Tidal and diel fluctuations in abundance of meiobenthic copepods on an intertidal estuarine sandbank

Abstract

Short-term changes in the population density of two abundant species of sand dwelling meiobenthic copepod and the population structure of the dominant species were investigated in a New Zealand estuary. Average sediment densities of Parastenhelia megarostrum were higher during periods of exposure than during periods of cover by tidal waters. Mean abundance of juveniles (copepodites) and adult males differed significantly in relation to the state of the tide. Females with and without egg sacs only indicate day/night differences at low tide. There were no tidal or diel differences in abundance for the interstitial species Paraleptastacus sp. For P. megarostrum, it is suggested that sediment abundance variability is tidal current flow/body size interactive. While the role of passive erosion is clearly important, behavioural factors might also predispose copepodites to resuspension in the overlying water column. Diel differences in abundance of adult females may indicate a response to changes in patchiness of presumed autotrophic food resources. -from Author