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Phylogenetic analyses of the genes involved in carotenoid biosynthesis in algae
Shanshan WANG, Lei ZHANG, Shan CHI, Guoliang WANG, Xumin WANG, Tao LIU, Xuexi TANG
doi: 10.1007/s13131-018-1178-4
Carotenoids play a crucial role in absorbing light energy for photosynthesis, as well as in protecting chlorophyll from photodamage. In contrast to the Streptophyta, few studies have examined carotenoid biosynthetic pathways in algae, owing to a shortage of datasets. As part of the 1000 Plants Project, we sequenced and assembled the transcriptomes of 41 marine macroalgal species, including 22 rhodophytes and 19 phaeophytes, and then combined the datasets with publicly available data from GenBank (National Center for Biotechnology Information) and the U.S. Department of Energy Joint Genome Institute. As a result, we identified 68 and 79 full-length homologs in the Rhodophyta and Phaeophyceae, respectively, of seven inferred carotenoid biosynthetic genes, including the genes for phytoene synthase (PSY), phytoene desaturase (PDS), ζ-carotene desaturase (ZDS), ζ-carotene isomerase (Z-ISO), prolycopene isomerase (crtISO), lycopene β-cyclase (LCYB), and lycopene ε-cyclase (LCYE). We found that the evolutionary history of the algal carotenoid biosynthetic pathway was more complex than that of the same pathway in the Streptophyta and, more specifically, that the evolutionary history involved endosymbiotic gene transfer, gene duplication, and gene loss. Almost all of the eukaryotic algae that we examined had inherited the seven carotenoid biosynthesis genes via endosymbiotic gene transfer. Moreover, PSY, crtISO, and the ancestral lycopene cyclase gene (LCY) underwent duplication events that resulted in multiple gene copies, and the duplication and subsequent divergence of LCYB and LCYE specialized and complicated the cyclization of lycopene. Our findings also verify that the loss of LCYE in both the microphytic rhodophytes and phaeophytes explains the differences in their carotenoid patterns, when compared to the macrophytic rhodophytes. These analyses provide a molecular basis for further biochemical and physiological validation in additional algal species and should help elucidate the origin and evolution of carotenoid biosynthetic pathways.
key words: carotenoid biosynthesis, algae, phylogenetic analysis
Distribution of green algae micro-propagules and their function in the formation of the green tides in the coast of Qinhuangdao, the Bohai Sea, China
Hongbin Han, Wei Song, Zongling Wang, Dewen Ding, Chao Yuan, Xuelei Zhang, Yan Li
doi: 10.1007/s13131-018-1278-1
Since 2015, a novel green tide has been recurring in the coastal areas of Qinhuangdao at the western coast of the Bohai Sea in China, threatening the environment and ecosystem of the Beidaihe seaside holiday resort along the coast. Micro-propagules of the green algae including gametes, spores, micro-germlings and micro-vegetative fragments play an important role in the formation of green tides. They serve as a " seed source” of green macroalgae, and their distributions could reflect and influence the " algae source” of green tides. In this study, monthly surveys in the inshore and offshore areas of the Qinhuangdao coast were conducted from April to September 2016 and in January 2017 to investigate the tempo-spatial distribution patterns and the biomass variations of the green algae micro-propagules. The obtained results show that micro-propagules were mainly distributed in the inshore areas with a significantly decreasing abundance towards offshore areas. Their biomass was highest in July and August, and lowest in winter. The areas that were affected by the green tides showed a remarkably higher abundance of micro-propagules compared to other areas. These micro-propagules could serve as the " seed” source of green tides. Their distribution patterns indicate that the green tide in the coastal areas of Qinhuangdao originated locally.
key words: green tides, micro-propagules, macroalgae, Qinhuangdao, Bohai Sea
The first record of Pavlova pinguis (Pavlovophyceae, Haptophyta) in China seas
Xiaodong ZHANG, Shuang YANG, Jun SUN, Yanlong QIAO, Jing WANG, Haijiao LIU
doi: 10.1007/s13131-018-1294-1
One strain of unicellular flagellated yellow-green algae was successfully isolated from the coastal area near Tianjin in the Bohai Sea in May 2015. The strain ranged from round to elongated in shape. Most of the cells possessed active motility, and some cells formed non-motile aggregation. Based on evidences from morphology, ultrastructure and molecular analysis, we identified the strain as Pavlova pinguis which belonged to Pavlovophyceae, Haptophyta. For Pavlovophyceae, only Pavlova viridis (Diacronema viridis) was reported in China seas prior to this study and it played an important role in aquaculture. This is the first record of Pavlova pinguis in Chinese waters.
key words: Pavlova, Pavlovophyceae, Haptophyta, morphology, 18S rRNA gene, China seas
Composition of algal pigments in surface freshen layer after ice melt in the central Arctic
Yanpei ZHUANG, Haiyan JIN, Fan GU, Yang ZHANG, Youcheng BAI, Zhongqiang JI, Yong LU, Jianfang CHEN
doi: 10.1007/s13131-017-1024-0
Seasonal meltwater input creates a thin freshen layer in surface seawater under ice, which largely shifts the algae assemblages. Our recent observation of photosynthetic pigments in the high Arctic showed that ice bottom and 5 m of seawater under ice contained relatively high concentration of fucoxanthin, while chlorophyll b and lutein were the major diagnostic pigments in ice-water interface and 0 m of seawater under ice. Additionally, a notable change of dominant phytoplankton occurred in the top 5 m of seawater under ice, from chlorophytes-dominated at surface to diatoms-dominated at 5 m depth, which might attribute to the sharp salinity gradient (salinity from 12.5 to 28.1) in the surface seawater under ice. Our results imply that phytoplankton community in surface layer under ice would become more chlorophytes in the future warming Arctic Ocean.
key words: the Arctic Ocean, seawater under ice, pigments, nutrients, phytoplankton community
Response of phytoplankton community to different water types in the western Arctic Ocean surface water based on pigment analysis in summer 2008
Haiyan JIN, Yanpei ZHUANG, Hongliang LI, Jianfang CHEN, Shengquan GAO, Zhongqiang JI, Yang ZHANG
doi: 10.1007/s13131-017-1033-z
Nutrients and photosynthesis pigments were investigated in the western Arctic Ocean during the 3rd Chinese Arctic Research Expedition Cruise in summer 2008. The study area was divided into five provinces using the K-means clustering method based on the physical and chemical characteristics of the sea water, and to discuss the distribution of the phytoplankton community structure in these provinces. CHEMTAX software was performed using HPLC pigments to estimate the contributions of eight algal classes to the total chlorophyll a (TChl a). The results showed that on the Chukchi Shelf, the Pacific Ocean inflow mainly controlled the Chl a biomass and phytoplankton communities by nutrient concentrations. The high nutrient Anadyr Water and Bering Shelf Water (AnW and BSW) controlled region have high Chl a levels and the diatom dominated community structure. In contrast, in the region occupied by low-nutrient like Alaska Coastal Water (ACW), the Chl a biomass was low, with pico- and nano-phytoplankton as dominated species, such as prasinophytes, chrysophytes and cryptophytes. However, over the off-shelf, the ice cover condition which would affect the physical and nutrient concentrations of the water masses, in consequence had a greater impact on the phytoplankton community structure. Diatom dominated in ice cover region and its contribution to Chl a biomass was up to 75%. In the region close to the Mendeleev Abyssal Plain (MAP), controlled by sea-ice melt water with relatively high salinity (MW-HS), higher nutrient and Chl a concentrations were found and the phytoplankton was dominated by pico- and nano-algae, while the diatom abundance reduced to 33%. In the southern Canada Basin, an ice-free basin (IfB) with the lowest nutrient concentrations and most freshened surface water, low Chl a biomass was a consequence of low nutrients. The ice retreating and a prolonged period of open ocean may not be beneficial to the carbon export efficiency due to reducing the Chl a biomass or intriguing smaller size algae growth.
key words: photosynthetic pigments, phytoplankton community, biological pump, organic carbon, ice retreat, Chukchi Sea and Canada Basin
Morphology, ultrastructure and phylogeny of Cyanothece sp. (Cyanobacteriaceae: Cyanophyceae) isolated from the eastern Indian Ocean
Xiaodong ZHANG, Shuang YANG, Jun SUN, Chao WU, Jing WANG, Guicheng ZHANG, Changling DING
doi: 10.1007/s13131-018-1297-y
One strain of unicellular greenish algae embedded by mucilage was successfully isolated from equatorial area in the Indian Ocean. Microscopic observation, ultrastructure features and genetic identification confirmed that the strain was closely related to Cyanothece sp., which was a cyanobacteria species with great ecological significance. Cells were solitary with oval or bacilliform shapes. Diameters of this strain were relatively small, ranging from 2.5 to 6.5 μm on average. Ultrastructure of cells was simple. Thylakoids were arranged parietal and keritomized content were observed in the thylakoid region. Various electron-transparent granules with low electron-dense region as well as cyanophycin or glycogen granules-like organelle and carbonxysomes were also observed. For pigment composition, the dominant pigments were chlorophyll a, β-Carotene, Zeaxanthin and an unknown pigment, contributing 23.8%, 26.1%, 14.7% and 15.7% to total pigments respectively. The phylogenetic analysis of 16S rRNA gene and nifH gene confirmed that Strain EIO409 was closely related with Cyanothece sp. .
key words: Cyanothece, cyanobacteria, morphology, 16S rRNA gene, nifH gene, Indian Ocean
Variation of bacterial community associated with Phaeodactylum tricornutum in response to different inorganic nitrogen concentrations
Feng SHI, Xiaoxue WEI, Jianfeng FENG, Yingxue SUN, Lin ZHU
doi: 10.1007/s13131-018-1272-7
Specific bacterial communities interact with phytoplankton in laboratory algal cultures. These communities influence phytoplankton physiology and metabolism by transforming and exchanging phytoplankton-derived organic matter. Functional bacterial groups may participate in various critical nutrients fluxes within these associations, including nitrogen (N) metabolism. However, it is unclear how bacterial communities and the associated algae respond to changes of phycosphere N conditions. This response may have far-reaching implications for global nutrient cycling, algal bloom formation, and ecosystem function. Here, we identified changes in the bacterial communities associated with Phaeodactylum tricornutum when co-cultured with different forms and concentrations of N based on the Illumina HiSeq sequencing of 16S rRNA amplicons. Phylogenetic analysis identified Proteobacteria and Bacteroidetes as the dominant phyla, accounting for 99.5% of all sequences. Importantly, bacterial abundance and community structure were more affected by algal abundance than by the form or concentration of inorganic N. The relative abundance of three gammaproteobacterial genera (Marinobacter, Algiphilus and Methylophaga) markedly increased in N-deficient cultures. Thus, some bacterial groups may play a role in the regulation of N metabolism when co-cultured with P. tricornutum.
key words: Phaeodactylum tricornutum, nitrogen concentrations, nitrogen forms, bacterial diversity, community structure, Gammaproteobacteria
Effects of key species mud snail Bullacta exarata (Gastropoda) on oxygen and nutrient fluxes at the sediment-water interface in the Huanghe River Delta, China
Baoquan Li, Tjeerd J. Bouma, Quanchao Wang, Laura M. Soissons, Francesco Cozzoli, Guanghai Feng, Xiaojing Li, Zhengquan Zhou, Linlin Chen
doi: 10.1007/s13131-019-1430-6
Since the mud snail Bullacta exarata was introduced for economic aquaculture in the Huanghe River (Yellow River) Delta in 2001, its quick population growth and expanded distribution make it a key-species in the intertidal zone of this area. This significantly contributed to the economic income of the local people, but its potential ecological impact on the benthic ecosystem remains unknown. A mesocosm study was conducted to test whether its bioturbation activities affect the microphytobenthos (MPBs; i.e., sedimentary microbes and unicellular algae) productivity and the nutrient exchange between the sediment-water interface. Our results show that the mud snail significantly impacted the dissolved oxygen (DO) flux across the sediment-water interface on the condition of normal sediment and light treatment, and significantly increased the ammonium efflux during recovery period in the defaunated sediment and dark treatment. The presence of micro- and meiofauna significantly increased the NH4-N flux in dark treatment. Whereas, in light treatment, these small animals had less effects on the DO and NH4-N flux between sediment-water interface. Our results provide better insight into the effect of the mud snail B. exarata on the ecosystem functioning via benthic fluxes.
key words: bioturbation, mud snail Bullacta exarata, oxygen flux, nutrient flux, benthic metabolism, Huanghe River (Yellow River) Delta
In situ diet of the copepod Calanus sinicus in coastal waters of the South Yellow Sea and the Bohai Sea
Xiaoyan YI, Yousong HUANG, Yunyun ZHUANG, Hongju CHEN, Feifei YANG, Weimin WANG, Donghui XU, Guangxing LIU, Huan ZHANG
doi: 10.1007/s13131-017-0974-6
Copepods are a key trophic link between primary producers and predatory animals at higher trophic levels in the marine ecosystem. Knowledge of the in situ composition of the copepod diet is critical for the accurate evaluation of trophic relationships and energy transfer in marine food webs. In this study, we applied a PCR-based cloning technique developed previously to investigate the in situ diet of Calanus sinicus, an ecologically important large-sized calanoid copepod that dominates in the shelf waters around China, Japan and Korea. Analyses of the 18S rDNA sequences obtained from the copepod diet revealed the diverse food composition of C. sinicus from two stations (Y19 in the South Yellow Sea and B49 in the Bohai Sea). A total of 43 operational taxonomic units (OTUs) were detected, which belonged to 13 diverse lineages: Bacillariophyta, Dinoflagellata, Dictyochophyceae, Chrysophyta, Katablepharidophyta, Pelagophyceae, Apusozoa, Hydrozoa, Ctenophora, Echinodermata, Tunicata, Chaetognatha and marine fungi. The results indicate that during an algae bloom, C. sinicus can graze on the bloom causative species. When the abundance of phytoplankton in ambient water is relatively low, C. sinicus can choose eggs, larvae, or organic particles/detritus of various metazoans, especially hydrozoans and ctenophores, as alternative food sources. Our result suggests that C. sinicus is an omnivorous species, and its prey choice may depend on the food availability in the ambient waters.
key words: copepod, in situ diet, molecular analysis, 18S rDNA, ciliate blocking primer
Reducing eutrophication risk of a reservoir by water replacement: a case study of the Qingcaosha reservoir in the Changjiang Estuary
Yizhong CHEN, Jianrong ZHU
doi: 10.1007/s13131-018-1183-7
Eutrophication of freshwater systems in cities is a major concern worldwide. Physical, biological and chemical methods have been used in eutrophic lakes and reservoirs to reduce their eutrophic state and algal biomass, but these approaches are not effective without a substantial reduction in nutrients input, which could take decades to achieve in the developing countries. This study aims to assess the risk of eutrophication and algal bloom in a coastal reservoir with high nutrient inputs to confirm the feasibility of inhibiting the reservoir's eutrophic state by hydrodynamic operations. A variety of water quality indexes (e.g., water temperature, secchi depth, dissolved oxygen, total nitrogen, total phosphorus, phytoplankton chlorophyll a) at five observed sites were investigated in the Qingcaosha reservoir, which located in the Changjiang Estuary, during the construction, trial and normal operation periods from 2009 to 2012. No water exchange happened during the construction from April 2009 to October 2010, and the water exchange increased during the trial from October 2010 to January 2011, and during normal operation period from January 2011. The comprehensive nutrition state index (TLI) calculated by several representative water quality indexes was adopted to evaluate the variation of the trophic state in the reservoir. The peak values of TLI reached 51 in the summer of 2009, and 55 in the summer of 2011, higher than the eutrophication threshold value 50. The lowest TLI, about 32, appeared in the summer of 2010. The values of TLI in other observation periods could keep under 50. The results showed that the reservoir could easily deteriorate into the eutrophic state because of excess nutrients and algal blooms in the summer of 2009 and 2011, while the eutrophication and algal blooms could be reduced by the lack of nutrients in 2010 or adequate water replacement in 2012. The temporal and spatial variations of water quality indexes were presented based on observation data and analysis. The adequate water replacement in the reservoir driven by tides was tested to be an efficient and economical method for controlling eutrophication and algae blooms in the water environment with high nutrient inputs.
key words: estuarine reservoir, eutrophic state, algal bloom, operation way

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