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Research Document - 2012/071

Optical, chemical, and biological oceanographic conditions in the Maritimes Region in 2011

By C. Johnson, G. Harrison, E. Head, B. Casault, J. Spry, C. Porter, and I. Yashayaeva

Abstract

Optical, chemical, and biological oceanographic conditions in the Maritimes Region (Georges Bank, eastern Gulf of Maine, Bay of Fundy, and the Scotian Shelf) during 2011 are reviewed and related to conditions during the preceding year and over the longer-term, where applicable. In addition to descriptions of Atlantic Zone Monitoring Program (AZMP) core data collections (fixed stations, seasonal sections, ecosystem trawl or groundfish surveys, Continuous Plankton Recorder), some data from outside the Region are also discussed to provide the larger, zonal perspective.

Optical properties at both Maritimes fixed stations (Halifax-2 and Prince-5) indicated shallower than normal photic depths in 2011. Seasonal stratification and mixed-layer development, however, were similar to conditions seen previously.

Seasonal nutrient inventories at the fixed stations were below normal in 2011, and summertime nutricline depths were the deepest on record. Shallow (<50 m) nutrient inventories were higher than normal along the seasonal sections and possibly linked to a later spring bloom; however, deep (>50 m) nutrients were generally below normal. The exception was the Halifax section, where deep nutrients were higher than usual, coincident with low oxygen saturation, and suggesting the influence of warm slope water on the central shelf at the time of sampling. Overall, nutrient conditions were near normal in the Maritimes Region in 2011.

The spring phytoplankton bloom at both fixed stations was later, smaller in magnitude, and of shorter duration than typically seen; however, chlorophyll levels outside the bloom period at Halifax-2 were higher than normal. Microplankton (diatoms, dinoflagellates, flagellates, ciliates) abundance at the fixed stations was also lower than normal although the relative abundance of diatoms was up. In contrast to observations at the fixed stations, a strong spring bloom was evident from the seasonal sections, particularly on the eastern shelf. Overall, phytoplankton conditions were near normal in the Maritimes Region in 2011.

Zooplankton biomass and Calanus finmarchicus abundance were lower than average overall in 2011 at the fixed stations and on shelf sections and trawl surveys. Copepod community composition was similar to normal at Halifax-2, but the spring—summer period of higher abundance started about a month later and ended about a month sooner than average; warm-water copepods were more abundant than usual in the fall. At Prince-5, total copepod abundance was lower than average throughout the year, particularly in the late summer to early fall, and shelf species dominated more than usual while nearshore species were low in abundance.

Continuous Plankton Recorder data reported for 2010 indicate an increase in abundance of arctic zooplankton species on the eastern Scotian Shelf, Southern Newfoundland Shelf, and east of Flemish Cap since the 1980s. There is no evidence of a decline in calcifying (acid-sensitive) plankton since the 1980s.

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