Relative roles of Ekman transport and Ekman pumping in driving summer upwelling in the South China Sea(SCS) are examined using QuikSCAT scatterometer wind data.The major upwelling regions in the SCS are the coastal regions east and southeast of Vietnam(UESEV),east and southeast of Hainan Island(UESEH),and southeast of Guangdong province(USEG).It is shown that the Ekman transport due to alongshore winds and Ekman pumping due to offshore wind stress curl play different roles in the three upwelling systems.In UESEV,Ekman pumping and Ekman transport are equally important in generating upwelling.The Ekman transport increases linearly from 0.49 Sv in May to 1.23 Sv in August,while the Ekman pumping increases from 0.36 to 1.22 Sv during the same period.In UESEH,the mean estimates of Ekman transport and Ekman pumping are 0.14 and 0.07 Sv,respectively,indicating that 33% of the total wind-driven upwelling is due to Ekman pumping.In USEG,the mean Ekman transport is 0.041 Sv with the peak occurring in July,while Ekman pumping is much smaller(0.003 on average),indicating that the upwelling in this area is primarily driven by Ekman transport.In the summers of 2003 and 2007 following El Ni o-Southern Oscillation(ENSO) events,both Ekman transport and Ekman pumping decrease in UESEV due to the abnormally weak southwest monsoon.During the same events,however,Ekman transport is slightly enhanced and Ekman pumping is weakened in UESEH and USEG.
Aquatic animals are susceptible to sudden changes of their living environment but they adopt strategies to cope with adverse environmental challenges.Contamination by suspended solids,often associated with a dramatic change in the concentrations of important water-quality variables is a frequent occurrence in China's coastal waters and estuaries.Here we studied the impact of suspended solids on the activities of the antioxidant enzymes superoxide dismutase(SOD)and catalase(CAT),as well as adenosine triphosphates(including Na^(+)K^(+)-ATPase,Mg^(++)-ATPase,Ca^(++)-ATPase)and H^(+)K^(+)-ATPase in the gills and visceral mass tissues of the molluscan bivalve Sinonovacula constricta exposed(4,8,12,16,20,and 24 days)to various concentrations of suspended solids.Our results showed that the antioxidant enzymes cooperated closely to effectively scavenge superoxide anion free radicals and H2O2(which can ultimately inhibit gill activity)through the modification of SOD and/or CAT enzymatic activities.ATPases activity(considered to be a sensitive indicator of toxicity)could play an effective role in the maintenance of functional integrity of the plasma membranes as well as some other intracellular functions.After the exposure,a decrease in the Nat K^(+)-ATPase,Mg^(++)-ATPase,and Ca^(++)-ATPase activity of the gills was observed suggesting that they were inhibited by the treatments.These results also indicated that,from day 4 to day 16,exposure to high concentrations of suspended solids had an inhibitory effect on the activity of H^(+)-K^(+)-ATPase in the visceral mass of S.constricta.However,after a period of adaptation the H^(+)-K^(+)-ATPase activity was restored to original levels.Our results suggest that long-term exposure to high levels of suspended solids disturb osmoregulation,gastric acid secretion and digestion,cause oxidative damage,as a consequence of antioxidant enzymes inactivation which eventually damages the gills,affect the food intake and transformation,ultimately resulting in systems failure and eventually de
