A brief overview of deep-sea neoichnology: recent advances and prospects for interpreting the trace fossil record

The deep sea is the largest ecosystem on Earth, yet it is still one of the least understood. Neoichnology is the study of modern interactions between fauna and substrates, which primarily occur through bioturbation. Unlike in shallow environments, deep-sea neoichnology is still in its infancy due to the cost and difficulty of exploration. This paper summarizes recent approaches in the field and future directions aimed at closing major knowledge gaps that ultimately can improve trace fossil interpretations. Considering the benthic fauna and the two main types of tracemakers, the manuscript is divided into two sections: (1) endobenthic and (2) epibenthic. The endobenthic bioturbation section covers the latest results and approaches for calculating bioturbation intensity (i.e. the biodiffusion intensity coefficient) and mixed layer depth. Additionally, it summarizes past and recent methods for characterizing the resulting fabric (i.e. biogenic sedimentary structure). The epibenthic bioturbation section covers recent advances in classifying lebensspuren morphotypes, i.e. biogenic traces left on the seafloor by the tracemakers, as well as diversity and density calculations and their applicability. The seafloor bioturbation intensity calculation is synthesized, and its limitations are discussed. Finally, the behavioral quantification of epibenthic tracemakers and their associated lebensspuren is discussed. The purpose of this contribution is to provide an overview of modern approaches to deep-sea neoichnological analysis and the current state of its procedures, limitations, and applicability when using trace fossils for paleoenvironmental reconstructions.