Abstract: In February (winter), 2012, an investigation was conducted on the chlorophyll a (Chl-a) and phaeopigments (Pha-a) contents and their distribution in the sediments of Daya Bay, and the relationships of the Chl-a in surface layer of the sediments with the environmental variables (water depth, temperature, transparency, granularity, nutrients, and TOC) were analyzed. The Chl-a and Pha-a in the sediments had the same source. The contents of Chl-a and Pha-a decreased significantly with increasing sediment depth, and there were several leaps in the vertical distribution of Chl-a and Pha-a, which might reflect the effects of bioturbation and environmental change. The Chl-a and Pha-a contents in the surface layer (0-1 cm) of the sediments varied from 0.98 to 1.55 μg·g^-1 and from 3.97 to 6.65 μg·g^-1, respectively, with the mean contents being 1.24 μg·g^-1 for Chl-a and 5.55 μg·g^-1 for Pha-a. The most important factor affecting the Chl-a content was the particle size of the sediments. The high proportion of sand in the sediments would provide more living space for microphytobenthos, but this type of sediments would save less Pha-a. The comparison between the Chl-a content in the sediments and in the upper water as well as in the other marine areas showed that the ratio of the Chl-a content in the sediments and in the upper water ranged from 50.28% to 150.79%, suggesting that the primary productivity in the sediments of coastal area should not be ignored.

Key words: rapeseed (Brassica napus), nitrogen application, waterlogging, yield, nitrogen use efficiency.