Abstract
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 G0 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 G0 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.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 39-88 |
| Number of pages | 50 |
| Journal | Progress in Oceanography |
| Volume | 76 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 1 2008 |
| Externally published | Yes |
Bibliographical note
Funding Information:This work was funded by the Natural Environment Research Council Marine Productivity Programme (grants: NER/T/S/2001/00164, NER/T/S/2001/01256, NE/C508393/1, and NER/T/S/2001/00142) and The Scottish Executive Environment and Rural Affairs Department project MF0754. A large number of staff at the participating institutes contributed in very many ways at sea and in a support capacity, and we thank them all. We especially thank the students (L. Bambini, M. Baptie, C. Booth, A. Chapman, G. Cleary, C. Cooke, D. Demain, A. Donald, H. Flint, Y. Garcia-Santiago, R. Harries, N. Jacob, A. Korycinska, A. Mair, J. McNeill, S. McRobert, R. Nevins, C. Ni Dhubhgaill, D. Nixon, E. O’Mahony, I. Roberts, H. Selley, R. Taylor, N. Thompson, H. Vatanen, G. Velema & V. Vigiani) who participated in the plankton analysis summer schools where the majority of the plankton samples were processed. Thanks also to three reviewers of the manuscript who contributed a number of ideas and suggestions for improvement.
Keywords
- Atlantic Ocean
- Copepods
- Feeding
- Greenland
- Mortality
- Oceanography
- Plankton
ASJC Scopus subject areas
- Aquatic Science
- Geology
