Effect of temperature on lower feeding thresholds, gut evacuation rate, and diel feeding behavior in the copepod Acartia hudsonica

Abstract

Lower feeding thresholds of 280, 127, 282, and 214 cells ml-1 respectively at 4, 8, 12, and 16°C were indicated. The thresholds corresponded to carbon concentrations of 30.5, 11.6, 20.7, and 16.4 μg C l-1, and were not significantly different at the four temperatures. Highest gut contents occurred at night, and were c4-fold higher than the lowest measured gut contents. Total daily ingestion rates were respectively 11 460 and 14 430 cells d-1, or 1.34 and 2.40 μg C and 0.24 and 0.42 μg N d-1, and 33.4 and 56.5 body C and 23.3 and 38.5 body N d-1. The instantaneous gut evacuation rates had mean values of 0.0239, 0.0494, 0.0518 and 0.0645 min-1 respectively at 4, 8, 12, and 16°C, yielding a Q10 of 1.88. -from Authors