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PLOURDE, S., G. WINKLER, P. JOLY, J.-F. ST-PIERRE, M. STARR, 2011. Long-term seasonal and interannuel variations of krill spawning in the lower St Lawrence Estuary, Canada, 1979-2009. J. Plankton Res., 33(5): 703-714 .
This study describes the long-term seasonal and interannual variations in krill spawning using abundance of krill eggs collected during an on-going long-term monitoring program at an anchor station in the lower St Lawrence Estuary from 1992 to 2009 and data collected in the same region in 1979 to 1980. The longterm seasonal semi-monthly climatology in egg abundance revealed that krill generally reproduced during two periods, i.e. in late spring (mid-May to late June) and in late summer (August to mid-September), when phytoplankton biomass in the upper 50 m was greater than 75 mg chlorophyll a m-2. The identification of krill eggs to the species level in 2007 revealed that Meganyctiphanes norvegica egg abundance was related to the biomass of phytoplankton averaged over the month prior to sampling, corresponding to the duration of one spawning cycle (two intermolt periods) known for this species. Overall krill egg abundance varied significantly between years, showing high abundance every 3–5 years with no long-term interannual trend. The annual mean egg abundance normalized for the duration of krill spawning showed the same interannual long-term pattern. Both egg abundance indices were independent of the annual phytoplankton biomass, indicating that interannual variations in krill spawning biomass would be the most likely candidate to explain interannual variability in egg abundance. We propose that such normalized annual egg abundance based on high-resolution seasonal sampling could be a useful index of interannual variations in krill spawning biomass which is otherwise difficult to sample.©2011 Oxford University Press
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
Initiated in 1991 in support of specific research projects, sampling at the Rimouski station located in the lower St. Lawrence estuary has continued for 18 years with more than 400 sampling sorties. The limited sampling protocol followed during the first years revealed the usefulness of such a monitoring project in describing seasonal and interannual patterns in plankton dynamics in the region. These results led to the long duration of the sampling at this station and eventually to its inclusion in the Atlantic Zone Monitoring Program (AZMP) starting in 2005. In addition to its contribution to the monitoring program, the sampling at the Rimouski station has supported several research activities related to key and emergent topics in biogeochemical oceanography. The maintenance of such a long-term time series has only been possible with the contribution of numerous people through the years.
PLOURDE, S., P. JOLY, X. IRIGOIEN, 2008. A Preliminary Assessment of the Performance of an Automated System for the Analysis of Zooplankton Samples from the Gulf of St. Lawrence, Northwest Atlantic. AZMP Bull. PMZA, 7: 42-46 .
[Abstract only available in French]
Une analyse préliminaire de la performance dun système danalyse automatisée avec le logiciel ZooImage déchantillons de zooplancton pro-venant du golfe du Saint-Laurent est présentée. La méthode est basée sur lacquisition dimages digitalisées dune fraction de chaque échantillon (station) de zooplancton, lextraction automatisée des organismes (vignettes), de la construction dun sous-ensemble de référence représentatif de la communauté en différentes catégories, et de loptimisation dun «classeur» suite à lanalyse de ce sous-ensemble avec différents algorithmes. Lutilisation dun «classeur simplifié» comportant 8 catégories a permis de bien estimer la biomasse de zooplancton dans des échantillons récoltés avec un filet 333 μm de vide de maille. Bien que prometteuse avec un succès de classification global de 70 %, lestimation de labondance de catégories représentant différents groupes de stades de développement et/ou despèces de copépode dans des échantillons récoltés avec un filet 158 μm de vide de maille sest avérée beaucoup plus variable. Une analyse détaillée de matrices de confusion comparant la performance des classifications automatisées et manuelles a démontré des échanges complexes dimages mal classifiées (perte et contamination) entre différentes catégories. Ce travail est la première étape dune étude en cours visant à déterminer lapplicabilité de cette approche automatisée pour lanalyse déchantillons de zooplancton de l'Atlantique Nord-Ouest.
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 .
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
RUNGE, J.A., S. PLOURDE, P. JOLY, B. NIEHOFF, E. DURBIN, 2006. Characteristics of egg production of the planktonic copepod, Calanus finmarchicus, on Georges Bank: 1994-1999. Deep-Sea Res., Part II, Top. Stud. Oceanogr., 53: 2618-2631 .
We present here a synthesis of observations of egg production rates (EP) of the planktonic copepod, Calanus finmarchicus, carried out during process cruises of the US GLOBEC Northwest Atlantic/Georges Bank program between January and June 1995, 1997 and 1999. Female C. finmarchicus produced eggs at relatively high rates in at least some regions of Georges Bank during all months between January and June. Median, monthly EP varied between 24 eggs female-1 d-1 in January to 50 eggs female-1 d-1 in AprilJune; the highest mean EP was 86 eggs female-1 d-1. Mean egg diameter was negatively related to ambient mean water-column temperature (0100 m or bottom), decreasing from 149 to 142 μm between January and June. Direct measurements of body C or N or prosome lengthmass relationships were used to determine mass-specific egg production rates. The relationships between estimates of chlorophyll a standing stock (mg chl. a m-2) and both C- and N-specific rates ( % d-1) are reasonably well (r2=0.42) described by Ivlev curves. It is likely that chlorophyll standing stock serves as a proxy of both phytoplankton and microzooplankton food concentrations available to adult females. Chlorophyll standing stocks were below the critical concentration (at which EP is 95 :% of the calculated maximum) at approximately 55% of stations occupied over the study period, indicating frequent food limitation to varying extent. There were periods (e.g., over at least 6 d in April, 1997 on the southern flank) during which food limitation was severe. There was no detectable influence of mean water-column temperature on mass-specific EP. Hatching success varied between 50 % and 95 % without any seasonal trend. Our qualitative observations suggest the possibility that a significant proportion of hatching nauplii incubations were non-viable, meriting further study.© 2006 Elsevier Ltd.
MAPS, F., J.A. RUNGE, B. ZAKARDJIAN, P. JOLY, 2005. Egg production and hatching success of Temora longicornis (Copepoda, Calanoida) in the southern Gulf of St. Lawrence. Mar. Ecol. Prog. Ser., 285: 117-128 .
Egg production rate (EPR) and subsequent egg-hatching success of Temora longicornis from the southern Gulf of St. Lawrence were measured in the laboratory and at sea during 2 cruises in late June and early July of 2000 and 2001. A quantitative, functional Ivlev relationship between EPR, food concentration (μg C 1-1) and temperature was fit to the laboratory results. This relationship can serve as a template for expressing environmental control of T. longicornis egg production in models of the species population dynamics. Among the findings was a very low EPR at high temperature (18 °C) when food was limiting (<200 μg C1-1). The EPR of T. longicornis in the southern Gulf of St. Lawrence in early summer varied as a function of chlorophyll a concentration (integrated 0 to 50 m), and corresponded well with the functional laboratory relationship using a carbon/chlorophyll a conversion factor of 80. Mean hatching success in the laboratory was 42.8 % for experimental temperatures <14 °C, but declined dramatically to 7.5% at temperatures over 14°C. No relationship between hatching success and food concentration was observed. In the southern Gulf of St. Lawrence in late June, hatching success varied between 0 and 56 % for mean temperatures between 3.3 and 10.9 °C (median 6.6 °C). While the presence of resting eggs at this time of year is the most probable explanation of our observations of low hatching success, other factors that may inhibit egg hatching, including methodology, insufficient fertilization and food quality, may also be implicated. We conclude that for T. longicornis, EPR is food-limited in early summer in this region. Comparison with other studies indicated that environmental controls on fecundity of T. longicornis may differ among regions where this species is the dominant copepod.©2005 Inter-Research
PLOURDE, S., P. JOLY, J.A. RUNGE, J. DODSON, B. ZAKARDJIAN, 2003. Life cycle of Calanus hyperboreus in the lower St. Lawrence Estuary and its relationship to local environmental conditions. Mar. Ecol. Prog. Ser., 255: 219-233 .
HARVEY, M., J.-F. ST-PIERRE, P. JOLY, G. MORRIER, 2002. Oceanographic conditions in the Estuary and the Gulf of St. Lawrence during 2001 : zooplankton ; Conditions océanographiques dans l'estuaire et le golfe du St-Laurent en 2001 : zooplancton. DFO, Canadian Science Advisory Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2002/046, 30 p .
This report: 1) describes the results on the temporal variability of the zooplankton biomass, abundance, and species composition at two fixed stations and six transects of the Atlantic Zonal Monitoring Program (AZMP; Anticosti Gyre and Gaspé Current) in 2001 and 2) gives an overview of the interannual variability of the macrozooplankton species composition, abundance, and biomass in the Lower St. Lawrence Estuary and the northwest Gulf of St. Lawrence (GSL) as measured in September in each year between 1994 and 2001. We focus on the conditions during 2001 but compare those observations with previous information from 1999 and 2000 for the AZMP results and from 1994 to 2001 for the macrozooplankton results.
IRIGOLEN, X., R.P. HARRIS, H.M. VERHEYE, P. JOLY, J. RUNGE, M. STARR, D. POND, D. CAMPBELL, R. SHREEVE, P. WARD, A.N. SMITH, H.G. DAM, W. PETERSON, V. TIRELLI, M. KOSKI, T. SMITH, D. HARBOUR, R. DAVIDSON, 2002. Copepod hatching success in marine ecosystems with high diatom concentrations. Nature, 419: 387-389 .
HARVEY, M., J.A. RUNGE, J.-F. ST-PIERRE, P. JOLY, 2000. Oceanographic conditions in the Estuary and the Gulf of St. Lawrence in 1999 : zooplankton. DFO, Canadian Stock Assessment Secretariat, Research Document ; MPO, Secrétariat canadien de consultation scientifique, Document de recherche, 2000/117, 19 p .
This report describes : 1) an overview of the spatial variability of the mesozooplankton and krill biomass in the lower St. Lawrence Estuary and the northwest Gulf of St. Lawrence (GSL) measured in September in each year between 1994-1999 and 2) results on the temporal variability of the zooplankton biomass, abundance, and species composition at two fixed stations of the Atlantic Zonal Monitoring Program (AZMP; Anticosti Gyre and Gaspé Current) in 1999. Within the lower St. Lawrence Estuary and the northwest GSL, the biomass of mesozooplankton and krill was not evenly distributed and showed very high interannual variability. The estimated average wet biomass of mesozooplankton varied between 106.5 and 209.2 t km-2 from 1994 to 1999 with the highest and the lowest values found in 1994 and 1996 respectively. From 1994 to 1999, the overall average biomass of mesozooplankton for the whole lower St. Lawrence Estuary and northwest GSL was estimated at 1.6 106 ± 0.3 106 t. Likewise, the estimated average biomass of krill varied between 7.2 and 38.1 t km-2 from 1994 to 1999 with the highest and the lowest values found in 1994 and 1996 respectively. The overall average biomass of krill for the whole lower St. Lawrence Estuary and northwest GSL was estimated to be 1.7 105 ± 0.9 105 t. The temporal variability of the zooplankton biomass, abundance, and species composition at the two AZMP fixed stations (Anticosti Gyre and Gaspé Current) showed that copepods were clearly dominant at all sampling dates in 1999, accounting for more than 80 % of the zooplankton community for both stations. Small copepods (Oithona similis, Oncea borealis) dominated in abundance at all sampling dates at both stations except in the Gaspé Current in July and August, where larger species (Calanus finmarchicus, C. glacialis, Metridia longa) were more abundant. Total zooplankton biomass was much higher in the Anticosti Gyre than in the Gaspé Current for all seasons in 1999 except in May, when the biomass was equal at both stations. The integrated copepod abundance showed the same pattern of variation with season at both stations, with a maximum abundance of copepod eggs in spring and a maximum abundance of adult copepods and copepodite stages (CI-CV) in late fall. The total integrated abundance of adult copepods and copepodite stages (CI-CV) did not vary significantly between stations for all seasons. Finally, all proposed indices describing the state of the zooplankton community at each station in 1999 varied with season and their annual mean values varied between stations. However, it is too soon to say if they will be useful to describe the interannual variability of the zooplankton community or to detect any changes of the environmental conditions.
ST-PIERRE, J.-F., J. RUNGE, P. JOLY, Y. DE LAFONTAINE, 1996. Données physiques, chimiques et biologiques sur le plancton du nord du golfe du Saint-Laurent. Partie 1 : juin 1989. Rapp. stat. can. sci. halieut. aquat., 986, 99 p .
This report forms part of a study of the trophic interactions in the pelagic ecosystem of the north-central Gulf of St. Lawrence. The data presented here were collected during two simultaneous research cruises in the northern Gulf of St. Lawrence in June 1989. Measured variables include salinity; temperature; light extinction; nutrient concentrations; particulate carbon and nitrogen concentrations; size-fractionated chlorophyll a concentrations; abundance, composition and vertical distribution of phytoplankton, microzooplankton and mesozooplankton; copepod egg production rates; and the composition, abundance, vertical distribution, size, and diet of redfish larvae (Sebastes fasciatus-mentella). The methods used to obtain this information are described. The study focuses in particular on the interaction between microplankton, the dominant planktonic copepod, Calanus finmarchicus, and larval redfish, which dominate the ichthyoplankton
RUNGE, J., P. JOLY, 1995. Zooplankton (Euphausids and Calanus) in the estuary and Gulf of St. Lawrence. Pages 123-132 in L. Savard (ed.). Status report on invertebrates in 1994 : crustaceans and molluscs on the Québec coast, northern shrimp and zooplankton in the estuary and Gulf of St. Lawrence. DFO (Can. Manuscr. Rep. Fish. Aquat. Sci., 2323) .
RUNGE, J.A., P. JOLY, 1995. Zooplancton (Euphausiacés et Calanus) de l'estuaire et du golfe du Saint-Laurent. Pages 128-137 in L. Savard (éd.). Rapport sur l'état des invertébrés en 1994 : crustacés et mollusques des côtes du Québec, crevette nordique et zooplancton de l'estuaire et du golfe du Saint-Laurent. MPO (Rapp. manus. can. sci. halieut. aquat., 2323) .
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