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Research Document - 2013/051

Optical, chemical, and biological oceanographic conditions on the Newfoundland and Labrador Shelf during 2011-12

By P. Pepin, G. Maillet, S. Fraser, T. Shears, and G. Redmond


Across the region, surface inventories of nitrate were generally higher during first half of 1999‑2011 period and lower during the second half. There has been a general decline in bottom inventories throughout that period. Phytoplankton standing stock has been highly variable from year-to-year but overall abundance was generally low in 2011. Satellite imagery indicates a high degree of coherence in the interannual variations in the timing and magnitude of spring phytoplankton bloom. After a period with progressively earlier blooms, conditions in 2011 and 2012 were near normal in the north and late in the south. Zooplankton abundance has shown a general increase during the decade, with some taxa (e.g., Calanus finmarchicus, Oithona atlantica, Centropages, Metridia longa) demonstrating more consistent upward trends than others. Changes in community composition and overall abundance appears to be the result of variations in movement of water masses, with the balance on/off shelf communities appearing to be more important on the Newfoundland Shelf while the balance between warm and cold water species being more significant on the Grand Banks. We noted some significant changes in the phenology of Calanus finmarchicus and Pseudocalanus spp. based on observations at S27, our high frequency monitoring site but the causes and consequences of these changes need to be explored further.

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