Age-dependent Bioturbation of Deep-sea Sediments: Tests of Mechanisms at Three Bathyal Sites

9527382掌握被称为生物扰动的动物取食和移动引起的沉积物混合的机制和速率，可能对深海海底的化学循环、微地层学和动物群落结构产生深远影响。最近对海底动物摄食的研究表明，它们摄取新沉积的高度有机颗粒。如果这种选择性进食普遍存在，基于单一生物扰动示踪的生物地球化学模型将提供关于生物扰动、微生物新陈代谢、沉积物成岩作用和地层形成的不可靠预测。这项研究将检验三种可供选择的机械假说：通过分析沉积物供给者肠道和不同大小的沉积物颗粒中的比率示踪活性。具体地说，示踪剂依赖的混合可能源于(1)沉积物喂食者对富含Th-234的颗粒的依赖大小的摄取，(2)沉积物喂食者对年轻的富含食物的颗粒的选择性摄取，与大小无关，或(3)动物洞穴中新沉积的颗粒的被动级联和/或主动隔离。***

9527382 DeMaster The mechanisms and rates of sediment mixing by the feeding and movements of animals,termed bioturbation, may profoundly influence chemical recycling, microstratigraphy, and faunalcommunity structure at the deep-sea floor. Recent studies of ingestion by bottom-dwelling fauna suggest they consume newly sedimented, highly organic particles. If such selective feeding is widespread, biogeochemical models, based on single bioturbation tracers, would provide unreliable predictions about bioturbation, microbial metabolism, sediment diagenesis, and strata formation. This study will test three alternative, mechanistic hypotheses by: assaying ratiotracer activities in deposit-feeder guts and on sediment particles of various sizes. Specifically, tracer-dependent mixing may result from (1) sizedependent ingestion of Th- 234-rich particles by deposit feeders, (2) selective ingestion of young, food-rich particles by deposit feeders, independent of size, or (3) passive cascade and/or active sequestering of newly deposited particles in animal burrows. ***