Effects of dropstone-induced habitat heterogeneity on Arctic deep-sea benthos with special reference to nematode communities

Abstract

During an expedition to the deep-sea long-term observatory HAUSGARTEN in the eastern Fram Strait in summer 2003, the availability of a Remotely Operated Vehicle allowed a targeted sampling of surface sediments around a relatively large dropstone (0.9 m²) to determine suspected differences in community structure and dynamics of nematode assemblages in relation to the confined flow regime and patchy food availability in the immediate vicinity of the stone. The almost rectangular dropstone was about 150 cm in length, 60 cm in width, and up to 15 cm in height. Small-scale current measurements around the dropstone using a MAVS-3 acoustic current meter exhibited a rather complex pattern. A computational fluid dynamics simulation revealed areas of constantly flowing near-bottom currents as well as the generation of vortices in certain areas around the dropstone. Concentrations of biogenic compounds in the sediments surrounding the dropstone generally followed the complex flow pattern. The differences in physical and biochemical conditions around the dropstone were reflected in species composition and diversity, trophic structure and life-history traits of the nematode communities, and to a lesser extent in their total abundance and biomass.

Keywords:

• Dropstones
• Arctic
• deep sea
• Nematoda
• diversity

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

We wish to thank the crews of RV Polarstern and of the ROV Victor 6000 for their helpful support during the expedition in 2003, Anja Pappert for assistance with the measurements of various biogenic sediment compounds, bacterial counts and the meiofauna sortings, and Thorben Wulff for assistance with data analysis. This is publication 23367 (Eprint ID) of the Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark