Effects of experimentally increased near-bottom flow on meiofauna diversity and community structure in the ArcticOcean

Abstract

Effects of increased near-bottom flow velocities on the sedimentary environment and its associated small biota were studied in a long-term in situ experiment at 2500m water depth at the Deep-Sea Observatory HAUSGARTEN in the eastern Fram Strait. In 2003, the Remotely Operated Vehicle (ROV) “Victor 6000” was used to install a stainless steel flume of about 8.5m in length, consisting out of a 6m long passageway with a cross-section of 50×50cm and 3–4m wide funnel-like doorways to increase bottom currents by a factor of approximately 6. Sediment sampling for biochemical sediment analyses, bacterial studies and meiofaunal investigations (with special focus on the nematode communities) was carried out 4 years after the installation of the flume using the ROV “Quest 4000”. The data showed clearly reduced values for parameters indicating organic matter (food) availability in the sediments, and corresponding lower bacterial and meiofaunal densities inside the flume, compared to control sites outside the channel. Results suggest that increased near-bottom currents and food deficiency not only diminish sediment-inhabiting meiofaunal assemblages but also alter the meiobenthic composition. Compared to background sediments, the nematode community inside the flume evidently showed adaptations to the overall reduced food availability and a more heterogeneous environment due to generally increased and more turbulent flow velocities. The variable environmental conditions inside the flume have an effect not only on the number of genera present, but also on the identities of the genera and the functional composition of the nematode community.