Organic carbon remineralization rate in global marine sediments: A review

The remineralization of organic carbon (OC) in marine sediments has crucial implications for global carbon cycling and climate change. However, OC turnover rates differ significantly owing to complex spatiotemporal variations in sediment depositional conditions. This review discusses the dominant methodologies through laboratory or in situ methods to measure oxygen consumption or dissolved inorganic carbon production rates to assess OC remineralization rates. The influencing factors in marine sediments are briefly described, including characteristics of OC interactions with the sediment matrix, redox effect, temperature, and biotic activities. Lastly, we provide a comparison of the OC remineralization rates among near-shore (0–50 m), continental shelf and slope (50–2000 m), deep sea (2000–6000 m), and trench (>6000 m) sediments. The remineralization rates generally decreased with distance from the continent, excluding the trench region. While conditions such as redox oscillation, nutrient input, and temperature were severely influenced by global warming and human activities on large scales, reactions between OC and degradation functional genes of microorganisms helped to reveal the microbial scale of sedimentary OC remineralization. Thus, it is pivotal to understand both the processes of OC remineralization and the underlying mechanisms in marine sediments.