Abstract: Sediment chlorophylla (Chl-a) in intertidal zone is an indicator of the primary productivity of microphytobenthos in intertidal ecosystem. In order to understand the distribution patterns of the Chl-a in Spartina alterniflora salt marshes and bare flats at the Rudong coast of Jiangsu, surface (0-8 cm) sediment cores were collected from 11 sites in July and October 2010, with the Chl-a content determined. Except for the sites 1-5 in October, the vertical distribution of the Chl-a at other sites presented a similar trend, i.e., a rapid reduction with the depth in the top 2 cm and little change at the depth of 2-8 cm. The decrease of illumination was a major factor for this pattern. The horizontal distribution of the Chl-a in the salt marshes and bare flats was different between summer and autumn. In summer, the Chl-a content was higher in salt marshes than in bare flats; but in autumn, it was in adverse. Such a difference was due to the combined effects of illumination and sediment grain size. The shading of illumination and the trapping of finegrained sediment by S. alterniflora at its different growth stages varied, which directly affected the growth of benthic microalgae, and further, affected the primary productivity of microphytobenthos in the intertidal ecosystem.

Key words: PM_2.5, meteorological factors, forest stand.