| Samples of the seawater, sediment and animal were collected and analyzed for temperature, salinity, radiation, chlorophyll a in both sea water and sediment, species of phytoplankton and microphytobenthos, grain size and macrobenthos biomass in September 2007,April 2008 and July 2008 in the intertidal areas of the Yellow River Delta, as well as a monthly monitoring station from July 2007 to July 2008.The main results and conclusions are presented as follows:1.Environmental factorsTemperature of the seawater varied from 4.6-33.7℃(mean 17.3℃),with the minimum in December 2007 and maximum in August 2007.Seasonal changes in PAR was similar to that of temperature, varied from 387-851μEm-2 sec-1(mean 636μEm-2 sec-1),while salinity from 24.0 to 29.8 (averaged at 27.0).The sediment type was silt, unanimous and simple, while the median size increased from inshore to offshore areas.The median size varied from 0.030～0.081 mm(mean 0.045±0.014 mm)in 2007.9,0.025～0.067 mm(mean 0.043±0.013 mm)in 2008.4,as well as 0.030mm～0.069mm(mean 0.047±0.013 mm)in 2008.7.The sediment components were classified into two groups.One was the sediment component in July-December 2007 (mean 0.037 mm) with smaller median size, and the other was the sediment component in March-July 2008 (0.051 mm) with larger median size. The median size of sediment did not change significantly with depth, and the sediment types of each layer kept as silt.2.Distribution of chlorophyll aChlorophyll a in the overlying seawater ranged from 1.582 to 6.275 mg/m3 (average of 3.759 mg/m3)with the highest in 2007.7 and lowest in 2008.4.Chl-a concentrations in the surface sediment ranged at 4.749～0.426μg/g (mean value 1.591μg/g) in autumn and 5.195～0.307μg/g (mean value 1.832 ug/g) in summer. It show the tendency of increasing from the north to the south, especially in the near shore areas,while decreasing from high tide zone to low tide zone. Chl-a concentrations at 0～0.5 cm and 0.5～1 cm varied from 1.398～6.794μg/g and 0.630～3.342μg/g, respectively, in which Chl-a concentrations in 0～0.5 cm was 2 times higher than that in 0.5～1 cm.Chlorophyll a in sediment decreased with increasing depth vertically, varied from 0.157～5.255μg/g (mean 1.040μg/g),in which that within surface 1 cm accounted for 89.5% of that in the top 10 cm.3.Influencing factoresDIN:P of the overlying seawater in Yellow River Delta was 361.4 in April,42.4 in July, and 249.5 in September. Thus, P acted as the potential limiting factors on the growing and reproducing of benthic algae.Chl-a concentrations in the overlying water were effected by P, SPM, temperature and salinity while Chl-a concentrations in the surface sediment were effected by the grain size and stability. Analysis result suggested that soft, flat and stable sediment supported the growth and aggregation of microphytobenthos.4. Productivity15 dominant species was investigated in the southern yellow River Delta. The macrobenthic biomass plays the turn of summer> spring> autumn with the pattern of increasing from high tide zone to low tide zone and reaching to the maximum at the middle tide zone.The primary productivity of phytoplankton in the southern yellow River Delta varied from 0.2 to 29.6 mgC·m-2·d-1(averaged at 5.7 mgC·m-2·d-1).And the primary productivity of microphytobenthos was averaged at 79.507 mg/m2/h,was 6973.7 times higher than that of phytoplankton.The macrobenthos abundance in the monitoring station was 200 ind/m2/a, which equals to 63.21 g/m/a. The secondary productivity of the macrobenthos was averaged at 35.35 g/m2/a.Moreover, the secondary productivity of Mactra.Veneriformis Deshayes was 24.64 g/m2/a.5.Food source of Mactra. Veneriformis DeshayesChl-a in the surface sediment (72.047 mg/m2) was about 22.7 times higher than that in the seawater (3.759 mg/m2).And the microphytobenthos dominated in the overlying water for 68.3% in individual density. This suggested that the microphytobenthos might primarily support on the secondary production.The d13C abundance in the mussels of Mactra.Veneriformis Deshayes ranged from-18.73×10-3 to-21.02×10-3 (averaged at-19.82×10-3).The d13C abundance of the microphytobenthos was -22.93×10-3,and that of phytoplankton -17.74×10-3.It was calculated that microphytobenthos was the main food source for Mactra. Veneriformis Deshayes in 2008.7,which was agreed with the Chl-a distribution in the sediment and seawater.
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