ENVIRONMENTAL IMPACT OF FISH CULTURE ON IN SITU SEDIMENTARY MICROBIAL COMMUNITIES AND THEIR RESPONSES - SIGNATURE LIPID BIOMARKER ANALYSIS

近年来，沿海地区鱼类养殖对环境的影响引起了人们的广泛关注。从养鱼场大量未消耗的饲料和粪便进入环境，导致沉积物中的有机富集，导致微生物过程的氧气需求增加，最终导致高度减少或缺氧状态。虽然微生物群落是分解过程的主要参与者，但由于缺乏适当的方法，在有机富集地区微生物群落的变化尚未得到审查，这将表明环境健康。特征脂质生物标志物（Signature脂质biomarker， SLB）分析被认为是比较灵敏的化学方法之一，用于研究鱼类养殖区及其周围环境中微生物生物量及其群落结构和沉积物特征的季节和区域变化。在广岛县田岛和横岛的养殖场分别选取了8个和3个养殖场和4个监测站，并在4个季节采集了表层沉积物样本。分析了沉积物样品的温度、pH、氧化还原电位（Eh）、酸性挥发性硫化物-硫（AVS-S）、着火失重（IL）、脂质磷酸盐和磷脂酯连接脂肪酸（PLFA）。在实验室进行了培养试验，以评价饲料对微生物生物量的影响。鱼的沉淀物。培养区Eh低，IL高，AVS-S高，表明沉积物处于高度还原或缺氧状态。环境区沉积物的特征与养鱼区完全不同。除温度变化外，各沉积参数的季节变化不如区域变化明显。作为微生物生物量指标的磷酸脂在区域上存在显著差异。来自养鱼区的沉积物中脂质磷酸盐的浓度明显高于周围沉积物，表明来自养鱼场的高有机质输入的影响。孵育实验结果表明，添加饲料的沉积物中脂质磷酸盐含量始终高于对照组，支持饲料对有机质和脂质磷酸盐含量的影响。PLFA组区域差异显著，养殖区水平高，环境区水平低。8种微生物生物标记物PUFA（微真核生物）、16:1、17:1和18:1（细菌）、10Me 16:0 （SRB; desulobacter sp.）、br17:1 （Desulfovibrio sp.）、iso和anteiso（15:0和17:0（厌氧菌））的比例描述了微生物群落结构。除10Me 16:0和br17:1外，鱼类养殖区微生物指标均显著高于环境区。根据脂质磷酸盐的年平均值，将研究区划分为一级（<=30 nmol/g）， IL、AVS和微生物标志物低，Eh（氧）高；IV级（>=100 nmol/g）： IL、AVS和微生物标志物值高，Eh值低（高度缺氧）；II级（31 ~ 70 nmol/g）和III级（71 ~ 99 nmol/g）：这些参数的水平介于I级和iv级之间。除了II级和III级之间，沉积物参数和微生物生物标志物在这些区域之间存在显著差异，表明沉积物微生物群落结构存在差异。微生物标志物在IL（8-10%）和Eh （-200 ~ -100 mV）范围内的变化显著大于IL（3-8%）和Eh （>-100 mV）范围内的变化。养鱼对环境面积的影响不明显。这些结果表明，生物标志物分析可以很容易地检测到沉积物参数中无法检测到的变化。此外，100 nmol/g的磷酸脂水平可以被认为是一个临界水平，定期监测磷酸脂将提供有关环境健康状况的信息。少

Recently, considerable attention has been focused on the environmental impact of fish culture in coastal areas. A large input of unconsumed feeds and fecal matter from fish farms into the environment results in an organic enrichment in sediments leading to an increased oxygen demand for microbial processes and ultimately highly reduced or anoxic conditions. Although microbial communities are principal playrs in decomposition processes, changes in microbial communities in areas of organic enrichment, which will indicate the environmental health, have not however been examined due to the paucity of suitable methods. Signature lipid biomarker (SLB) analysis, which is reported to be one of the more sensitive chemical methods, was used to examine the seasonal and regional variation in microbial biomass and its community structure along with sediment characteristics in fish culture areas and their ambient environment.Eight and three stations from fish culture and ambient areas were selected, … More respectively from culture farms in Tashima and Yokoshima of Hiroshima Prefecture and surface sediment samples were collected during four seasons. Sediment samples were analyzed for temperature, pH,oxidation-reduction potential (Eh), acid volatile sulfide-sulfur (AVS-S), weight loss on ignition (IL), lipid phosphate, and phospholipid ester-linked fatty acids (PLFA). In laboratory, incubation experiments were conducted to evaluate the influence of feed on microbial biomass. Sediments from fish.culture areas were characterized by low Eh, and high IL and AVS-S,indicating that the sediments were either under highly reduced or anoxic condition. The characteristics of sediments from ambient areas were totally different from fish culture areas. Seasonal was less pronounced than regional variation of sediment parameters, except temperature. Lipid phosphate, an indicator of microbial biomass, showed a marked regional variation. Sediments from fish culture areas contained significantly higher concentrations of lipid phosphate than the ambient sediments, indicating the influence of high organic matter input from fish farms. Results of incubation experiments revealed that the levels of lipid phoshphate in sediments added with feed were always high in comparison with the control, supporting the influence of feed on the levels of organic matter and lipid phosphate. Marked regional variation of PLFA groups was observed with high levels in fish culture areas and low values in ambient areas. The proportions of eight microbial biomarkers PUFA (microeukaryotes), 16 : 1,17 : 1 and 18 : 1 (bacteria), 10Me 16 : 0 (SRB ; Desulfobacter sp.), br17 : 1 (Desulfovibrio sp.), iso and anteiso of 15 : 0 and 17 : 0 (anaerobes) were used to describe the microbial community structure. The microbial biomarkers, except 10Me 16 : 0 and br17 : 1, in fish culture areas were significantly higher than that in ambient areas.Based on the annual mean values of lipid phosphate, the study area was divided into Level I (<=30 nmol/g) : low values of IL,AVS and microbial biomarkers, and high values of Eh (oxic) ; Level IV (>=100 nmol/g) : high values of IL,AVS and microbial biomarkers and low values of Eh (highly anoxic) ; and Level II (31-70 nmol/g) and Level III (71-99 nmol/g) : levels of those parameters were found between Levels I and IV.Sediment parameters and microbial biomarkers differed significantly among these areas, except between Level II and III,indicating the differences in microbial community structure of sediments. The variations of microbial biomarkers at a narrow range of IL (8-10%) and Eh (-200 to -100 mV) were significantly greater than that observed in a range of IL (3-8%) and Eh (>-100 mV). Effect of fish culture on ambient areas was not evident. These results suggest that changes which are not detectable from sediment parameters can be easily detected by biomarker analysis. Furthermore, the level of 100 nmol/g lipid phosphate can be considered as a critical level and a regular monitoring of lipid phosphate will provide information about the status of environmental health. Less