Much of the deep sea encompasses soft-sediment plains, with very few hard substrates for invertebrates to colonise. At first glance, these habitats seem barren, but they are actually teeming with life. Compared to organisms from shallow water, many animals here are quite small. In addition, most of the animals are infaunal, meaning they live within the sediment. During feeding and burrowing, these animals form a range of features called lebensspuren, defined as any type of sedimentary structure produced by a living organism. Sampling deep sea animals can be a challenge, and traditional methods of grabs and boxcores provide only a single snapshot of a small area to characterise broad regions. Underwater imagery facilitates the characterisation of biological communities over a larger area, but the quantification of biodiversity from video is often restricted to larger epifauna, thus reducing its utility to measure biodiversity in deep sea soft sediments where animals are often small or infaunal. High resolution still images provide an interesting avenue with which to quantify biological activity based on lebensspuren.
In this study, we used thousands of still images taken along the edge of the Eastern and Western margins of Australia to identify and characterise deep-sea lebensppuren. The features identified were compiled into a Lebensspuren Directory (Section 7), and the data was used to correlate abiotic factors to lebensspuren and to valuate whether the quantification of lebensspuren from still photographs is an appropriate technique for broadly quantifying biological activity and diversity in the deep sea (Sections 2 - 6).
