Zooplankton Sample Variation on the Scotian Shelf

Abstract

Zooplankton sampling experiments on the Scotian Shelf during September 1973 and August 1974 using vertical tows demonstrated that numbers of many zooplankton species had a periodic fluctuation over 26 h. The fluctuations appeared related to the tide during 1974 but not in 1973. The periodic fluctuations accounted for a major portion of the sample variation in many species during both years. The mean numbers of small forms of zooplankton (copepods) obtained from the 26-h time series on a single station were very similar to means obtained during the same cruise over a wide area of the shelf. This suggested that a single station sampled over a period of two tidal cycles may be representative of the sample variation encountered over a wide geographic area of many hundreds of kilometres. Only Calanus and Pseudocalanus were correlated during all the experiments and from year to year. The abundance and distribution of the other species of zooplankton compared from one year to the next were not significantly correlated. This suggested the species populations were independent of one another. Key words: zooplankton, sample variation, time series, Scotian Shelf, fish larvae, Copepoda, tide