IMPACT OF IRRIGATION ON OXYGEN FLUX INTO THE SEDIMENT - INTERMITTENT PUMPING BY CALLIANASSA-SUBTERRANEA AND PISTON-PUMPING BY LANICE-CONCHILEGA

O-2-flux into sediments attributed to the pumping behaviour of two mac rofauna species, Callianassa subterranea (Decapoda) and Lanice conchil ega (Polychaeta) was investigated, Samples were obtained from the Nort h Sea near Helgoland in 1989 and 1990. The two species were found to t ransport roughly similar amounts (3 mmol m(-2) d(-1)) of oxygen into t he sediment although they displayed markedly different pumping behavio urs. Irrigation by C. subterranea was intermittent and characterized b y regularly recurring breathing currents which lasted 2.6 min and were separated by 40-min pauses. In addition to this regular intermittent irrigation, an irregular mode was observed. C. subterranea constructed a complex burrow system. At least half of the burrow wall was not in contact with oxygenated water, however, and thus not effective as addi tional interface for O-2-exchange. Sediment expelled from the burrow i ncreased the total oxygen uptake (TOU) relative to the surrounding sed iment surface. L. conchilega moved water much more frequently (every 4 min) than C. subterranea. We suggest that L. conchilega acted as a pi ston when moving in its tube, exchanging burrow water with the overlyi ng water. This mechanism, termed 'piston-pumping', is also potentially important in other smaller tube dwelling organisms. At a shallow wate r station in the southern North Sea 21 ind of C. subterranea construct ed 1.6 m(2) burrow surface per m(2). L. conchilega (300 ind m(-2)) cre ated only 0.37 m(2) m(-2) tube surface. On the basis of the abundance and oxygen transport associated with pumping activity, it is calculate d that the two species increase TOU by 85% compared to O-2-flux across the sediment-water interface.