The distribution of green algal micro-propagules and macroalgae at the early stage of green tide in the coastal area of South Jiangsu Province in 2014

An integrated investigation was carried out during late April to late May of 2014 in the coastal area of South Jiangsu Province to understand the early development of green tide in the Yellow Sea and discover the temporal and spatial distribution of green algal micro-propagules and macroalgae at the early stage of green tide. The results showed that green algal micro-propagules distributed in all stations from late April to late May, and micro-propagules of high density( 300 ind. L~(-1)) concentrated in the adjacent Porphyra aquaculture area. Floating macroalgae were initially observed in the northern survey areas, and increased gradually. The dominant species was U. prolifera in the floating macroalgae, ranging between 90% and 100%. The seawater surface temperature and salinity in the above mentioned time period were suitable for the growth of macroalgae. This work can help government to strengthen management to reduce the blooms of macroalgae in the coastal area of South Jiangsu Province and also facilitate the decision-making for managers at the early stage of green tide.     

A New Molecular Label Applied to the Study of the Yellow Sea Green Tide

From 2007 to 2017, large-scale green tides occurred every year in the Yellow Sea of China, and Ulva prolifera was the main species leading to the green tide. In this study, we used the Polymerase chain reaction and 3' Rapid-amplification of c DNA ends technique to amplify the nr DNA-LSU and IGS sequences in U. prolifera and one species of Blidingia. These techniques showed 3259 bp of nrD NA-LSU and 3388 bp of IGS in U. prolifera and 3282 bp nr DNA-LSU and 3059 bp IGS in Blidingia sp. At the same time, tandem repeats, short dyads, palindromic and multiple simple repeat sequences in the IGS sequence were found by analyzing the structure of the IGS sequence in U. prolifera and Blidingia sp. G + C contents of the IGS sequence in U. prolifera and Blidingia sp. were 52.42% and 53.09%, respectively. We divided the U. prolifera into two types according to the morphological characteristics. Although the specimens of U. prolifera from the Qingdao coastal area, Jiangsu coastal area and the Yellow Sea have different morphologies, their ITS and IGS sequences are almost identical. Therefore, the main species of the green tides in the Qingdao coastal area, Jiangsu coastal area and the Yellow Sea are the same and have the same origin.     

Flocculation of Ulva microscopic propagules using modified clay: a mesocosm experiment

Microscopic propagules of Ulva species(UMPs) spread on Subei Shoal are believed to play a significant role in the formation of the Yellow Sea green tide.Previous laboratory and ship-based studies indicated that modified clay(MC) can effectively remove UMPs from the water column and restrict their germination.To evaluate the effectiveness of this method under natural conditions,a mesocosm experiment was conducted on the Zhugensha sandbank on Subei Shoal.The results show that the suspended particles on the sandbank would partially disturb the flocculation process between the MC and UMPs.However,the MC at a proper dose could effectively remove UMPs from the water column and decrease the adhesion and germination of UMPs on the nylon ropes that comprised the mariculture rafts by75%.This method was proven a potential strategy to restrict the initial biomass accumulation of green algae on Subei Shoal.However,field trials in larger time-space scales are still needed to assess the efficiency of this method when used in the open sea.     

Bacterial diversity in surface water of the Yellow Sea during and after a green alga tide in 2008

From May to August 2008, a large "green tide", consisting of the alga Ulva (Enteromorpha) prolifera, occurred in the Yellow Sea, China, affecting the local marine ecosystem and human activities. We investigated the influence of the green tide on the microbial community in the surface seawater, at four sites from July to August 2008, using bacterial 16S rRNA gene clone libraries. We sequenced 228 clones of unique patterns identified by restriction fragment length polymorphism (RFLP) techniques. The results show that 228 sequenced clones fell into six bacterial phyla:Proteobacteria, Bacteroidetes, Cyanobacteria, Verrucomicrobia, Actinobacteria, and Planctomycetes. Alphaproteobacteria (33%), Gammaproteobacteria (25%), Bacteroidetes (23%) and Cyanobacteria (9%) dominated the assemblage. Comparison between samples collected in July (during the tide) and those collected in August (after the tide) showed that, in the microbial community, diversities of Alphaproteobacteria and Cyanobacteria increased after the tide, while those of Gammaproteobacteria and Bacteroidetes decreased. These results indicate that the green tide influenced the growth of some bacteria, and provide information for further studies on the interactions and relationships between U. prolifera and the bacterial community. This study suggests that microbial community analysis is a good approach to monitoring green tides.     

Morphology and molecular identification of Ulva forming green tides in Qingdao, China

Green tides are caused by the proliferation of chlorophytes under suitable hydrographic conditions.These blooms lead to environmental degradation and negatively impact the waters and seagrass beds,as well as fishing and other recreational activities in the bay.A comprehensive ecological understanding of the bloom dynamics,including the origin and persistence,is needed to foster management decisions.The algae in the great majority of green tide blooms usually belong to two genera of Ulvophyceae,Ulva and Enteromorpha.Ulva has been observed more often in recent years.In China,green tides occurred for the first time in the middle area of the Yellow Sea in 2007,and a large-scale algae blooming broke out in the middle and southern areas of the Yellow Sea in late May 2008.We identified them as Ulva prolifera by comparative analysis of the rDNA internal transcribed spacer 1 (ITS1),5.8S and ITS2 sequences in combination with microscopic observation.Morphological differences were found between the free-floating algae and the attached thalli.Various reproduction patterns of the free-floating algae include sexual,asexual and vegetative propagations,which played important roles in the long-term green tide persistence in China.The ITS sequences of the blooming algae were identical to those of the samples from the Lianyungang sea area but were different from the attached samples from the Qingdao sea area.The results infer that the blooms are originated from other sea areas rather than from the local attached populations.     

The Ulva prolifera genome reveals the mechanism of green tides

The genome of green microalgae has rarely been reported.Ulva prolifera is a green microalga that has received much attention.Despite research articles about U.prolifera in recent years,we know very little about its genome.Therefore,the 87.9-Mb haploid genome(containing 10 311 protein-coding genes)of U.prolifera was studied,and the genome was compared with that of U.mutabilis,which is the only published Ulva species.Results showed that the two species are closely related.A phylogenetic tree was constructed among U.prolifera and other green algae available in GenBank,revealing the evolutionary status of U.prolifera in Chlorophyta.To understand why U.prolifer a could grow rapidly,we identified some genes related to growth,such as those involved in cell division,phosphorylation,and cell proliferation.In addition,genes related to stress resistance were found,which supports the notion that U.prolifera grows vigorously in nature.These results help to characterize green tides from a new perspective and reveal some important insight into the biology of U.prolifera.     

Pyrolytic characteristics and kinetics of the marine green tide macroalgae, Enteromorpha prolifera

The marine macroalgae Enteromorpha prolifera was one of the main algal genera that occurred in the widespread green tides in Qingdao, China, during the summers of 2007, 2008 and 2010. It is thus a plentiful source of biomass and could be used as a biofuel. In this study, the pyrolytic characteristics and kinetics of E. prolifera were investigated using thermogravimetric analysis (TGA) method. Cornstalk and sawdust were used as comparisons. Pyrolytic characteristics were studied using TG-DTG (thermogravimetry-derivative thermogravimetry) curves. Three stages in the pyrolytic process were determined: dehydration, dramatic weight loss and slow weight loss. E. prolifera was pyrolyzed at a lower initial temperature than the two terrestrial biomass forms. The apparent activation energy values for the three types of biomass were calculated and the mechanism functions were determined using 16 different mechanism functions, frequently used in thermal kinetics analysis. Activation energy values varied with mechanism function and the range of activation energy values for E. prolifera, cornstalk, and sawdust were 25-50 kJ/mol, 60-90 kJ/mol and 120-155 kJ/mol, respectively. This indicates that E. prolifera has low thermal stability for pyrolysis and good combustion characteristics.     

Introduction,spat-rearing and experimental culture of bay scallop,Argopecten irradians lamarck

Bay scallops were introduced from the east coast of the U.S. into China to shorten the economic turn-over from 2 to 1 year. Parent scallops were carried to Qingdao on Dec. 20, 1982 and stocked in indoor tanks at controlled temperature and fed with a mixture ofPhaeodictylum tricornutum, Pyramimonas sp. andChlorella sp. They spawned on Jan. 26 of the next year. The larvae were reared at a temperature of 18–21°C and fed withIsochrysis galbana, Pyramimonas sp. andChorella sp. In 4 weeks’ growing, the spats averaged 827 μm. They attained a height of 6.9 mm on May 9. In the middle of May, the seed scallops were transferred to Luoyuan Bay in Fujian Province, and Jiaozhou Bay, as well as the area off Taiping Jiao Cape, Qingdao, Shandong Province for experimental culture in plastic netcages suspended on a single line raft. Bay scallops cultured in Luoyuan Bay grew to an averaged shell height of 10.4 mm. In Jiaozhou Bay and the Taiping Jiao Cape culture area, they grew to 50 mm in average shell height (marketable size) and 26 g in average weight by late September; and attained 59 mm in average shell height (R. 39–75 mm) and 46 g in average weight in late December. The ovary and testis could be distinguished by color in August. In early September, eggs and sperms were collected for our laboratory where the second generation of seed scallops was successfully reared to suitable size for growing outdoor and breeding. This species can be harvested within a year after fertilization of the eggs, so we consider it suitable for culture in the Yellow Sea and East China Sea. This is the first reported successful introduction of Atlantic mollusks to the China Seas. This paper was published in Chinese inOceanologia et Limnologia Sinica 17 (5): 367–374, 1986.     

Comprehensive analysis of the origin of giant jellyfish near Qinhuangdao in summer

A massive bloom of the giant jellyfi sh Nemopilema nomurai occurred in waters off Qinhuangdao,a port city in Hebei Province,in July 2013.However,jellyfi sh larvae were not found in this location during the previous winter and spring.To determine the possible origin of the giant jellyfi sh medusa in the Bohai Sea,we developed a backward particle-tracking model and a series of numerical simulations were conducted by using the hydrodynamic,three-dimensional Regional Ocean Modeling System(ROMS)results.The simulated results showed that passive particles,representing jellyfi sh medusae,released in surface waters at diff erent dates during the summer had consistent trajectories.Particles released at the sea surface on August1 and 15 could be traced back to the center of the Bohai Sea and to waters between Feiyan Shoal and the new Huanghe(Yellow)River estuary.Particles released on July 1 and 15 could also be traced back to the center of the Bohai Sea and to waters between Feiyan Shoal and only to Zhuangxi tide station.However,none of the particles released in the middle and bottom water layers could be traced back to those areas.Based on the results of the numerical simulations,the distribution characteristics of seafl oor sediments,and observational data for giant jellyfi sh in the region,we suggest that waters between Feiyan Shoal and the new Huanghe River estuary are the likely origin of giant jellyfi sh observed near Qinhuangdao in summer.     

Impact of estuarine reclamation projects on saltwater intrusion and freshwater resource

Estuarine projects can change local topography and influence water transport and saltwater intrusion. The Changjiang (Yangtze) River estuary is a multichannel estuary, and four major reclamation projects have been implemented in the Changjiang River estuary in recent years: the Xincun Shoal reclamation project (RP-XCS), the Qingcao Shoal reclamation project (RP-QCS), the Eastern Hengsha Shoal reclamation project (RP-EHS), and the Nanhui Shoal reclamation project (RP-NHS). The effects of the four reclamation projects and each project on the saltwater intrusion and water resources in the Changjiang River estuary were simulated in a 3D numerical model. Results show that for a multichannel estuary, local reclamation projects change the local topography and water diversion ratio (WDR) between channels and influence water and salt transport and freshwater utilization in the estuary. During spring tide, under the cumulative effect of the four reclamation projects, the salinity decreases by approximately 0.5 in the upper reaches of the North Branch and increases by 0.5–1.0 in the middle and lower reaches of the North Branch. In the North Channel, the salinity decreases by approximately 0.5. In the North Passage, the salinity increases by 0.5–1.0. In the South Passage, the salinity increases by approximately 0.5 in the upper reaches and decreases by 0.2–0.5 on the north side of the middle and lower reaches. During neap tide, the cumulative effects of the four reclamation projects and the individual projects are similar to those during spring tide, but there are some differences. The effects of an individual reclamation project on WDR and saltwater intrusion during spring and neap tides are simulated and analyzed in detail. The cumulative effect of the four reclamation projects favors freshwater usage in the Changjiang River estuary.

     

Effect of temperature and irradiance on the growth and reproduction of Enteromorpha prolifera J. Ag. （Chlorophycophyta, Chlorophyceae）

Effect of temperature and irradiance on growth and reproduction of Enteromorpha prolifera that bloomed offshore along the Qingdao coast in summer 2008, was studied. It was showed that E. prolifera propagated mainly asexually with specific growth rate (SGR) of 10.47 at 25°C/40 μmol m-2s-1. Under this condition, gametes with two flagellate formed and released in 5 days. At the beginning of the development, the unicell gamete divided into two cells with heteropolarity, and then the apical cell developed into thalli primordial cells, whereas the basal cell developed into rhizoid primordial cells. In 8-day culture, the monoplast gamete developed into juvenile germling of 240 μm in length. Unreleased gametes can develop directly within the alga body. E. prolifera could either reproduce through lateral branching or fragmenting except apomixis revealed by Microscopic observation. On aged tissue of E. prolifera, although the degraded pigments partially remained in faded algal filaments, numerous vegetative ceils could still divide actively in the algal tissues.     

Comparative chloroplast genomes of Ulva prolifera and U. linza (Ulvophyceae) provide genetic resources for the development of interspecific markers

Journal of Oceanology and Limnology - The green seaweeds Ulva linza and U. prolifera are closely related species. They usually co-occur widely and have important ecological significance as primary...     

Study of red tide prediction model for the Changjiang Estuary

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DNA barcoding assessment of green macroalgae in coastal zone around Qingdao,China

An assessment with assistance of DNA barcoding was conducted on green macroalgae in coastal zone around Qingdao, China, during the period of April–December, 2011. Three markers were applied in molecular discrimination, including the plastid elongation factor tufA gene, the internal transcribed spacer (ITS) region of the ribosomal cistron and rubisco large subunit gene 3′ regions (rbcL-3P). DNA barcoding discriminated 8 species, excluding species of genus Cladophora and Bryopsis due to failures in amplification. We ascertained and corrected 4 species identified by morphological methods for effectively assisting the classification. The gene tufA presented more advantages as an appropriate DNA marker with the strongest amplification success rate and species discrimination power than the other two genes. The poorest sequencing success largely handicapped the application of ITS. Samples identified by tufA and rbcL as Ulva flexuosa were clustered into the clade of U. prolifera by ITS in the neighbor-joining tree. Confusion with discrimination of the complex of U. linza, U. procera and U. prolifera (as the LPP complex) still existed for the three DNA markers. Based on our results, rbcL is recommended as a preferred marker for assisting tufA to discriminate green macroalgae. In distinguishing green-tide-forming Ulva species, the free-floating sample collected from the green tide in 2011 was proved to be identical with U. prolifera in Yellow Sea for ITS and rbcL genes. This study presents a preliminary survey of green macroalgae distributed in the coastal area around Qingdao, and proves that DNA barcoding is a powerful tool for taxonomy of green macroalgae.     

Analysis of expressed sequence tags from the Ulva prolifera (Chlorophyta)

In 2008, a green tide broke out before the sailing competition of the 29th Olympic Games in Qingdao. The causative species was determined to be Enteromorpha prolifera (Ulva prolifera O. F. Müller), a familiar green macroalga along the coastline of China. Rapid accumulation of a large biomass of floating U. prolifera prompted research on different aspects of this species. In this study, we constructed a nonnormalized cDNA library from the thalli of U. prolifera and acquired 10 072 high-quality expressed sequence tags (ESTs). These ESTs were assembled into 3 519 nonredundant gene groups, including 1 446 clusters and 2 073 singletons. After annotation with the nr database, a large number of genes were found to be related with chloroplast and ribosomal protein, GO functional classification showed 1 418 ESTs participated in photosynthesis and 1 359 ESTs were responsible for the generation of precursor metabolites and energy. In addition, rather comprehensive carbon fixation pathways were found in U. prolifera using KEGG. Some stress-related and signal transduction-related genes were also found in this study. All the evidences displayed that U. prolifera had substance and energy foundation for the intense photosynthesis and the rapid proliferation. Phylogenetic analysis of cytochrome c oxidase subunit I revealed that this green-tide causative species is most closely affiliated to Pseudendoclonium akinetum (Ulvophyceae).     

Impact of climatic change on sea surface temperature variation in Subei coastal waters,East China

Sea surface temperature （SST） variation in the Subei coastal waters, East China, which is important for the ecological environment of the Yellow Sea where Enteromorphaprolifera blooms frequently, is affected by the East Asian winter monsoon （EAWM）, El Nifio-Southem Oscillation （ENSO）, and Pacific Decadal Oscillation （PDO）. In this study, correlations between climatic events and SST anomalies （SSTA） around the Subei （North Jiangsu Province, East China） Coast from 1981-2012 are analyzed, using empirical orthogonal function （EOF） and correlation analyses. First, a key region was determined by EOF analysis to represent the Subei coastal waters. Then, coherency analyses were performed on this key region. According to the correlation analysis, the EAWM index has a positive correlation with the spring and summer SSTA of the key region. Furthermore, the Nifio3.4 index is negatively correlated with the spring and summer SSTA of the key region 1 year ahead, and the PDO has significant negative coherency with spring SSTA and negative coherency with summer SSTA in the key region 1 year ahead. Overall, PDO exhibits the most significant impact on SSTA of the key region. In the key region, all these factors are correlated more significantly with SSTA in spring than in summer. This suggests that outbreaks ofEnteromorpha prolifera in the Yellow Sea are affected by global climatic changes, especially the PDO.     

Antioxidant system responses in two co-occurring green-tide algae under stress conditions

Green tides have occurred every year from 2007 to 2014 in the Yellow Sea. Ulva prolifera(Müller) J. Agardh has been identified as the bloom-forming alga,co-occurring with U. intestinalis. We observed distinct strategies for both algal species during green tides. U. prolifera exhibited a high abundance initially and then decreased dramatically,while U. intestinalis persisted throughout. The antioxidant system responses of these two macroalgae were compared in the late phase of a green tide(in-situ) and after laboratory acclimation. Lipid peroxidation and antioxidant system responses differed significantly between the two. Malondialdehyde and hydrogen peroxide contents increased significantly in-situ in U. prolifera,but not in U. intestinalis. In U. prolifera,we observed a significant decrease in total antioxidant ability(T-AOC),antioxidant enzymes(SOD and Apx),and non-enzyme antioxidants(GSH and As A) in-situ. U. intestinalis showed the same pattern of T-AOC and SOD,but its Gpx,Apx,and GSH responses did not differ significantly. The results suggest that U. prolifera was more susceptible than U. intestinalis to the harsh environmental changes during the late phase of a Yellow Sea green tide. The boom and bust strategy exhibited by U. prolifera and the persistence of U. intestinalis can be explained by differences in enzyme activity and antioxidant systems.     

星载高光谱Hyperion数据在海滩涂调查应用中的分析

以江苏苏北地区为研究区,较系统地分析了目前世界上星载传感器中光谱分辨率最高的EO-1卫星Hyperion数据的基本特点和处理方法,研究了将图像的灰度值转变为辐射能量值和反射率的方法和步骤,并选取了15类典型地物,进行了样本采集、辐射亮度和反射率反演,最后对典型地物的光谱曲线进行综合分析研究,并概括了苏北沿海滩涂典型地物的基本光谱特征。     

Dynamic Diurnal Changes in Green Algae Biomass in the Southern Yellow Sea Based on GOCI Images

Macroalgae blooms of Ulva prolifera have occurred every summer in the southern Yellow Sea since 2007, inducing severe ecological problems and huge economic losses. Genesis and secular movement of green algae blooms have been well monitored by using remote sensing and other methods. In this study, green algae were detected and traced by using Geostationary Ocean Color Imager(GOCI), and a novel biomass estimation model was developed from the relationship between biomass measurements and previously published satellite-derived biomass indexes. The results show that the green algae biomass can be determined most accurately with the biomass index of green algae for GOCI(BIGAG), which is calculated from the Rsurf data that had been atmospherically corrected by ENVI/QUAC method. For the first time, dynamic changes in green algae biomass were studied over an hourly scale. Short-term biomass changes were highly influenced by Photosynthetically Available Radiation(PAR) and tidal phases, but less by sea surface temperature variations on a daily timescale. A new parameter of biomass changes(PBC), calculated by the ratio of the biomass growth rate to movement velocity, could provide an effective way to assess and forecast green tide in the southern Yellow Sea and similar areas.     

Effect of temperature and irradiance on the growth and reproduction of Enteromorpha prolifera J. Ag. （Chlorophycophyta,Chlorophyceae）

Effect of temperature and irradiance on growth and reproduction of Enteromorpha prolifera that bloomed offshore along the Qingdao coast in summer 2008, was studied. It was showed that E. prolifera propagated mainly asexually with specific growth rate （SGR） of 10.47 at 25℃/40 μmol m^-2s^-1. Under this condition, gametes with two flagellate formed and released in 5 days. At the beginning of the development, the unicell gamete divided into two cells with heteropolarity, and then the apical cell developed into thalli primordial cells, whereas the basal cell developed into rhizoid primordial cells. In 8-day culture, the monoplast gamete developed into juvenile germling of 240 μm in length. Unreleased gametes can develop directly within the alga body. E. prolifera could either reproduce through lateral branching or fragmenting except apomixis revealed by Microscopic observation. On aged tissue of E. prolifera, although the degraded pigments partially remained in faded algal filaments, numerous vegetative cells could still divide actively in the algal tissues.