Microphytobenthic biomass and species composition in intertidal flats of the Nakdong River estuary, Korea

Intertidal microphytobenthos (MPB) were investigated monthly from August 2006 to March 2008 at four different sites in the sand flats of Nakdong River estuary, Korea. Samples of surface sediment (ca. 1 cm) were collected, and chlorophyll a was extracted as biomass estimation. Species identification and enumeration were carried out by light microscopy, assisted where necessary by scanning electronic microscopy. Biomass varied between 0.47 and 16.58 μg cm⁻³, abundance changed from 5.25 to 414.75 × 10³ cells cm⁻³, while the Shannon diversity indexes ranged between 0.69 and 2.35 H′. Thirty-nine MPB taxa were identified, primarily composed of epipelic diatoms, among which Amphora and Navicula were the most abundant genera. Based on the biomass, abundance, species composition and their dynamics, MPB assemblages of sampling sites were grouped into three distinct communities corresponding to their sediment composition characteristics. Multivariate correlation analysis revealed that biomass was positively related to mud and very fine sand, negatively related to fine and medium sand, but not significantly related to environmental factors such as pore water nutrients, light intensity and salinity, which fluctuated rapidly during emersion period. Cluster analysis corroborated the division of MPB communities according to site types on seasonal scales, and also showed seasonality between sites by cluster of all summer groups. Principal component analysis identified that variability in species composition was significantly affected by mud, very fine sand, fine sand, light intensity, and sediment temperature. This study suggests that sediment composition plays an important role in the functioning of intertidal MPB communities in estuarine ecosystems.     

渤海湾西北岸中全新世埋藏牡蛎礁的硅藻记录及古环境意义

通过对渤海湾西北岸大吴庄牡蛎礁壳体内部的泥质填充物中硅藻组合的研究,试图探讨该区沉积硅藻组合变化指示的礁体古气候环境变化.分析结果表明,在 7 200～5 600 cal. a BP 整个礁体建造期间,沿岸种 Cyclotella stylorum 是含量最丰富的硅藻种类,其与海水种 Thalassionema nitzschioides 的含量变化指示了礁体生长区河流径流与海水相互作用的强弱波动,主要包括三个阶段:7 200～6 500 cal. a BP,礁体建造初期,礁体受海水影响显著;6 500～5 720 cal. a BP,礁体建造中期,礁体生长区的盐度降低,海水作用减弱,淡水作用增强;5 720～5 600 cal.a BP,礁体建造结束期,礁体生长区的盐度显著降低,礁体受海水影响进一步减弱.     

一株抗硅藻附着的海绵附生菌的鉴定及发酵条件优化

为了从海绵共附生微生物中寻找天然高效抗污损活性物质,本文针对前期研究获取的4株具有显著抗硅藻附着的活性菌株进行活性验证和比较,选出其中最优菌株进行菌种鉴定及发酵条件优化.比较了活性菌株对小新月菱形藻(Nitzschia closterium)、咖啡双眉藻(Amphora coffeaeformis)、碎片菱形藻(Nitzschia frustulum)附着的抑制活性,确定菌株UST050418-715为最优菌株;通过16S r DNA的测序分析,结合平板的菌落形态和扫描电镜下菌体特征,鉴定活性菌株UST050418-715为短小芽孢杆菌(Bacillus pumilus).为优化该菌株的培养条件,选择了酵母粉、蛋白胨、Na Cl、p H值进行四因素三水平的正交实验,对菌株培养条件进行优化.发现选择的4个因素对应的菌株发酵产物对硅藻附着的抑制活性大小不同,影响显著性顺序是酵母粉蛋白胨Na Clp H值,综合菌株发酵产物活性、粗提物产量和菌株生长情况进行分析,确定菌株UST050418-715基于海洋2216E培养基的最佳发酵条件为:蛋白胨含量7.5 g/dm3,酵母粉含量3 g/dm3,Na Cl含量10.45 g/dm3,p H值9.5.     

南海北部15 kaBP以来表层海水温度变化:来自海洋硅藻的记录

对西太平洋边缘海148个表层硅藻样品中菱形海线藻(Thalassionema nitzschioides)及其小形变种(Thalassionema nitzschioidesvar.parva)的分布与表层海水温度(SST)之间关系进行研究,将菱形海线藻小形变种与所有菱形海线藻百分含量的比值(简称硅藻Rparva值)视为温度指数,开展南海北部MD05-2904孔附近海域15kaBP以来表层海水温度变化研究。结果表明:(1)南海北部15 kaBP以来表层海水温度呈现明显的阶段性波动特点,即末次冰消期气候转暖过程中,12.9~11.5 kaBP前后温度略有下降,与新仙女木事件对应,全新世南海北部气候依次经历了升温期、高温期和降温期3个变化阶段;(2)全新世大暖期鼎盛期结束后,南海北部海水温度阶段下降,两次明显降温分别发生于4 kaBP前后和1.5 kaBP前后;(3)MD05-2904孔硅藻Rparva值时间序列曲线与董哥洞D4石笋δ18O曲线对比表明,南海北部表层海水温度变化与末次冰消期以来东亚季风强度变化关系较为密切。     

杂色鲍苗大规模脱落死亡的初步研究

研究了杂色鲍(Haliotis diversicolorReeve)鲍苗脱落死亡周期中水质、硅藻和细菌变化情况。结果显示,鲍苗脱落前各水质指标无明显变化,脱落前硅藻数量大幅度增加,以卵形藻(Cocconeisspp.)和舟形藻(Naviculaspp.)为主要种类。同时发现一株可疑致病菌,初步鉴定为溶藻弧菌(Vibrio alginolyticus)。实验表明水质等相关因子与鲍苗脱落无直接关系,而硅藻很可能是致病菌的“载体”,整个附着膜微环境与鲍苗存亡息息相关。     

围隔实验研究台湾海峡2005年夏季小型浮游动物对硅藻水华的摄食

为了研究小型浮游动物对近岸浮游植物藻华的摄食调控作用,于2005年7月,应用"稀释法"并结合高效液相色谱(HPLC)光合色素分析技术,研究了台湾海峡船基围隔实验条件下浮游植物生长率及小型浮游动物摄食率的日变动。结果表明:由于营养盐添加的影响,迅速形成了以尖刺伪菱形藻(Pseudo-nitzschia pungens)为优势种的藻华,生物量(叶绿素a)从实验初始7月6日的1.45μg/dm3迅速增加到7月8日的29.80μg/dm3,随后消退。镜检和光合色素分析的结果显示,实验期间一直以此硅藻占绝对优势。浮游植物的生长率在藻华峰值(7月8日)前保持了较高的生长速率(>1.0/d)且大于小型浮游动物的摄食率;小型浮游动物的摄食率也逐渐增加,7月7日时达到0.86/d,显示有57%以上的浮游植物现存量被摄食。7月8日后,水华迅速消退,摄食率除13日外,均大于浮游植物的生长率。小型浮游动物主要由急游虫(Strombidium spp.)、侠盗虫(Strobilidium spp.)等无壳纤毛虫、异养甲藻-螺旋环沟藻(Gyrodinium spirale)及砂壳纤毛虫等组成,其对浮游植物的生长迅速作出了反应,各类群的丰度在水华峰值后的7月9日均几达最大值,水华后期(11日)大型的无壳纤毛虫达最大值。小型浮游动物的这种组成及变动特点是其保持较高摄食率及一定程度上控制和促进藻华消退的原因之一。     

Starvation effects on pathogenic Vibrio alginolyticus in natural seawater

To get a better understanding of the starvation survival strategy of pathogenic Vibrio alginolyticus, log-phase cells were inoculated into sterile natural seawater for starvation studies. The results showed that all of total bacteria number, viable bacteria number and CFU number of V. alginolyticus increased remarkably at the initial starvation stage; after reaching their peaks at 5 d, both total bacteria number and viable bacteria number of V. alginolyticus fell slowly, while the CFU number fell more quickly after reaching its peak at 10 d; V. alginolyticus elongated their cells at the prophase of starvation, and then shrunk their volume and turned their shapes into ovals from rods at the anaphase of starvation; starved cells showed more sensitivity to heating and UV; starved cells showed no significant difference from unstarved ones at the lowest detection limit determined by indirect enzyme-linked immu- nosorbent assay （ELISA） ; starved cells＇ ability to adhere to the skin mucus of large yellow croaker （ Pseudosciaena crocea） showed a sharp decline as the starvation time increases; the cellular protein of V. alginolyticus increased remarkably at the ariaphase of starvation. The results indicated that pathogenic V. alginolyticus could survive in starvation for relatively long periods of time （ ≥2 months） in 28℃ natural seawater due to the morphological and physiological changes; however, starved V. alginolyticus cells showed less virulence and higher sensitivity under environmental stresses.     

海带配子体克隆细胞附着的初步研究

海带是我国海水养殖主要品种之一,其综合应用价值较高[1].20世纪90年代末期,海带配子体克隆在海带苗种繁育中的应用,为海带育苗生产开辟了新途径[2].主要运用生长发育调控技术实现海带配子体克隆细胞大量扩增和同步成熟来繁育海带优良苗种,这样可大幅度降低育苗成本,缩短育苗周期,该项技术具有良好的应用前景.目前海带配子体克隆育苗技术尚未在海带育苗生产中得到规模化应用,其作为一项高新技术,部分关键技术仍有待进一步解决.在与有关生产单位进行海带配子体克隆育苗实验的工作中,笔者认为克隆细胞的附着是影响海带商品苗质量(出苗密度及出苗均匀程度)的关键问题之一.     

中国南海表层沉积硅藻的分布及其与环境关系探讨

通过对中国南海62个站位表层沉积硅藻的分析,查明研究海区硅藻的种类组成及分布特点。共鉴定到硅藻56属的235个种(包括变种和变型),以热性外洋种为优势,伴有一定量的近岸广布种。总体上,南海硅藻丰度变化呈现从陆架向陆坡至海盆递增的趋势。根据表层沉积硅藻中具有指示意义的硅藻种的分布和生态变化,划分6个硅藻组合带,各组合分别反映不同的海洋环境,其分布主要受到海洋环流的影响,表现为黑潮暖流、印度洋暖水的入侵以及沿岸流对南海表层沉积硅藻分布的影响。与南海相邻海区硅藻种类比较结果表明,研究海区表层沉积硅藻种类组成与临近的菲律宾海域相似程度最大,其次是中国东海海域、太平洋东北部海域。     

西湖硅藻对桡足类浮游动物繁殖的影响

本文报道从杭州西湖筛选分离的两种淡水硅藻,即尖针杆藻Ｓｙｎｅｄｒａａｃｕｓ和谷皮菱形藻Ｎｉｔｚｓｃｈｉａｐａｌｅａ对西湖两种淡水浮游桡足类,即近亲拟剑水蚤Ｐａｒａｃｙｃｌｏｐｓａｆｆｉｎｉｓ和大尾真剑水蚤Ｅｕｃｙｃｌｏｐｓｍｕｃｒｒｏｉｄｅｓ卵孵化率的影响。结果表明,在较高密度的硅藻培养液（１．２×１０４～５．４×１０４个／ｃｍ３）中培养的桡足类动物,其卵的孵化率比生活在自然水体中的有明显降低,并发现该密度的实验硅藻对其摄食者——桡足类的母体也产生一定的毒害作用。该实验结果与已报道的某些海洋硅藻对海洋桡足类存在毒害作用的结果,对水域生态系食物链（网）中硅藻作用的传统概念提出了挑战,对水域生态学研究提出了新课题。