Brine characterization and Artemia population dynamics in Bohai Bay solar saltworks, China

A field study was conducted in Hangu saltworks, a typical Bohai Bay solar salt production site, where a population of Artemia has established. The samples of the brine and of the Artemia population were collected once a month in the period of May to November 2016. According to the salinity range in which Artemia occurs in nature, seven saltponds were chosen in the range of 60 g/l to 240 g/l, covering grades of 30 g salts/l. The physicochemical characteristics of the brine as well as the population dynamics of the Artemia were analysed. The pH value was 7.35-8.94 and decreased slightly with increasing brine temperature. The ionic composition of the brine changed along with progressive evaporation and successive, fractional crystallization. The content of Na+, Cl− and Mg2+ were 66.71-225.43 mg/l, 43.99-197.71 mg/l, and 2.64-14.88 mg/l, respectively, and increased with salinity going up. The content of Ca2+ ranged from 0.69 mg/l to 1.69 mg/l with the maximum value observed at the salinity of 120 g/l. The content of SO42− ranged from 3.84 mg/l to 20.16 mg/l and two peak values were observed at salinities of 90 g/l and 180 g/l, respectively. The contents of DOC (dissolved organic carbon), TN (total nitrogen), and TP (total phosphorus) were 11.45-97.45 mg/l, 1.61-10.54 mg/l, and 0.07-0.63 mg/l, respectively, and these increased with increasing salinity. The density of the Artemia population, its composition and mode of reproduction were found to be remarkably influenced by brine temperature and salinity. The Artemia populations were mainly concentrated in the salinity range from 90 g/l to 150 g/l, and in the summer time. Both parthenogenetic and bisexual Artemia coexisted in the saltponds, with the local parthenogenetic population dominating in summer and in the lower salinity range. Female Artemia tended to produce cysts in autumn and in the higher salinity range. Our study provides general information on the physiochemical characterization and the Artemia population dynamics in Hangu saltworks, which is of importance for a better understanding of the ecological situation of Bohai Bay saltworks, and provides basic information for a biological management of the saltponds.