Identifier

etd-06172009-115912

Degree

Master of Science (MS)

Department

Oceanography and Coastal Sciences

Document Type

Thesis

Abstract

The calanoid copepod Calanus finmarchicus is broadly distributed in the North Atlantic, where it dominates the spring zooplankton biomass of shelf ecosystems. Calanus finmarchicus diapauses in the deep basins of the Gulf of Maine (GOM) during late-summer through early-winter. During diapause, predators that co-occur in regions of high copepod abundance may reduce survivorship through predation. Consequently it is important to measure the distribution patterns of C. finmarchicus and its predators. Two cruises were carried out during December of 1998 and 1999 in the GOM. Video Plankton Recorder (VPR) data collected in Wilkinson, Jordan and Georges Basins were used to describe the fine- to basin-scale distributions of C. finmarchicus and its predators. The locations of individual zooplanktors were mapped by towyoing a Video Plankton Recorder (VPR), mounted on the towed-body BIOMAPER-II, across the basins. Volumetric distribution patterns were estimated by interpolated abundance data using 3D Kriging. The abundance of C. finmarchicus was lower in December 1998 than in December 1999. This difference is discussed in terms of the spatial distributions and abundances of cnidarian, ctenophore, and crustacean predators. Gelatinous plankton were more abundant during December 1998 than in December 1999. Gelatinous plankton (siphonophores, ctenophores and medusae) were identified as the most aggressive taxa preying on C. finmarchicus. An inverse spatial pattern between C. finmarchicus and predators was observed in all three deep basins during December 1998, suggesting depletion of C. finmarchicus through predation. Water temperatures were generally cooler and fresher during December 1998 and warmer and saltier during December 1999. This hydrological regime changes caused by the shift between the Labrador Subarctic Slope Water and the Slope Water, respectively, seemed to affect both, C. finmarchicus and its invertebrate predators. During December 1998, C. finmarchicus was broadly distributed (0-200 m) in the water column probably due to broader distribution of cooler temperatures. During December 1999 C. finmarchicus was found below 150 m, where cooler temperatures dominated. The low C. finmarchicus abundances observed during December 1998 were possibly caused by the combined action of predation and advection losses since diapausing populations above sill depth (~200 m) are likely advected out of the system.

Date

2009

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Benfield, Mark C.

DOI

10.31390/gradschool_theses.1581

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