Comparative ecology of over-wintering Calanus finmarchicus in the northern North Atlantic, and implications for life-cycle patterns

Abstract

. 2000. Comparative analysis of Calanus finmarchicus demography at locations around the Northeast Atlantic.Standardized time-series sampling was carried out throughout 1997 at seven locations around the Northeast Atlantic to investigate regional variations in the seasonal demography of Calanus finmarchicus. Sites ranged from an inshore location in the North Sea, where C. finmarchicus formed only a small component of the zooplankton (<10 mgC m 2 during spring and early summer), to the shelf south of Iceland, and Weathership M in the Norwegian Sea, where the species dominated the zooplankton (>2000 mgC m 2 during spring and summer). The internal consistency of the demographic time series from each site was investigated by three partial models of life-cycle processes. In general, the demography of late copepodites could be accounted for by a relatively simple forecast model of stage development and diapause. However, there was a large discrepancy between nowcast estimates of egg production based on female abundance, temperature, and chlorophyll, and hindcast simulations of the egg production required to account for the observed abundance of early copepodite stages. The results point to a gap in our understanding of seasonal variations in rates of egg production and/or survival of nauplii. Overall, the population sampled at Weathership M appeared to be reasonably self-contained, but all other sites were reliant on invasion of overwintered stock in spring. At least two generations were observed at all but one site, but the extent to which these were generated by discrete bursts of egg production varied between sites and seemed to be partly dependent on the proximity to an overwintering location.

Calanus finmarchicus seasonal cycle and diapause in relation to gene expression, physiology, and endogenous clocks

“…In the open ocean, C. finmarchicus diapauses at depths between 400 m and 1000 m (Hirche ; Heath et al ) where seasonal changes of environmental parameters are minimal or absent. The potential lack of seasonal cues for triggering emergence has led to the proposal of an hourglass model based on the gradual depletion of wax esters (Miller et al ; Campbell et al ; Saumweber and Durbin ; Clark et al ) mediated by lipid‐derived hormones (Irigoien ; Pond et al ) or based on continuous slow development (Hind et al ).…”

“…A general point to consider is that while light levels in loch Etive are similar to the typical open ocean Calanus habitats due to high turbidity, pressure is lower and water temperatures are higher than would be expected at depth in the open ocean. This may have increased energy consumption in the copepods (Ingvarsdóttir et al ; Heath et al ), resulting in heterotrophic feeding and possibly an overall weaker diapause than in the open ocean. Our gene expression data resemble the few existing records from the open ocean, but it is clear that extensive field campaigns in open ocean habitats will be needed to compare the presented findings with other populations.…”

“…During diapause, the copepods have reduced gut epithelium and show reduced metabolic activity and development (Hallberg and Hirche ; Hirche ; Ingvarsdóttir et al ). Diapause depth in the open ocean is usually between 400 m and 1000 m (Hirche ; Heath et al ) but in coastal habitats (lochs and fjords) C. finmarchicus has been found to diapause close to the bottom between 100 m and 150 m (Clark et al ). The copepods stay in diapause for several months before increasing metabolic activity and the development of gonadal tissues mark the emergence from diapause (Hirche , b ).…”

Larval Transport Modeling of Deep-Sea Invertebrates Can Aid the Search for Undiscovered Populations

“…Some marine invertebrates (e.g. copepods) are known to deliberately exploit the difference in surface and deeper current speeds [35], [36]. There is a suggestion that some planktotrophic larvae of deep sea species exploit faster near-surface currents to increase dispersal [37], [38], [39], although warmer surface waters would also reduce expected PLDs.…”

Lipid content in overwintering Calanus finmarchicus across the Subpolar Eastern North Atlantic Ocean

“…It accumulates WEs as a pre adult stage C3–C5 before overwintering usually as stage C5 in deep ocean basins for a period that lasts from 120 to > 300 d (Hirche ; Maps et al ; Melle et al ; Jónasdóttir et al ; Wilson et al ). The winter distribution of C. finmarchicus is probably the best known of all copepod species (Heath et al ). The winter population reaches densities of 35–56,000 individual m −2 in the Eastern and Central Norwegian Sea (Dale et al ; Heath et al ) and Lofoten Basin (Halvorsen et al ) with pockets of high densities of 15–60,000 individual m −2 in the Nova Scotia and Newfoundland basins (Head and Pepin ), Gulf of Maine (Runge et al ), and Iceland Sea (ICS; Gislason and Silva ).…”