Eutrophication-driven sediment microbial processes can explain the regional variation in phosphorus concentrations between Baltic Sea sub-basins
Eutrophication-driven sediment microbial processes can explain the regional variation in phosphorus concentrations between Baltic Sea sub-basins
复制标题
DOI：
10.1016/j.jmarsys.2008.04.001
复制
发表时间：
2008-11-01
影响因子：
2.8
通讯作者：
Pitkaenen, Heikki
中科院分区：
文献类型：
--
作者：
Lehtoranta, Jouni;Ekholm, Petri;Pitkaenen, Heikki
尽管微生物铁和硫酸盐还原在水生环境中的生态意义，所涉及的过程一直很少在波罗的海沉积物研究。间接证据的基础上，我们得出结论，底部沉积物的非分层和贫营养的最北端，分层差和中营养的下北方，子流域的波罗的海已经容忍外部营养负荷相当不错，因为他们仍然是在铁还原和铁和磷的耦合循环盛行在表层沉积物中的状态。由于铁还原菌不能完全还原铁氧化物，部分铁结合磷可能永久埋藏在沉积物中。沉积物保持磷的良好能力导致水中低浓度的磷，这种状态反过来促进初级生产的磷限制。相比之下，沉积物的营养负载和分层的子盆地，芬兰湾（最富营养化的子盆地）和波罗的海适当的，似乎已经达到了硫酸盐还原是主要矿化途径的状态。硫酸盐还原，然后形成硫化物，导致三价铁氧化物的有效还原。随后，铁结合磷溶解到孔隙水中，并被输送到上覆水，而铁被掩埋的硫化物（非耦合铁和磷循环）。沉积物保留磷的能力是有限的;大量的生物可利用的磷酸盐存在于水体中，初级生产往往是有限的氮和广泛的蓝绿藻水华是常见的。我们认为，控制上述区域分布的铁和硫酸盐还原的决定性因素是不稳定有机质的沉积物和水动力的变化通量。当有机质通量达到临界阈值时，会引发硫酸盐还原，导致沉积物-水界面缺氧，从而导致底栖动物的崩溃和铁再氧化的抑制。驱动沉积物回到铁还原状态的唯一方法是大力减少波罗的海的生物可利用的氮和磷负荷，从而减少不稳定的有机物的沉积物的通量。即便如此，开采也可能需要有利的水动力条件。(C)2008 Elsevier B. V.保留所有权利。
Despite the ecological significance of microbial iron and sulphate reduction in aquatic environments, the processes involved have been poorly studied in Baltic Sea sediments. On the basis of indirect evidence, we conclude that the bottom sediments of the non-stratified and oligotrophic northernmost, and the poorly stratified and mesotrophic next northern, sub-basins of the Baltic have tolerated the external nutrient load rather well, as they are still in a state in which iron reduction and coupled cycling of iron and phosphorus prevail in the surface sediments. Since iron-reducing bacteria are unable to reduce ferric oxides completely, part of the iron-bound phosphorus may be permanently buried in the sediments. The good ability of the sediment to retain phosphorus results in low concentrations of phosphorus in water, a state that in turn promotes phosphorus limitation of primary production. In contrast, the sediments of the nutrient-loaded and stratified sub-basins, the Gulf of Finland (the most eutrophied sub-basin) and the Baltic Proper, appeared to have reached a state in which sulphate reduction is the dominant mineralisation pathway. Sulphate reduction followed by sulphide formation leads to efficient reduction of ferric oxides. Subsequently, iron-bound phosphorus dissolves into the pore water and is transported to the overlying water, whereas iron is buried as sulphides (uncoupled iron and phosphorus cycling). The capacity of sediments to retain phosphorus is limited; high amounts of bioavailable phosphate exist in the water column, primary production tends to be nitrogen limited and extensive blue-green algal blooms are common. We maintain that the decisive factors controlling the above regional distribution of iron and sulphate reduction are the flux of labile organic matter to the sediments and the variation in hydrodynamics. Sulphate reduction will be triggered when the flux of organic matter reaches a critical threshold value, resulting in anoxia at the sediment-water interface, followed by the collapse of benthic fauna and inhibition of iron re-oxidation. The only way to drive the sediments back into an iron-reduced state is to strongly reduce bioavailable nitrogen and phosphorus loading to the Baltic Sea, and thus the flux of labile organic matter to the sediments. Even so, recovery may also necessitate favourable hydrodynamic conditions. (C) 2008 Elsevier B.V. All rights reserved.