厦门海域2011年中肋骨条藻和血红哈卡藻赤潮期间细菌群落结构变化

【目的】研究2011年8月厦门海域爆发的由中肋骨条藻和血红哈卡藻共同引发的赤潮生消过程中细菌群落结构变化。【方法】应用变性梯度凝胶电泳技术(Denaturing gradient gel electrophoresis,DGGE)对两个赤潮站位和一个非赤潮站位的细菌群落结构进行研究。通过DGGE图谱分析确定赤潮生消过程中细菌群落中的关键菌群,借助Canoco软件分析细菌菌群与环境因子的相关性。【结果】在赤潮起始阶段细菌的群落结构与pH、N/P的相关性较大,在赤潮消亡阶段细菌的群落结构与盐度、温度呈明显的正相关。γ变形杆菌(Gammaproteobacteria)(47.7%)在赤潮期间处于主导位置,假交替单胞菌属(Pseudoalteromonas)、假单胞菌属(Pseudomonas)、交替单胞菌属(Alteromonas)、噬氢菌属(Hydrogenophaga)、Actibacter、Oleibacter等属均为优势菌群。香农-威列多样性指数表明,赤潮站位细菌多样性随着赤潮生消呈先升高后降低趋势,而非赤潮站位细菌多样性基本保持不变。通过Canoco对细菌菌群的主成分分析发现,在赤潮开始阶段Hydrogenophaga属为优势菌群,而在赤潮消退阶段则以Pseudomonas和Pseudoalteromonas属为主。赤潮站位藻际细菌和游离细菌群落多样性在藻密度较大时均达到最大值,然而两者与环境因子的相关性有较大差别。【结论】研究结果表明赤潮站位细菌群落多样性远高于非赤潮站位,细菌丰度随着赤潮藻密度的升高而增加,细菌与赤潮藻有着密切的关系。本文首次研究了多种优势藻引发的赤潮环境下细菌群落结构的变化,这对于多种藻引发的赤潮生消过程中细菌菌群结构有了深入的了解,为赤潮调控的研究提供了理论依据。     

一株赤潮藻溶藻菌的筛选鉴定及溶藻特性分析

为缓解赤潮微藻对海洋生态环境的危害性问题, 从潮间带泥样中筛选溶藻菌进行生物学特征分析, 通过稀释涂布平板法及平板划线分离法从浙江舟山桃花岛潮间带泥样分离筛选菌株, 以中肋骨条藻(Skeletonema costatum)及东海原甲藻(Prorocentrum donghaiense)为受试对象, 通过丙酮法提取、测定叶绿素含量变化从中筛选高效抑制赤潮微藻生长的菌株。经形态学观察、生理生化特征检测及16S rDNA序列分析比对初步确定菌株的分类地位。通过不同pH、发酵时间、添加比例等单因素实验, 对菌株溶藻特性和溶藻活性物质特性进行研究。从潮间带泥样中共获得43株菌, 以菌株2-1-2抑制效果最佳, 经鉴定属于芽孢杆菌属, 初步命名为Bacillus sp. 2-1-2。溶藻菌Bacillus sp. 2-1-2以胞外分泌溶藻物质的方式进行间接溶藻, 最适生长pH为7.0±1.0, 菌液最佳发酵时间2—4d、最佳添加比例20%; 溶藻活性物质耐热性好, 对酸碱耐受性佳, 但不耐强酸, 在pH=10、80℃处理后溶藻率分别可达(90.57±0.43)%和(89.52±0.96)%。对赤潮藻细胞ROS水平与MDA含量具有显著影响(P<0.01)。推测菌株溶藻机制可能为分泌溶藻活性物质间接接触藻细胞, 胁迫藻细胞动态氧化平衡失衡, 影响藻细胞正常生理状态, 藻细胞脂质过氧化破坏了结构完整性使之内容物外泄并逐渐破碎, 抑制藻细胞的生长。     

潮滩底栖微藻生物量垂直变化对其遥感反演模式的影响

遥感信号与潮滩表层沉积物底栖微藻生物量的定量关系, 与定义生物量对应的沉积物深度相关。以叶绿素浓度表征沉积物底栖微藻生物量, 对烟台四十里湾潮滩表层沉积物柱样分别以3 mm 和1 mm 间隔分层, 分析研究其叶绿素垂直分布特征; 模拟、分析以指数衰减曲线斜率表征的叶绿素垂直分布变化对叶绿素浓度遥感反演模式的影响。结果显示, 潮滩表层1 cm 和3 cm 内, 叶绿素浓度均随着深度增加呈指数式衰减; 垂直衰减曲线斜率逐渐变大时, 沉积物表层1 cm 内的叶绿素浓度逐渐降低, 基于叶绿素浓度与光谱指数NDI-MPB 间回归方程的遥感反演模式亦发生变化。     

大米草对赤潮藻的抑制作用及其抑藻物质的分离鉴定

以赤潮异弯藻和海洋原甲藻为研究对象,研究了海洋滩涂植物大米草对两种赤潮微藻的抑制作用及抑藻物质.结果表明：大米草对赤潮异弯藻的影响表现为高浓度抑制生长,低浓度则有一定的促进作用,大米草新鲜组织、干粉末和提取物浓度分别为4.8、0.8和0.5 mg·ml^-1以上时对赤潮异弯藻有致死作用;大米草对海洋原甲藻则表现出明显的抑制作用,且大米草新鲜组织、干粉末和提取物浓度分别为9.6、1.6和1.25 mg·ml^-1以上时对海洋原甲藻有致死作用.对大米草提取物进行抑藻活性物质的分离纯化,从中分离鉴定了2个具有抑藻活性的黄酮糖苷类化合物：异鼠李素-3-O-槐二糖-7-O-鼠李糖苷和丁香亭-3-O-半乳糖苷.     

Effects of temperature, salinity, and irradiance on the growth of the dinoflagellate Akashiwo sanguinea

The effects of temperature, salinity, and irradiance on the growth of the dinoflagellate Akashiwo sanguinea were examined in the laboratory. The irradiance at the light compensation point (I₀) was 14.40 μmol m^− 2 s^− 1 and the irradiance at growth saturation (I_s) was 114 μmol m^− 2 s^− 1. We exposed A. sanguinea to 48 combinations of temperature (5-30 °C) and salinity (5-40) under saturating irradiance; it exhibited its maximum growth rate of 1.13 divisions/day at a combination of 25 °C and salinity of 20. A. sanguinea was able to grow at temperatures from 10 to 30 °C and salinities from 10 to 40. This study revealed that A. sanguinea was a eurythermal and euryhaline organism; in Japan it should have formed blooms in early summer, when salinity was relatively low. In addition, it was noteworthy that A. sanguinea had markedly cold-durability, retaining the motile form of vegetative cells for more than 50 days at 5 °C and at salinities of 25-30.     

Parasitism as a biological control agent of dinoflagellate blooms in the California Current System

Amoebophrya is a marine parasite recently found to infect and kill bloom-forming dinoflagellates in the California Current System (CCS). However, it is unknown whether parasitism by Amoebophrya can control dinoflagellate blooms in major eastern boundary upwelling systems, such as the CCS. We quantified the abundance of a common bloom-forming species Akashiwo sanguinea and prevalence of its parasite (i.e., % infected cells) in surface water samples collected weekly from August 2005 to December 2008 at the Santa Cruz Wharf (SCW), Monterey Bay, CA. Additionally, we measured physical and chemical properties at the SCW and examined regional patterns of wind forcing and sea surface temperature. Relative abundance of the net phytoplankton species was also analyzed to discern whether or not parasitism influences net phytoplankton community composition. Epidemic infection outbreaks (>20% parasite prevalence in the host species) may have contributed to the end or prevented the occurrence of A. sanguinea blooms, whereas low parasite prevalence was associated with short-term (≤2 weeks) A. sanguinea blooms. The complete absence of parasitism in 2007 was associated with an extreme A. sanguinea bloom. Anomalously strong upwelling conditions were detected in 2007, suggesting that A. sanguinea was able to outgrow Amoebophrya and ‘escape’ parasitism. We conclude that parasitism can strongly influence dinoflagellate bloom dynamics in upwelling systems. Moreover, Amoebophrya may indirectly influence net phytoplankton species composition, as species that dominated the net phytoplankton and developed algal blooms never appeared to be infected.     

An unusual bloom of the dinoflagellate Akashiwo sanguinea off the central Oregon, USA, coast in autumn 2009

An algal bloom caused by the dinoflagellate Akashiwo sanguinea was observed in October–November 2009 along the central Oregon coast (44.6°N), off Newport, Oregon, U.S.A. In this paper, the conditions are described which led to the development and demise of this bloom. The bloom was observed for 1 month from 5-October until 4-November with the peak of abundance on 19-October (347,615 cells L⁻¹). The A. sanguinea bloom followed September blooms of the diatoms Pseudo-nitzschia spp, Chaetoceros debilis, and the dinoflagellate Prorocentrum gracile. The bloom occurred when nitrate and silicate concentrations were <2 μM and <8 μM, respectively, and when the water column was stratified. This A. sanguinea dinoflagellate bloom event was closely related to the anomalous upwelling conditions in 2009: upwelling ceased early, at the end of August, whereas a normal upwelling continues into early October. This relaxation extended to near the end of September as a prolonged downwelling event, but then active upwelling reappeared in October and November. The explanation for the occurrence of the A. sanguinea bloom in October may be related to a combination of a prior diatom bloom, a stratified water column with low nutrient concentration in September, and an active upwelling event in October. As for the ultimate source of the cells, the hypothesis is that the seed stock for the A sanguinea bloom off Oregon was southward transport of cells from the Washington coast where a massive bloom of A. sanguinea was first observed in September 2009.     

Distribution and toxicity of a new colonial Microcystis aeruginosa bloom in the San Francisco Bay Estuary,California

The first distribution, biomass and toxicity study of a newly established bloom of the colonial cyanobacteria Microcystis aeruginosa was conducted on October 15, 2003 in the upper San Francisco Bay Estuary. Microcystis aeruginosa was widely distributed throughout 180 km of waterways in the upper San Francisco Bay Estuary from freshwater to brackish water environments and contained hepatotoxic microcystins at all stations. Other cyanobacteria toxins were absent or only present in trace amounts. The composition of the microcystins among stations was similar and dominated by demethyl microcystin-LR followed by microcystin-LR. In situ toxicity computed for the >75 m cell diameter size fraction was well below the 1 g l^–1 advisory level set by the World Health Organization for water quality, but the toxicity of the full population is unknown. The toxicity may have been greater earlier in the year when biomass was visibly higher. Toxicity was highest at low water temperature, water transparency and salinity. Microcystins from the bloom entered the food web and were present in both total zooplankton and clam tissue. Initial laboratory feeding tests suggested the cyanobacteria was not consumed by the adult copepod Eurytemora affinis, an important fishery food source in the estuary.     

粤东柘林湾中肋骨条藻（Skeletonema costatum）种群生态学

于2000年5月~2004年12月对粤东大规模养殖区柘林湾的赤潮藻中肋骨条藻（Skeletonema costatum）种群的时空分布进行了长达5a的调查。结果表明,中肋骨条藻种群密度的周年变动模式基本为双峰型,平面分布没有显著的空间差异。调查期间,中肋骨条藻种群密度的站位实测值为0~1.4×10⁷ cells/dm³,总均值为3.3×10⁵ cells/dm³,占浮游植物总细胞数的67.1%,为调查海区第1优势种。在总共1045份样品中,有中肋骨条藻出现的样品数为1020份。其中,种群密度大于10⁶ cells/dm3的样品有65份,大于10⁷ cells/dm³则有4份。以大于10⁶ cells/dm³为中肋骨条藻的赤潮密度标准,在调查期间至少于2000年、2003年发生4次赤潮。运用灰关联理论对中肋骨条藻种群密度与13个环境因子的关系进行排序分析发现,水温、pH值和浮游动物是影响柘林湾中肋骨条藻种群时空分布的关键因子。水温还与中肋骨条藻种群密度的对数值具极显著意义的线性关系,而达到赤潮密度的样品均落在24.5~32.0℃区间,即每年的5~9月份高温季节。由于柘林湾浮游动物的年高峰期也出现在高温季节,说明浮游动物摄食压力的存在可能是柘林湾中肋骨条藻赤潮发生的重要抑制因子。2004年调查海区中肋骨条藻种群密度和在浮游植物群落中的优势度骤然降低,可能与水体营养盐结构和Fe含量的变化有关。因此,长期调查与监测对于研究海湾生态学和赤潮发生机制是极为重要的。     

Perkinsosis in the Manila clam Ruditapes philippinarum affects responses to the harmful-alga, Prorocentrum minimum

The dinoflagellate Prorocentrum minimum is increasingly recognized as a harmful algal bloom (HAB) species that affects filter-feeding shellfish. An experiment was done to investigate possible interactions between parasitic diseases and exposure to P. minimum in Manila clams, Ruditapes philippinarum. Manila clams, with variable levels of infection with Perkinsus olseni, were exposed for three or six days to the benign phytoplankton species Chaetoceros neogracile or a mixed diet of C. neogracile and P. minimum. After three or six days of exposure, clams were assessed individually for condition index, parasite status, and plasma and hemocyte parameters (morphological and functional) using flow-cytometry. Histological evaluation was also performed on individual clams to assess prevalence and intensity of parasitic infection, as well as other pathological conditions.Prorocentrum minimum caused several changes in Manila clams, especially after six days of exposure, such as decreased hemocyte phagocytosis and size and clam condition index. Pathological conditions observed in Manila clams exposed to P. minimum were hemocyte infiltration in the intestine and gonad follicles, myopathy, and necrosis of the intestine epithelial cells. The parasite P. olseni alone had no significant effect on Manila clams, nor did it modulate the hemocyte variables in clams exposed to P. minimum; however, the parasite did affect the pathological status of Manila clams exposed to the P. minimum culture, by causing atrophy and degeneration of residual ova in the gonadal follicles and hyaline degeneration of the muscle fibers, indicating synergistic effects of both stressors on the host over a short period of time. Additionally, an in vitro experiment also demonstrated detrimental effects of P. minimum and exudates upon P. olseni cells, thus suggesting HAB antagonistic suppression of transmission and proliferation of the parasite in the natural environment over a longer period of time. The results of this experiment demonstrate the complexity of interactions between host, parasite, and HAB.     

Ethno-ecological evidence for Hydnora abyssinica occurring in Johannesburg and Durban traditional medicine markets

Large quantities of plants are traded annually in South Africa's traditional medicine or ‘muthi’ markets. A resource in high demand in the Faraday (Johannesburg) and Warwick (Durban) markets is uMavumbuka, a root holoparasite usually identified as either Hydnora africana Thunb. or Sarcophyte sanguinea Sparrm. subsp. sanguinea. However, rhizomes regularly observed in Faraday between 1994 and 2008 did not resemble either species, thereby suggesting that a third, and undocumented, species was being harvested. This was confirmed when the rhizomes were identified as H. abyssinica A.Br. by an American parasitic plant expert. An ethno-ecological study was initiated to verify its occurrence in selected muthi markets. The study further aimed to investigate the distribution of H. abyssinica through trader interviews, host species localities and some previously misidentified herbarium specimens. The study revealed that H. abyssinica was the only uMavumbuka species present in Faraday and Warwick in 2009. Furthermore, the rhizomes were being harvested in KwaZulu-Natal—an area not previously known to be part of its distribution range. Re-evaluated herbarium vouchers and recent photographs taken in the Kruger National Park have confirmed that H. abyssinica occurs in KwaZulu-Natal, Limpopo, Mpumalanga, Gauteng and Swaziland and hence eastern southern Africa. Fragments of Acacia xanthophloea Benth. roots were identified on 93% of the samples that had host roots attached, and we suspect that H. abyssinica follows the distribution of A. xanthophloea in suitable habitats north from KwaZulu-Natal and adjoining the South African border with Swaziland and Mozambique. Acacia karroo Hayne and A. grandicornuta Gerstner have also been positively identified as host species in South Africa from herbarium records. Plant harvesters in the markets cited the common names of several other species that uMavumbuka “grows under” that may be identified as hosts to H. abyssinica in the future. The collection of specimens in areas identified by the harvesters and in areas of suitable habitat is important to verify the occurrence, distribution and habitat of H. abyssinica in eastern southern Africa.