Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 6 6 2002 10.5194/hess-6-999-2002 http://www.hydrol-earth-syst-sci.net/6/999/2002/ http://www.hydrol-earth-syst-sci.net/6/999/2002/hess-6-999-2002.html http://www.hydrol-earth-syst-sci.net/6/999/2002/hess-6-999-2002.pdf 999 1005 0000-00-00 Bioturbation, ecosystem functioning and community structure C. L. Biles D. M. Paterson R. B. Ford M. Solan D. G. Raffaelli School of Biological Sciences, Gatty Marine Laboratory, University of St Andrews, Fife KY16 8LB, UK Leigh Marine Laboratory, PO Box 349, Warkworth, New Zealand Ocean Laboratory, University of Aberdeen, Newburgh, Aberdeenshire, Scotland. AB41 6AA, UK Environment, University of York, Heslington, York, YO10 5DD, UK Email for corresponding author: clb3@st-andrews.ac.uk The effect of community structure on the functioning of the ecosystem is an important issue in ecology due to continuing global species loss. The influence of infaunal community structure on the functioning of marine systems is proposed here to act primarily through bioturbation of the sediment. Nutrient concentration in the water column, generated by release from the sediment, was used as a measure of ecosystem functioning. <i>In situ</i> and laboratory experiments showed a significant difference in nutrient concentrations with different species treatments. Bioturbation profiles showing the incorporation of tracer particles also differed between communities with different dominant species. The behavioural differences between infaunal species, generating different modes and rates of bioturbation, are therefore proposed to influence nutrient release. The presence and quantity of bioturbating infauna also influenced the amount of sediment suspended in the water column. The increase in surface area available for microbial activity may generate an increase in nutrient cycling. Abiotic influences on sediment structure, such as flow, may have a similar effect on nutrient concentration. Annular flumes used in both laboratory and <i>in situ</i> experiments to generate flow conditions produced a significant increase in ammonia (NH₄-N) production in macrofaunal treatments. Flow may influence the behaviour of macrofaunal species, causing changes in NH₄-N production through modifying bioturbation of the sediment.</p> <p style="line-height: 20px;"><b>Keywords: </b>bioturbation, community structure, ccosystem functioning, estuaries, flow, infauna</p>