Microbial Resource Management for improved viability of marine fish larvae by community level selection of microbiota

Transcription

1 1 Microbial Resource Management for improved viability of marine fish larvae by community level selection of microbiota Olav Vadstein Co-authors: J. Skjermo *, K. Attramadal, I. Bakke, Y. Olsen Norwegian University of Science & Technology (NTNU), Departments of Biotechnology and Biology * SINTEF Fisheries and Aquaculture MRM Symposium, 30. June 1.July Problems in larval rearing: The symptoms The larvae do not start to eat properly The larvae grow slowly Normal development may stop at a critical stage Abrupt mortality is a normal phenomenon Poor reproducibility between replicates The Same for all Industrially Produced Animals Or in one point: Poor results and Lack of reproducibility

2 3 The possible causal connections: Egg quality (developmental and biochemical aspects) Nutrition Microbial conditions 4 The first feeding ecosystem Fish larvae (top predator) Zooplankton Bacteria DOM Phytoplankton

3 5 Requirements for a functional microbiota: Who/Names 6 The alternative Black-box approach: We know more about what we do not want It is possible to set up selection regimes to avoid opportunist K-selection, contrary to r-selection, will serve such a purpose K-selection can be set up by securing competition for resources Competition is a result of low nutrient supply per microbe Controlled (re)colonization!

4 7 What happens after disinfection of seawater: CFU/ml 1e+7 1e+6 1e+5 Vibrio Pseudom. Others % Opportunists 1e Days 8 The hypothesis: Larvae who are reared in water dominated by K- strategist (mature microbial communities) will perform better because they are less likely to encounter opportunistic (r-selected) microbes and detrimental host/micobe interactions

5 9 Two approaches for K-selection 1. Microbially matured water: Flow-through system Disinfection Controlled re-colonization in a biofilter 2. Re-circulated cultivation systems: Particle removal ± Disinfection Consumption of ammonia and organic matter in biofilter Both secure K-selection because the populations in the biofilters are large compared to resource supply 10 The selection gives different community composition: In-flowing water 0.15 NMS, Bray-Curtis Similarity, Sqrt transf ANOSIM analysis: R = 0.894, p < Coordinate RAS FTS MMS vs FTS RAS vs FTS RAS vs MMS FTS MMS RAS B E T W E E N W I T H I N MMS Bray-Curtis similarity ± SEM Coordinate 1

6 11 Different communities give different stability Recirculation partly closes the gap RAS Rearing system MMS FTS Bact. Production Bact. Numbers % in in-flowing relative to tank water 12 µg C larva -1 The effect on larvae 1: Flow-through versus Microbially Matured Day Day Exp.I Exp.II Exp.III F F+A M M+A F: Flow-through M: Microbially Matured A: Added microalgae F FA M MA

7 13 The effect on larvae 2: Comparing the three water treatment systems Survival to day 60 ph (end of experiment) Survival to day 32 ph (live feed period) 29 ± 3 % Survival ± 2 28 ± FTS 1 FTS 2 FTS 3 MMS 1 MMS 2 MMS 3 RAS 1 RAS 2 RAS 3 14 Conclusions: Community level K-selection of microbes works in aquaculture systems,.. but more knowledge is needed on: microbial community composition under K-selection systems design Larval stages of fish perform better when exposed to a K-selected microbial community Ecological theory can be used to solve practical problems

8 15 Acknowledgements: This talk is based on published and unpublished work by several PhD students To culture fish one has to culture the water Financial support by: NTNU, Norw. Res. Council, EU-FP Part of the projects: CODTECH and PROMICROBE Thank you 16 RAS MMS FTS Fish tank Nitrifying biofilter Vacuum aerator R3 Heterotrophic biofilter R2 R1 Protein skimmer Protein skimmer Sand filter Maturation UV Intake Flow scheme of the three systems for water treatment: flow through system (FTS), microbial maturation system (MMS) and recirculating aquaculture system (RAS).