The Critical Role of Bioturbation for Particle Dynamics, Priming Potential, and Organic C Remineralization in Marine Sediments: Local and Basin Scales
The Critical Role of Bioturbation for Particle Dynamics, Priming Potential, and Organic C Remineralization in Marine Sediments: Local and Basin Scales
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DOI：
10.3389/feart.2019.00157
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发表时间：
2019-06-25
影响因子：
2.9
通讯作者：
Cochran, J. Kirk
中科院分区：
文献类型：
--
作者：
Aller, Robert C.;Cochran, J. Kirk
生物扰动以多种方式促进沉积有机物（C-org）的启动和完全再矿化。一个主要的本地模式是注入反应Corg从水柱，表面沉积物，粘液分泌物到存款。在底栖动物的摄食、挖洞和建造活动中，不稳定的基质在很宽的时间尺度、几何形状和深度范围内与更难降解的材料密切相关，从而增强了反应性较低的组分的分解（引发）。这些局部相互作用的一个量度是粒子混合系数D-B，它可以从粒子反应性放射性核素进入沉积物的平均穿透率来估计。在长岛湾，一个河口系统与天然存在的放射性核素的明确来源的D-B的模式，显示一致的正相关性之间的D-B和总库存过剩Th-234（t（1/2）= 24天）和Pb-210（t（1/2）= 22年）在当地和流域尺度。这些相关性，在Th-234的情况下保持季节性，不仅证明了来自莱顿的渗透，在每月的生物扰动期间，（类似于5-10厘米）到年代际时间尺度（类似于20-100 cm）而且，作为改造的强度，增大在长岛海峡，沉积叶绿素a分布和底栖营养物再生（例如，NH 4+通量）反映了这些颗粒交换过程。盆地和区域规模的捕获不稳定的基质进入生物扰动沉积物一般可以证明，例如，沿着高生产力的哈特拉斯角大陆边缘。因此，总矿化和净矿化必然随着沉积物中不稳定颗粒基质数量的生物增强而增加。这种反应性和难降解底物的捕获、混合和紧密结合（还原剂混合），以及因此引发潜力的优化，代表了重要的、经常被忽视的途径，通过该途径，生物扰动产生有利于最大效率的生物矿化的生物地球化学条件。
Bioturbation promotes priming and total remineralization of sedimentary organic matter (C-org) in multiple ways. A primary local mode is the injection of reactive Corg from the water column, surface sediment, and mucus secretions into deposits. During feeding, burrowing, and construction activities by benthic fauna, labile substrates are brought into close association with more refractory material over a wide range of time scales, geometries, and depths, enhancing decomposition of the less reactive components (priming). One measure of these local interactions is the particle mixing coefficient, D-B, which can be estimated from the averaged penetration of particle-reactive radionuclides into deposits. Patterns of D-B in Long Island Sound, an estuarine system with well-defined sources of naturally occurring radionuclides, show consistent positive correlations between D-B and total inventories of excess Th-234 (t(1/2) = 24 days) and Pb-210 (t(1/2) = 22 years) at local and basin scales. These correlations, maintained seasonally in the case of Th-234, demonstrate not only the penetration of plankton-derived, reactive Corg into deeper regions of deposits during bioturbation over monthly (similar to 5-10 cm) to decadal timescales (similar to 20-100 cm) but also the enhanced capture of labile substrates from the water column across basin scales into bioturbated patches as the intensity of reworking increases. In Long Island Sound, sedimentary Chl-a distributions and benthic nutrient regeneration (e.g., NH4+ fluxes) reflect these particle exchange processes. Basin and regional scale capture of labile substrates into bioturbated deposits can be generally demonstrated, for example, along the highly productive Cape Hatteras continental margin. Thus, total and net remineralization necessarily increase with the biogenic enhancement of the quantity of labile particulate substrate in deposits. This capture, intermixing, and close association of reactive and refractory substrates (reductant blending), and thus the optimization of priming potential, represent important, often overlooked, pathways by which bioturbation generates biogeochemical conditions conducive to maximum efficiency of remineralization.