Research Document - 2007/042

Biological and Chemical Oceanographic Conditions on the Newfoundland and Labrador Shelf During 2006

By Pepin, P., G.L. Maillet, S. Fraser, D. Lane and T. Shears

Abstract

We review the information concerning the seasonal and inter-annual variations in the concentrations of chlorophyll a, major nutrients, as well as the abundance of major taxa of phytoplankton and zooplankton measured from Station 27 and along standard transects of the Atlantic Zone Monitoring Program (AZMP) on the Newfoundland and Labrador Shelf in 2006. The inventories of nitrate, the principal limiting nutrient, has remained relatively stable throughout the time series although there appears to be a decline in near-surface levels and an overall reduction in the magnitude of the seasonal cycle in recent years compared to earlier observations. Indications of a decrease in phytoplankton abundance at Station 27 since 2002 were reversed in 2006 but the magnitude of the change is not statistically significant nor was it reflected along the oceanographic transects. In 2006, the overall abundance of zooplankton at Station 27 was low relative to the long term average in 6 of the 12 dominant species groups, including C. glacialis and C. hyperboreus. In contrast, the abundance of Calanus finmarchicus at Station 27 rebounded substantially from its lowest level in the previous year, as did the abundance of euphausiids and Metridia spp.. The abundance of the dominant copepod species was at near record levels on both the Newfoundland shelf as well as off the coast of Labrador. The abundance on the northern and southern Grand Banks was generally at or near the lowest levels since 2000.

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