珠江口自源有机颗粒物沉降对沉积物反硝化过程的影响

Effect of autochthonous particulate organic matter on the nitrogen removal inthe Pearl River Estuary sediment

由微生物主导、依赖有机物供给的反硝化过程是珠江口氮移除的主要途径之一,可有效地将生态系统中的固定氮转化为N2或N2O释放到大气中。珠江口水体存在大量富含多糖和蛋白的生源有机颗粒物,该类有机颗粒物沉降到底层,影响反硝化过程的机制迄今尚不明确。通过培养实验,分析了富含蛋白的中肋骨条藻(Skeletonema costatum)和多糖颗粒对珠江口沉积物反硝化速率和反硝化功能基因的影响。研究结果表明:这两类有机物的添加能够刺激微生物矿化过程的发生,16S rRNA丰度和反硝化过程有关的基因nosZ与nir S丰度显著提高,矿化发生同时能够有效的为沉积物脱氮过程提供碳源与能量,提高了反硝化速率。就有机质可利用性而言,富含蛋白的中肋骨条藻和多糖的生物利用性存在差异,在添加中肋骨条藻组中,因有机质中蛋白含量高于多糖组,有机质降解速率高于多糖组,其可利用性高于多糖类有机质,并且蛋白类物质矿化过程中产生的NH4+也比多糖组高,NH4+通过硝化作用转换为硝酸盐,继续为反硝化过程提供硝酸盐,因此添加中肋骨条藻组反硝化速率显著高于添加多糖组。总之水体中生源有机颗粒沉降促进了沉积物—水界面中氮移除过程,并且这种促进作用与生源有机颗粒的可利用性呈正相关。

Microbial mediated denitrification,which depends on the organic matter loading,is the most important nitrogen removal pathway in the Pearl River Estuary.There are a lot of autochthonous organic particulate matter rich in polysaccharides and proteins in Pearl River Estuary,and how this kind of sinking organic particulate matter affects the denitrification process at the sediment-water interface is not yet clear.The effects of protein-rich Skeletonema costatum and polysaccharide particles on the denitrification rate and denitrification function genes in the sediments of the Pearl River Estuary were analyzed by culture experiments.The results showed that the addition of these two kinds of organic matter into the sediment could stimulate the microbial remineralization process,and the abundances of 16S rRNA,nosZ and nirS genes related to denitrification process were significantly increased,indicating that remineralization could provide carbon source and energy for nitrogen removal process and increase denitrification rate.In terms of organic matter availability,in the algal addition,higher rate of degradation of organic matter and more NH4+produced from the remineralization were observed,due to higher content of protein than the added polysaccharide group.The highest denitrification rate was observed in the sediment with the addition of Skeletonema costatum,since more NH4+was converted to nitrate through nitrification and continued to provide nitrate to the denitrification process.The results showed that the deposition of autochthonous organic particles promoted the nitrogen removal process at the sediment-water interface and this promotion was positively correlated with their availability.