Research Document - 2000/111

Biological and Chemical Oceanographic conditions on the Newfoundland Shelf during 1998 and 1999 with comparisons to the (1993-97) observations.

By P. Pepin and G.L. Maillet

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 1998 and 1999 but contrast those observations with previous information from the period of 1993-1997. Fluctuations in chlorophyll and nitrate levels around recent average conditions, from positive to negative anomalies about the average seasonal cycle, appear to take place on the scale of a few months in contrast to variations in the physical environment which appear to occur on longer time scales. We found evidence that the summer zooplankton community underwent substantial changes during the period of 1996-98 in contrast to previous years, largely du to increases in the abundance of small copepods which significantly reduced species diversity. Preliminary results from 1999 indicate that large copepods, which make up most of the biomass, have now increased in both relative and absolute abundance.  

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