不同营养盐条件下赤潮高发区围隔生态系内多胺的变化

在东海赤潮爆发区域运用围隔生态系实验方法,研究了不同营养盐条件下围隔生态系内多胺浓度变化。结果表明:2010年选用东海原甲藻赤潮爆发处海水,东海原甲藻是各围隔生态系内主要优势种,没有种群演替现象发生。两种营养盐添加方式下各围隔内精胺浓度维持较高水平,都呈现先波折下降后波折上升的趋势,与东海原甲藻的生长变化正好相反;各围隔内腐胺浓度水平较高,变化起伏较大,其中有两个实验组腐胺整体变化趋势与东海原甲藻生长趋势类似;所有围隔内亚精胺浓度最低,波动较小。2011年取用中肋骨条藻赤潮爆发处海水,所有围隔生态系内优势种都发生了从中肋骨条藻到东海原甲藻的演替。各围隔生态系内腐胺浓度最高,在中肋骨条藻生长初期腐胺浓度下降,随着中肋骨条藻的生长有所上升,实验后期随着东海原甲藻的生长又整体呈现出下降趋势;各实验组精胺浓度较低,在中肋骨条藻消亡东海原甲藻出现的种群演替期间,都呈现出较大波动;各围隔内亚精胺浓度较低,在整个种群演替过程中没有明显的变化。围隔生态系中补充营养盐,通过对浮游植物生长的影响,间接影响围隔生态系内的多胺变化。     

SPECIES BOUNDARIES IN THE TOXIC DINOFLAGELLATE PROROCENTRUM LIMA (DINOPHYCEAE,PROROCENTRALES), BASED ON MORPHOLOGICAL AND PHYLOGENETIC CHARACTERS1

Wild and cultured specimens of Prorocentrum lima (Ehrenb.) F. Stein from 26 widely different areas in 13 countries were examined in order to determine consistent characters for delimiting species boundaries in this taxon. The morphological characters valve shape, valve size, valve ornamentation, number and shape of valve pores, number and shape of marginal pores, and periflagellar platelets were observed using LM and SEM, and two molecular genetic regions were sequenced. We identified stable morphological characters that were consistent among wild specimens and all cultures, which were valve shape, valve ornamentation, and number and arrangement of periflagellar platelets. All cultures of P. lima identified by these characters formed a monophyletic group in phylogenetic analyses based on the two genes, which, however, included the species Prorocentrum arenarium. P. arenarium was determined to be within the range of morphological variation of P. lima, and therefore we synonymize the two taxa. Within this monophyletic group, P. lima was divided into several subclades in the all phylogenetic analyses. There were no morphological characters specifically related to any one subclade. The subclades appeared to correlate broadly to sample collection regions, suggesting that geographically separated populations may have become genetically distinct within this epi‐benthic species. We have emended species boundaries in P. lima.     

Biochemical compositions of two dominant bloom- forming species isolated from the Yangtze River Estuary in response to different nutrient conditions

Variations of cellular total lipid, total carbohydrate and total protein content of two dominant bloom-forming species (Skeletonema costatum and Prorocentrum donghaiense) isolated from the Yangtze River Estuary were examined under six different nutrient conditions in batch cultures. Daily samples were collected to estimate the cell growth, nutrient concentration and three biochemical compositions content during 7 days for S. costatum and the same sampling procedure was done every other day during 10 days for P. donghaiense. Results showed that for S. costatum, cellular total lipid content increased under phosphorus (P) limitation, but not for nitrogen (N) limitation; cellular carbohydrate were accumulated under both N and P limitation; cellular total protein content of low nutrient concentration treatments were significantly lower than that of high nutrient concentration treatments. For P. donghaiense, both cellular total lipid content and total carbohydrate content were greatly elevated as a result of N and P exhaustion, but cellular total protein content had no significant changes under nutrient limitation. In addition, the capability of accumulation of three biochemical constituents of P. donghaiense was much stronger than that of S. costatum. Pearson correlation showed that for both species, the biochemical composition of three constituents (lipid, carbohydrate and protein) had no significant relationship with extracellular N concentration, but had positive correlation with extracellular and intracellular P concentration. The capability of two species to accumulate cellular total lipid and carbohydrate under nutrient limitation may help them accommodate the fluctuating nutrient condition of the Yangtze River Estuary. The different responses of two species of cellular biochemical compositions content under different nutrient conditions may provide some evidence to explain the temporal characteristic of blooms caused by two species in the Yangtze River Estuary.     

东海原甲藻(Prorocentrum donghaiensis)对原生动物群落结构影响的现场船基实验

2005年在长江口赤潮频发海域调查期间,分别于4月27日、5月4日和5月8日,在zzf1、zc18a和ra5站位利用现场船基培养的方法,研究了添加到赤潮密度10^6cells L^-1的东海原甲藻（Prorocentrum donghaiense）对原生动物群落结构的影响。结果发现,赤潮密度的东海原甲藻抑制了小型无壳纤毛虫的种群数量,而没有抑制中大型砂壳纤毛虫和夜光虫（Noctiluca scintillans）的种群数量,从而使得原生动物群落向中大型种类演替,这种影响的程度与原生动物本身的群落组成和浮游植物的组成密切相关。添加东海原甲藻72h后,在以小型无壳纤毛虫管游虫（Cyrtostrombidium sp．）为优势种的zzf1站位,演替为以大型原生动物夜光虫为优势种的群落;在以中大型原生动物百乐拟铃虫（Tintinnospsis beroidea）和夜光虫为优势种的zc18a站位,仍然是以此为优势种,且大型原生动物夜光虫在群落中的比例上升;在以小型无壳纤毛虫急游虫2（Strombidium sp．2）为优势种的ra5站位,演替为以中大型原生动物百乐拟铃虫和亚速岛网纹虫（Favella azorica）为优势种的群落。zzf1和ra5站位实验组中原生动物的总丰度都呈下降趋势,而zc18a站位变化不明显,这是由于前两个站位的最优势种管游虫（zzf1站位）和急游虫2（ra5站位）的丰度迅速下降,而zc18a站位的优势种百乐拟铃虫和夜光虫的丰度比较稳定造成的。在zzf1和zc18a站位,对照组和实验组中原生动物的总生物量在实验前后都没有大的变化,而在ra5站位却均呈下降的趋势。这可能与浮游植物的组成有关,zzf1和zc18a站位是以无毒的锥状斯氏藻（Scrippsiella trochoidea）和螺旋环沟藻（Gyrodinium spirale）为主,而ra5站位是以有毒的亚历山大藻（Alexandriumsp．）为主。综上可见,可预测当东海大规模赤潮爆发时,会使原生动物群落向中大型种类演替,进而可能影响海洋生态系统的结构和功能。     

三种典型赤潮藻产生与消耗二甲基硫化物的速率估算

采用抑制剂加入法估算了中肋骨条藻、棕囊藻和东海原甲藻在不同生长期内二甲基硫化物的产生与消耗速率.结果表明:颗粒态二甲基巯基丙酸(DMSPp)和颗粒态二甲亚砜(DMSOp)在3种藻类的不同生长期内均为净消耗,溶解态二甲基巯基丙酸(DMSPd)和溶解态二甲亚砜(DMSOd)的含量受藻类产生与细菌病毒消耗控制,在藻类不同生长期内存在不同的产生与消耗速率,而二甲基硫(DMS)在3种藻不同生长期内均为净产生.同一种藻在不同生长期内以及不同藻在相同生长期内二甲基硫化物的产生与消耗速率均存在较大差异,表明藻类的生理状态和种间差异均对二甲基硫化物的产生与消耗速率产生影响.     

Delayed luminescence of Prorocentrum minimum under controlled conditions

Delayed luminescence (DL), also termed delayed fluorescence or delayed light emission, is the phenomenon of long-lived light emission by plants and cyanobacteria after being illuminated with light and put into darkness. Culture growth of three Prorocentrum minimum strains was studied with DL measurements. DL decay kinetics was measured from 1–60 s after a pulse of white light. The strains used were from the Adriatic Sea (PmK), from Chesapeake Bay, USA (D5), and from the Baltic Sea (BAL), cultured at salinity of 32, 16, and 8 (practical salinity scale), respectively. The strains differed in cell size and chlorophyll a content (PmK > D5 > BAL), as well as in DL parameters. The DL results were compared to standard measurements of culture density and carbon content (calculated from biovolumes). DL decay curves had a specific peak, which changed with culture growth and showed more similarities between the strains PmK and D5. The DL intensity increased with cell density and carbon content in a two-stage process, corresponding to the lag and exponential phases of growth. DL intensity was best correlated with carbon content irrespective of strain and is proposed as an estimate of biomass and for differentiating between lag and exponential phases of growth.     

Impacts and potential effects due to Prorocentrum minimum blooms in Chesapeake Bay

The dinoflagellate Prorocentrum minimum (P. minimum) can be found in all seasons and over a broad range of habitat conditions in the Chesapeake Bay and its tributaries. Blooms (>3000 cells ml⁻¹), locally referred to as ‘mahagony tides’, were restricted to salinities of 4.5–12.8 psu, water temperatures of 12–28 °C, and occurred most frequently in April and May. P. minimum blooms have been detected at routine water quality monitoring stations located in the main channel of the Bay and tidal tributaries. Nearshore investigations of bloom events, however, have accounted for the majority of events recorded in excess of 10⁵ cells ml⁻¹. Mahogany tides were associated with widespread harmful impacts including anoxic/hypoxic events, finfish kills, aquaculture shellfish kills and submerged aquatic vegetation losses. We summarize the state of knowledge regarding physical and chemical factors related to P. minimum blooms, their abundance, distribution and frequency, and ecological effects in Chesapeake Bay.     

Influence of humic, fulvic and hydrophilic acids on the growth, photosynthesis and respiration of the dinoflagellate Prorocentrum minimum (Pavillard) Schiller

Blooms of the dinoflagellate Prorocentrum minimum often occur in coastal regions characterized by variable salinity and elevated concentrations of terrestrially derived dissolved organic carbon (DOC). Humic, fulvic and hydrophilic acid fractions of DOC were isolated from runoff entering lower Narragansett Bay immediately after a rainfall event and the influence of these fractions upon P. minimum growth, cell yield, photosynthesis and respiration was examined. All organic fractions stimulated growth rates and cell yields compared with controls (no organic additions), but the extent of stimulation varied with the fraction and its molecular weight. Greatest stimulations were observed with humic and fulvic acids additions; cell yields were more than 2.5 and 3.5 times higher than with hydrophilic acid additions while growth rates were 21 and 44% higher, respectively. Responses to additions of different molecular weight fractions of each DOC fraction suggest that growth rate effects were attributable to specific molecular weight fractions: the >10,000 fraction of humic acids, both the >10,000 and <500 fractions of fulvic acids and the <10,000 fraction of hydrophilic acids. The form and concentration of nitrogen (as NO₃⁻ or NH₄⁺) present also influenced P. minimum response to DOC; 10–20 μg ml⁻¹ additions of fulvic acid had no effect upon growth rates in the presence of NH₄⁺ but significantly increased growth rates in the presence of NO₃⁻, a relationship probably related to fulvic acid effects upon trace metal bioavailability and subsequent regulation of the biosynthesis of enzymes required for NO₃⁻ assimilation. The influence of DOC additions on P. minimum respiration and production rates also varied with the organic fraction and its concentration. Production rates ranged from 1.1 to 3.4 pg O₂ cell⁻¹ h⁻¹, with highest rates observed upon exposure to fulvic and hydrophilic acid concentrations of >10 μm ml⁻¹. Low concentrations (5–10 μg ml⁻¹) of humic acid had no statistically significant effect upon production, but exposure to concentrations >25 μg ml⁻¹ resulted in a 30% decrease in O₂ evolution, probably due to light attenuation by the highly colored humic acid fraction. Respiration rates ranged from 1.2 to 2.7 pg O₂ cell⁻¹ h⁻¹ and were elevated upon exposure to both fulvic and hydrophilic acids, but not to humic acid. These results demonstrate that terrestrially derived DOC fractions play an active role in stimulation of P. minimum growth via direct effects upon growth, yield and photosynthesis as well as via indirect influences such as interactions with nitrogen and effects upon light attenuation.