Feeding adult of Artemia salina (Crustacea-Branchiopoda) on the dinoflagellate Gyrodinium corsicum (Gymnodiniales) and the Chryptophyta Rhodomonas baltica

Experimentos foram desenvolvidos para estudar as taxas de alimentação e de sobrevivência de Artemia salina alimentada com cepas não tóxicas do dinoflagelado Gyrodinium corsicum e da Chryptophyta Rhodomonas baltica. As taxas de filtração sobre R. baltica e G. corsicum variaram entre 3,35 e 7,14 ml.artemia-1.h-1 e 2,97 e 15,86 ml.artemia-1.h-, respectivamente. As taxas de ingestão observadas para A. salina não indicaram disfunção digestiva ou prejuízo fisiológico nos organismos alimentados com G. corsicum, sendo a resposta funcional destes organismos similar a observada em copépodos alimentados com diferentes concentrações de alimento. As taxas de mortalidade de A. salina oscilaram entre 2,5 e 100% quando alimentada com R. baltica e G. corsicum, respectivamente. As maiores taxas de mortalidade observadas para os organismos alimentados com G. corsicum indicam que este dinoflagelado apresenta algum efeito nocivo sobre A. salina, embora não tenha sido possível confirmar se sua origem está relacionada com a produção de toxinas ou com a inadequação nutritiva deste dinoflagelado para alimentação de organismos desta espécie.

Eutrophication process recorded in dinoflagellate cyst assemblages — a case of Yokohama Port, Tokyo Bay, Japan

To investigate temporal changes of water quality, a role of dinoflagellate cysts preserved in surface sediments was examined in Yokohama Port in Tokyo Bay, Japan. Two cores were collected, and sedimentation rates and ages of both were dated as approximately 1900 years or slightly older on the basis of 210Pb and 137Cs concentrations. The temporal change in dinoflagellate cyst assemblages in the two cores reflects eutrophication in Yokohama Port in the 1960s. Abrupt increases in the cysts of Gyrodinium instriatum cysts strongly suggests that a red tide was caused by this species around 1985. Dinoflagellate cyst assemblages in surface sediments appear to be good biomarkers of changes in the water quality of enclosed seas.

Morphological and phylogenetic analysis of a Gymnodinium-like species from the Chinese Coast

A Gymnodinium-like species was studied with light microscopy (LM) and scanning electron microscopy (SEM). Also, the internal transcribed spacers (containing 5.8S rDNA) and large ribosomal subunit DNA (D1-D2) sequences were obtained by PCR amplification, and then sequenced to explore the relationships within our isolate, Gymnodinium and other Gymnodinium-like species, including Karenia, Gyrodinium, Karlodinium and Symbiodinium. The LM observation showed that the species was characterized by moving in a levorotatory direction, visible hypocone, epicone and transverse groove, all of which are typical for Gymnodinium. In addition, two flagella could be found under SEM. The phylogenetic analysis revealed that the isolate grouped with Symbiodium, rather than other relevant dinoflagellates. All results showed our isolate belongs to Symbiodium. The strain was isolated from a red tide water sample, denoting that Symbiodium may be causative species for algal bloom.

几种赤潮微藻的形态和系统进化分析及荧光原位杂交检测

赤潮也称红潮，通常是指由于一些海洋浮游生物在水体中过度繁殖或聚集而使海水变色的现象。赤潮特别是有害赤潮造成了严重的生态环境问题，给水产养殖业和滨海旅游业造成了巨大损失，并可直接危害人类健康。研究赤潮，进而预防和控制赤潮，首先要对引发赤潮的生物种类进行准确鉴定并对自然水域的赤潮生物进行监控，并建立赤潮藻的快速鉴定与检测方法。本文分别对几株赤潮微藻进行了形态和系统进化分析，并探讨了荧光原位杂交在赤潮检测中的应用。 分别对5株分离自中国沿海不同水域的中肋骨条藻[Skeletonema costatum (Greville) Cleve]类似种 (SK-BH、SK-FQ、 SK-HH、SK-DH和SK-XM) 进行光镜和扫描电镜观察，并PCR扩增了转录内间隔区 (含5.8S rDNA)(ITS) 和核糖体大亚基 (D1-D2)区 (LSU)，获得的序列与其它已报道的骨条藻的同源序列进行了进化分析，以探讨５株骨条藻与已报道的骨条藻之间的进化关系。5株骨条藻在形态上各不相同，其中，只有1株 (SK-XM)被鉴定为中肋骨条藻，而其余4株皆与已报道的骨条藻的形态学特征不符。ITS树和LSU树具有不同的拓扑结构，并表明5株骨条藻至少分属3个不同的种。遗传距离分析提示了在地理距离上靠近的种，在进化上也可能靠近。此外，还可以观察到这5株藻之间的细微的形态学“进化”关系。所有结果表明了中国沿海骨条藻属种的多样性。 对1株分离自赤潮水域的裸甲藻 (Gymnodinium)类似种进行了形态学分析，并探讨了该藻与裸甲藻、凯伦藻(Karena)、旋沟藻(Gyrodinium)、下沟藻(Karlodinium)和共生甲藻(Symbiodinium)的进化关系。光镜观察表明该藻具有裸甲藻的一些典型的形态学特征，而我们没能获得细胞形态保存完好的电镜样品；进化分析初步鉴定该藻为一种共生甲藻。 获得了赤潮异湾藻[Heterosigma akashiwo (Hada) Hada]的LSU和ITS序列，设计了以胞质rRNA和胞核rDNA为靶序列的特异性探针，建立了赤潮异湾藻的全细胞和细胞核荧光原位杂交技术，对探针的特异性进行了验证，并考察了杂交信号和检测率在整个细胞周期的变化情况。探针能分别使整个细胞和细胞核呈现明亮的绿色荧光。探针是特异性的，不与其它受试藻进行交叉反应。杂交信号在整个细胞周期内变化不明显，且检测率为70%–80%。整个检测过程不到1 ｈ，能实现赤潮异湾藻的快速、准确、特异和半定量检测。 获得了海洋原甲藻(Prorocentrum micans Ehrenberg)的LSU和ITS序列，设计了以胞质rRNA为靶序列的特异性探针，建立了海洋原甲藻的全细胞荧光原位杂交技术，并对探针的特异性进行了验证。探针能使整个细胞呈现强烈的绿色荧光。探针不与其它受试藻种进行交叉反应，表明是特异性的。

Questioning the role of phenology shifts and trophic mismatching in a planktonic food web

In a warming climate, differential shifts in the seasonal timing of predators and prey have been suggested to lead to trophic ‘‘mismatches’’ that decouple primary, secondary and tertiary production. We tested this hypothesis using a 25-year time-series of weekly sampling at the Plymouth L4 site, comparing 57 plankton taxa spanning 4 trophic levels. During warm years, there was a weak tendency for earlier timings of spring taxa and later timings of autumn taxa. While this is in line with many previous findings, numerous exceptions existed and only a few taxa (e.g. Gyrodinium spp., Pseudocalanus elongatus, and Acartia clausi) showed consistent, strong evidence for temperature-related timing shifts, revealed by all 4 of the timing indices that we used. Also, the calculated offsets in timing i.e. ‘‘mismatches’’) between predator and prey were no greater in extreme warm or cold years than during more average years. Further, the magnitude of these offsets had no effect on the ‘‘success’’ of the predator, in terms of their annual mean abundance or egg production rates. Instead numerous other factors override, including: inter-annual variability in food quantity, high food baseline levels, turnover rates and prolonged seasonal availability, allowing extended periods of production. Furthermore many taxa, notably meroplankton, increased well before the spring bloom. While theoretically a chronic mismatch, this likely reflects trade-offs for example in predation avoidance. Various gelatinous taxa (Phaeocystis, Noctiluca, ctenophores, appendicularians, medusae) may have reduced these predation constraints, with variable, explosive population outbursts likely responding to improved conditions. The match–mismatch hypothesis may apply for highly seasonal, pulsed systems or specialist feeders, but we suggest that the concept is being over-extended to other marine systems where multiple factors compensate.

Identification of bacteria associated with Dinoflagellates (Dinophyceae) Alexandrium spp. using tyramide signal amplification fluorescent in situ hybridization and confocal microscopy

In the marine environment, phytoplankton and bacterioplankton can be physically associated. Such association has recently been hypothesized to be involved in the toxicity of the dinoflagellate genus Alexandrium. However, the methods, which have been used so far to identify, localize, and quantify bacteria associated with phytoplankton, are either destructive, time consuming, or lack precision. In the present study we combined tyramide signal amplification–fluorescent in situ hybridization (TSA-FISH) with confocal microscopy to determine the physical association of dinoflagellate cells with bacteria. Dinoflagellate attached microflora was successfully identified with TSA-FISH, whereas FISH using monolabeled probes failed to detect bacteria, because of the dinoflagellate autofluorescence. Bacteria attached to entire dinoflagellates were further localized and distinguished from those attached to empty theca, by using calcofluor and DAPI, two fluorochromes that stain dinoflagellate theca and DNA, respectively. The contribution of specific bacterial taxa of attached microflora was assessed by double hybridization. Endocytoplasmic and endonuclear bacteria were successfully identified in the nonthecate dinoflagellate Gyrodinium instriatum. In contrast, intracellular bacteria were not observed in either toxic or nontoxic strains of Alexandrium spp. Finally, the method was successfully tested on natural phytoplankton assemblages, suggesting that this combination of techniques could prove a useful tool for the simultaneous identification, localization, and quantification of bacteria physically associated with dinoflagellates and more generally with phytoplankton.

A theoretical and mass spectrometry study of the fragmentation of mycosporine-like amino acids

In the present study, the mycosporine-like amino acids (MAAs) were isolated from the marine red alga Gracilaria tenuistipitata and analysed by high-resolution accurate-mass sequential mass spectrometry (MSn). In addition to the proposed fragmentation mechanism based on the MSn analysis, it is clearly demonstrated that the elimination of mass 15 is a radical processes taking place at the methoxyl substituent of the double bond. This characteristic loss of a methyl radical was studied by theoretical calculations and the homolytic cleavage of the O-C bond is suggested to be dependent on the bond weakening. The protonation site of the MAAs was indicated by analysis of the Fukui functions and the relative Gibbs energies of the several possible protonated forms. (C) 2008 Elsevier B.V. All rights reserved.

Chlorophyll a content, protist biomass and experimental plankton growth and mortality in West Greenland water samples

We evaluated the role of microzooplankton (sensu latto, grazers <500 µm) in determining the fate of phytoplankton production (PP) along a glacier-to-open sea transect in the Greenland subarctic fjord, Godthabfjord. Based on the distribution of size fractionated chlorophyll a (chl a) concentrations we established 4 zones: (1) Fyllas Bank, characterized by deep chl a maxima (ca. 30 to 40 m) consisting of large cells, (2) the mouth and main branch of the fjord, where phytoplankton was relatively homogeneously distributed in the upper 30 m layer, (3) inner waters influenced by glacial melt water and upwelling, with high chl a concentrations (up to 12 µg/l) in the >10 µm fraction within a narrow (2 m) subsurface layer, and (4) the Kapisigdlit branch of the fjord, ice-free, and characterized with a thick and deep chl a maximum layer. Overall, microzooplankton grazing impact on primary production was variable and seldom significant in the Fyllas Bank and mouth of the fjord, quite intensive (up to >100% potential PP consumed daily) in the middle part of the main and Kapisigdlit branches of the fjord, and rather low and unable to control the fast growing phytoplankton population inhabiting the nutrient rich waters in the upwelling area in the vicinity of the glacier. Most of the grazing impact was on the <10 µm phytoplankton fraction, and the major grazers of the system seem to be >20 µm microzooplankton, as deducted from additional dilution experiments removing this size fraction. Overall, little or no export of phytoplankton out of the fjord to the Fyllas Bank can be determined from our data.

Abundance and biomass of dinoflagellates and ciliates at time series station Helgoland Roads, North Sea, 2007-2009

A monitoring programme for microzooplankton was started at the long-term sampling station ''Kabeltonne'' at Helgoland Roads (54°11.30' N; 7°54.00' E) in January 2007 in order to provide more detailed knowledge on microzooplankton occurrence, composition and seasonality patterns at this site and to complement the existing plankton data series. Ciliate and dinoflagellate cell concentration and carbon biomass were recorded on a weekly basis. Heterotrophic dinoflagellates were considerably more important in terms of biomass than ciliates, especially during the summer months. However, in early spring, ciliates were the major group of microzooplankton grazers as they responded more quickly to phytoplankton food availability. Mixotrophic dinoflagellates played a secondary role in terms of biomass when compared to heterotrophic species; nevertheless, they made up an intense late summer bloom in 2007. The photosynthetic ciliate Myrionecta rubra bloomed at the end of the sampling period. Due to its high biomass when compared to crustacean plankton especially during the spring bloom, microzooplankton should be regarded as the more important phytoplankton grazer group at Helgoland Roads. Based on these results, analyses of biotic and abiotic factors driving microzooplankton composition and abundance are necessary for a full understanding of this important component of the plankton.