Rapid oxygen drawdown in decay experiments on marine ( <i>Palaemon varians</i> ) and freshwater ( <i>Neocaridina davidi</i> ) shrimps

Abstract Soft tissue preservation in the fossil record provides valuable insights into the evolution of life. Anoxia, through its negative impact on aerobic bacteria and scavengers, plays a key role in the formation of such fossils. Experimental taphonomy has examined how chemical gradients affect the decay process, but little has been done to investigate the link between carcass decay and oxygen concentration in the water around it. Herein, decay experiments on marine and freshwater shrimps were conducted in closed and open systems. Using oxygen microsensors, it is shown that oxygen surrounding the carcasses is fully consumed shortly after the animal’s death in most environmental conditions. Early decay-induced anoxia was followed by substantial anaerobic decay of the major anatomical characters. The rapid decline in oxygen concentration in all settings suggests most decay proceeds anoxically, even in settings fully open to atmospheric diffusion.