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Marine Ecology Progress Series

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MEPS 138:149-156 (1996)  -  doi:10.3354/meps138149

The lugworm (Arenicola marina) pump: characteristics, modelling and energy cost

Riisgård HU, Berntsen I, Tarp B

The lugworm Arenicola marina was studied in an observation aquarium; the typical undisturbed stroke frequency of the piston pump was ƒ = 6 to 7 strokes min-1. A new experimental setup was used for direct measurement of volume flow at zero and different imposed back pressures. The back pressure characteristic was a nonlinear function, the stroke frequency being reduced with increasing imposed back pressure, attaining a maximal pressure head of 20 cm H2O, which is 30 to 150 times higher than previously found in filter-feeding macro-invertebrate pumps. The back pressure -volume flow characteristic was modelled. At the (assumed) normal operation pressure (5 cm H2O) the power output from the 'standard' (0.5 g dry wt) lugworm pump was calculated to be P p = 12.6 uW. The respiration rate (R, ul O2 h-1) measured in lugworms kept in glass tubes was dependent on the stroke frequency and correlated with dry weight (W, g) according to R = aWb, where a = 344 and b = 0.64 at ƒ = 7 strokes min-1. The total respiration of the 'standard' worm was Rtot = 232 ul O2 h-1 = 1281 uW, and thus the overall pump efficiency was mu = P p/Rtot = 1% which suggests that the energy cost of pumping is modest (<5%). The volume of water pumped per ml oxygen consumed was only 0.4 l ml-1 O2 which is >100 times lower than values previously found for true filter-feeders. This very low value shows that it is unlikely that the lugworm can live by filter-feeding.

Pumping costs . Ventilatory flow rate . Piston stroke frequency . Respiration rate . Filter-feeding

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