Tidal transport of planktonic copepods across the sill of a British Columbia fjord

Estimates of plankton transport into and out of semi-enclosed bodies of water could be of value in long-term ecological monitoring. The study reported here examined the problems associated with the estimates of tidal transport of four species of planktonic copepods across the sill of a British Columbia fjord. Transport was estimated by applying calculated tidal volume exchange to plankton field data collected over a 13-month period. Hydrographic data during the period indicated that tidal exchange was the dominant mechanism for the transport of water Differences in depth distribution and behaviour resulted in a species-specific effect of tidal exchange. The diel vertical migration of Metridia lucens and the ontogenetic migration of Eucalanus bungi resulted in transport only during those periods when organisms were present in water near or above sill depth. Corycaeus anglicus was present above sill depth at all times and transport occurred throughout the study period. Euchaeta japonica , although present in water above sill depth throughout the year, was transported across the sill only during the winter months. Transport estimates could be related to estimates of fjord concentrations for C. anglicus and E. bungii . For M. lucens and E. japonica , it is suggested that natality and mortality within the inlet was sufficient to mask the effect of tidal transport on the species concentration.