A model for microbial phosphorus cycling in bioturbated marine sediments: Significance for phosphorus burial in the early Paleozoic
A model for microbial phosphorus cycling in bioturbated marine sediments: Significance for phosphorus burial in the early Paleozoic
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DOI：
10.1016/j.gca.2016.05.046
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发表时间：
2016-09-15
影响因子：
5
通讯作者：
Wallmann, Klaus
中科院分区：
文献类型：
--
作者：
Dale, Andrew W.;Boyle, Richard A.;Wallmann, Klaus
用成岩作用模型模拟了海洋沉积物中颗粒有机碳(C-org)和磷(P)的成岩作用和埋藏过程。后者由穿过表层沉积物的动物在物理上混合(生物扰动)，并由穴居、管居的生物通风(生物灌溉)。模型使用经验数据库进行约束，该数据库包括C-org相对于有机P(C-org：P-org)和总反应P(C-org：P-reac)的埋藏率、C-org和P-org的埋藏效率以及无机碳/磷再生率。如果P-org在有氧呼吸过程中相对于C-org优先矿化，正如许多先前的研究所表明的那样，那么模拟的P-org池被发现完全耗尽。一个改进的模型纳入了依赖氧化还原的微生物合成聚磷酸盐和P-org(称为微生物P泵)，允许在好氧和厌氧呼吸过程中相对于C-org优先矿化大部分P-org池，并与数据库一致。应用该模型的结果表明，在动物所在的沉积物中，磷的埋藏得到了强烈的加强。动物将高度不稳定的P-org从矿化率最高的好氧沉淀层中混合，从而缓解了向底层水中扩散的PO43-通量。它们还扩大了微生物吸收磷的氧化还原生态位。该模型被应用于假设的早古生代陆架环境，当时是底栖动物第一次辐射的时期。结果表明，当时即使是浅层的生物扰动也可能对磷的埋藏产生重大影响。我们的模型支持了最近的一项研究，该研究提出，海洋沉积物中的动物群辐射导致了磷埋藏的增加，并可能稳定了大气中的O-2水平。这些结果也有助于解释地质记录中的C-org：P-org比值和P-org在古代海洋沉积物中的持久性。(C)2016爱思唯尔有限公司。保留所有权利。
A diagenetic model is used to simulate the diagenesis and burial of particulate organic carbon (C-org) and phosphorus (P) in marine sediments underlying anoxic versus oxic bottom waters. The latter are physically mixed by animals moving through the surface sediment (bioturbation) and ventilated by burrowing, tube-dwelling organisms (bioirrigation). The model is constrained using an empirical database including burial ratios of C-org with respect to organic P (C-org: P-org) and total reactive P (C-org: P-reac), burial efficiencies of C-org and P-org, and inorganic carbon-to-phosphorus regeneration ratios. If P-org is preferentially mineralized relative to C-org during aerobic respiration, as many previous studies suggest, then the simulated P-org pool is found to be completely depleted. A modified model that incorporates the redox-dependent microbial synthesis of polyphosphates and P-org (termed the microbial P pump) allows preferential mineralization of the bulk P-org pool relative to C-org during both aerobic and anaerobic respiration and is consistent with the database. Results with this model show that P burial is strongly enhanced in sediments hosting fauna. Animals mix highly labile P-org away from the aerobic sediment layers where mineralization rates are highest, thereby mitigating diffusive PO43- fluxes to the bottom water. They also expand the redox niche where microbial P uptake occurs. The model was applied to a hypothetical shelf setting in the early Paleozoic; a time of the first radiation of benthic fauna. Results show that even shallow bioturbation at that time may have had a significant impact on P burial. Our model provides support for a recent study that proposed that faunal radiation in ocean sediments led to enhanced P burial and, possibly, a stabilization of atmospheric O-2 levels. The results also help to explain C-org: P-org ratios in the geological record and the persistence of P-org in ancient marine sediments. (C) 2016 Elsevier Ltd. All rights reserved.