Pochon 2,4 and Nick King 1 ![]()
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