盐沼植物对沉积物间隙水营养盐分布的影响

通过2007年8月~2008年5月对长江口崇明东滩中部潮间带4个不同植被带沉积物间隙水营养盐进行季节观测来研究盐沼植物对沉积物间隙水营养盐分布的影响.结果表明,大型植物生长带间隙水的NH4+-N、PO43--P浓度低于光滩,尤其是夏、秋两季NH4+-N的浓度比光滩低1个数量级以上.在植物生长季节,间隙水各种营养盐含量要明显高于冬季,且植物生物量与间隙水氮、磷有明显的相关关系.氮盐受植物的影响最明显,NH4+-N在互花米草与芦苇带分别是44.21、74.38μmol.L-1,明显低于光滩与海三棱草带(分别是340.14、291.87μmol.L-1);NOx--N的浓度比NH4+-N低1~2个数量级,但以芦苇带最高(5.94μmol.L-1).沉积物-水界面分子扩散通量结果表明,潮滩沉积物是上覆水中SiO32--Si、NH4+-N、PO43--P的源,NOx--N(NO3--N、NO2--N的总和)的汇,其中NOx--N从上覆水向沉积物的扩散通量16.23μmol.(m2.h)-1]大于NH4+-N从沉积物向上覆水的扩散通量15.53μmol.(m2.h)-1].植物的生长还通过影响沉积物-水界面的物质交换与间隙水中营养盐比值及其与上覆水间营养盐比值,对毗邻富营养化河口生态系统营养盐结构起到调节作用.

Vegetation Influence on Nutrients Distribution in Pore Water of Salt Marsh Sediment

The variations of nutrients in pore water of salt marsh sediment were surveyed in the middle intertidal zone of Chongming Dongtan during August 2007 to May 2008 to identify plant impact on nutrients distribution. The results show that NH_4~+ -N and PO_4~(3-) -P concentrations are lower in pore water of Spartina altemiflora and Phragmites australis zones than in bare flat, and specially, NH_4~+ -N concentrations in summer and autumn decrease by one more orders of magnitude. Compared to winter, nutrients concentrations are obviously higher during the period of plant growth, and plant biomass is clearly correlative to nitrogen and phosphorus. Vegetation growth influences nitrogen content intensively. NH_4~+ -N concentrations in Spartina altemiflora and Phragmites australis zones are 44.21 and 74.38 μmol·L~(-1) respectively, distinctly lower than that in bare flat and Scirpus mariquete zone (340.14 and 291.87 μmol·L~(-1) respectively) . Moreover,NO_x~- -N concentration is one to two order ( s) of magnitude lower than NH_4~+ - N, and its highest value exists in Phragmites australis zone (5.94 μmol·L~(-1) ). The results of molecule diffusive flux of nutrients in the surface sediment-overlying water interface indicate that marsh sediment is the source for SiO_3~(2-) -Si, NH_4~+ -N and PO_4~(3-) -P, and the rank for NO_x~- -N (NO_3~- -N + NO_2~- -N), and NO_x~- -N flux from overlying water to sediment 16.23 μmol· (m~2 ·h)~(-1)] is higher than NH_4~+ - N flux from sediment to overlying water 15.53 μmol· (m~2 ·h)~(-1)] . Vegetation growth accommodates nutrient structure of the estuarine ecosystem by affecting sediment-water interface mass flux and nutrient ratios in pore water and overlying water.