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  • 1
    Publikationsdatum: 2021-05-19
    Beschreibung: Phytoplankton, especially community characteristics, in coastal waters of Da Nang have not been well studied. This present study analyzed data of phytoplankton for diversity and abundance from surveys from 2002 to 2016 at 44 stations in the coastal Da Nang waters. A total of 316 taxa from 9 classes were identified: Dinophyceae (134 taxa), Mediophyceae (77 taxa), Coscinodiscophyceae (44 taxa), Bacillariophyceae (36 taxa), Cyanophyceae (3 taxa), Dictyochophyceae (2 taxa), Bacillariophyta classis incertae sedis (1 taxon), Conjugatophyceae (1 taxon) and Thecofilosea (1 taxon). A list of 36 species of potentially harmful microalgae was recorded in coastal waters of Da Nang. In which, Pseudo-nitzschia spp. often had higher cell densities in some locations during the northeast monsoon. Analyzing diversity indices in different locations showed that there were significance differences of Margalef and Shannon indices, low in estuarine area (CS) and higher in the south of Son Tra peninsula (NST). Meanwhile no strong differences of Pielou and Simpson indices were found among the locations. However, there were strong differences of Margalef, Simpson and Pielou indices, which were found over the three studied years (2004, 2005, and 2006), mainly in NST, the northeast of Son Tra peninsula (DBST) and Da Nang bay (VDN). Analysis of species accumulation curves indicated that only 56–95% of species was found compared to maximal expected species richness in all studied locations. DMS analysis showed that there was year-based similarity among the years (ca. 50% of similarity) of phytoplankton communities. Among the studied years, average phytoplankton cell densities in Da Nang bay and the northeast of Son Tra were higher than those in other years and locations. This present study on species richness, expected species richness and variation in phytoplankton abundance suggested that there is a need of increasing sampling efforts, especially in riverine area and DBST for better understanding of characteristics of phytoplankton communities in coastal Da Nang waters.
    Beschreibung: Published
    Schlagwort(e): Phytoplankton
    Repository-Name: AquaDocs
    Materialart: Journal Contribution , Not Known
    Format: pp. 43-58
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Publikationsdatum: 2021-05-19
    Beschreibung: Long-term variations of phytoplankton communities in coastal waters have been rarely studied in many places over the world and in Vietnam. We analyse variations in species number and abundance of phytoplankton in Van Phong bay, South Central Vietnam during the last three decades basing on data of various projects. These variations were remarkable and depended upon changes in seasons, tides, and sampling depths over the time. Scales of these changes reflected sampling locations, water-exchange intensities and the environmental characteristics of sampling site. There were lower numbers of species recorded before 2004 probably because of limitations in sampling and species identification. A total of 229 species taxa were identified during May 2013, in which 39 species were firstly recorded in the study waters. High cell densities were found in February 2004, November 2005, and October 2009, mostly during northeast monsoon. In summary, small cell - size diatoms of genera Chaetoceros, Pseudo-nitzschia, Bacteriastrum, and Skeletonema frequently dominated. However, by large species, e.g. Noctiluca scintillans and Rhizosolenia imbricata were occasionally dominant in carbon biomass.
    Beschreibung: Published
    Schlagwort(e): Phytoplankton
    Repository-Name: AquaDocs
    Materialart: Journal Contribution , Not Known
    Format: pp. 104-120
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Publikationsdatum: 2021-05-19
    Beschreibung: Red anchovy egg spawning in the wild is an isolated pelagic with elliptical form, the egg size is 0.93-1.39mm, average 1.23mm in length and 0.48 0.72mm in width. The egg membrane is transparent and smooth, with no oil globule. The yolk is roughly segmented and also has long elliptical form, the length ranges 0.81 - 1.08mm, the width ranges 0.39 - 0.57mm. The eggs have been spent the stages of development after fertilization. The yolk distributed throughout the egg, not yet matched the perivitelline space yolk, then the fish eggs cleaved cells appearing in the extreme of the perivitelline space yolk and egg membrane. The cells were cleaved and spread down to the embryo ring and wrapped the yolk. At the end stage of embryo development, the germ appeared membrane of dorsal, anal and tail fins and bud of pectoral fin with eyes without pigment and eggs were prepared to hatch. The egg development to stage IV was after about 4 hours at 31oC, but it was after 6 hours at 26oC. The eggs were hatched after 6 hours of cultured conditions and until 8 hours hatching rates got up to 40% for 31oC and the hatching of egg were started after 8 hours at 26oC. After 23 hours of culture in test plots, eggs were hatched completely at 31oC. The average hatching rate after 23 hours was 63.33% at 31oC and 52.50% at 26oC. The verification of the difference between two experimental plots of temperature effects on hatching rate over time by ANOVA test showed significant difference with FCalculated = 8.3〉 Fα= 5.3 (p〈0.05).
    Beschreibung: Published
    Schlagwort(e): Anchovy ; Ecrasicholina punctifer ; Embryonic development
    Repository-Name: AquaDocs
    Materialart: Journal Contribution , Not Known
    Format: pp. 99-107
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Publikationsdatum: 2021-05-19
    Beschreibung: Tidal effects on variability in species number, abundance and community structure of phytoplankton were analyzed using monitoring data during 20 years at Nha Trang marine monitoring station, Khanh Hoa province. CCA and SIMPER analysis showed that the impact of tide on phytoplankton community at surface was clearer than that at bottom. The average similarity percentage of species composition between high tide and low tide of surface communities (10.07%) was lower than that of bottom ones (14.17%) (p〈0.05, Kruskal-Wallis test). Small cell-size centric diatoms Chaetoceros spp. were dominant in cell density and correlated to tidal range while small cell-size unidentified dinoflagellates and pennate diatom Thalassionema frauenfeldii were in the opposite trends. Number of species, Shannon biodiversity index at surface layer were lower than those at bottom layer while cell density at surface layer (42.400 cells/L) was higher than that at bottom layer (19.200 cells/L) showing phytoplankton community at bottom layer was more diverse, and more stable than that at the surface one.
    Beschreibung: Published
    Schlagwort(e): Phytoplankton ; Tide
    Repository-Name: AquaDocs
    Materialart: Journal Contribution , Not Known
    Format: pp.188-200
    Standort Signatur Einschränkungen Verfügbarkeit
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