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Spatial demography of Calanus finmarchicus in the Irminger Sea

Heath, M.R.; Rasmussen, J.; Ahmed, Y.; Allen, J.; Anderson, C.I.H.; Brierley, A.S.; Brown, L.; Bunker, A.; Cook, K.; Davidson, R.; Fielding, S.; Gurney, W.S.C.; Harris, R.; Hay, S.; Henson, S.; Hirst, A.G.; Holliday, N.P.; Ingvarsdottir, A.; Irigoien, X.; Lindeque, P.; Mayor, D.J.; Montagnes, D.; Moffat, C.; Pollard, R.; Richards, S.; Saunders, R.A.; Sidey, J.; Smerdon, G.; Speirs, D.; Walsham, P.; Waniek, J.; Webster, L.; Wilson, D.. 2008 Spatial demography of Calanus finmarchicus in the Irminger Sea. Progress in Oceanography, 76 (1). 39-88. 10.1016/j.pocean.2007.10.001

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Abstract/Summary

Continuous Plankton Recorder data suggest that the Irminger Sea supports a major proportion of the surface-living population of the copepod Calanus finmarchicus in the northern North Atlantic, but there have been few studies of its population dynamics in the region. In this paper, we document the seasonal changes in the demographic structure of C finmarchicus in the Irminger Sea from a field programme during 2001/2002, and the associations between its developmental stages and various apparent bio-physical zones. Overwintering stages were found widely at depth (>500 m) across the Irminger Sea, and surviving females were widely distributed in the surface waters the following spring. However, recruitment of the subsequent generation was concentrated around the fringes of the Irminger Sea basin, along the edges of the Irminger and East Greenland Currents, and not in the central basin. In late summer animals were found descending back to overwintering depths in the Central Irminger Sea. The key factors dictating this pattern of recruitment appear to be (a) the general circulation regime, (b) predation on eggs in the spring, possibly by the surviving GO stock, and (c) mortality of first feeding naupliar stages in the central basin where food concentrations appear to be low throughout the year. We compared the demographic patterns in 2001/2002 with observations from the only previous major survey in 1963 and with data from the Continuous Plankton Recorder (CPR) surveys. In both previous data sets, the basic structure of GO ascent from the central basin and G1 recruitment around the fringes was a robust feature, suggesting that it is a recurrent phenomenon. The Irminger Sea is a complex mixing zone between polar and Atlantic water masses, and it has also been identified as a site of sporadic deep convection. The physical oceanographic characteristics of the region are therefore potentially sensitive to climate fluctuations. Despite this, the abundance of C finmarchicus in the region, as measured by the CPR surveys, appears not to have responded to climate factors linked to the North Atlantic Oscillation Index, in contrast with the stocks in eastern Atlantic areas. We speculate that this may because biological factors (production and mortality), rather than transport processes are the key factors affecting the population dynamics in the Irminger Sea.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.pocean.2007.10.001
Programmes: BAS Programmes > Global Science in the Antarctic Context (2005-2009) > DISCOVERY 2010 - Integrating Southern Ocean Ecosystems into the Earth System
ISSN: 0079-6611
Additional Keywords: plankton; oceanography; Atlantic Ocean; Greenland; copepods; mortality; feeding
NORA Subject Terms: Marine Sciences
Biology and Microbiology
Zoology
Ecology and Environment
Date made live: 14 Jan 2011 16:31
URI: http://nora.nerc.ac.uk/id/eprint/11513

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