He Peimin

Molecular detection and analysis of green seaweeds from Rudong coasts in Jiangsu Province

Since 2007, massive green tides have occurred every year in the Yellow Sea in areas such as Qingdao, Lianyungang and Rudong. In 2008, Qingdao experienced the largest Ulva bloom in the world, which caused an ecological disaster. In 2009, survey and monitoring of green seaweeds was conducted in the Rudong sea area of Jiangsu Province. We sequenced and analyzed the nuclear encoded internal transcribed spacer (ITS) and associated 5.8S rDNA regions as well as the chloroplast rbcL genes for 11 attached samples and 15 free-floating samples of green algae collected from Rudong coasts. The investigation showed that a large amount of sessile Ulva existed in Rudong coastal areas. In addition, the floating green algae clusters appeared earliest in Rudong, and gradually drifted northwards. The phylogenetic analysis of ITS sequences revealed that the samples fell into five distinct clades: the Ulva compressa clade (6 samples), the Ulva linza-procera-prolifera (LPP) complex clade (12 samples), the Ulva flexuosa clade (3 samples), the Blidingia sp. clade (3 samples) and the Urospora spp. clade (2 samples). However, the 26 samples formed just four clades in the phylogenetic tree of rbc L sequences, which indicated the higher conservativeness of rbc L. DNA sequencing analysis implied there were Ulva compressa , Ulva flexuosa and LPP complex in both the free-floating Ulva and the attached species from Rudong coasts and that the final free-floating strain was the same as the dominant Ulva species ( U. prolifera ) of the 2008 bloom in the Yellow Sea. This study laid significant foundations for source-tracing and prevention of Ulva blooms in the Yellow Sea.

不同途径感染白斑综合征病毒(WSSV)对日本沼虾的致病性

Macrobrachium nipponensis is delicious and has high economic value, but its susceptibility to white-spot syndrome virus (WSSV) is unknown. Susceptibility, morbidity, and multiplication of WSSV in M. nipponense were studied by epidemiological survey, infection experiment and qPCR. M. nipponense was the natural host of WSSV, and the natural carrying rate was about 8.33%. M. nipponense could be infected with WSSV via oral administration, muscle injection and immersion, and the cumulative infection rate of 10 d exposure was 100%, and the cumulative mortality rates were 100%, 75% and 0%, respectively. The infection of WSSV is fast by muscle injection. The virus content after 5 days injection is 1 000 times higher than that of the first day of infection, and the mortality rate reached 100% after 8 days. The median lethal dose (LD₅₀) measured as the mortality of infected M. nipponense via injection indicated the LD₅₀ in the concentration of WSSV of 2.71×10⁵ virions/μL. In shrimp farming, M. nipponense can be infected by ingesting WSSV infected shrimp or dead shrimp, and also by soaking in WSSV-containing water and thus become a vector, consequently affecting the spread and pathogenicity of WSSV.

Effects of nitrogen and phosphorus on the growth,photosynthesis and pigments of Ulva prolifera

Eutrophication is the most serious environmental problem in the coastal marine pollution.Macroalgal blooms tend to have the potential for rapid absorption of nutrients and rapid proliferation.In order to investigate the physiological and biochemical responses of Ulva prolifera to nitrogen(N)and phosphorus(P)in the eutrophic seawater,the growth rate,photosynthesis and the pigments of U.prolifera were determined under different nutrients conditions and different culture densities.The experiment was divided into four treatments:the control group,+N group,+P group,and +N+P group(+N,+P represents adding NaNO3,Na2 HPO4,respectively.).The algae were pre-cultured in four nutrition conditions for 3 d.The temperature was set at 20 ℃,light intensity was approximately 6 000 lx,and photoperiod L∶ D was 12 h∶ 12 h with continuous aeration.Our results showed that either N or P supplies could increase the growth rate of U.prolifera,but much more significant enhancement was found in the N enrichment than P enrichment.When the original biomass was set as 0.1 g/L,the relative growth rates of the control group,+P group,+N group and +N+P group were 0.68,0.69,0.72 and 0.75,respectively.There was a negative relation between the relative growth rate and biomass density.The biomass doubling time significantly shortened when N and P were added.When the original biomass was 0.2 g/L,the biomass doubling time of control group,+P group,+N group and +N+P group was 1.60,1.53,1.16,and 1.03 d,respectively.The fastest biomass doubling time was found in the thalli grown at N and P enrichments condition and 0.1 g/L initial biomass density,with the period of 0.92 d.Either N enrichment or P enrichment could increase the chlorophyll and carotenoid contents,as well as the net photosynthetic rate of U.prolifera.The maximum net photosynthetic rate and pigments contents in U.prolifera were found in the culture condition with a combination of simultaneous enrichment of N and P.There was a siganificant interaction between N and P enrichment.In summary,N,P enrichments can significantly promote the growth,increase the photosynthetic pigments and photosynthetic rate of U.prolifera,which may be an important mechanism of the bloom of U.prolifera.