Based on literature data and shipboard observations,this study investigated the main environmental characteristics of the seafloor topography,current field,front,and upwelling that are closely related to hypoxia occurrence off the Changjiang estuary.The physical processes of the plume front and upwelling off the Changjiang estuary in summer were coupled.The vertical distribution pattern of the plume front was closely related to the upwelling.By reviewing and analyzing the historical summer hypoxia events off the Changjiang estuary,we statistically demonstrated the spatial structure of the horizontal distribution of the hypoxic zone and investigated the location of occurrence zone of the hypoxia.We found that the dissolved oxygen(DO)concentration on the inner continental shelf off the estuary showed a"V"shape in relation to station depth.Therefore,we noted that the hypoxic water on the inner continental shelf mostly occurred on the slopes with steep seafloor topography.Base on the current understanding of the hypoxic mechanisms off the Changjiang estuary,we analyzed the biogeochemical mechanisms that could cause the steep terrain off the Changjiang estuary to become the main areas prone to summer hypoxia and explained the internal relations between the location of the hypoxic zone on the slopes and the plume front and upwelling.The plume front and upwelling off the Changjiang estuary and their coupling were important driving forces of summer hypoxia.The continuous supply of nutrients affected by the interaction of the plume front extension of the Changjiang Diluted Water(CDW)and upwelling and the favorable light conditions were important mechanisms causing the phytoplankton blooms and benthic hypoxia off the Changjiang estuary in summer.By analyzing oxygen utilization,organic carbon mineralization,and nutrient regeneration in the hypoxic zone,we observed that the significant oxygen utilization process off the Changjiang estuary in summer also mainly occurred near the steep slopes with front and upwelling features
Alexandrium catenella DH01 is a toxic dinoflagellate species that is able to not only produce paralytic shellfish toxins,but also cause harmful algal blooms along the coast of China.In this study,we presented a new protocol for specific labeling and detection of the cell surface proteins(CSPs) of A.catenella DH01 cells using CyDye difference gel electrophoresis(DIGE) fluor minimal dyes.CSPs were identified using two-dimensional gel electrophoresis(2-DE) and MALDI TOF-TOF mass spectrometry(MS).The results showed that the fluorescent cyanine dye Cy3 could specifically label the CSPs of A.catenella DH01,with minimal labeling of intracellular proteins.Among three protein extraction methods evaluated,the Trizol method was the most efficient to extract CSPs with respect to protein spot number and resolution.Forty-one CSPs were separated and identified from A.catenella DH01 by 2-DE,in which 14 were identified in the protein database using MALDI TOF-TOF MS analysis.This work represents the first attempt to investigate the CSPs of A.catenella using the CyDye DIGE fluor dyeing method that provides a potentially important tool for future comprehensive characterization of CSPs and elucidation of the physiological functions of CSPs in dinoflagellates.
LI ChengWANG DaZhiDONG HongPoXIE ZhangXianHONG HuaSheng
