Key Laboratory of Science and Engineering for Marine Ecological Environment

SOA, China

Key Laboratory of Science and Engineering for Marine Ecological Environment

SOA, China
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Wang Y.,Ocean University of China | Wang Y.,First Institute of Oceanography | Wang Y.,Key Laboratory of Science and Engineering for Marine Ecological Environment | Li R.,First Institute of Oceanography | And 7 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2011

As the most important primary producer in the marine ecosystem, phytoplankton forms the foundation of the structure and function of the marine food webs. Most of the primary productivity is turned into phytoplankton biomass, which is a good indicator to reflect the spatio-temporal distribution of marine organic matter production and dynamics of the phytoplankton community. Consequently, the estimation of phytoplankton biomass has ecological significance in marine ecosystem studies. Several methods have been established to estimate phytoplankton biomass, such as cell counting method, chlorophyll a determination method, cell carbon and nitrogen contents determination method, conversion of cell volume to biomass method etc. Among them, the conversion of cell volume to biomass method is relatively more accurate as with this method, the cell volume is worked out and organic matter content per cell was measured. The results could be used to address phytoplankton biomass at the cell level and the change of ecosystem function. Therefore, this method gradually becomes the most common and effective method to estimate phytoplankton biomass. The key of conversion of cell volume to biomass method is to study the relationship between cell volume and cell organic matter (carbon, nitrogen or others) content. In the past several decades, there were a number of studies on biomass of diatom, but fewer studies on dinoflagellates. It is needed to study dinoflagellates cell volume and cell organic matter contents. Ten common dinoflagellates were investigated to determine the relationship between cell volume and their contents of carbon and nitrogen. The morphological characteristics of ten species were observed using a Nikon ECLIPSE TE2000-U optical microscope. Then cell-geometry analogous models were built accordingly. The model of Alexandrium tamaren, Alexandrium affine and Protoceratium reticulatum is sphere, that of Akashiwo sanguinea, Amphidinium carterae, Prorocentrum donghaiense, Prorocentrum gracile and Prorocentrum minimum is ellipsoid, that of Gonyaulax spinifera circular cone and half sphere and Lingulodinium polyedra circular cone and circular truncated cone. From these models, the cell volumes for each dinoflagellate can be calculated by microscope measurement including cell length, width or diameter and breadth. Furthermore, cell carbon and nitrogen content was determined using a CHN analyzer. Then the relationships between both carbon and nitrogen contents and cell volume could be established. Large differences were observed among the ten dinoflagellates in cell volume, carbon and nitrogen contents. The range of cell volumes are from 2. 97 X102 μm3 (Amphidinium carterae) to 4. 50X104 μm3(Akashiwo sanguinea). Amphidinium carterae had the lowest carbon and nitrogen contents (54. 50 and 11. 42 pictogram per cell), while Gonyaulax spinifera had the greatest carbon and nitrogen contents (2238. 00 and 482. 28 pictogram per cell), showing a difference of a factor of 40. It was more appropriated to analyze these relationships by logarithmic models due to the wide range of cell volume, which was mentioned by Verity et al (1992). In the present study, the cell volume thus determined is positively correlated to their cell carbon and nitrogen contents significantly (P <0. 0001), which indicated that the cell carbon and nitrogen contents would increase with cell volume increased. On the other hand, the cell volume thus determined is negatively correlated to their cell carbon and nitrogen contents per unit volume significantly (P <0. 0001), which indicated that the smaller cells contained more carbon and nitrogen per unit volume. In order to allow conversion among cell volume, carbon and nitrogen, in the marine ecology field, it is important to establish regression equations between these parameters.


Fu M.Z.,First Institute of Oceanography | Fu M.Z.,Key Laboratory of Science and Engineering for Marine Ecological Environment | Sun P.,First Institute of Oceanography | Sun P.,Key Laboratory of Science and Engineering for Marine Ecological Environment | And 7 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

Phytoplankton plays a vital role in marine ecosystem functioning. It generates roughly 50% of the global primary production, affects the climate process and biogeochemical cycles and sets the upper limits to fishery yield. In addition, due to its fast population responses to water quality and environment stressors, phytoplankton is usually employed as an indicator for assessing eutrophication caused by excess nutrient input and ecosystem health. Jinzhou Bay (120°55′-121°14′E,40° 42′-40°52′N)is a small and shallow semi-enclosed bay in north China with a area of 151.5 km2 and an averaged depth of 3.5 m. It has a long history of heavy pollution featured by water column eutrophication and heavy metals contamination. Two cruises were carried out during August 2011 and May 2012 respectively to study the spatial distribution and assemblage structure of phytoplankton as well as their ecological responses to the environment changes. Surface water phytoplankton samples were collected at 26 stations and the relevant environmental parameters, i.e. water temperature, salinity, pH, DO, SPM, and nutrient (nitrate, phosphate, silicate) concentrations were measured or sampled simultaneously. The phytoplankton assemblages in Jinzhou Bay were mainly composed by diatom and dinoflagellates groups, and most of them were temperate coastal types. A total of 62 species belong to 4 phylum and 41 genera were identified in the summer and spring cruises. Diatoms were dominant both in species number and cell abundance, with a relatively higher proportion of benthic species. The phytoplankton community structures were significantly different between the two sampling periods. In August 2011, the average cell abundance was 41.44×103 cell/ L and the first two dominant species were Thalassiosira spp. and Cerarium furca. In May 2012, the average cell abundance was 13.80×103 cell/ L and the first two dominant species were Cylindro thecaclosterium and Skeletonema costatum. The species diversity was relatively higher in spring (mean 2.46) than in summer (mean 1. 98). Multivariate ordination techniques were employed to explore the relationships between phytoplankton species and environmental parameters by CANOCO 4.5. Detrended correspondence analysis (DCA) for the species data showed the maximum gradient length was lower than 3, therefore linear model was applied. Furthermore, the results of redundancy analysis (RDA) indicated that nitrate concentrations and water temperature was the most important influencing factor in summer and spring respectively. Compared with the historic data, the dominant phytoplankton species significantly changed during the last 30 years. Smaller-sized phytoplankton and the species typically found in the eutrophicated environment tended to dominant in Jinzhou Bay. In contrast, the Chaetoceros sp. and Coscinodiscus sp. which were common and important in coastal areas, were both low in species number and cell abundance. This variation trend suggested that the culture eutrophication together with other contaminants might produce certain impacts to the species composition of phytoplankton community in Jinzhou Bay. Systematic and long-term monitoring and study is needed to reveal the ecological responses of phytoplankton assemblage to environment changes and to identify the species capable of indicating the water column eutrophication and heavy metal pollution status of Jinzhou Bay.

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