Effect Of Artemia Inoculation On Biological Management Of Saltpond Ecosystem

As a small crustacean in hypersaline environment, Artemia is not only a major biological regulator in the solar saltpond biotope, but also a suitable live food for hatchery production. In recent years the Artemia cysts and biomass production in the Bohai Bay salt ponds has been challenged by extensive discharge of effluents of desalination and subsequent bromine extraction into lower salinity evaporation ponds, as well as over harvesting, which resulted in un-balanced saltpond ecosystem and consequently inferior salt quality and yield. Controlled inoculation of Artemia, particularly high quality Artemia cysts, not only benefits the ecological environment of saltponds, but also imporves the yeild of Artemia cysts and biomass in the region.Vinh Chau (VC) A. franciscana is commercially produced in the saltponds in Vinh Chau, Vietnam through artificial inoculation and culture of San Francisco Bay (SFB) A. franciscana. It is characterized by smaller cysts diameter, higher hacthability, better tolerance to higher temperature and eaiser to break diapause, and thus highly demanaded by market. This paper investigated the effect of VC A. franciscana inoculation on the Bohai Bay saltpond ecosystem in following three aspects:1) Laboratory studying the adaptability of VC A. franciscana on Bohai Bay ecological factors, aiming to provide basic information for the inoculation of exotic Artemia strain in Bohai Bay saltworks. Survival, growth and reproductive traits of autochthonous parthenogenetic Artemia from Bohai Bay saltworks, China and bisexual A. franciscana obtained from the saltponds of San Francisco Bay (SFB), USA and Vinh Chau, Vietnam were studied in condition of different salinities (70,125and180g L-1), culture temperature (14,25and33℃) and feeding level (100,50and25%of optimal feeding level). The results indicated that, compared to the parthenogenetic Artemia and SFB A. franciscana, VC A. franciscana had better survival and cysts yield at25℃,70g/L and better feeding condition. In general VC A. franciscana could tolerance broader range of salinity and temperature, thus more adapted to the conditions of Bohai Bay saltponds and may be a more effective colonizer in Bohai Bay salt ponds.2) Together with ecological survey, the inoculation of VC A. franciscana was conducted in Chengkou Saltworks, Shandong Province, aiming to investigate the effect of VC A. franciscana inoculation on the Bohai Bay saltpond ecosystem. The inoculation were conducted in April and May in2010and2011, when water temeprature was low enough and local parthenogenetic Artemia population had not emerged. The stocking density was5nauplii/L and20nauplii/L, resepctively, in2010and2011. Monthly-based analysis for physical and chemical composition of brine and population dynamics of Artemia indicated, Artemia density, cysts production per unit surface and salt yield per unit surface in the inoculated saltponds remarkbly increased.3) In the framework of cooperation between Tianjin University of Science and Technology and Can Tho University, Vietnam, training course on Artemia pond production was followed up in Can Tho in February to May,2011. And the effects of carbon (C) and nitrogen (N) supplementation in pond production of Artemia franciscana cysts was studied in Vinh Chau. The C/N of10was chosen as a fixed ratio but with increasing amount of tapioca (Carbon) and pig manure (Nitrogen) in different levels:100%(control),110%,115%and120%, respectively. Results indicated that the total cysts yield in the ponds supplemented with more pig manure and tapioca were higher than the control, particularly for treatment2, which was more than double (2.7times) to the control. Taking into account the cost of pig manure and tapioca, treatment2with supplementation level of110%of control treatment (0.231and0.351kg ww pond-1day-1of pig manure and tapioca, respectively) should be more cost-effective fertilization regime for pond production of Artemia cysts. This is possibly due to the contribution of microalgal bloom and biofloculation development in the water column upon adding nitrogen and carbon resources.