SMALL-SCALE TURBULENCE AND ZOOPLANKTON METABOLISM - EFFECTS OF TURBULENCE ON HEARTBEAT RATES OF PLANKTONIC CRUSTACEANS

The effects of small-scale turbulence on heartbeat rate (HBR), an esti mator of zooplankton metabolism, have been determined in some fresh-wa ter and marine planktonic crustaceans. Quantified levels of turbulence (approximately 5 mm2 s-3) enhanced HBR in Daphnia by 14.3% compared t o calm water conditions. Supplementary observations with four other sp ecies showed that these species also had higher HBR in turbulent than in calm situations, the average percent increase ranging from approxim ately 5% in a marine cladoceran (Penilia avirrostris) to 93% in a mari ne copepod (female Calanus gracilis). These results agree with previou s studies that indicated a relevant effect of small-scale turbulence o n behavior and rate processes of planktonic crustaceans.