Research Document - 2005/015

Biological and Chemical Oceanographic conditions on the Newfoundland and Labrador Shelf during 2004

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

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) in 2004. The timing of the spring bloom was earlier than in 2003, reversing a trend of increasing delay in the onset of the bloom that had started in 2000, at least over the central portion of the Newfoundland and Labrador Shelf. Deep nutrient inventories at Station 27 remained below the 2000-01 levels but showed signs of increased variability toward the end of 2004. Surface nutrient inventories were higher than in 2003, possibly due to a less intense spring phytoplankton bloom brought on by a deeper winter mixed layer and an abrupt stratification in the spring. The abundance of the dominant zooplankton taxa at Station 27 and on the Grand Banks reached the lowest levels encountered since the inception of the AZMP. In contrast, zooplankton abundance levels along the Bonavista and Seal Island transects were generally close to the maximum levels encountered. The signal was strongest for Calanus finmarchicus, C. glacialis and C. hyperboreus, the three species which make up the bulk of the zooplankton biomass in the region. Although other species did show similar trends, these were generally not statistically significant.

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