UBC Theses and Dissertations
Copepod community dynamics in a highly variable environment : the Strait of Georgia Black, Graeme Robert
Along the Strait of Georgia's north-south axis there exists a kinetic energy continuum from a high in the Southern Strait which is characterized by strong tidal mixing, to a low in the Central Strait where a stable stratified water column is the dominant physical feature. The copepods for this region were found to arrange themselves along the north-south axis in an ecological continuum where small r-selected species dominated the Southern Strait while in the Central Strait the trend was towards larger more K-selected species. The life histories of the various copepod species are discussed and appear to play an important role in maintaining the "r-K" continuum. Many of the K-selected animals undergo an ontogenetic migration which constricts them to the deeper regions of the Central Strait through fall and winter. This migration counterbalances the movement of juvenile copepods which appear in the surface waters through most of the spring. At the surface, the juvenile copepods are exposed to estuarine, tidal and wind derived circulations which tend to concentrate them in the boundary regions of the extreme northern Central Strait and in the Southern Strait, away from the overwintering areas. Similarities exist between the copepod members of the North Central Pacific Gyre and the Strait of Georgia, yet, those members which are abundant in both environments show life histories which are markedly different between the two regions. Based on their ecological role, the Strait of Georgia copepods may be divided into five groups: reproductive, growth, reproductive and growth, carnivorous, and r-selected. The first four are composed primarily of the more K-selected species. Each group shows unique distributional patterns reflecting the different forces affecting them, yet none of the groups can be said to be completely independent of the others.
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