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Typhoons frequently affect the South China Sea (SCS), playing an important role in changing the coastal marine system. To determine which process has the greatest impact on material transport in the coastal marine area during a typhoon, the sea temperature, salinity, concentration of nutrients, chlorophyll-a, total suspended matter, and δ 13 C of particulate organic carbon (δ 13 C-POC) in the water column of coastal Northern SCS (NSCS) were measured during two cruises in June 2017, in the pre-and post-typhoon Merbok periods. The results show that all parameters changed significantly between the two periods. During the pre-typhoon period, stratification of nutrients and physicochemical parameters, combined to high nutrient concentrations, high temperature, and low salinity in the water column of the nearshore area, suggests that the nearshore area is influenced by the river diluted water originated in the coastal cities adjacent to our study area. In the offshore area, mineralization may be responsible for the high nutrient concentration in the bottom water. However, during the post-typhoon, the stratification of nutrients is less significant and their distribution more homogenous in the whole water column of the nearshore area. In the upper water, the nutrient concentration increased and the temperature decreased significantly. These results suggest that the enhanced vertical mixing induced by the typhoon was the dominant process in changing the nutrient distribution pattern in the coastal NSCS.

This paper first reported species composition and distribution of biomass, habitat density and characteristics of community structure of benthos. The result has showed that 64 species is first recorded from intertidal zone at Sanmen, of which, most are eurythermal and eurychoric species, and the predominant species are Bluecoat exert, Morale iridescent,Cerithidea cingulata, Lunatia gilva, Laternula marilina and Gaetice depressus etc. .The range of benthic biomass is from 234.25g/m2 to 440g/m2; and habitat density is from 955.0 ind./m2 to 2950.0 ind./m2. The vertical distribution has shown that species, biomass and habitat density sequence on the intertidal zone are middle tide region > low tide region > high tide region.

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