Plankton Dynamics and Nutrient Enrichment of the Scotian Shelf

Abstract

Four seasonal cruises were conducted on a 270 km long transect normal to the coast of Nova Scotia [Canada]. Most biological variables measured along this transect show maximum values in the outer 90 km. These maxima usually occur closely associated with an oceanic front which is a consistent feature of this region. Enhanced vertical transport of nutrients is postulated to occur along this front, although the mechanism is unknown. A model proposed several years ago to explain shelf enrichment off the northeastern USA was examined and was consistent with the Scotian Shelf data. Sporadic advection of nutrient-rich slope water onto the shelf at the average rate of 0.33 cm/s would, upon entering the euphotic zone, satisfy 20% of phytoplankton nutrient requirements during the spring and summer. Recycling would account for the remaining 80%.