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Research Document - 2002/056

Optical, chemical and biological oceanographic conditions on the Scotian Shelf, in the Gulf of Maine and the Southern Gulf of St. Lawrence in 2001

By G. Harrison, D. Sameoto, J. Spry, K. Pauley, H. Maass and V. Soukhovtsev

Abstract

Optical, chemical, and biological oceanographic conditions in the Maritimes Region (eastern Gulf of Maine/Bay of Fundy, Scotian Shelf and Southern Gulf of St. Lawrence) during 2001 are reviewed and related to conditions during the preceding year and over the longer-term where applicable. In addition to descriptions of AZMP core data collections (fixed stations, seasonal sections, groundfish surveys, CPR, remote-sensing), some data from outside the Maritimes Region are discussed also to provide the larger, zonal perspective.

Optical properties, nutrients and phytoplankton (abundance and community composition) in 2001 and 2000 were generally comparable. Nutrient and phytoplankton levels in 2001 were also similar to the climatological mean condition where data exist, i.e. the Scotian Shelf. Some oceanographic properties did change between years, however. Summer oxygen saturation in bottom waters of the Scotian Shelf was higher in 2001 than in previous years, particularly on the eastern shelf. On the other hand, fall nutrient concentrations in the Southern Gulf were lower in 2001 than in 2000. Although the overall biomass of phytoplankton in the Maritimes Region was similar in 2001 to levels in 2000, based on remote-sensed ocean colour, the duration of the spring bloom was apparently longer on central Scotian Shelf and shorter on the eastern shelf than during the previous year. Feeding/reproducing zooplankton were somewhat more abundant in the Maritimes Region in 2001 than in 2000 (although community composition was similar) but over-wintering populations were generally lower, and significantly lower in 2001 than the long-term mean abundance in deep-water basins. The CPR data record suggested that the abundance of large phytoplankton on the Scotian Shelf in recent years has been significantly higher than the long-term mean while important components of the zooplankton (Calanus species, euphausiids) have declined during the same period.

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