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>A Doubling of Microphytobenthos Biomass Coincides with a Tenfold Increase in Denitrifier and Total Bacterial Abundances in Intertidal Sediments of a Temperate Estuary
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A Doubling of Microphytobenthos Biomass Coincides with a Tenfold Increase in Denitrifier and Total Bacterial Abundances in Intertidal Sediments of a Temperate Estuary
Surface sediments are important systems for the removal of anthropogenically derived inorganic nitrogen in estuaries. They are often characterized by the presence of a microphytobenthos (MPB) biofilm, which can impact bacterial communities in underlying sediments for example by secretion of extracellular polymeric substances (EPS) and competition for nutrients (including nitrogen). Pyrosequencing and qPCR was performed on two intertidal surface sediments of the Westerschelde estuary characterized by a two-fold difference in MPB biomass but no difference in MPB composition. Doubling of MPB biomass was accompanied by a disproportionately (ten-fold) increase in total bacterial abundances while, unexpectedly, no difference in general community structure was observed, despite significantly lower bacterial richness and distinct community membership, mostly for non-abundant taxa. Denitrifier abundances corresponded likewise while community structure, both for nirS and nirK denitrifiers, remained unchanged, suggesting that competition with diatoms for nitrate is negligible at concentrations in the investigated sediments (appr. 1 mg/l NO3 -). This study indicates that MPB biomass increase has a general, significantly positive effect on total bacterial and denitrifier abundances, with stimulation or inhibition of specific bacterial groups that however do not result in a re-structured community.
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机译:地表沉积物是去除河口中人为来源的无机氮的重要系统。它们的特征通常在于存在微底栖生物(MPB)生物膜,例如通过分泌细胞外聚合物(EPS)和争夺养分(包括氮),可以影响下层沉积物中的细菌群落。在Westerschelde河口的两个潮间带表面沉积物上进行了焦磷酸测序和qPCR,其特征是MPB生物量有两倍的差异,但MPB组成没有差异。 MPB生物量增加一倍,总细菌丰度却成比例增加(十倍),而出乎意料的是,尽管细菌丰富度显着降低,并且社区成员明显不同,但大多数群落结构并未观察到差异,主要是非丰富的分类单元。反硝化剂的丰度也相同,而对于nirS和nirK反硝化剂的群落结构均保持不变,这表明在所调查的沉积物中,硅藻与硝酸盐的硝态氮竞争微不足道(大约1 mg / l NO3 - sup>) 。这项研究表明,MPB生物量的增加对总细菌和反硝化菌的丰度具有普遍的,显着的积极影响,但可以刺激或抑制特定的细菌群,但不会导致结构重组。
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