2008年浒苔大暴发末期黄海小型底栖动物现存量及空间分布

在2008年夏季浒苔暴发末期,对黄海33个站位(其中冷水团中22个,浒苔暴发区域9个)进行了小型底栖动物现存量、分布及沉积环境研究.结果表明:在浒苔灾害严重的南黄海区域,沉积物中的粉砂-粘土含量较往年(2007年)有明显增加;沉积物中叶绿素a和脱镁叶绿素a含量在大多区域较2007年变化不大,但在苏南至长江口近岸海域的含量有明显降低.所获的16个小型底栖动物类群的垂直分布及各类群对现存量的贡献较往年未见明显差异.小型底栖动物平均丰度为(1375±793)ind·10 cm-2,生物量为(1203±707)μg·10cm-2.黄海小型底栖动物总体现存量较2007年低约1/3,并在浒苔暴发区域下降尤为明显,而南黄海冷水团海域则略有上升,由此导致南黄海的小型底栖动物现存量分布呈现从中央冷水区向外围减小的反常现象;相较于此,在浒苔灾害影响较小的北黄海则呈从冷水区向外围增加的趋势.统计分析显示,浒苔暴发区域的小型底栖动物丰度与盐度呈正相关,与叶绿素a含量不相关.浒苔的暴发对近岸的小型底栖生物现存量产生了明显的抑制,但导致小型底栖动物现存量降低的主要因素并非缘于饵料匮乏,而更可能是浒苔暴发后的沉积与降解过程产生的影响所致.     

Tracing the origin of green macroalgal blooms based on the large scale spatio-temporal distribution of Ulva microscopic propagules and settled mature Ulva vegetative thalli in coastal regions of the Yellow Sea,China

From 2008 to 2016, massive floating green macroalgal blooms occurred annually during the summer months in the Yellow Sea. The original source of these blooms was traced based on the spatio-temporal distribution and species composition of Ulva microscopic propagules and settled Ulva vegetative thalli monthly from December 2012 to May 2013 in the Yellow Sea. High quantities of Ulva microscopic propagules in both the water column and sediments were found in the Pyropia aquaculture area along the Jiangsu coast before a green macroalgal bloom appeared in the Yellow Sea. The abundance of Ulva microscopic propagules was significantly lower in outer areas compared to in Pyropia aquaculture areas. A molecular phylogenetic analysis suggested that Ulva prolifera microscopic propagules were the dominant microscopic propagules present during the study period. The extremely low biomass of settled Ulva vegetative thalli along the coast indicated that somatic cells of settled Ulva vegetative thalli did not provide a propagule bank for the green macroalgal blooms in the Yellow Sea. The results of this study provide further supporting evidence that the floating green macroalgal blooms originate from green macroalgae attached to Pyropia aquaculture rafts along the Jiangsu coastline of the southern Yellow Sea.     

Discrimination of the common macroalgae (Ulva and Blidingia) in coastal waters of Yellow Sea,northern China,based on restriction fragment-length polymorphism (RFLP) analysis

Since 2007, reoccurring large-scale green algae blooms have caused deleterious effects to the estuarine ecosystem of Yellow Sea, northern China and subsequent economical losses. Previous surveys indicated the green tides were initiated in the coastal water of southern Jiangsu province where Porphyra farming was intensively conducted; however, the main ‘seed source’ of floating green algae is still under debate. Ulva prolifera was confirmed to be the major causative species of green tides. The multiple sympatric ulvoid species in the natural environment has complicated species identification in both field surveys and laboratory studies due to their morphological plasticity. Thus, we developed a genetic identification key based on restriction fragment length polymorphism (RFLP) analysis of the ITS nuclear marker to discriminate the common Ulva and Blidingia species in the Yellow Sea. Ten genetic lineages (1 in Blidingia, 9 in Ulva) were detected along the coast of China through phylogenetic analysis of ITS sequences. They can be separated by virtual restriction digestion using the four selected restriction enzymes (BspT107 I, EcoO109 I, Hin1 I and VpaK11B I). With additional PCR amplification of the 5S spacer region, we were able to discriminate U. prolifera from Ulva linza. Using this genetic key, we screened macroalgal samples collected from the coast of the Yellow Sea, and the results indicated 6 common lineages (U. prolifera, U. linza, Ulva compressa, Ulva pertusa, Clade 6 and Blidingia sp.) in this region, which could be explicitly distinguished by a single enzyme (BspT107 I) coupled with 5S spacer polymorphism. U. prolifera was confirmed to be present on the Porphyra aquaculture rafts with seasonal variation in the species composition. This genetic key will facilitate our long-term field surveys to investigate the origin of the floating U. prolifera and furthermore to explore its bloom dynamics along the coast of the Yellow Sea. It also provided a framework for the future inclusion of more Ulva species, which will expand the usage of this key.     

Allelopathic interactions between the opportunistic species Ulva prolifera and the native macroalga Gracilaria lichvoides

Allelopathy, one type of direct plant competition, can be a potent mechanism through which plant communities are structured. The aim of this study was to determine whether allelopathic interactions occur between the opportunistic green tide-forming species Ulva prolifera and the native macroalga Gracilaria lichvoides, both of which were collected from the coastline of East China sea. In laboratory experiments, the presence of G. lichvoides at 1.25 g wet weight L(-1) significantly inhibited growth and photosynthesis of U. prolifera at concentrations of 1.25, 2.50, and 3.75 g wet weight L(-1) (p<0.05) in both semi-continuous co-culture assays and in co-culture assays without nutrient supplementation. In contrast, although U. prolifera had a density effect on G. lichvoides, the differences among treatments were not significant (p>0.05). Culture medium experiments further confirmed that some allelochemicals may be released by both of the tested macroalgae, and these could account for the observed physiological inhibition of growth and photosynthesis. Moreover, the native macroalgae G. lichvoides was a stronger competitor than the opportunistic species U. prolifera. Collectively, the results of the present study represent a significant advance in exploring ecological questions about the effects of green tide blooms on the macroalgal community.     

Phylogeographical structure, distribution and genetic variation of the green algae Ulva intestinalis and U. compressa (Chlorophyta) in the Baltic Sea area

The marine algae Ulva intestinalis and U. compressa are morphologically plastic with many overlapping characters and are therefore difficult to distinguish from each other. The present distribution of U. intestinalis and U. compressa is investigated along the salinity gradient in the Baltic Sea area through analyses of internal transcribed spacer (ITS) sequence data. Also, the amount and distribution of intraspecific genetic polymorphism in the ITS region is studied allowing inferences on the phylogeographical pattern and postglacial recolonization of the Baltic Sea area. The data show that of the two species only U. intestinalis occurs in the Baltic Sea. The distribution of U. compressa is more restricted than previously reported, and it was not found in salinities lower than 15 ppt. All of Scandinavia and the Baltic Sea were covered with ice during the last ice age and the organisms in the Baltic Sea must have colonized the area after the ice had started to melt. The genetic diversity of U. intestinalis and U. compressa in the Baltic Sea and the neighbouring area was found to be reduced compared to that in the British Isles. This reduction may be the result of either a historical reduction of diversity or an adaptation of specific clones to the northern environmental conditions.     

Culture and hybridization experiments on an ulva clade including the Qingdao strain blooming in the yellow sea

In the summer of 2008, immediately prior to the Beijing Olympics, a massive green tide of the genus Ulva covered the Qingdao coast of the Yellow Sea in China. Based on molecular analyses using the nuclear encoded rDNA internal transcribed spacer (ITS) region, the Qingdao strains dominating the green tide were reported to be included in a single phylogenetic clade, currently regarded as a single species. On the other hand, our detailed phylogenetic analyses of the clade, using a higher resolution DNA marker, suggested that two genetically separate entities could be included within the clade. However, speciation within the Ulva clade has not yet been examined. We examined the occurrence of an intricate speciation within the clade, including the Qingdao strains, via combined studies of culture, hybridization and phylogenetic analysis. The two entities separated by our phylogenetic analyses of the clade were simply distinguished as U. linza and U. prolifera morphologically by the absence or presence of branches in cultured thalli. The inclusion of sexual strains and several asexual strains were found in each taxon. Hybridizations among the sexual strains also supported the separation by a partial gamete incompatibility. The sexually reproducing Qingdao strains crossed with U. prolifera without any reproductive boundary, but a complete reproductive isolation to U. linza occurred by gamete incompatibility. The results demonstrate that the U. prolifera group includes two types of sexual strains distinguishable by crossing affinity to U. linza. Species identification within the Ulva clade requires high resolution DNA markers and/or hybridization experiments and is not possible by reliance on the ITS markers alone.     

Ulva diversity in the Yellow Sea during the large‐scale green algal blooms in 2008–2009

In the Yellow Sea of China, large‐scale green tides have broken out for three consecutive years from 2007 to 2009. As part of the efforts to localize the algal source, two cruises were conducted in the early stage and the outbreak stage of the bloom in 2009. We analyzed the morphological and genetic diversity of drifting Ulva specimens and culture‐derived isolates from seawater sampled in different localities. For phylogenetic analyses, the nuclear encoded ribosomal DNA internal transcribed spacer region (ITS nrDNA) and the plastid encoded large subunit of ribulose‐1, 5‐bisphosphate carboxylase/oxgenase gene (rbcL) were used. Our molecular and morphological data indicate that the dominant free‐floating Ulva species in 2008 and 2009 possibly belonged to a single strain of the U. linza‐procera‐prolifera (LPP) clade. The ITS sequences from bloom‐forming algal samples with dense branches were identical to those from U. linza‐like specimens without branches derived from the Yellow Sea. Microscopic individuals of the dominant Ulva strain were detected in eight stations, revealing that spore dispersal in the water helped to enlarge biomass in the water during the outbreak stage of green tide in the Yellow Sea.     

从藻类生理生态学角度解析绿潮爆发的内在机制

绿潮是在特殊环境条件下,海水中某些大型绿藻爆发性增殖或高度聚集而引发的海洋生态异常现象。自2007年起,黄海已连续15年爆发绿潮,对沿岸生态环境、社会发展、经济建设造成极其严重的危害,解决绿潮问题刻不容缓。绿潮的形成是外因和内因综合作用的结果。目前,国内外学者对绿潮爆发的外因,即环境因子已具有科学的认知,并围绕绿潮藻类对某些环境因子的生理响应展开系列研究,且取得了一定成果。然而,针对绿潮爆发的内因,即绿潮藻类为应对大幅波动的环境因子而产生的极强的生理生态适应性尚未进行深入探讨。本文从藻类生理生态学角度入手,综述绿潮成因种对多种生态因子波动的响应机制,包括光照强度、二氧化碳、温度、盐度与干出、营养盐、重金属及生物因素,归纳了绿潮藻类的光合生长生理、营养生理和繁殖生理对环境因子波动的适应性调节机制,揭示了绿潮藻类爆发的内因。     

Morphological and molecular characterization of free-floating and attached green macroalgae Ulva spp. in the Yellow Sea of China

During the summer of 2008 and 2009, massive algal blooms repeatedly broke out in the Yellow Sea of China. These were undoubtedly caused by the accumulations of one or more species in the macroalgal genus Ulva. In previous reports, morphological observation indicated that the species involved in this phenomenon is Ulva prolifera but molecular analyses indicated that the species belongs to an Ulva linza–procera–prolifera (LPP) clade. Correct identification of the bloom species is required to understand and manage the blooms, but the taxonomic status of the bloom species remains unclear. In the current study, the taxonomic status of 22 selected specimens from the Yellow Sea was assessed by using both morphological and molecular (ITS and rbcL sequences) data. In addition, 5S rDNA analyses were performed for those samples clustering in the LPP clade, and phylogenetic tree and ribotype analyses were constructed for determining the possible origin of the bloom. Three free-floating and two attached Ulva species were distinguished and described: Ulva compressa Linnaeus and Ulva pertusa Kjellman were found in free-floating samples; U. linza Linnaeus was found on rocks; and U. prolifera O.F. Müller was found in both habitats. Diversity in free-floating Ulva of the Yellow Sea appears to be greater than previously thought. The dominant free-floating Ulva species, U. prolifera, was not closely related to local populations attached to rocks but was closely related to populations from Japan.     

中国沿海海鞘的物种多样性

至今,中国海已经记录了66种海鞘。其中,渤海有5种,黄海21种,东海24种,南海53种。种类分布从北往南逐渐递增,柄瘤海鞘在黄海、渤海数量很大(8100个/m²),但往南分布,未发现超过罗源湾。皱瘤海鞘在南海数量很大(2225个/m²),往北也未发现超过罗源湾。玻璃海鞘和乳突皮海鞘在全国沿海都有分布。     

Novel morphology in Enteromorpha (Ulvophyceae) forming green tides

"Green tides" are vast accumulations of unattached green macroalgae associated with eutrophicated marine environments. They have major ecological and economic impacts globally, so an understanding of their origin and persistence is required in order to make management decisions. Blooms predominantly consist of two common fouling genera of the Ulvales, Ulva (distromatic sheets) and Enteromorpha (monostromatic tubes). In the Baltic Sea and elsewhere green tides have increased over the last few decades. On the west coast of Finland, summer blooms consist of monostromatic sheets resembling Monostroma (Codiolales). We identified these as Enteromorpha intestinalis by comparative analyses of rDNA internal transcribed spacer 1 (ITS1), 5.8S, and ITS2 sequences, the first time monostromatic sheets have been found in the genus Enteromorpha. Ordinary attached E. intestinalis sporulated freely in culture, but the sheets reproduced only by cell regeneration into typical tubular thalli. The ITS sequences were identical to those of attached E. intestinalis populations in southwestern Finland, but differed by two substitutions from other Baltic sequences. We infer that this bloom originated from local attached populations and now reproduces clonally by fragmentation. This study provides further evidence of radical changes in gross morphology of green algae under eutrophicated conditions and the need for molecular identification.     

Can dispersions be used for discriminating water quality status in coastal ecosystems? A case study on biofilm-dwelling microbial eukaryotes

Multivariate dispersions are an effective ecological indicator to evaluate the environmental heterogeneity and human disturbance in global ecological research. To explore the feasibility of the dispersions for assessing water quality status, a dataset of the biofilm-dwelling microbial eukaryote communities was studied in coastal waters of the Yellow Sea, northern China at two numerical resolutions. The community dispersion patterns represented a significant variability in both community structure and species composition in response to environmental heterogeneity. Multivariate approaches revealed that the species composition was the primary contributor to the community dispersion. Mantel analysis showed that the spatial variations in both community structure and species composition were significantly correlated with the changes of the nutrients, pH, dissolved oxygen (DO) and chemical oxygen demand (COD). The dispersion measures at both numerical resolutions were found to be remarkably related to the nutrient ammonium nitrogen and DO. Thus, we suggest that multivariate dispersions of the microbial eukaryote communities may be used as a potential bioindicator of water quality status in marine ecosystems.     

Spatial and temporal variability of biomass and composition of green tides in Ireland

Although nutrient enrichment of estuarine and coastal waters is considered a key factor for the development of green tides, the extent, distribution, and species composition of blooms vary among systems of similar nutrient loading, which compromises our ability to predict these events based on information about nutrient status alone. Additional factors may play a role in the control and development of macroalgal blooms. The identification of relevant scales of variation is a necessary prerequisite before explanatory models can be proposed and tested. In this study spatial and temporal patterns of biomass distribution were assessed for two Ulva morphologies in two Irish estuaries heavily affected by green tides (wet biomass >1 kg m⁻² during the peak bloom). Moreover, using genetic markers, the species composition of these green tides was assessed. Results revealed that these blooms were multi-specific, with Ulva prolifera, U. compressa and U.rigida the most frequent species. The species U. prolifera and U. compressa usually showed a tubular morphology, while U. rigida was mainly laminar. A seasonal succession common to both estuaries was also identified, with the bloom dominated by tubular species during spring and early summer, and co-dominated by tubular and laminar morphologies during late summer and autumn. Moreover, tubular and laminar morphologies exhibited different distribution patterns, with tubular morphologies varying at bigger spatial scales and higher biomass than the laminar. As tubular and laminar morphologies exhibited different distribution patterns, varying tubular morphologies along bigger spatial scales with higher biomass levels than the laminar. Considering that tubular morphologies were usually anchored to the sediment, while laminar Ulva were usually observed free-floating, these differences could explain a differential influence by water motion. An important annual and decadal variability in biomass levels of Ulva was observed, in the case of the Tolka estuary a noticeable increase over the last two decades. These findings should be considered for the development of management and monitoring strategies since the different habitat of laminar and tubular morphologies (anchored vs. free-floating) may play an important role in the balance of nutrients and biomass in the estuary, or determine the response to pollutant exposure. Furthermore, the presence of different species with different ecological requirements could favour the duration and extension of the bloom though temporal and spatial successions.     

东海区大型水母数量分布特征及其与温盐度的关系

以 2 0 0 4年 4月和 6月东海区中北部海域大型水母的监测调查结果为依据 ,分析了东海区大型水母的主要种类组成、数量分布及其与温度、盐度环境的关系、以及主要种类间的个体生长差异。结果表明 :4月大型水母的优势种类多管水母约占 75 %、霞水母约占 15 %和沙水母约占 5 % ;6月大型水母的优势种类沙海蜇约占 6 0 %、多管水母约占 2 0 %和霞水母约占 10 %。其中沙海蜇和霞水母为往年东海区大量暴发的种类。沙海蜇为低温高盐种 ,适温范围为 12～ 17℃ ,主要分布于黄海冷水团伸向东海舌锋的锋面以北海域 ,密集分布区最高网产为 10 0 0 0 kg/ h左右 ;霞水母为暖水高盐种 ,适温范围为 2 0～ 2 5℃ ,主要密集分布于东海北部的暖水控制海域。黄海冷水团势力强弱可作为判别沙海蜇暴发程度的一个重要参考因子。东海区大型水母主要优势种的生长速度以沙海蜇最快 ,其次为霞水母 ,而多管水母相对较慢 ,且个体偏小     

北海区海洋生态灾害的主要类型及分布现状研究

本文将海洋生态灾害定义为局部海域一种或少数几种海洋生物数量过度增多引起的海洋生态异常现象,包括赤潮、绿潮、水母旺发和外来种入侵等,根据相关研究及调查资料,探讨了北海区赤潮、绿潮、水母、外来生物入侵等生态灾害发生特点及趋势。结果表明,北海区赤潮和绿潮灾害频发,影响面积较大,渤海北部秦皇岛附近海域赤潮灾害严重,黄海西部山东半岛近岸海域浒苔绿潮灾害严重;水母灾害呈上升趋势,对人体健康威胁较大,北海区滨海城市都曾发生过水母蛰伤致死案例;黄河三角洲区域米草和泥螺入侵扩展速度较快。面对这些海洋生态灾害巨大威胁,北海区亟需加强海洋生态灾害防控研究。     

Changes in morphological plasticity of Ulva prolifera under different environmental conditions: A laboratory experiment

The large-scale green tides, consisting mainly of Ulva prolifera, have invaded the coastal zones of western Yellow Sea each year since 2008, resulting in tremendous impacts on the local environment and economy. A large number of studies have been conducted to investigate the physiological traits of U. prolifera to explain its dominance in the green tides. However, little has been reported regarding the response of U. prolifera to changing environmental factors via morphological variation. In our experiments, we found remarkable morphological acclimation of U. prolifera to various temperature (20 and 25 °C) and salinity (10, 20, and 30) conditions. U. prolifera had more, but shorter branches when they were cultured at lower temperature and salinity conditions. To investigate the significance of these morphological variations in its acclimation to changes of environmental factors, physiological and biochemical traits of U. prolifera grown under different conditions were measured. Higher temperature increased the relative growth rate while salinity did not affect it. On the other hand, higher temperature did not enhance the net photosynthetic rate whilst lower salinity did. The increased net photosynthetic rate at lower salinity conditions could be attributed to more photosynthetic pigments—chlorophyll a, chlorophyll b, and carotenoids—in thalli due to there being more branches at lower salinity conditions. Increased numbers of branches and thus an increased intensity of thalli may be helpful to protect thalli from increased osmotic pressure caused by lower salinity, but it led to more shading. In order to capture enough light when being shaded, thalli of U. prolifera synthesized more photosynthetic pigments at lower salinity levels. In addition, higher temperature increased nitrate reductase activity and soluble protein content but variations in salinity did not impose any effect on them. Our results demonstrate conclusively that U. prolifera can acclimatize in the laboratory to the changes of environmental factors (salinity and temperature) by morphology-driven physiological and biochemical variation. We suggest that the morphological plasticity of U. prolifera may be an important factor for it to outcompete other algal species in a changing ocean.     

Comparative study on mitogenomes of green tide algae

Since 2007, the annual green tide disaster in the Yellow Sea has brought serious economic losses to China. There is no research on the genetic similarities of four constituent species of green tide algae at the genomic level. We previously determined the mitochondrial genomes of Ulva prolifera, Ulva linza and Ulva flexuosa. In the present work, the mitochondrial genome of another green tide (Ulva compressa) was sequenced and analyzed. With the length of 62,311 bp, it contained 29 encoding genes, 26 tRNAs and 10 open reading frames. By comparing these four mitochondrial genomes, we found that U. compressa was quite different from the other three types of Ulva species. However, there were similarities between U. prolifera and U. linza in the number, distribution and homology of open reading frames, evolutionary and codon variation of tRNA, evolutionary relationship and selection pressure of coding genes. Repetitive sequence analysis of simple sequence repeats, tandem repeat and forward repeats further supposed that they have evolved from the same origin. In addition, we directly analyzed gene homologies and translocation of four green tide algae by Mauve alignment. There were gene order rearrangements among them. With fast-evolving genomes, these four green algal mitochondria have both conservatism and variation, thus opening another window for the understanding of origin and evolution of Ulva.     

Spatiotemporal variations of inorganic nutrients along the Jiangsu coast,China, and the occurrence of macroalgal blooms (green tides) in the southern Yellow Sea

Large macroalgal blooms (i.e. green tides of Ulva prolifera) occurred in the southern Yellow Sea, China, yearly from 2007 to 2016. They were among the largest of such outbreaks around the world, and these blooms likely originated along the coast of the Jiangsu Province, China. Understanding the roles of nutrients in the onset of these macroalgal blooms is needed to identify their origin. This study analyzes the spatiotemporal variations in dissolved inorganic nitrogen and phosphorus (DIN and PO₄–P) and the N/P ratio along the Jiangsu coast from 1996 to 2014 during late-March to April, the months which corresponds to the pre-bloom period of green tides since 2007. A zone of high DIN and PO₄–P concentrations has developed along the Jiangsu coast, between the cities of Sheyang and Nantong, since 1996. There was an 18-year trend of increasing DIN concentrations during the pre-bloom period as well as a positive correlation between the U. prolifera biomass and DIN concentrations. Nutrient inputs from rivers and mariculture in the Jiangsu Province may have provided nitrogen that contributed the magnitude of macroalgal blooms that subsequently spread into the southern Yellow Sea.     

渤海浒苔属绿藻调查

于2009年至2010年对渤海及其周边10个沿海城市和6个岛屿的浒苔属绿藻进行了调查,初步确定该海区缘管浒苔、肠浒苔、扁浒苔、浒苔、条浒苔5个种类的地理分布情况。并对生物量进行了评估。与历史资料相比,渤海中辽东湾、渤海湾和莱州湾三个湾内的浒苔多样性和生物量下降明显或保持较低水平,湾周边地区则维持较高水平。此外,在近海人工基质上,以浒苔属为主的绿藻相对于红藻、褐藻分布更为广泛。     

东海具齿原甲藻的扫描电子显微结构

在光学显微镜分析鉴定的基础上,通过高分辨率的扫描电子显微镜,对东海赤潮原甲藻标本和美国国家海洋藻种中心(CCMP)的具齿原甲藻(Prorocentrum dentatum)藻株(CCMPl517)的细胞表面结构进行观察和比较,认为两者为同一种类．在分析大量文献资料的基础上,可以认为发生在我国东海水域的赤潮原甲藻种类是具齿原甲藻(Prorocentrum dentatum),而非新种．