Bacterial composition,abundance and diversity in fish polyculture and mussel–fish integrated cultured ponds in China

Bacterial community and abiotic environmental parameters in twelve freshwater aquaculture ponds were analysed. According to the major component of stocked animals, the ponds were grouped into four types: black carp Mylopharyngodon piceus, largemouth bass Micropterus salmoides, yellow catfish Pelteobagrus fulvidraco and pearl mussel Hyriopsis cumingii ponds. Each type of pond was stocked with three species of Chinese carps (silver carp, bighead carp and gibel carp) to form a unique mode of fish polyculture or mussel–fish integrated culture. The bacterial composition was identified using 16S rDNA sequencing. Totally, 3701 and 11 150 operational taxonomic units (OTUs) were identified from the water and sediment samples respectively. The number of OTUs, abundance‐based coverage estimator, Chao1 index and Shannon diversity index were lower in the water column than in the sediment, suggesting that diversity and stability of bacterial community were higher in the sediment. In the water column, Proteobacteria, Actinobacteria and Bacteroidetes dominated at the phylum level, and 26 dominant genera were identified. In the sediment, Proteobacteria, Chloroflexi, Bacteroidetes, Acidobacteria and Nitrospirae dominated at the phylum level, and 25 dominant genera were identified. Bacterial compositions between the ponds with different aquaculture modes were similar at the phylum levels, but varied at the genus levels. The bacterial composition in the ponds was correlated with hardness, ammonia and total nitrogen in the water column. This study indicates that the type of aquaculture mode is a factor regulating the microbial community, which provides an insight towards microbial management through probiotic manipulation in pond culture.     

Effect of different culture conditions on the structural diversity of prokaryote communities in the sediment of earth ponds stocked with gilthead seabream Sparus aurata (Linnaeus, 1758)

In this study, we evaluate the use of polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) for monitoring the effect of different aquaculture practices on sediment prokaryote (Archaea and Bacteria) communities. The effect of initial fish (gilthead seabream Sparus aurata) stocking density on the structural diversity of prokaryote communities of earth ponds bottom sediments was evaluated using PCR‐DGGE after a 5 month grow‐out period. An identical approach was used to monitor the effect of supplying different fish feeds [commercial feed (CD) versus an ecofeed (ECO)]. One additional variable was the use of copper sulphate (CuSO₄) as an algicide in some of the experimental rearing tanks. The statistical analyses of prokaryote community profiles showed that the presence of fish in earth ponds significantly influenced the structure of sediment prokaryote communities, when compared with earth ponds without fish, independently of the stocking density. Our results also indicated that the structure of the prokaryote communities of earth ponds supplied with the ECO feed shared a strong similarity with that fed CD. Curiously, the use of CuSO₄ in ponds receiving the ECO feed promoted significant differences on the structural composition of the bacterial community, but not on the archaeal community. DGGE molecular fingerprints are suitable for fast evaluation of new management practices in food‐fish production on earth ponds by monitoring shifts on microbial communities in bottom sediments.     

Bacterial diversity in various coastal mariculture ponds in Southeast China and in diseased eels as revealed by culture and culture‐independent molecular techniques

Mariculture ponds are widely distributed in Chinese coasts and have become a threat to the health of coastal ecosystems. In order to improve our understanding on the microbial composition in mariculture environments, we sampled a variety of ponds farming different animals or plants around the Dongshan Island and Xiamen Island in Southeast China and isolated cultures from the tissues of diseased eels. Analysis by polymerase chain reaction (PCR)‐denaturing gradient gel electrophoresis (DGGE), clone library and direct culturing methods revealed highly diverse bacterial communities in these samples. Bacterial communities in the Dongshan samples were dominated by Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes. The Gracilaria verrucosa pond harbours the most abundant species (20 DGGE bands), followed by Epinephelus diacanthus pond (18 bands), Haliotis diversicolor supertexta pond I (18 bands) and Penaeus vannamei pond (11 bands). In comparison with surface waters, Penacus orientalis pond sediment showed a much more complex bacterial community, from which only sequences affiliated with Deltaproteobacteria, Firmicutes, Acidobacteria and candidate phylum TM6 were found. Bacterial cultures in diseased eels were closely related to two pathogenic genera, Aeromonas in Gammaproteobacteria and Bacillus, in Firmicutes. Clones affiliated with another two genera, Escherichia and Vibrio, that have pathogenic potentials were also identified. Phylogenetic analysis of a total of 131 sequences showed that 48.9% of the sequences were clustered into Gammaproteobacteria and formed the most abundant group, followed by Alphaproteobacteria (19.1%), Firmicutes (7.6%), Bacteroidetes (5.3%), Deltaproteobacteria (5.3%), Actinobacteria (4.6%), Chloroplast (3.8%), Acidobacteria (2.3%), Cyanobacteria (1.5%), Betaproteobacteria (0.7%) and TM6 (0.7%). 43.7% (28/64) of the phylogenetic clusters cannot be classified into any known genus and 44.3% (58/131) of the sequences show <95% similarity to public database records, suggesting that abundant novel species exist in mariculture ponds. Gathering bacterial diversity data in mariculture ponds and diseased fish is meaningful for the prevention and control of fish diseases and for the improvement of our understanding of microbial ecology in a pond environment.     

The effect of C/N ratio on bacterial community and water quality in a mussel‐fish integrated system

A 30‐day experiment was conducted to evaluate the effect of C/N ratio on water quality and bacterial community in an integrated system comprising one molluscan species (pearl mussel Hyriopsis cumingii) and two fish species (gibel carp Carassius gibelio and silver carp Hypophthalmichthys molitrix) at five C/N ratios (6, 8, 10, 12 and 14). The mussel and fishes were reared in the experimental tanks (400 L), but gibel carp received formulated feed. Water quality in the experimental tanks was analysed on day 0, 10, 20 and 30, and bacterial community in the water column and sediment was analysed on day 30. Total nitrogen, total phosphorus and total organic carbon accumulated in the tanks over time. Ammonia and nitrite decreased with the increase in C/N ratio. Bacterial community in the water column and sediment changed at the phylum and genus levels with the increase in C/N ratio, and the critical C/N ratio causing a functional shift of bacterial community occurred at 10 in water column and 12 in sediment. The increase in C/N ratio benefited the growth of both potential probiotics and pathogenic bacteria. The high C/N ratio enhanced the bacterial functions of chemoheterotrophy and hydrocarbon degradation, but depressed the functions of nitrification and denitrification in the water column and sediment respectively. This study reveals that the C/N ratio can be used as a tool to manipulate the bacterial community and water quality in the mussel‐fish integrated system.     

Comparison of bacterial communities in channel catfish Ictalurus punctatus culture ponds of an industrial ecological purification recirculating aquaculture system

The industrial aquaculture pond system has gradually replaced the use of traditional earthen pond, as it causes less pollution and is more economical. In this study, an industrial ecological purification recirculating aquaculture system consisting of the water source pond, high‐density culture ponds, a deposit pond, and ecological purification ponds for channel catfish cultivation was established. Twelve water samples from different ponds were sequenced, and the bacterial communities were analysed. The abundances of Cyanobacteria and Merismopedia varied in different functional ponds of the system. The water quality was stable after two months of cultivation at 1.89 ± 0.22 mg/L total nitrogen, 1.1 ± 0.08 mg/L NH₄‐N and 0.43 ± 0.1 mg/L total phosphorus. The fish weight increased in a nearly linear manner, reaching 237.63 ± 23.8 per fish at day 120. An analysis of the environmental parameters, water quality and fish weight suggested that the system had an effective water purification process. Canonical correspondence analysis showed that the community was affected at the genus and phylum levels by different environmental parameters. We identified several dominant beneficial bacteria with nutrient removal abilities. Overall, our results demonstrated that the ecological purification recirculating aquaculture system had notable effects on water quality improvement and promoted changes in bacterial populations. These results provide important information on the microbial ecology of pond industrial eco‐aquaculture systems.     

Limnology of Macrobrachium amazonicum grow‐out ponds subject to high inflow of nutrient‐rich water and different stocking and harvest management

We evaluated the water characteristics and particle sedimentation in Macrobrachium amazonicum (Heller 1862) grow‐out ponds supplied with a high inflow of nutrient‐rich water. Prawns were subject to different stocking and harvesting strategies: upper‐graded juveniles, lower‐graded juveniles, non‐graded juveniles+selective harvesting and traditional farming (non‐grading juveniles and total harvest only). Dissolved oxygen, afternoon N‐ammonia and N‐nitrate and soluble orthophosphate were lower in the ponds in comparison with inflow water through the rearing cycle. Ponds stocked with the upper population fraction of graded prawns showed higher turbidity, total suspended solids and total Kjeldahl nitrogen than the remaining treatments. An increase in the chemical oxygen demand:biochemical oxygen demand ratio from inlet (4.9) to pond (7.1–8.0) waters indicated a non‐readily biodegradable fraction enhancement in ponds. The sedimentation mean rate ranged from 0.08 to 0.16 mm day^?1 and sediment contained >80% of organic matter. The major factors affecting pond ecosystem dynamic were the organic load (due to primary production and feed addition) and bioturbation caused by stocking larger animals. Data suggest that M. amazonicum grow‐out in ponds subjected to a high inflow of nutrient‐rich water produce changes in the water properties, huge accumulation of organic sediment at the pond bottom and non‐readily biodegradable material in the water column. However, the water quality remains suitable for aquaculture purposes. Therefore, nutrient‐rich waters, when available, may represent a source of unpaid nutrients, which may be incorporated into economically valued biomass if managed properly.     

不同肥料对池塘细菌种群的影响

运用PCR-DGGE技术分析有机肥(干鸡粪)和化肥(碳酸氢铵和磷酸一铵)对鱼苗池塘中的理化因子和细菌数量及其种群结构的影响,以探讨细菌种群结构对不同肥料的响应。结果显示:施肥后池塘中NH4+-N、PO43--P、NO 3--N和NO 2--N等浓度增加,透明度降低,细菌数量、种群多样性和丰富度指数均增加;化肥增加溶氧和升高pH,有机肥却降低溶氧和pH。施肥后蓝细菌门(Cyanobacteria)和拟杆菌门(Bacteroidetes)种群成为优势种群,有机肥能增加厚壁菌门(Firmicutes)种群的相对丰度,而化肥却降低其相对丰度;β-和γ-变形杆菌纲种群的相对丰度在施入化肥后增加,有机肥却限制γ-和δ-变形杆菌纲种群,化肥明显降低放线菌门种群的相对丰度。池塘中理化因子、细菌种群数量及其结构因施入不同肥料发生相应的变化。     

Microbiota of yellow grouper (Epinephelus awoora Temminck & Schlegel, 1842) fed two different diets

The rapidly growing yellow grouper industry has experienced relatively severe bacterial disease problems in China. The proliferation of pathogens in fish can be suppressed by commensal microbiota. In this background, we used nested polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) and sequence analysis to investigate microbiota in the skin, gills and intestines, including adherent bacteria and non‐adherent bacteria in yellow grouper fed with natural diet and complete feed. A total of 21 bacterial species were identified using phylogenetic analysis. The γ‐Proteobacteria group (81.0%, 17 species) dominated the bacterial communities in yellow grouper completely. Others belonged to Firmicutes (9.5%, two species), Actinobacteria (4.75%, one species) and Verrucomicrobia (4.75%, one species). The higher similarities (above 91%) of the DGGE band patterns in skin, gill and intestinal‐non‐adherent bacteria between two groups of fish indicated that existed more stable microbial communities existed in these specifically ecological niches in yellow grouper. However, considerable differences existed between two intestinal‐adherent bacteria (IAB) samples; that is, compared with natural diet fed yellow grouper, higher bacterial apparent species richness and possibly less abundance existed in IAB in fish fed with complete diets, probably indicating that the community structures in IAB were affected easily and significantly by diet.     

Intestinal Microbiota in Large Yellow Croaker,Larimichthys crocea,at Different Ages

The polymerase chain reaction–denaturing gradient gel electrophoresis (PCR‐DGGE) of 16S ribosomal RNA gene was used to investigate bacterial communities in the intestines of large yellow croaker at six different ages (12 d, 18 d, 26 d, 40 d, 3 mo, and 1 yr old) as well as within the corresponding feed and culture water. In addition, Illumina Miseq sequencing was utilized to compare intestinal microbiota between 12‐d‐old and 1‐yr‐old individuals. PCR‐DGGE results revealed that the culture water had the highest bacterial diversity, followed by the feed, while the intestines had the lowest diversity. The intestinal microbiota at six ages changed severely; however, the change did not follow any trend. The large yellow croaker intestines harbored specific bacterial communities that differed from those in both feed and water. Illumina Miseq sequencing results revealed that the diversity of intestinal bacteria in 12‐d‐old fish was higher than that in 1‐yr‐old fish, and the bacterial composition differed significantly between them. γ‐Proteobacteria and Pseudoalteromonas supplied the most abundant phylum and genus in the 12‐d‐old fish intestine. However, in the 1‐yr‐old fish intestine, Firmicutes and Clostridium were the most dominant, respectively. The study may contribute to a better understanding of gut microbiota and dynamics of the large yellow croaker and the relationship with their surrounding environment.     

Physical and chemical characteristics of sediments in catfish, freshwater prawn and carp ponds in Thailand

Sediment samples were collected from 42 catfish (Clarias hybrid) ponds, 40 freshwater prawn (Macrobrachium rosenbergii) ponds and 18 carp (Puntius spp.) ponds in Thailand. Regression analysis revealed that pond age (1–30 years) was not a major factor influencing the physical and chemical composition of pond sediments. Sediment depth, F+S horizon thickness and bulk density of S horizon were greater (P<0.05) in carp ponds than in catfish and prawn ponds. This occurred because sediment was removed from catfish and prawn ponds more frequently than from carp ponds. Total carbon, organic carbon and total nitrogen concentrations were greater (P<0.05) in carp ponds than prawn and catfish ponds. Few ponds had sediment organic carbon concentrations above 3%, and carbon:nitrogen ratio values did not differ (P>0.05) among ponds for the three species. Total phosphorus and other sediment phosphorus fractions increased in the order prawn ponds, carp ponds and catfish ponds. Sediment sulphur concentrations also increased in the same order. There were no differences in major or minor nutrient concentrations in sediment that would influence aquacultural production. Although there were significant correlations (P<0.05) between various sediment quality variables, no single variable or group of variables would be useful in estimating sediment quality. Pond bottom management practices used by producers in Thailand included drying of pond bottoms between crops, liming, tilling and periodic sediment removal. These practices have maintained relatively good bottom quality. They should be continued in Thailand and adopted in other places.     

First report on the autochthonous gut microbiota of brown trout (Salmo trutta Linnaeus)

A study was conducted to characterize the autochthonous gut microbiota present in the pyloric caeca (PC), anterior mucosa (AM) and posterior mucosa (PM) of brown trout (Salmo trutta). Total viable counts (TVC) bacterial populations were enumerated using tryptone soy agar, lactic acid bacteria (LAB) levels were enumerated on de Man, Rogosa & Sharpe agar and PCR‐DGGE was employed as a culture‐independent method to assess the total communities. No significant differences were observed between the different gut regions for TVC or LAB levels. 16S rRNA sequencing identified all LAB isolates as Carnobacterium maltaromaticum. In contrast, the TVC community was more diverse; Firmicutes and Bacteroidetes were present but all gut regions were dominated by Proteobacteria, accounting for 88.4–92.6% of the communities. Citrobacter freundii was the dominant species and accounted for 51.0–57.8% of the isolates. Complex bacterial communities were observed using PCR‐DGGE and a trend towards the reduction in the number of operational taxonomic units (OTUs), microbial richness and microbial diversity was observed from the PC to the PM. The similarity between regions was low (52–68%) and cluster analysis revealed that the communities grouped into two distinct clusters; one dominated by the PM samples and the other contained the AM and PC samples. OTUs from the DGGE were identified as members of the phyla Proteobacteria and Firmicutes. Many OTUs were detected in all gastrointestinal regions, however, some OTUs showed regional specialization. Further studies are required to elucidate the activity of these genera in situ and how their actions impact the host.     

Viability of a Freshwater Mussel (Elliptio complanata) as a Biomechanical Filter for Aquaculture Ponds II: Effects on Aquaculture Pond Water Quality

Bivalves have been proven to be an inexpensive method for removing suspended solids, dissolved nutrients, and controlling algal growth through suspension feeding. The freshwater mussel, Elliptio complanata, is one of the most abundant species in Delaware, and it is additionally favorable for this experiment because of its hardiness against environmental stress and its filtration efficiency. This study examines the possibility that biomechanical filters such as E. complanata can supplement existing chemical and mechanical filtration regiments in aquaculture pond management. Twelve earthen aquaculture ponds located at the Delaware State University were stocked at a density of 4,000 catfish (Ictalurus punctatus) per hectare. Four different concentrations (0, 75, 150, and 300) of E. complanata were placed in trays within the ponds with three replicates of each concentration. The trays were suspended 15 cm below the surface of the water for a period of five months. Fish were fed a 32% protein diet twice daily at a rate of 1% of their body weight. Water quality was analyzed weekly while fish and mussel growths were measured biweekly. Results from water quality parameters varied significantly and were not conclusive based on the data obtained in this study. Water quality did not improve within the mussel treatment ponds during the course of this study and was found to be significantly below that of control ponds for all of the water chemistry parameters measured, with the exception of ammonia. Catfish in the 150 mussel treatment ponds grew the fastest; the 75 mussel treatment provided the most growth in mussels; and the 300 mussel group maintained the highest mussel survivorship. Although there were differences between ponds, fish growth and survivorship were not significantly different between treatments. While our mussel densities may have not been sufficient, their placement within the water column may have added additional stress. Being removed from the sediment can result in a decreased clearance rate in a benthic species such as E. complanata. This study may not have been conclusive in proving that mussels can be used to maintain water quality in aquaculture ponds, but we did see positive growth and survivorship of mussels and fish that indicated that the mussels were thriving in the aquaculture pond setting. This study may show that aquaculture ponds provide a suitable habitat in which propagated mussels may be held until their release into native areas.     

Nitrogen dynamics in the settlement ponds of a small-scale recirculating shrimp farm (<Emphasis Type="Italic">Penaeus monodon</Emphasis>) in rural Thailand

Rural shrimp farmers in Thailand are being encouraged to adopt practices that will reduce the quantity and improve the quality of their effluent. A simple and cheap option for small-scale shrimp farmers is to use settlement ponds to store and remediate discharge water before being re-used. We undertook a detailed study of the settlement ponds in a small-scale commercial black tiger shrimp farm typical of rural Thailand. We found that over a 9-week period, following the harvest of one of the two farm production ponds, total nitrogen (TN) concentrations in the water column were reduced by 30%, with the greatest removal (56%) occurring during the fifth week. There was a 10% increase in dissolved organic nitrogen (DON) concentrations during the trial. Sediments were a source of total ammonia nitrogen (TAN), and the re-mineralisation rate was the highest in the first two settlement ponds. Coconut fronds added to two of the four settlement ponds to increase the surface area available for microbial activity were found to provide a site for microbial re-mineralisation of TAN, the photosynthetic uptake of TAN and oxidised nitrogen (NO _x ) and nitrification. The water column was a net assimilator of TAN through autotrophic uptake. This study has shown that settlement ponds are capable of reducing water column N concentrations; however, sediment must be managed to reduce re-mineralisation during successive cropping cycles. In addition, coconut fronds were shown to improve N removal, although they should be periodically removed to maintain efficiency.     

Changes in soil and water quality at sediment–water interface of Penaeus vannamei culture pond at varying salinities

The health of the pond environment in shrimp farming is important for sustainable and profitable aquaculture, in which sediment–water interface is the most important influencing area. With this objective, the key parameters of water and sediment at the interface was studied in shrimp ponds with varying salinities and compared with the surface water and soil to understand the variations and the underlying causes. Total ammonia nitrogen and total alkalinity were higher in water at the interface as compared to surface water, whereas pH, nitrite, oxide forms of nitrogen (NO₃), phosphorus (PO₄) and oxidizing bacteria were observed to be lower. There was no significant difference with respect to macrominerals such as sodium, potassium, calcium and magnesium between water at the interface and surface. These changes are profoundly influenced by the uppermost 1.0‐cm thick sediment layer, where the maximum transition of nutrients takes place with the water column. The outcome of the study highlights the effectiveness of water sampling for metabolites at the interface, which reflects at an early stage any potential deterioration of pond environment, which will help the farmer to initiate timely mitigation measures.     

Bacterial community of pond's water,sediment and in the guts of tilapia (Oreochromis niloticus) juveniles characterized by fluorescent in situ hybridization technique

Information about bacterial community structure and functioning in fish farming ponds remains scarce, mainly due to methodological difficulties in counting and identifying uncultured bacteria. The main objective of this study was to evaluate the degree of similarity between the bacterial community of the digestive tract of tilapia (Oreochromis niloticus) juveniles and that of the test pond's water and sediment, using the Fluorescent In Situ Hybridization (FISH) technique. Samples of water, sediment and gut content of 30 tilapia juveniles from a single nursery ground were collected in January 2010. Potentially probiotic and pathogenic bacteria of the species Bacillus, Lactobacillus brevis, Lactobacillus collinoides, Lactobacillus coryniformis, Lactobacillus farciminis, Vibrio and Pseudomonas fluorescens were found in different samples using specific fluorescent probes. The similarity between bacterial community environments and gastrointestinal tracts was determined using the Morisita‐Horn index. The fish guts presented higher abundances of Pseudomonas fluorescens, Bacillus, Lactobacillus brevis and Lactobacillus collinoides. The bacterial community composition of tilapia gastrointestinal tract was more similar to the water than the sediment of the pond. The results of this study showed that the FISH technique can be easily used for monitoring of probiotics and pathogen detection in aquaculture systems.     

微生物制剂对养殖池塘细菌群落影响的PCR-DGGE分析

为了解微生物制剂在水产养殖环境修复中的作用机制,采用聚合酶链式反应—变性梯度凝胶电泳(PCR-DGGE)方法,研究不同微生物制剂对养殖池塘上覆水和沉积物中细菌群落的影响。结果显示,施用微生物制剂前后,试验塘上覆水样品中细菌的DGGE优势条带无明显变化,细菌群落组成没有明显差异,提示微生物制剂对试验塘上覆水中的细菌群落组成影响很小。相对而言,施用过微生物制剂的池塘相对于对照池塘其细菌群落结构发生的变化较大;泼洒EM菌原粉3 000 g/hm2加芽孢杆菌原粉750 g/hm2的试验塘沉积物中细菌群落2 d内发生了较大变化,之后相对稳定,对照池塘和泼洒EM菌原粉3 000 g/hm2加光合细菌原粉1 500 g/hm2的试验塘沉积物中细菌群落组成变化很小。     

Microbial communities in sea cucumber (Apostichopus japonicus) culture pond and the effects of environmental factors

This study investigated microbial community composition as well as their correlation with environmental factors of Apostichopus japonicus culture ponds in northern China by 16S rRNA gene amplicon sequencing. The results showed that microbiota richness varied consistently with diversity in the pond ecosystem. Microbiota richness and diversity were highest in sediment, followed by gut of A. japonicus and water. The dominant bacterial phylum in the pond ecosystem is Proteobacteria. Gammaproteobacteriaeria and Flavobacteria are two dominant bacterial classes in the ecosystem. There is significant difference (p < 0.05) between dominant bacterial communities at the levels of order, family and genus. There is also remarkable regional difference (p < 0.05) between microbial community composition in the pond ecosystems. Specifically, microbial community composition in Changhai and Yingkou show a high similarity, so do those of Laoting and Rushan. According to the redundancy analysis of the microbial community composition and pond environmental factors, chemical oxygen demand is the dominant environmental factor determining microbial community composition in pond water; sulphide has the greatest influence on the microbial community composition in pond sediment; the rest of environmental factors have varied influence on microbial community composition in pond ecosystems.     

Phosphatase activity with reference to bacteria and phosphorus in tropical freshwater aquaculture pond systems

The bio‐geochemical cycle of phosphorus is significantly influenced by microbes in the aquatic environment. Organic phosphorus compounds are decomposed and mineralized by enzymatic complexes such as phosphatases produced by microbes. Enzymatic catalysis results in the production of orthophosphate, which can be used readily by primary producers. Even the smallest concentration of phosphate in water has an influence over the production process in aquaculture systems. Extracellular alkaline phosphatase activity was observed in water and sediment media of aquaculture ponds with different management practices. Heterotrophic bacterial populations as well as phosphatase‐producing bacterial populations were higher in sediments compared with water. In the freshwater fish ponds, Bacillus spp. were the dominant forms of bacteria producing phosphatase. The alkaline phosphatase activity of sediment was always higher than that of water. The partitioning of extracellular alkaline phosphatase in pond water by a 0.22‐µm membrane filter revealed that a proportion was often free rather than cell associated and might have originated as free enzymes released by enriched sediments or by fish or microbes. In the case of water, although the dissolved alkaline phosphatase activity was lower than the total alkaline phosphatase activity, the former was nevertheless unimportant, as it constituted about 20% of the ‘total’ activity. Free alkaline phosphatase activity shared a negative correlation with the orthophosphate concentration of water, whereas gross alkaline phosphatase activity was positively correlated with the total phosphorus and bacterial population of water.     

Characterization of microbial communities in intensive GIFT tilapia (Oreochromis niloticus) pond systems during the peak period of breeding

Aquaculture pond is a complex ecosystem where the microorganisms in the sediments, in the animal intestinal tract and in water interact with each other to influence the water quality and health of aquatic animals. In order to understand the spatial distribution and relationship of microbial communities in intensively farmed genetically improved farmed tilapia (GIFT, Oreochromis niloticus), 454 high‐throughput pyrosequencing was applied to analyse the 16S rRNA gene of bacteria in intensive GIFT ponds in Wuxi City, Jiangsu Province, China. A total of 72 747 initial sequences were obtained from four depths of pond water, from tilapia large intestines and from pond sediment. The most common phylum in all samples was Proteobacteria, Actinobacteria and Cyanobacteria were the most abundant in water, Fusobacteria and Firmicutes in the large intestine and Chloroflexi in sediment samples. The sediment microbial community structure was comparatively similar to that of the tilapia large intestine. The microbial communities from different water depths were somewhat similar, especially the three most shallow samples, although the abundance of Actinobacteria gradually decreased with increased water depth. This data offer a preliminary exploration of the response mechanisms of the bacterial communities to aquafarming and contributes to the understanding of the status of bacterial communities of tilapia pond systems during the peak period of breeding from the aspect of their spatial distributions.     

池塘养殖仿刺参(Apostichopus japonicus)肠含物、附着基和底泥中的菌群结构及其相关性

2014年10月,利用 PCR-DGGE 技术分析了标准化养殖池塘中仿刺参(Apostichopus japonicus)肠含物及附着基和底泥中细菌的菌群结构及其相关性。结果显示,仿刺参肠含物、附着基、底泥中细菌多样性较高,分别平均获得30.00±1.00、15.33±1.70、21.67±2.62条带,肠含物中细菌种类数显著高于附着基和底泥。聚类分析和戴斯系数表明,不同池塘的仿刺参肠含物样本单独聚为一支,相似性达到0.785,附着基和底泥样品聚为一支,平均相似性达到0.532。不同样品 DGGE 图谱中20条优势条带的切割、克隆、测序,共获得了20条细菌序列,表明肠含物细菌种类以聚球藻属(Synechococcus sp.)、脱硫杆菌属(Desulfobacterium)、脱硫叠球菌属(Desulfosarcina sp.)、极地杆菌属(Polaribacter)、Algibacter sp.为主,附着基中主要以 Robiginitalea sp.和 Silicibacter sp.为主,底泥样品中主要以假单胞菌属(Proteobacterium）、噬胞菌属(Cytophaga）、Desulfosarcina sp.为主,肠含物中细菌特有种类的分离与鉴定为仿刺参养殖潜在益生菌的开发提供基础数据。