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Bibliographie de l'Institut Maurice-Lamontagne

Crustacés - Copépodes / Metridia longa / 

POMERLEAU, C., G. WINKLER, A.R. SASTRI, R.J. NELSON, S. VAGLE, V. LESAGE, S.H. FERGUSON, 2011. Spatial patterns in zooplankton communities across the eastern Canadian sub-Arctic and Arctic waters : Insights from stable carbon (δ 13C) and nitrogen (δ15N) isotope ratios. J. Plankton Res., 33(12): 1779-1792.

[Résumé disponible seulement en anglais]
This study defined the status quo of biogeographic domains and examined spatial patterns of stable isotopes (Sis) of carbon and nitrogen in relation to biophysical groupings to gain greater insight into how mesozooplankton may respond to continuous environmental change in the Canadian Arctic and sub-Arctic regions. Mesozooplankton communities were sampled during the summer of 2007 along a transect from Belle-Isle Strait, NFL, to Kugluktuk, NU (Canada), and during the early autumn of 2009 along a transect extending from Pelly Bay to Hall Beach, NU. Five broad water mass types corresponded to geographical regions. In general, we found relationships between water mass and species composition; however, this relationship was not always straightforward. Mesozooplankton community composition varied along the transect, revealing eight species assemblages. Calanus finmarchicus was abundant in the warmer and saltier Atlantic waters of the Labrador Sea, whereas Calanus hyperboreus, Calanus glacialis and Metridia longa were most abundant in the cold Arctic waters of Central Baffin Bay and in the eastern portion of the Canadian Arctic Archipelago. Nitrogen and carbon SI analysis revealed that δ15N (but not δ13C) varied spatially for C. glacialis, C. hyperboreus, Paraeuchaeta spp. And Themisto libellula. δ15N values were less enriched in Davis Strait and more enriched in the Gulf of Boothia. Seasonality, oceanic fronts and changes in the trophic structure at the base of each regional food web may explain some of the observed variability. This study represents the first broad-scale characterization of the composition and isotopic signatures for mesozooplankton communities ranging from the sub-Arctic Atlantic to the western Central Arctic Archipelago. Our study provides a baseline of the zooplankton community for monitoring species biogeographical range.©2011 Oxford University Press

POMERLEAU, C., S.H. FURGUSON, W. WALKUSZ, 2010. Stomach contents of bowhead whales (Balaena mysticetus>/i>) from four locations in the Canadian Artic. Polar Biol., 34(4): 615-620.

[Résumé disponible seulement en anglais]
Abstract The stomach contents of four bowhead whales (Balaena mysticetus) harvested between 1994 and 2008 from the Canadian Arctic were examined to assess diet composition. Three samples were collected from bowhead whales of the Eastern Canada––West Greenland (EC––WG) population and represent, according to our knowledge, the first diet analysis from this bowhead whale stock. We also examined the stomach content of one bowhead whale from the Bering-Chukchi-Beaufort (BCB) population hunted in 1996. All four whales had food in their stomachs and their diet varied from exclusively pelagic (BCB whale), with Limnocalanus macrurus being the main prey, to epibenthic and benthic (EC––WG) with Mysis oculata playing an important role. These results indicate broad foraging spectrum of the bowhead whales and add to a basic knowledge of their diet.&Copy;2010 Springer-Verlag

CAMPBELL, R.G., E.B. SHERR, C.J. ASHJIAN, S. PLOURDE, B.F. SHERR, V. HILL, D.A. STOCKWELL, 2009. Mesozooplankton prey preference and grazing impact in the western Arctic Ocean. Deep-Sea Res., Part II, Top. Stud. Oceanogr., 56(17): 1274-1289.

[Résumé disponible seulement en anglais]
The role of mesozooplankton as consumers and transformers of primary and secondary production in the Beaufort and Chukchi Seas was examined during four cruises in spring and summer of both 2002 and 2004 as part of the western Arctic Shelf-Basin Interactions (SBI) program. Forty-seven grazing experiments using dominant mesozooplankton species and life stages were conducted at locations across the shelf, slope, and basin of the Chukchi and Beaufort Seas to measure feeding rates on both chlorophyll and microzooplankton and to determine mesozooplankton prey preferences. Mesozooplankton biomass was at all times dominated by life stages of four copepod taxa: Calanus glacialis, Calanus hyperboreus, Metridia longa, and Pseudocalanus spp. Significant interannual, seasonal, regional, between species and within species differences in grazing rates were observed. Overall, the dominant zooplankton exhibited typical feeding behavior in response to chlorophyll concentration that could be modeled using species and life-stage specific Ivlev functions. Microzooplankton were preferred prey at almost all times, with the strength of the preference positively related to the proportion of microzooplankton prey availability. Average mesozooplankton grazing impacts on both chlorophyll standing stock (0.6±0.5 % d-1 in spring, 5.1±6.3 % d-1 in summer) and primary production (12.8±11.8 % d-1 in spring, 27.6±24.5 % d-1 in summer) were quite low and varied between shelf, slope, and basin. Coincident microzooplankton grazing experiments [Sherr, E.B., Sherr, B.F., Hartz, A.J., 2009. Microzooplankton grazing impact in the Western Arctic Ocean. Deep-Sea Research II] were conducted at most stations. Together, microzooplankton-mesozooplankton grazing consumed only 44 % of the total water-column primary production, leaving more than half directly available for local export to the benthos or for offshore transport into the adjacent basin.©2009 Elsevier Ltd.

PLOURDE, S., F. MAPS, P. JOLY, 2009. Mortality and survival in early stages control recruitment in Calanus finmarchicus. J. Plankton Res., 31(4): 371-388.

[Résumé disponible seulement en anglais]
We present a data set describing the seasonal climatology and the spatial pattern in mortality and recruitment in early stages of Calanus finmarchicus in the lower St Lawrence estuary (LSLE) and the Gulf of St Lawrence (GSL), respectively. Contrary to the common assumption of constant mortality, daily mortality during development from egg to N3 or N6 showed important seasonal and spatial variations mostly independent from patterns in population egg production. Patterns in recruitment rate to late naupliar stages were mainly associated with patterns in survival, and dictated patterns in abundance of nauplii N4–6 (seasonal, LSLE) and early copepodite C1–2 (spatial, GSL). Consequently, recruitment to late naupliar and early copepodid stages was largely independent from patterns in population egg production. A multiple regression model showed that phytoplankton biomass and female abundance exerted opposite effects in the control of mortality, illustrating the beneficial effect of high phytoplankton biomass on the survival due to a relaxation of the cannibalism pressure or mortality owing to food shortage. A sensitivity analysis using a stage-based model clearly showed variations in the amplitude and the timing in recruitment to late naupliar stages solely due to different mortality formulations. Moreover, our simulations suggested that temperature alone should not be of primary importance in determining patterns in survival because of its general scaling effect on metabolism. Our study reinforces the importance of an adequate description of mortality and survival in studies of population dynamics and illustrates the importance of developing dynamic mortality formulations integrating multiple effects for future use in models of C. finmarchicus.©2009 Oxford University Press

PLOURDE, S., P. JOLY, 2008. Comparison of in situ egg production rate in Calanus finmarchicus and Metridia longa: discriminating between methodological and species-specific effects. Mar. Ecol. Prog. Ser., 353: 165-175 .

[Résumé disponible seulement en anglais]
A comparison of the in situ egg production rate (EPR) in Calanus finmarchicus and Metridia longa was conducted using freshly collected adult females (C6f), individually incubated in 45 ml dishes with and without egg separators at 6 °C for 24 h. Incubations with egg separators resulted in significantly greater clutch size and in situ EPR in M. longa than without egg separation, while no significant effect was measured in C. finmarchicus. The use of egg separators resulted in lower hatching success and naupliar viability (%), an effect more pronounced in M. longa. A highly significant effect of food on egg removal was observed in M. longa, with C6f removing up to 85 % of their eggs when the ambient algal biomass at capture was less than 50 mg chl a m-2, suggesting an effect of the feeding ′history′ of C6f. In the absence of cannibalism on the eggs, the combined effect of smaller clutch size and longer spawning interval resulted in a lower EPR in M. longa by a factor of 4 to 5 relative to C. finmarchicus. Based on egg and C6f weight, the weight-specific EPR (growth) in M. longa was half that in C. finmarchicus. M. longa produced eggs at a rate similar to C. finmarchicus only when C6f were incubated at a higher temperature (+4 °C). These results are discussed in the context of the paradox between the low EPR and high abundance in Metridia species and the different life history strategies developed by Metridia and Calanus species..©2008 Inter-Research