Preliminary Study On The Probiotic Effect Of Functional Microbial Agent Assisted Evolution On Coral Pocillopora Damicornis

Coral reefs are one of the most important ecosystems in the ocean.They maintain high primary productivity and biodiversity in oligotrophic waters.However,as global warming and seawater temperatures rising,coral reefs are in face of an unprecedented bleaching crisis.The application of Beneficial Microorganism for Corals(BMC)in coral assisted evolution to increase tolerance and resilience of coral to environmental stress is considered as a promising approach to coral conservation.Nitrogen-fixing bacteria and phosphorus-solubilizing bacteria can alleviate the limitation of nitrogen and phosphorus in oligotrophic environment.It is of great ecological importance to study the probiotic effect of their microbial agents and their ability to shape the microbial community of corals.1.The diversity of scleractinian corals associated culturable microbesMicroorganisms in 5 species of reef-building corals in Luhuitou Sanya,Hainan Province were isolated using six kinds of culture medium.A total of 152 strains belonging to 27 genera in 4 phyla were obtained.The vibrio and psuedoalteromonas which all belong to ?-proteobacteria and the psuedovibrio of?-proteobacteria are dominant groups in all 5 coral species.The diversity of bacteria isolated by six culture mediums is in the order as follow: 10% LB> MA> 10% 2216E>GA > 2216 E > Ashby.The culturable microorganisms in coral have host species-specificity.The isolation and purification of coral associated microorganisms provided rich resources for the application of Beneficial Microorganism for Corals.2.The growth-promoting effect of microbial agents on coral Pocillopora damicornisThree microbial agents combined of 2 strains of nitrogen-fixing bacteria and 2strains of phosphorus-solubilizing bacteria were added into the aquatic culture system of coral fragments of Pocillopora damicornis for 21-day culture observations.The calcification rate was measured by buoyant weighing,the photochemical efficiency(Fv/Fm)of corals was measured using a Pulse-Amplitude-Modulation(PAM),and the physiological and biochemical indexes were measured.The results showed that microbial agents can increase the coral calcification significantly;and promote the total energy reserve of coral.But there is no significant effect on the content of chlorophyll a and photochemical efficiency.It is suggested that microbial agents may promote the growth and calcification of coral Pocillopora damicornis by increasing the heterotrophic process or reducing energy metabolism of corals.3.Coral microbial community responded to microbial agentThe next-generation sequencing was applied to analyze the microbial community structure response to three combinations of microbial agents.The results showed that the addition of microbial agents had no significant effect on the diversity of the coral associated microbial community structures in Pocillopora damicornis.The dominant groups in Pocillopora damicornis are ?-Proteobacteria,?-Proteobacteria,?-Proteobacteria and Bacteroides.At the early stage of bacterial agents addition,theabundance of Aestuarispira in the added group increased by 42% to 92%,whereas that of the desulfovibrio decreased by 36% to 75%.At the late stage of addition,the relative abundance of both Desulfovibrio and Aestuarispira recovered to the level before the addition.The results showed that the addition of the microbial agents could transiently reshape the community structure in Pocillopora damicornis.However,the microbial community structure will be stabilized again after a transient adjustment and adaption,which revealed the addition of the microbial agents will not destroy the energy circulating system of the microorganisms associated with the corals.