We analyzed the archaeal community in tropical aquaculture farm sediments in Dapeng Cove, located in the southwest of Daya Bay, southern China. Sediment cores samples (5 cm and 30 cm in depth) were collected by a core-sampler in summer (August, 2014). Results show that the abundance of archaea in deep layers was higher than that in surface layer. The dominant species in surface and deep layers were Class Thermoplasma, Phylum Euryarchaeota, and Class MCG (Miscellaneous Crenarchaeotic Group), Phylum Crenarchaeota. In general, the abundance of Crenarchaeota was higher than that of Euryarchaeota. The abundance of predominant species was higher in aquaculture farms than in non-aquaculture area. The difference in archaeal community structure between surface and deep layers was more significant in aquaculture farms than that in non-aquaculture area. Results indicate that the archaeal community structure might be affected by intensive aquaculture activities, whose underlying mechanism needs further study.

Based on a survey on the species diversity, dominant species composition, cell abundance and horizontal distribution of Chaetoceros in the coastal waters of Hainan conducted during May 28 and June 3 in 2011, we identified 28 species of Chaetoceros, among which 25 species were found in the northwestern waters, 22 in the eastern waters and 21 in the southern waters. The dominant species in these coastal waters were C.siamense, C.pseudocurvisetus, C.decipiens and C.lorenzianus, while C.anastomosans, C.rostratus, C.densus, C.affinis and C.messanensis were also abundant in these coastal waters of Hainan. Eastern waters had the highest cell abundance with an average number of (162.70±415.16)×10⁴ ind · m^-3, while northwestern waters was slightly lower in cell abundance with an average number of (102.81±206.26)×10⁴ ind · m^-3, and southern waters had a minimum value of(70.43±142.09)×10⁴ ind · m^-3. Horizontal distribution of Chaetoceros in these three waters had a declining trend from onshore to offshore. There was no significant correlation between Chaetoceros abundance and environmental factors.

We conducted an experiment on the polyculture of Litopenaeus vannamei.GILI tilapia had been cultured in 24 enclosures in a pond located at Dianbai, Maoming City, Guangdong Province from June to August, 2011. We set 6 treatments with 4 replicates each, and a single enclosure was a replicate. Each enclosure was stocked with 3 000 shrimp seeds. Treatments A, B, C, D and E were polycultured with 4, 8, 12, 18 and 24 juvenile GILI tilapia after 28-day shrimp seeding, while the other 4 enclosures without tilapia were set as the control group F. Quantity of suspended particulate matter and Vibrio in polyculture enclosures were observed periodically so as to analyze the effect of tilapia polyculture on the quantity of suspended particulate matter and Vibrio in L.vannamei rearing enclosure. The results show that: 1) The content of total particular matter (TPM), particular organic matter (POM), particular inorganic matter (PIM), POM/TPM and PIM/TPM were identical among treatments at earlier culture stage; at the mid and later stage, POM/TPM, the contents of TPM and PIM were higher in experimental groups than in the control, while PIM/TPM was higher in the control than in experimental groups; PIM /TPMs in group C, group D and group E were higher than in Group A and Group B. 2)At later stage, the Vibrio quantity ranged from 1.01×10³ CFU · mL^-1 to 152.33×10³ CFU · mL^-1 [average (15.08±24.50) ×10³CFU ·mL^-1].The quantity of Vibrio was the highest in Group A, followed by Group B, Group C and Group D. These results indicat that under the shrimp-tilapia polyculture model with big tilapia fries, when the initial stocking ratio of shrimp to tilapia was about 250 : 1, the sediment organic matter accumulation and over reproduction of Vibrio could be decreased effectively, which can improve environment and economic benefit.

We studied the food composition of pearl oysters (Pinctada fucata) cultured in six habitats (Xincun and Li′an of Hainan Province, Xuwen and Leizhou of Guangdong Province, and Bailong and Yingpan of Guangxi) by using fatty acid biomarkers. The fatty acid biomarkers indicate that diatoms, dinoflagellates/protozoa, chlorophyta/terrestrial plants particles, brown seaweed and bacteria could be the food compositions of P.fucata. The biomarker of chlorophyta/terrestrial plants (∑[C_{18 : 2}(n-6)+C_{18 : 3}(n-3)]) was significantly higher in Xincun (4.64%) than in the other places; the biomarkers of bacteria {[C_{18 : 1}(n-7)/C_{18 : 1}(n-9)] and Odd&brFAs} were higher in Li′an (1.29 and 4.21%) than in the others; the markers of diatoms (C_{16 : 1}(n-7)/C_{16 : 0} and DHA/EPA) were significantly higher in Leizhou (1.06 and 1.13) than in the others; the biomarker of brown seaweed [C_{20 : 4}(n-6)] was significantly higher in Bailong (9.08%) than in the others; the biomarker of dinoflagellates/protozoa (DHA) was significantly higher in Xincun, Li′an, Xuwen, Bailong and Yingpan than in Leizhou. It is indicated that the food composition of the pearl oysters was closely related with their habitats.

To screen the specific genes of Streptococcus agalactiae induced in Oreochromis niloticus, the genomic expression library of the virulent strain Hod-1 was constructed. The Sau3AⅠ was used to digest genomic DNA of S.agalactiae strain Hod-1 incompletely. The DNA fragments ranging from 0.5 kb to 2 kb were recycled and ligated into pET-28 a/b/c expression vectors which had been digested by BamHⅠ and dephosphorylated by SAP before using. The recombinant vectors were transformed into BL21 (DE3). The results show that the genomic expression library of S.agalactiae contained 1.024×10⁵ clones, considerably more than the minimum number of clones (45 579 clones) covering the whole genomic DNA of S.agalactiae. Results of PCR detection show that the rate of fragment insertion was 94% and different sizes of inserted fragments ranged from 0.5 kb to 2.0 kb. The results of sequencing show that the homology between inserted sequences and the genomic DNA sequnce of S.agalactiae was over 99%. In conclusion, the genomic expression library of S.agalactiae strain Hod-1 was constructed successfully, which can be used for screening genes of S.agalactiae induced expression in O.niloticus.

We cloned the complete cDNA sequence of Ubiquitin-conjugating enzyme gene from black tiger shrimps (Penaeus monodon) (PmUbc) by rapid amplification of cDNA ends (RACE) methods based on the partial sequence of PmUbc obtained from the hepatopancreas transcriptome database. The cDNA of PmUbc was 598 bp, including 154 amino acids with an open reading frame (ORF) of 465 bp, 17 bp of 5′ untranslation region (UTR) and 116 bp of 3′ UTR. Blast analysis shows that PmUbc shared high identity with Ubiquitin-conjugating enzyme of Litopenaeus vannamei. Real time quantitative PCR analysis reveals that PmUbc was constitutively expressed in seven selected tissues (brain, thoracic nerve, heart, hepatopancreas, ovary, muscle, hemolymph). The PmUbc mRNA expression reached the maximum at Stage Ⅲ of ovarian development, followed by StageⅠand Ⅳ. It is concluded that PmUbc might play an important role in ovarian development of P.monodon.

By using two-factor central composite design (CCD) and response surface methodology(RSM), we studied the synergistic effect of temperature (19~31 ℃) and salinity (22~38) on the superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-PX) activities of Chlamys nobilis. The results show that the linear and quadratic effects of temperature on SOD, CAT and GSH-PX activities were significant (P < 0.05). The linear effects of salinity on SOD and CAT activities were significant (P < 0.05), but the linear effect of salinity on GSH-PX activity was not significant (P>0.05). Salinity had significant quadratic effect on SOD, CAT and GSH-PX activities (P < 0.05). The interactive effects of temperature and salinity were significant on SOD and CAT activities (P < 0.05), but there was no significant effect on GSH-PX activity (P>0.05). By response surface methodology, we established a model equation for the relationship of antioxidant enzyme activities to the two factors, with the R² of 0.950 1, 0.981 5 and 0.967 9. It is suggested that the fitting capability of the model was satisfactory and could be practicably applied for prediction. The antioxidant enzyme activities reached their maximum (33.02 U · mg^-1, 35.73 U · mg^-1 and 27.94 U · mg^-1) when the 2-factor combination was 26.4 ℃/27.7, with the desirability value being 0.989.

The nitrofuran metabolites (AMOZ, SEM, AHD and AOZ) were determined by liquid chromatography tandem mass spectrometry (LC-MS/MS) in aquatic products. The sample pretreatment method and chromatographic conditions were optimized. The sample pH value was adjusted to 7.0~7.5 after derivation. Then the analytes were extracted by 8 mL ethyl acetate. Following centrifugation, the supernatant was transferred and evaporated to dryness under a gentle stream of nitrogen at 40 ℃. The residues were redissolved in 1 mL mobile phase of acetonitrile and 0.1% formic acid (5/95, V/V), and then centrifuged at 20 000×g for 10 min at 4 ℃. Gradient elution for LC separation was performed by using acetonitrile and 0.1% formic acid in water solution, and four nitrofuran metabolites were excellently separated with a C₁₈ column. This accurate optimized method can promote efficiency greatly and is suitable for lot determination of nitrofuran metabolites in aquatic products.

In this study, we investigated the effect of different concentrations of water-soluble fraction of No.0 diesel oil (DWSF), the most used fuel oil in China, on antioxidant enzymes activities of Manila clam (Ruditapes philippinarum). The activities of catalase (CAT), glutathione S-transferase (GST), superoxide dismutase SOD and peroxidase (POD) were significantly induced or depressed in hepatopancreas and gills of R.philippinarum at different concentrations and time intervals. Generally, the response of antioxidases in gills exhibited higher sensitivity than that in hepatopancreas. Among these four antioxidase, CAT, SOD and POD were highly sensitive to No.0 diesel oil exposure, especially POD activity in gills with the highest induction of approximate three times of the control. Integrated biomarker response (IBR) index reflected that the antioxidant defense systems of R.philippinarum were more sensitive to the high concentration of DWSF. Thus, it is concluded that the water-soluble fraction of No.0 diesel oil can damage the antioxidant enzyme system of R.philippinarum, demonstrating great potential as biomarker in biotesting of marine oil pollutions.

We studied the change of catalase activity in gill and liver and catalase gene expression in gill of juvenile Amphiprion clarkii at an abrupt change in salinity from 35 to 15 (at decrement of 5, control: 35). The results show that the change of salinity caused no significant difference in survival. The CAT activity in liver and gill of A.clarkii showed an upward trend at salinities of 30, 25, 20 and 15 in 24 h. Besides, the changing range of CAT activity increased with increasing salinity change. All CAT activities had been decreasing since 48^th hour and was not different from that of the control till 96^th hour (P>0.05). The CAT mRNA expressions in gill at salinities of 30, 25, 20 and 15 had been increasing since 6^th hour and increased significantly at 12^th hour, which were different from the control significantly (P < 0.05). All CAT mRNA expression showed no significant difference from the control (P>0.05) at 96^th hour. Therefore, salinity change had important effect on CAT activity of A.clarkii, and the CAT activities of tissues restored to the normal level in 96 h, showing strong salinity adaptability of A.clarkii.

Protein extracted from white shrimp (Penaeus vannamei) head and shell was hydrolyzed using five proteolytic enzymes (pepsin, trypsin, alkaline protease, flavor protease, papain) to prepare antioxidant peptides. The hydrolysis conditions of the optimal protease were also optimized and the antioxidant activity of the hydrolysates obtained from the optimal conditions was investigated. The results show that flavor protease was the most suitable enzymatic proteinase. The optimal conditions of flavor protease for hydrolysis were as follows: temperature 54 ℃, time 10.5 h, pH 8, E/S 8 000 U · g^-1. Under these conditions, the 1, 1-Diphenyl-2-picrylhydrazyl radical 2, 2-Diphenyl-1-(2, 4, 6-trinitrophenyl)hydrazyl (DPPH) free radical scavenging activity of the resulted hydrolysates was 96.58%;reducing power was 0.77;DH was 15.62%;ORAC (oxygen radical absorbance capacity) was 15.50 μmol · L^-1. The DPPH radical scavenging activity of 5 mg · mL^-1 hydrolysates was 82.09%, equal to 90.50% activity of the same concentration of Vc; ORAC value of 0.5 mg · mL^-1 hydrolysates was 126.16 μmol · L^-1, equal to 79.73% activity of Vc.

As one of the chief inhabitations for staple shrimps in the South China Sea, northern Beibu Gulf is abundant with shrimp resource. It consists of 13 shrimp fishing grounds of various sizes distributed mainly along Guangxi coast. Shrimp fishing methods include trawling, gear net, pot fishing and set net. Based on the fishing information and data collected from Guangxi vessels engaged in shrimp fishing, this paper makes assessment on shrimp catches and fishing composition. In addition, it analyzes the impact of Summer Fishing Moratorium (SFM) of the South China Sea on shrimp fishing. The results show that the shrimp catch in northern Beibu Gulf in 2014 was estimated to 8 357 905 kg. Catch from beam trawling made up 91.62% of the total. The economic indices of fishing vessels improved obviously after SFM. Ratio of staple shrimps to the total shrimp catch increased by 40.34%, while non-staples dropped by 28.53% at the same time. Practice of SFM significantly led to alleviation of fishing effort, recovery of shrimp resource, optimization of shrimp population composition, improvement of efficiency and profits of shrimp fishing, etc..It is suggested that illegal fishing should be wiped out and stock enhancement of staple shrimps should be implemented during SFM to improve efficiency and impacts of SFM and to promote sustainable development of shrimp fishing in northern Beibu Gulf.

We analyzed the relationship between mesh size of gillnet and body characteristics of target species for three kinds of gillnet fisheries. The results reveal that the morphological characteristics of Scomberomorus commersoni, Pampus chinensis and Harpodon nehereus are beneficial for gillnet fisheries. The catch rate curve of relative girth was similar to the selective curve of normal gillnet. Only 1 fish of 454 target species whose relative girth was less than 0.8, amounting to 0.002% of the total catch, and the relative girth of 41 fish was higher than 1.2, accounting for 0.09% of the total catch. The capture rate reached the maximum when the relative girth was 1.0~1.1. The minimal mesh sizes of three gillnet were 144 mm, 35 mm and 72 mm, respectively. It is suggested that the selectivity research should be combined with this study to provide references for promulgation of the minimal mesh size of gillnet in the South China Sea.

To obtain high and stable expression recombinant fusion protein of Pearlin, we constructed the recombinant vector by using the open reading frames (ORF) of Pearlin cloned from the mantle tissue of pearl oyster (Pinctada fucata) and optimized the expression conditions. The Pearlin ORF was cloned into the vector pET32a and the plasmids of pET32a-Pearlin were obtained and then transformed into E.coli BL21(DE3). His-tagged insoluble fusion protein was highly expressed and the molecular weight of the fusion protein was about 34.19 kD. We optimized the conditions for IPTG concentrations, induction duration and timing, and temperature and pH of the medium. The results showed that the optimal IPTG concentration ranged from 0.6 mmol·L^-1 to 1.4 mmol·L^-1 and the best temperature was 37 ℃ when IPTG concentration was 1.0 mmol·L^-1 and incubation time was 6 h. The expression levels of recombinant protein did not change significantly when the pH of medium was 6.0, 7.0 and 8.0. When IPTG concentration was kept constant (1.0 mmol·L^-1), 4~6 h induction was optimal; when IPTG concentration (1.0 mmol·L^-1) and induction duration (6 h) were kept constant, the best starting time for induction was 3~4 h after transformation. Solubility test indicates that fusion protein pET32a-Pearlin was mainly in the form of inclusion body.

Catalase (CAT) is an antioxidant enzyme and plays an important role in protection against oxidative stress by scavenging hydrogen peroxide (H₂O₂). We obtained the full-length cDNA sequence of CAT from black tiger shrimps (Penaeus monodon)(denoted as PmCAT) by transcriptome sequencing and RACE-PCR. The full-length cDNA of PmCAT was 1 909 bp, including an open reading frame (ORF) of 1 563 bp encoding a polypeptide of 520 amino acids, a 5′UTR of 134 bp and a 3′UTR of 212 bp. Blast and phylogenetic analyses suggest that PmCAT is a CAT family member. The expression of PmCAT mRNA showed a declining trend under the stress of CuSO₄ (P < 0.05), and then recovered to normal at 24^th hour and 48^th hour, being the highest in gill, and then in hepatopancreas and thoracic nerves.Under the stress of pH 7.0, PmCAT expression reached the maximum at 12^th hour (P < 0.05);under the stress of pH 9.0, the expression of PmCAT declined (P < 0.05). The results reveal that PmCAT plays a significant role in adaptive response to conditions of oxidative stress and environmental toxicity.

The intestinal structure and function of microbial flora, which play an important role in shrimp growth, are closely related to the physiological process of nutrition metabolism, energy balance, immune defense and gastrointestinal development, and are essential to maintain the stability of internal environment. The paper reviews the nutrition, digestion, immune and physiological function of shrimp intestinal microbial flora, analyzes the influence factors of the shrimp intestinal microbial flora structure and composition, and introduces the main research method of shrimp structure of shrimp intestinal microbial flora, so as to put forward the prospects of its application in shrimp aquaculture.