Studies On Artemia Population And Microbial Diversity In Saltworks

The ecological investigation of Artemia population and physio-chemical parameter analysis of brine were conducted in Tanggu and Hangu Saltworks,Tianjin,China,in 2016 and 2017.Nine saltponds with 30 g/L salinity gradient difference were chosen for Artemia and brine sampling.The sampling was conducted monthly from May to November of the year.In Tanggu Saltworks,pH and DO content of the brine declined slightly with increasing salinity,ranging from 7.6 to 8.9 mg/L,and from 1.9 to 4.5 mg/L,respectively.The content of DOC,TN and TP increased with increasing salinity,ranged 11.45-97.45 mg/L,1.61-10.54 mg/L and 0.07-0.63 mg/L,respectively.The same characteristics and trends were observed in Hangu Saltworks.The dynamic changes of microbial diversity,abundance and dominant bacterial and archaeal population in different saltponds in May and July and their correlation with the environmental factors such as TOC,TN,TP,pH and temperature were studied in Tanggu saltworks.The high-throughput analysis with universal bacterial primers showed that Pseudoalteromonas was the dominant genus in the samples with salinity 60 g/L.Psychroflexus was the dominant genus in the samples with salinity 120 g/L.Salinibacter,Spiribacter and Psychroflexus were dominant in salinity samples with salinity 180 g/L.Salinibacter,Halorubrum and Spiribacter were the dominant genus in the samples of salinity 240 g/L.The proportion of bacteria decreased from 99.99%to 40%,while that of archaea increased from 0.01%to 60%with increasing salinity.The microbial composition in brine with similar salinity were similar in different months,which were mainly affected by salinity.The results of high-throughput sequencing with archaeal primers indicate that,the proportion of archaea increased from 19%to 99.63%as salinity increasing,and the proportion of unclassified microorganisms decreased.And the dominant archaea population belonged to Phylum Euryarchaeota,Family Halobacteriaceae,Genus Halorubrum,which increased with increasing salinity.Except for the sample M1(from lower salinity saltponds,60 g/L)which composition was closely correlated with pH,TOC,TN and TP,those of other samples are mainly determined by the salinity.Based on its high female-male ratio of adults Artemia(1.5-9.0 and 1.1-4.3,respectively),we assumed that there existed the mixed Artemia populations of both parthenogenetic and bisexual Artemia in Tanggu and Hanggu Saltworks.The population density,composition and reproductive mode of Artemia were influenced remarkably by the brine temperature and salinity.In spring(May),Artemia density was lower,and parthenogenetic population and nauplii-producing female dominated in Artemia population.In summer(June to Aug),the highest Artemia density was observed with parthenogenetic population and naupliiproducing female dominating in Artemia population.In autumn(Sept to Nov),lower Artemia density was observed again,but the dominant status of parthenogenetic population reduced and females tended to produce cysts.In lower salinity range(80-180 g/L),higher Artemia density was observed dominating with parthenogenetic population and ovoviviparious reproductivity;while in higher salinity range(180-240 g/L),lower density was observed dominating with bisexual population and oviparity reproductivity.Artemia inoculation were conducted in May,2016,Artemia cysts produced from Bobai Bay saltworks were used as inoculum.Newly hatched Artemia nauplii were inoculated to the saltpond at salinity 100 g/L and at a density of 100 ind/L.The inoculation resulted increased Artemia population,which was 12%-544%more than that of the saltponds(salinity 90-210 g/L)without Artemia inoculatation in 2017,and 30%-410%more than that of the saltponds(salinity 90-210 g/L)in 2016.This study provides basic information on physio-chemical characterization of the brine,Artemia population compostion and dynamics,and microbial diversity,which are useful for the biological management in Bohai Bay saltworks.