Neoichnological analysis of the Aleutian Trench: characterization of lebensspuren assemblages and seafloor bioturbation intensity on both sides of the trench

Abstract

At six deep-sea stations (water depth range of 4299–5327 m) on the slopes of the Aleutian Trench (AT), a neoichnological analysis was conducted based on lebensspuren assemblage characterization and seafloor bioturbation intensity (SBI). Lebensspuren assemblages and SBI were assessed at three stations on either side of the AT. This study investigated whether the AT creates two distinct biogeographic areas for the tracemaker community. A total of 17,150 lebensspuren were classified, corresponding to 55 morphotypes. Although the density of lebensspuren was higher at the northern slope stations, no significant differences in diversity and general lebensspuren assemblage composition were observed between the two slopes. These results suggest that the AT may not act as a natural geomorphic barrier for the tracemaker community. Overall, SBI calculations showed a strong negative correlation with Chl-a, sand concentration, total organic carbon, and bottom currents; while a strong positive correlation was observed with depth, silt concentration, and temperature. However, SBI associated with digesting lebensspuren assemblages appeared to have been primarily influenced, Chl-a, total organic carbon, clay and sand concentration. SBI associated with resting and locomotion lebensspuren assemblages are controlled by multiple factors such as depth, silt concentration, temperature, silicate, phosphate and nitrate. These findings highlight the complexity of deep-sea ecosystems for tracemaker communities and the significant role of different environmental factors on lebensspuren assemblages and SBI, reinforcing the importance of further research in these heterogeneous and understudied environments.