Research Document - 2001/073

Biological and Chemical Oceanographic conditions on the Newfoundland Shelf during 2000 with comparisons with earlier observations

By Pepin, P. and Maillet, G.L.

Abstract

We review the information concerning the seasonal and internannual variations in the concentrations of chlorophyll a, nitrates, phosphates and silicates as well as the abundance of major taxa of zooplankton measured from Station 27 and standard oceanographic transects on the Newfoundland Shelf. We focus on the conditions during 2000 but contrast those observations with previous information from the period of 1996-1999 with particular emphasis on the last year. Nutrient levels were comparable to the previous year although there was some evidence of an influx of waters with higher nutrient concentrations along the bottom during late Fall. The Spring phytoplankton bloom was restricted to the upper 60m of the water column but the overall intensity was slightly greater than in 1999. In contrast to 1999, there were no subsurface phytoplankton blooms during the Summer of 2000 and we did not find evidence of a small Fall bloom. Overall, the zooplankton community was similar in abundance and composition to that observed in 1999. There was some indication of a greater abundance of Oithona similis and Pseudocalanus sp., but this may have reflected a competitive balance between these two numerically dominant species. The abundance of Calanus finmachicus and C. glacialis was similar to that observed in previous years but the overall abundance of large calanoid nauplii, most likely produced by these two species, was approximately twice that observed in 1999 at both Station 27 and across the entire Newfoundland Shelf.

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