Spatial and Temporal Oxygen Dynamics in Macrofaunal Burrows in Sediments: A Review of Analytical Tools and Observational Evidence

The availability of benthic O2 plays a crucial role in benthic microbial communities and regulates many important biogeochemical processes. Burrowing activities of macrobenthos in the sediment significantly affect O2 distribution and its spatial and temporal dynamics in burrows, followed by alterations of sediment microbiology. Consequently, numerous research groups have investigated O2 dynamics in macrofaunal burrows. The introduction of powerful tools, such as microsensors and planar optodes, to sediment analysis has greatly enhanced our ability to measure O2 dynamics in burrows at high spatial and temporal resolution with minimal disturbance of the physical structure of the sediment. In this review, we summarize recent studies of O2-concentration measurements in burrows with O2 microsensors and O2 planar optodes. This manuscript mainly focuses on the fundamentals of O2 microsensors and O2 planar optodes, and their application in the direct measurement of the spatial and temporal dynamics of O2 concentrations in burrows, which have not previously been reviewed, and will be a useful supplement to recent literature reviews on O2 dynamics in macrofaunal burrows.