Overview of biological and chemical conditions on the Flemish Cap with comparisons of the Grand Banks Shelf and slope waters during 1996-2003

Abstract

The seasonal dynamics of nutrients, phytoplankton and zooplankton populations are described for the period 1996-2003 along an oceanographic section extending from the inshore across the Grand Banks (GB) and Flemish Cap (FC). We present evidence of enhanced inventories of nitrate and silicate and biological productivity on the FC and adjacent Slope (SL) waters compared to the Grand Banks Shelf (GBS). The seasonal occupations along the oceanographic section indicated persistent and enhanced inventories of nitrate and silicate and the potential for higher nutrient fluxes in the SL water and the FC, in contrast to the GBS. The shallow water of the Flemish Cap combined with the proximity of large-scale oceanic circulation around the Bank, including the Labrador Current (LC) and North Atlantic Current (NAC) which generate an anticyclonic gyre, elevate water temperatures, and entrain NAC water rich in inorganic dissolved nutrients, that act to enhance primary and secondary production. The southerly flow of the LC through the Flemish Pass and northeastern flank of the FC act to transport subarctic copepod species from northern regions to the FC and SL waters. These subarctic Calanoid copepods tend to be much larger in body size compared to the community observed on the GBS and contribute to a significant increase in biomass on the FC and SL waters. Fluxes of "new" nitrogen (principally nitrate) delivered to the FC and SL waters appear to support significant levels of "new" primary productivity resulting in a higher productive capacity compared to the adjacent GBS environment. The biomass estimates obtained from the dominant copepod genera from the Continuous Plankton Recorder (CPR) survey and Atlantic Zonal Monitoring Program (AZMP) provide evidence in support of the hypothesis of higher primary productivity that enhances secondary production over the FC and adjacent waters.