Primary production in the Labrador Sea and adjacent waters : Atlantic Zone Off-Shelf Monitoring Program 1991-2011 / by W.G. Harrison and W.K.W. Li. : Fs97-18/307E

Results from 20 years (21 missions) of environmental and photophysiological observations of natural phytoplankton populations in the Labrador Sea are reported. Variability in environmental (temperature, nutrients) and biological (phytoplankton biomass, photosynthetic characteristics) were linked to sampling depth, season and geographical location. Time of year of sampling made the greatest contribution to variability of most properties although geography differences were also important. Inter-annual variability was significant but longer term trends were weak or absent. Synoptic satellite ocean colour data have helped to fill in the gaps, due to the limited field sampling, in order to provide a more complete picture of regional productivity. The annual phytoplankton growth cycle in the Labrador Sea is marked by early spring blooms on the Labrador and Greenland shelves, a summer bloom in the central basin and a brief, geographically confined, fall bloom off the Labrador Shelf. Measured and modeled total and new primary productivity in the Labrador Sea is typical of sub-polar regions. To date, there is little evidence of long term changes in productivity in the Labrador Sea despite indications of some nutrient, phytoplankton community structure and photophysiological changes over the past 20 years. Field and satellite data collected in the Northwest Atlantic over the past 2-3 decades, as described here, underpin new model-based estimates of primary productivity that are providing unprecedented spatial and temporal detail of this fundamental ecological process.

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