Assessment of pollutant loads discharged from aquaculture ponds around Taihu Lake,China

China is the world's largest producer of aquatic animals, and the Taihu Lake area is one of the most important contributors within China. To obtain the basic information needed to minimize environmental impacts of aquaculture, the water quality and volume of effluents from 48 ponds used for raising crab, shrimp, river prawn, black carp, grass carp and turtles near Taihu Lake were monitored, and their pollutant loads were estimated. Effluent volumes ranged from 12.7 ± 1.7 (crab) to 50.9 ± 15.8 (turtle) thousand tons ha^?1 year^?1. The concentration of pollutants in the effluents often exceeded acceptable limits for Taihu Lake. Crab ponds produced the lowest gross loads of total nitrogen, total phosphorus, chemical oxygen demand and total suspended solids, whereas turtle ponds produced the highest. The net loads of monitored pollutants comprised only 4–53% of the gross loads in crab ponds, but > 50% in other species ponds. Results indicate that the pollutant loads discharged from aquaculture ponds around Taihu Lake are mild, but precautions are still needed to treat the wastewater. Connecting the ponds in series with crab ponds downstream is a feasible way to decrease pollutant loads.     

应用高通量测序技术分析拟穴青蟹肠道及其养殖环境菌群结构

采用基于Illumina Hi Seq测序平台的高通量测序技术,对拟穴青蟹(Scylla paramamosain)肠道及其养殖池塘水体、底泥中细菌种类及丰度进行了研究。测序结果显示,3个样品共获得有效序列234575条,可聚类于2812个分类操作单元(OTUs),归属于拟穴青蟹肠道、养殖水体、池塘底泥样品的操作分类单元(OTU)个数分别为453、706和2547,其中有184个OTU均能在3个样品中检测到,在青蟹肠道和养殖水体、青蟹肠道和池塘底泥中分别检测到197和309个共有OTU。物种注释结果显示,拟穴青蟹肠道中优势细菌种类为变形菌门(Proteobacteria)(39.96%)、柔膜菌门(Tenericutes)(23.09%)和厚壁菌门(Firmicutes)(16.58%);养殖水体中优势细菌种类为变形菌门(63.02%)、放线菌门(Actinobacteria)(24.96%)和拟杆菌门(Bacteroidetes)(8.41%);池塘底泥中优势细菌种类为变形菌门(75.23%)、拟杆菌门(5.72%)和放线菌门(3.83%)。此外,对各样品中丰度最高的前10位OTU分析显示,不同样品中占优势地位的10种细菌在数据库(SILVA)缺乏相关已知序列,并且各样品中的优势细菌种类完全不同。实验结果表明拟穴青蟹肠道与其池塘养殖环境中菌群结构存在着密切的相关性,但肠道菌群同时具有一定的独立性,其优势细菌种类与养殖环境中优势细菌种类无关。本研究旨在为拟穴青蟹健康养殖和微生态调控提供实验依据。     

不同季节刺参养殖池塘沉积物菌群结构及其影响因素

本研究以辽宁省营口地区刺参(Apostichopus japonicus)养殖池塘为研究对象,利用高通量测序技术,构建不同季节刺参养殖池塘沉积物菌群16S rRNA基因测序文库,解析刺参养殖池塘沉积物菌群的季节性差异和共性,查明影响沉积物菌群构成的主导环境因子。结果显示,营口地区刺参养殖池塘沉积物菌群的丰度和多样性以夏季最高,春秋次之,冬季最低。不同季节刺参养殖池塘沉积物差异菌群呈显著性季节演替特征(P<0.05)。其中,春季差异菌群主要隶属于拟杆菌门(Bacteroides),夏季差异菌群主要隶属于酸杆菌门(Acidobacteria)、疣微菌门(Verrucomicrobia)和浮霉菌门(Planctomycetes),秋季差异菌群主要隶属于厚壁菌门(Firmicutes),冬季差异菌群主要隶属于放线菌门(Actinobacteria)。尽管不同季节沉积物细菌组分比例不同,但第一优势菌门均隶属于变形菌门(Proteobacteria)(相对丰度>43.19%)。环境因子中,影响刺参养殖池塘沉积物菌群的主导环境因子为温度、总有机碳、总氮和pH。本研究将为刺参养殖池塘微生态调控提供理论参考。     

Enrichment of aquaculture earthen ponds with Hediste diversicolor: Consequences for benthic dynamics and natural productivity

The present work analysed the potential impacts of the enrichment of semi-intensive production earthen ponds with the ragworm Hediste diversicolor in the benthic dynamics and natural productivity. The macrobenthos and sediment characteristics were analysed in two enriched ponds and two control ponds in May, June and September 2005. The number of species, Margalef species richness and biomass (AFDW) were generally significantly higher in enriched than in control ponds, while for abundance no clear pattern was visible. Multivariate analysis showed differences in macrobenthic community structure of control and enriched ponds. Differences were also visible when the introduced species was removed from the data set, indicating that differences were mainly due to changes in other species abundance. In general, gastropods (Akera bullata, Jujubinus striatus, Hydrobia ulvae, Rissoidae), bivalves (Abra ovata, Cerastoderma spp.), crustaceans (Ampithoe rubricata, Dexamine spinosa, Gammarus insensibilis, Gammarella fucicola, Iphinoe tenella), and also some polychaetes (Desdemona ornata, Terebella spp., Syllis gracilis and Neanthes caudata) greatly increased their abundances in enriched ponds. On the other hand, the abundance of Tubificidae, Capitella spp., Pseudopolydora paucibranchiata, Corophium acherusicum, and Mesopodopsis slabberi decreased. The organic matter content was significantly lower in enriched ponds, probably due to the positive impact of the polychaetes on sediment reworking, resulting in higher organic matter mineralization. Overall the present study indicates that stocking of earthen production ponds with H. diversicolor significantly altered community structure of benthic invertebrates and may improve environmental conditions for fish production by reducing the organic matter accumulation in pond sediments.     

浙江中部披山海域蟹类群落结构特征及其与环境因子的关系

根据2015年11月、2016年2、5、8月在浙江中部披山海域进行渔业资源调查所获得的资料,分析了浙江中部披山海域蟹类的种类组成、优势种、生物多样性等群落结构特征,同时,研究了群落结构的相似性,以及群落结构与环境因子之间的关系。结果显示,所得渔获物共鉴定出蟹类19种,隶属于6科9属,其中优势种为三疣梭子蟹、日本蟳、双斑蟳和隆线强蟹等4种。不同季节的蟹类种类组成差异较大,而优势种类组成变化较大,其中,蟹类种类数以夏季最多,冬季最少。从不同水深区域的渔获种类分布趋势分析,蟹类种类数以5~15 m水深带较多,小于5 m和15~20 m水深带较少。生物多样性指数夏季最高,冬季最低。从不同水深区域分析,多样性指数在10~15 m水深带较高,5~10 m水深带较低。冗余分析结果认为,表层水温、表层盐度和底层盐度是影响调查海域蟹类种类组成和群落结构特征的主要环境因子。     

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.     

强降雨对粤西凡纳滨对虾养殖池塘微生物群落的影响

于强台风"莫拉菲"环流云系带来的持续强降雨天气前后(2009年7月14日和7月28日),对广东省茂名市电白县凡纳滨对虾半集约化养殖土池的水样和泥样进行调查,研究施用微生态制剂和未施用微生态制剂的虾池水体及底泥中的异养细菌、弧菌和芽孢杆菌的变化情况,并利用BIOLOGECO微板对水体和底泥的微生物群落代谢变化进行探讨。结果发现,定期施用微生态制剂的虾池水体和底泥中的细菌数量和微生物群落功能在强降雨前后基本保持稳定;未施用微生态制剂的虾池在强降雨后,水体的弧菌数升高,Simpson指数和McIntosh指数显著降低(P0.05),水体和底泥微生物群落对碳源的利用率变化明显。研究结果表明,与施用微生态制剂的虾池相比较,未施用微生态制剂的虾池在强降雨后,水体及沉积物环境波动变化明显,强降雨对其水域环境产生很大的影响。因此建议在对虾养殖过程中定期施用微生态制剂,并针对恶劣天气采取有效措施,以稳定虾池水体及沉积物的微生物生态。     

强天气干扰条件下粤西凡纳滨对虾养殖池塘细菌群落动态特征

于暴雨频发的华南雨季（2009年5月-8月）对粤西凡纳滨对虾（Litopenaeus vannamei）养殖池塘水体和底泥进行调查,研究在强天气干扰条件下养殖池塘细菌数量动态及多样性指数变化情况。结果发现,水体异养细菌在104-106 cfu？mL-1间波动,弧菌数量在养殖初期高达105 cfu？mL-1, 虾池301# 和404# 自6月18日开始施用芽孢杆菌（Bacillus subtilis）等微生态制剂后,其弧菌（Vibrio sp.）数量维持在104 cfu？mL-1以下,403# 和305# 波动较大且多次超过105 cfu？mL-1;4口虾池水体弧菌与异养细菌的数量比值在养殖初期均超过20%,之后301# 和404# 保持在12%以下,403#和305# 在养殖后期分别达到21%和33%。底泥异养细菌先升高后稳定,弧菌数量除305# 较稳定外,其他虾池波动较大（103-107 cfu？g-1）。施用微生态制剂池塘301#和404#水体微生物群落多样性较前期降低,305#和403#较前期升高;底泥微生物群落多样性则呈现相同的变化规律,群落的丰富度、常见种的优势度和群落均度较前期有所降低。结果表明,施用微生态制剂的虾池可在气候多变的情况下保持养殖水体细菌群落的相对稳定,抑制弧菌滋生,降低微生态环境风险。     

Phylogenetic analysis of bacterial communities in the shrimp and sea cucumber aquaculture environment in northern China by culturing and PCR–DGGE

In this study, we investigated the bacterial communities in the shrimp and sea cucumber culture environment, including shrimp ponds (SP), sea cucumber ponds (SCP), mixed-culture ponds (MCP) and the effluent channel (EC) in Qingdao, China. Bacteria cultivation showed that the counts of heterotrophic, nitrate-reducing and sulfate-reducing bacteria in the sediment of SP were higher than that in the sediment of SCP and MCP, varying between 8.7 × 10⁴ and 1.86 × 10⁶, 2.1 × 10⁴ and 1.1 × 10⁵, and 9.3 × 10¹ and 1.1 × 10⁴ CFU g^?1, respectively. In contrast, the counts of ammonium-oxidizing and nitrifying bacteria in the sediment of SP was lower than that in the sediment of SCP and MCP. Denaturing gradient gel electrophoresis (DGGE) of 16S rDNA gene and dendrogram analyses showed that bacterial diversity in the mixed-culture environment was higher than that in the monocultures. The similarity of bacterial community between EC and SCP or MCP was higher than that between EC and SP. These results indicated that sea cucumber culture played a significant role in influencing the environmental bacterial communities that were composed mainly of Flavobacteriaceae (64.3%), Bacteriodetes (21%) and delta proteobacteria (14.7%), including the genera of Croceimarina, Lutibacter, Psychroserpens and so on. The results explained the benefit of sea cucumber culture in shrimp ponds at the level of microbial ecology.     

The cellular community in the intestine of the shrimp Penaeus penicillatus and its culture environments

In the present study, bacterial community diversities were investigated in the shrimp intestines, outside seawater and culture-associated environments using clone library analysis. Comparative analyses revealed that the bacterial community in the intestinal contents was most similar to that of the sediment. Bacteria in the phyla Proteobacteria and Firmicutes constituted the dominant components of the intestinal bacteria in the shrimp. The potential pathogens and probiotics were dominant members of the intestine in healthy or diseased shrimp. Intestinal bacterial communities in the healthy shrimp were composed of Bacillales, Rhodobacterales, Vibrionales, and Alteromonadales, whereas fewer bacterial groups were observed in the intestines of diseased shrimp, which were dominated by Vibrionales and Bacillales. Phylogenetic analysis revealed that nearly half of the sequences in the intestines of diseased shrimp were closely related to the potential pathogen Photobacterium damselae and Vibrio harveyi. Obvious differences in microbial diversity were also observed between outside seawater and culture-associated environments. Eukaryotes in the outside seawater were dominated by Skeletonema, Cyclotella, Thalassiosira, Guinardia, and Chaetoceros. The pond water showed less diversity in the eukaryotic community and was dominated by Skeletonema, Thalassiosira, Chaetoceros, and Oithona. The implications of the present study may be significant in the management of shrimp cultivation, as well as the detection of potential pathogens and the application of probiotics.     

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.     

Effects of a probiotic (Bacillus subtilis FY99‐01) on the bacterial community structure and composition of shrimp (Litopenaeus vannamei,Boone) culture water assessed by denaturing gradient gel electrophoresis and high‐throughput sequencing

In China, many commercial probiotics are added as water additives into shrimp culture ponds with no sediment. In these ponds, probiotics should have great effects on the bacterial community of culture water at different culture stages. However, the specific effects have not been clarified yet. In this study, the effects of applying the probiotic Bacillus subtilis FY99‐01 on the bacterial community of shrimp (Litopenaeus vannamei) culture water at different culture stages were determined by denaturing gradient gel electrophoresis and high‐throughput sequencing. The water quality parameters, shrimp production, survival rate and feed conversion ratio (FCR) were also analysed. The results showed that application of probiotics improved the water quality by reducing the levels of pH, nitrite and soluble reactive phosphorus, whereas there was no significant effect on shrimp production, survival rate and FCR. Application of probiotics brought no obvious effect on bacterial α diversity while had effect on bacterial β diversity. In addition, probiotics brought different effects on the bacterial community structure at different culture stages, and the effects are stronger in the early and middle phase than in the late phase. Sequencing results demonstrated that probiotics could increase the abundance of Flavobacteria, whereas decrease the abundance of α‐Proteobacteria in the late phase of culture. Besides, principle component analysis results indicated that using probiotics also could increase the abundance of beneficial microalgae (Bacillariophyta and Chlorophyta) and decrease the abundance of Vibrionaceae.     

Food sources and trophic relationships of three decapod crustaceans: insights from gut contents and stable isotope analyses

Chinese mitten crab (Eriocheir sinensis), freshwater shrimp (Macrobrachium nipponensis) and red swamp crayfish (Procambarus clarkii) are important culture species in China and have world‐wide introduced distributions. The trophic role of these three decapods has not been compared within a system although they consume plants, animals, and detritus and often co‐occur in freshwater ponds. A combination of stable isotope measurements and gut content analysis was used to determine the main food sources and trophic niche of three benthic decapods, in commercial crab ponds around Lake Gucheng, China. Observation of the gut contents reflected a variety of prey items ingested by three decapods. Macrophytes made up the highest contribution to the volume of their gut contents, followed by forage fish, corn and mollusks. Stable isotope analysis supported a stronger relationship between crayfish and vegetable matter than with animal matter, while both crab and shrimp were the opposite. An isotopic mixing model indicated that about 60% of crab and shrimp production originated from animal matter, while only 40% of crayfish production was ascribed to consumption of animal matter. Although results from the mixing model corroborate the gut content findings in most cases, stable isotope results showed that three decapods obtained more energy for growth from animal matter than what would be estimated if gut analysis was used alone. Estimates of niche overlap indices indicated a high degree of dietary overlap among the three decapods examined, suggesting that shrimp and crayfish density should be controlled if considering economic benefits of pond aquaculture.     

Impact of polyculture ecosystems of Ctenopharyngodon idellus with Eriocheir sinensis on bacterial communities in the sediments of Dongping Lake in China: Focus on optimization of polyculture modes

This study investigated the influence of polyculture ecosystems of grass carp (Ctenopharyngodon idellus) and Chinese mitten crab (Eriocheir sinensis) on the bacterial community of sediments in the Lake Dongping in China, using the Illumina HiSeq Sequencing approach. The bacterial community diversity was reduced to different extent due to the polyculture of animals. The bacterial community composition changed significantly among the ecosystems of control (without any animals cultured), G1C1 (with the highest animal biomass: C. idellus, 2 ind/m²; E. sinensis, 1 ind/m²) and G2C2 (with the lowest biomass: C. idellus, 1 ind/m²; E. sinensis, 0.5 ind/m²). Relative abundance increase for sulphide‐oxidizing bacteria and decrease for sulphate‐reducing bacteria were detected with more quantities of fish–crab cultured in ecosystems. Variations in the concentration of sediment sulphate mainly accounted for the shifts of both the bacterial diversity and community composition. Lastly, G2C2 was recommended as the optimal polyculture ecosystem that could be used in the Lake. The results suggested negative impacts of polyculture ecosystems of C. idellus with E. sinensis on the bacterial diversity but positive impacts on the community composition and indicated the role of total biomass of animas in shaping the bacterial community in the sediments of lake ecosystems.     

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.     

The effect of stocking density of Chinese mitten crab Eriocheir sinensis on rice and crab seed yields in rice-crab culture systems

Normally Chinese mitten crab Eriocheir sinensis were cultured for 2 years, 1 year is cultured from crab larvae to seeds or button sized crab in ponds, tanks or rice fields, the another year is cultured from seeds to market size in ponds, reservoirs or other waters. The present study was conducted to determine the effect of stocking density (0, 3.75, 15, 30 and 60 inds. per m², respectively) of Chinese mitten crab larvae on rice and crab seed yields in rice-crab culture systems using land-based enclosures (4 m × 7 m, with three replicates for each stocking density) at the Panjin Guanghe Fisheries Co. Ltd, in the Liaohe Delta, China. Zoobenthos biomass, production of crab and rice paddy, and economical profit among the treatments were determined. The experiment showed that zoobenthos biomass in rice-crab culture systems was relatively variant and not significantly correlated to these stocking density. The biomass of aquatic plant declined significantly with increasing stocking density. Specific growth rates (SGR) and survival rates of the crab were significantly higher at the lower stocking density (P < 0.05); in addition, the ratio of precocious crab and total crab significantly increased with the stocking density increasing (P < 0.05); There were not significant effect of presence of crab on yields of rice straw and rice paddy (P > 0.05). Net crab yield and net profit were the highest at the 15 treatment (P < 0.05), however, the net profits among 3.75, 15 and 30 treatments did not show significant difference (P > 0.05) economically. Based on the observations above, a stocking density of 3.75 to 30 inds. per m² was considered reasonable in rice-crab culture system.     

Bacterial communities in Chinese grass carp (Ctenopharyngodon idellus) farming ponds

Bacterial communities in the water column and sediment of 12 commercial grass carp (Ctenopharyngodon idellus) farming ponds were analysed. At the same time, physical and chemical environmental parameters were measured, including secchi depth (SD), total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD_Mn). From 12 water samples and 12 sediment samples, 39 different ribotypes were detected with PCR‐denaturing gradient gel electrophoresis (PCR‐DGGE). The ribotype richness showed that bacterial species in the water column differed among these ponds, and the result of sequencing further revealed the dominant and common bacterial species. In total, 32 bacterial species belonging to seven phyla (Proteobacteria, Bacteroidetes, Actinobacteria, Cyanobacteria, Acidobacteria, Fibrobacteres and Fusobacteria) were identified. Ordination via canonical correspondence analysis (CCA) on the DGGE data and environmental parameters indicated that the composition of bacterial community was significantly influenced by SD.     

Calcium content in pond sediment and its effect on neutralizing capacity of water and fish production

This paper deals with the assessment of the available insoluble calcium compounds in pond sediment and their conversion into soluble bicarbonate; its impact on the acid neutralizing capacity (ANC) or alkalinity of water and the influence of bioturbation by fish stock. The objective of the study was the assessment of the influence of different Ca contents in pond sediments of two groups of ponds: LCa (with a low content of available Ca) and HCa (with a high content of available calcium) on acid neutralizing capacity of water, conductivity and pH. In our experiments, the turbidity of water, content of chlorophyll, nutrients and natural gain of fish in general have been observed as well. The results revealed that ponds with a higher content of calcium with a mean concentration of 27.45 ± 7.9 mmol Ca/kg in dry matter reported a higher ANC (alkalinity; mean value of 2.31 ± 0.33 mmol/l); pH with smaller fluctuations (7.69 ± 0.37; p < 0.05) and higher average values of turbidity (30.9 ± 17.4 NTU) and conductivity of water (291 ± 40.5 μS/cm^?1; p < 0.01). Tight relations of the content of Ca in sediments and acid neutralizing capacity, conductivity and water pH during the growing season have been proven. The natural gain of fish was higher in the ponds with a higher content of available Ca in the sediment and a higher value of acid neutralizing capacity of water. The natural gain of fish was positively influenced also by a higher content of nutrients and chlorophyll, which was observed particularly in HCa ponds.     

Microbial changes occurring at the sediment-water interface in an intensively stocked and fed fish pond

The microbial changes occurring in the upper 1 cm of the solid sediment surface in intensively fed and aerated fish ponds located in northern Israel were examined. The bacterial groups enumerated included: total aerobes, total anaerobes, sulfate and iron reducing bacteria, ammonia and nitrite oxidizing bacteria, acid forming bacteria, and denitrifying bacteria. With the exception of the nitrifying bacteria, large microbial populations were observed in the pond sediment even prior to fish stocking. All the different groups enumerated displayed a rapid change in number during the first 2–8 days following fish stocking, and a subsequent approach toward a steady state. Since both microbial and chemical steady states were approached within a relatively short period of time, it does not appear that these components of the sediment are related to the inhibition of fish growth occurring 50–70 days after fish stocking. While the practice of pond draining and air drying the sediment does oxidize some of the accumulated organic material, it does not appear to affect the resident microbial flora significantly to an extent that could decrease the rate of reestablishment of the microbial community. Therefore, upon establishment of anaerobic conditions a large microbiological community is present capable of mediating the chemical reduction of SO₄^2? to H₂S, or other transformations resulting in products which contribute to fish growth inhibition commonly observed in such intensively stocked and fed fish ponds.     

菲律宾蛤仔垦区育苗技术优化及其对池塘理化环境、浮游植物和稚贝生长的影响

为改进菲律宾蛤仔垦区育苗技术,设置一口池塘(A)培育高密度浮游植物并定期添加至育苗池(B),未添加藻类育苗池(C)作为对照,比较了A、B、C以及邻近自然海区(D)的水体、沉积物、浮游植物状况和池塘B、C中稚贝生长情况。结果显示,池塘A、B、C之间水质和沉积物各指标无显著性差异,但三者水体中盐度、pH、溶解氧、氨氮、硝酸盐氮、活性磷酸盐和沉积物中有机碳、硫化物与自然海区D差异显著;浮游植物密度ABCD,但仅A、D间差异显著;池塘B稚贝壳长和密度均显著大于池塘C。这表明垦区与自然海区环境差异大,而育苗期间通过外源补充藻类能提高稚贝的生长率和成活率,进而提高菲律宾蛤仔垦区育苗成功率。