Changes in the zooplankton community of the British Columbia continental margin, 1985-1999, and their covariation with oceanographic conditions

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Mackas, D L, Thomson, Richard E, Galbraith, Moira
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2001
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Subarctic; Copepods
• Online Access: http://dx.doi.org/10.1139/f01-009; http://www.nrcresearchpress.com/doi/pdf/10.1139/f01-009

A 15-year zooplankton time series collected off southern Vancouver Island (48–49°N) shows large interannual anomalies of biomass for most major zooplankton species. Variations within groups of ecologically similar species have been more extreme (often 10-fold or greater) than the variation in total biomass (four- to six-fold). For both total biomass and species groups, the zooplankton anomalies develop and persist over time spans of several years and are correlated across a large spatial scale (>100 km longshore). One dominant mode of recent zooplankton variation was a 1990–1998 cumulative shift to a more "southerly" copepod and chaetognath fauna: order-of-magnitude declines in several species endemic to the Northeast Pacific continental shelf and order-of-magnitude increases of species endemic to the California Current (35–45°N). This trend abruptly reversed in 1999. A second major mode of zooplankton variability consisted of roughly mirror-image fluctuations in the abundance of euphausiids versus subarctic oceanic copepods. Zooplankton anomalies were correlated with year-to-year changes in several physical environmental indices. The patterns of covariance suggest that zooplankton community composition responds strongly to ocean climate fluctuations and in particular to changing current patterns.