Study On The Zooplankton Community In The Jiaozhou Bay And Its Adjacent Waters

The study of zooplankton was conducted on four cruises of investigation for the Jiaozhou Bay and its adjacent sea area in August.2006, December.2006, April.2007, October.2007. Zooplankton composition, abundance, biomass and dominant species in the area were studied. The zooplankton community structure and biodiversity were analyzed through multivariate analysis method. The correlations between zooplankton community and envionmental factors were also detected. The research can provide fundamental information for the long-term monitoring of zooplankton ecology in the Jiaozhou Bay and its adjacent waters.The main results of this research are as follows:1. A total of 124 zooplankton taxa were identified during four surveys. Including Protozoa(2 species), Coelenterata(38 species), Cladocera(4 species), Copepoda(29 species), other Arthropoda(11species), Chaetognatha(1 species), Urochordata (3 species), pelagic larvae(36 species). The species numbers presenting in the four cruises were:autumn>summer>winter>spring. The species number of Copepoda represented above 50% of pelagic crustacea species and was the most important component. The horizontal distribution of species number was highly correlated with depth, temperature and the density of phytoplankton in spring; And was highly correlated with temperature in summer and autumn, meanwhile, was highly correlated with depth in autumn; But there were no significance correlations with temperature, salinity, depth the density of phytoplankton in winter.2. The average abundance of zooplankton of the investigated area in spring, summer, autumn and winter was 2526ind/m3,176ind/m3,943ind/m3,199ind/m3, respectively, and an obvious trend of spring>autumn>winter>summer was obtained.3. The average biomass of zooplancton of the investigated area in spring, summer, autumn and winter was 1000.46mg/m3,107.89mg/m3,181.03mg/m3,130.78mg/m3, respectively, and an obvious trend of spring>autumn>winter>summer was obtained. 4. According to the zooplankton species composition and abundance at each station, three groups were distinguished by using the method of cluster analysis in spring, four groups in summer, three groups in autumn and winter. The relationship between enviromental factors and the zooplancton community structure was complicated. Meanwhile, factors played different roles in four seasons.5. The biodiversity, such as species number, Margalef richness, Pielou's evenness and Shannon-Weaner index of zooplankton of four seasons were compared. And biodiversity in the investigated area was higher in spring and autumn than that of in summer and winter.6. Seventeen species were identified as the dominant species in the research region in different seasons in accordance with their dominant values(Y). The composition of dominant species was different in every season, but four species Noctilucidae scientillans, Oithona similis, Paracalanus parvus and Sagitta crassa are always dominant in the four seansons. These four dominant species were researched in their horizontal distribution and diurnal vertical variations of abundance and the relationship with enviromental factors. The result shows that:(1)The average abundance of Noctilucidae scientillans of the investigated area in spring, summer, autumn and winter was 23109ind/m3,107ind/m3,4271ind/m3 and 476ind/m3 respectively, and an obvious trend of spring>autumn>winter>summer was obtained. The horizontal distribution of Noctilucidae scientillans was highly correlated with depth in spring but highly correlated with temperature in autumn, and there was no significance correlation with temperature, salinity, depth and the density of phytoplankton. The surface layer had the higher abundance compared with the bottom layer in the vertical distribution. (2) The average abundance of Oithona similis of the investigated area in spring, summer, autumn and winter was 791ind/m3,130ind/m3, 579ind/m3 and 342ind/m3, respectively; And an obvious trend of spring> autumn> winter>summer was obtained, same to the trend of Noctilucidae scientillans. The horizontal distribution of Oithona similis was highly correlated with the density of phytoplankton in autumn. The surface layer had the higher abundance compared with the bottom layer in the vertical distribution. The diurnal vertical variations of Oithona similis is obvious in spring, summer and autumn but little difference was observed in winter. Moreover, the diurnal vertical migration of Oithona similis in four cruises showed different characters. (3) The average abundance of Par acalanus parvus of the investigated area in spring, summer, autumn and winter was 161ind/m3,828ind/m3, 741ind/m3,430ind/m3, respectively; And an obvious trend of summer>autumn >winter>spring, different to the trend of Noctilucidae scientillans and Oithona similis. The horizontal distribution of Paracalanus parvus was highly correlated with depth in summer. The surface layer had the higher abundance compared with the bottom layer in the vertical distribution during the four seasons. The diurnal vertical variation of Paracalanus parvus was more obvious in summer and autumn. Paracalanus parvus goes up and down for two times in a day. Moreover, the diurnal vertical migration of Paracalanus parvus in four seasons shows different characters. The relationship between environmental factors and the distribution of Paracalanus parvus was complicated. However, the salinity, temperature, density of phytoplankton, and fish density do more to the distribution pattern. (4) The average abundance of Sagitta crassa of the investigated area in spring, summer, autumn and winter was 59ind/m3, 70ind/m3,81ind/m3,88ind/m3; And the tread of winter>autumn>summer>spring was not very obvious. The horizontal distribution of Sagitta crassa was highly correlated with the density of phytoplankton in spring and winter. The surface layer has the higher abundance compared with the bottom layer in the vertical distribution during the four seasons. In sum, zooplankton has diurnal vertical migration is a common phenomenon, and different species have differen patterns in different seansons and the environment facters play different roles about that.