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MAPS, F., J.A. RUNGE, A. LEISING, A.J. PERSHING, N.R. RECORD, S. PLOURDE, J.J. PIERSON, 2012. Modelling the timing and duration of dormancy in populations of Calanus finmarchicus from the Northwest Atlantic shelf. J. Plankton Res., 34(1): 36-54 .
Calanus finmarchicus relies on dormancy to thrive in the seasonal environment of the boreal Atlantic. The lipid accumulation window (LAW) hypothesis proposes that a seasonal window of environmental conditions allows developing individuals to store enough lipids for dormancy to be safely initiated. Successful dormancy requires a sufficient amount of lipids to fulfil the reduced metabolic demand of the dormant individual and to sustain the final maturation process. We used a pattern-oriented modelling approach that implements the LAW hypothesis and employs a genetic algorithm for parameter estimation, in order to reproduce the observed phenology and demography of C. finmarchicus populations from the two contrasting regions, the Gulf of St. Lawrence (GSL) and the Gulf of Maine (GoM) in the northwest Atlantic shelf. In the GSL, the model reproduced the timing of dormancy, the abundance and individual condition of late copepodid stages. In the GoM, the model produced a semi-annual dormancy pattern, as no locally produced individual could last the 6–8 months of dormancy inferred from the available observations. Further testing requires extending demographic time series, including lipid condition of late copepodid stages in the GoM, and the implementation of a 3-D modelling framework that would explicitly address the complex interactions between circulation and population dynamics of C. finmarchicus over the entire northwest Atlantic shelf.©2012 Oxford University Press
PARENT, G.J., S. PLOURDE, J. TURGEON, 2011. Overlapping size ranges of Calanus spp. off the Canadian Arctic and Atlantic Coasts : impact on species abundances. J. Plankton Res., 33(11): 1654-1665 .
In the North Atlantic, Calanus finmarchicus, C. glacialis and C. hyperboreus are identified based on subtle morphological traits, which is fastidious, or based on their allegedly non-overlapping prosome length ranges. We reappraised the prosome length-based diagnosis for the copepodite stage V stage by coupling prosome length and molecular identifications (mtDNA, 16S gene) for 1159 individuals collected over 2 years from 15 stations off the Canadian coast from the Arctic to the Atlantic. We observed spatial but no intra-annual variation in species average prosome length. At sympatric coastal sites, prosome length overlap was frequent between C. finmarchicus and C. glacialis and restricted to the Estuary/Gulf of St. Lawrence between C. glacialis and C. hyperboreus. We used discriminant analyses to redefine prosome length criteria to minimize errors in species identification. Species abundances were corrected and this affected mostly C. glacialis. In the St. Lawrence Estuary and on the Labrador shelf, abundance of C. glacialis was underestimated by 19 and 35 %, respectively, with important interannual variations since 2000. This increase in abundance could enhance estimation of the role of <Ic. Glacialis in the food web and potentially alter our view of the long-term changes along the eastern Canadian coast.© 2011 Oxford University Press
PLOURDE, S., S. DUBÉ, 2011. Processus consultatif scientifique régional sur lévaluation des stocks de crevette de lestuaire et du golfe du Saint-Laurent, 26 janvier 2011, Institut Maurice-Lamontagne ; Regional Science Advisory Process on the assessment of the Estuary and Gulf of St. Lawrence shrimp stocks, January 26, 2011, Maurice Lamontagne Institute. MPO, Secrétariat canadien de consultation scientifique, Série des comptes rendus; DFO, Canadian Science Advisory Secretariat, Proceedings Series, 2011/004, 21 p .
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
MAPS, F., B.A. SAKARDJIAN, S. PLOURDE, F.J. SAUCIER, 2011. Modeling the interactions between the seasonal and diel migration behaviors of Calanus finmarchicus and the circulation in the Gulf of St. Lawrence (Canada). J. Mar. Syst., 88(2) 183-202 .
The Gulf of St.-Lawrence (GSL) is a dynamic region supporting a productive pelagic ecosystem. This environment presents unique opportunities to study the interactions between the population dynamics of planktonic species and the variability of physical processes. The copepod Calanus finmarchicus is a dominant component of zooplankton biomass and abundance in the GSL. We developed a 3-D coupled physical-biological numerical model in order to study the population dynamics of C. finmarchicus in the GSL for the year 1999. We coupled a life cycle model of C. finmarchicus representing the average properties of the population in terms of egg production, development, migration behavior and mortality to a regional circulation model driven by realistic atmospheric, hydrological and oceanic forcing. The distribution and abundance patterns of C. finmarchicus were sensitive to the migration behavior owing to the strong vertical and horizontal shears in the circulation. Both the timing of seasonal ontogenetic vertical migrations and the diel vertical migrations appeared to be essential to produce simulation results similar to the observations and to ensure the perennial presence of a local population in the GSL. ©2011 Elsevier B.V. All rights reserved
We evaluated the efficacy of two ballast water exchange (BWE) methods during two transoceanic voyages of a bulk carrier in September 1999 and October 2000 between Rotterdam (The Netherlands) and Sept-Iles (Canada). The experimental design accounted for the uptake of new species during exchanges by considering only those taxa observed prior to BWE (initial taxa). To account for natural decreases due to mortality in the tanks, communities in exchanged ballast tanks were compared with those in control tanks, thus allowing the net BWE efficacyof the procedures to be determined. The efficacy of the removal of organisms varied among BWE methods, plankton communities (microplankton and zooplankton) and taxonomic groups. BWE efficacy was greater for zooplankton (72–90%) than microplankton (49–80%). When the fairly high natural mortality observed in control tanks was considered in the calculation of BWE efficacy (net BWE efficacy), much lower efficacy was observed (microplankton: 29–40%; zooplankton: 23–54%). The 300% flow-through method (FT) is the most effective BWE method (net efficacy) for removing initial microplankton taxa (1999 and 2000), whereas the FT was either similarly (1999) or less than (2000) effective compared with the procedure normally carried out on board this vessel (NORM method) for the zooplankton community. However, BWE was more efficient in removing microplankton than zooplankton in 1999 while the opposite pattern occurred in 2000. The seasonal timing of voyages and the BWE site influenced the density and composition of species introduced to tanks during BWE.©2011 Oxford University Press.
MAPS, F., S. PLOURDE, B. ZAKARDJIAN, 2010. Control of dormancy by lipid metabolism in Calanus finmarchicus : a population model test. Mar. Ecol. Prog. Ser., 403: 165-180 .
The life cycle of Calanus finmarchicus includes a prolonged dormancy phase that allows it to avoid the unfavourable environmental conditions typical of the upper ocean from late summer to early spring in the subarctic North Atlantic. Recent demographic, physiological and genetic evidence supports the hypothesis of a crucial role for lipid accumulation and metabolism in the control of dormancy. We present a stage-resolving biomass model of C. finmarchicus, implementing a mechanistic approach of the control of dormancy based on this lipid hypothesis. The dormancy process obeys 2 rules: (1) active copepodite stage Vs (C5s) enter dormancy when the ratio of lipid to total body carbon exceeds some threshold, and (2) diapausing C5s exit dormancy when their lipid storage approaches a lower threshold. We implemented the model into a 1-dimensional water column framework and compared our results to 2 consecutive years of observations of stage-specific copepodite abundances and lipid content of C5 from the Northwest Gulf of St. Lawrence, Canada. The model produced realistic phenology and temporal patterns in lipid content of C. finmarchicus in response to the observed environmental forcing. Interannual variations in the timing of entry and contributions of different generations to the overwintering stock were shown. Our results are consistent with the hypothesis of a lipid-mediated control of entrance and exit from dormancy in C. finmarchicus.©2010 Inter-Research
PLOURDE, S., I. McQUINN, 2009. Zones d'importance écologique et biologique dans le golfe du Saint-Laurent : zooplancton et production secondaire ; Ecologically and biologically significant areas in the Gulf of St. Lawrence : zooplankton and secondary production. MPO, Secrétariat canadien de consultation scientifique, Avis scientifique, 2009/104, 31 p .
This research document presents candidate ecologically and biologically significant areas (SA) for zooplankton (biomass, indices of secondary production) in the Gulf of St. Lawrence. Areas characterized by greater biomass of three distinct size classes/groups of zooplankton (mesozooplankton <1 mm et > 1 mm, macrozooplankton) and by a high index of secondary production estimated from the egg production of adult females of dominant copepod species have been determined using spatial data collected in 1999-2000 and 2005. Additionally, results from a 3-D coupled biological-physical model of the copepod Calanus finmarchicus ran for the year 1999 and acoustic data collected in 2005 are used to complete the information. Twelve SA have been identified, with the lower estuary, the northern area in the northwest GSL, the Gaspé Current, the coastal area in the southern GSL (including the Baie-des-Chaleurs), the Maximum Turbidity Zone (middle estuary), and the region extending from the tip of the Gaspé Peninsula into the outer Baie-des-Chaleurs being the most important SA. However, recognizing that these SA correspond to regions that have been better sampled, we recommend that this information should be carefully used and provide recommendations for future work.
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 .
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.
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
SIROIS, P., G. DIAB, A.-L. FORTIN, S. PLOURDE, J.A. GAGNÉ, N. MÉNARD, 2009. Recrutement des poissons dans le fjord du Saguenay;Fish recruitment in the Saguenay Fjord. Rev. Sci. Eau;J. Water Sci., 22(2): 341-352 .
In the Saguenay Fjord, the fish community is composed of more than 60 marine, diadromous and freshwater species, including many species exploited by the winter sport fishery such as the rainbow smelt (Osmerus mordax), redfish (Sebastes spp.), Atlantic cod (Cadus morhua), Greenland cod (Cadus ogac), and Greenland halibut (Reinhardtius hippoglossoides). We do not know if the recruitment of the fish species exploited by the winter sport fishery depends on the local production of recruits in the Saguenay Fjord or on exchanges with the St. Lawrence Estuary populations. Hence, we measured the spado-temporal distribution ofichthyoplankton in the Fjord to identify zones of larval production, retention or advection, in order to investigate the recruitment mechanisms of these stocks. We sampled ichthyoplankton at 21 stations on six occasions, from May to October 2004, and on five occasions, from June to September 2005. Results indicated that the recruitment of capelin (Mallotus villosus) and of the anadromous rainbow smelt (Osmerus mordax) relied on the local production and retention oflarvae within the Fjord. However, the recruitment of redfish (Sebastes spp.) and cods (Cadus spp.) depended on the immigration of juveniles from the St. Lawrence Estuary. Our results are corroborated by a review of previous studies of these fish populations. Studying the recruitment mechanisms of fish populations in the Saguenay Fjord supports a sustainable exploitation of these locally important fisheries resources, in accordance with the mission of Fisheries and Oceans Canada and consistent with the conservation program of the Saguenay St. Lawrence Marine Park.©2009 RSE inc.
PLOURDE, S., P. PÉPIN, E.J.H. HEAD, 2009. Long-term seasonal and spatial patterns in mortality and survival of Calanus finmarchicus across the Atlantic Zone Monitoring Programme region, Northwest Atlantic. ICES J. Mar. Sci., 66(9): 1942-1958 .
The vertical life table method was used to estimate stage-specific daily mortality rates and survival from 1999 to 2006 for Calanus finmarchicus sampled in the Canadian Atlantic Zone Monitoring Programme, which covers the Newfoundland–Labrador Shelf (NLS), Gulf of St Lawrence (GSL), and Scotian Shelf (SS). Stage-specific mortality rates and survival showed significant regional and seasonal differences, with the largest signal associated with variations in temperature. Density-dependent mortality, associated with the abundance of C6 females, was the main factor influencing mortality in the egg–C1 transition during the period of population growth in spring on the SS, and in summer in the GSL and on the NLS. In autumn, mortality in egg–C1 was positively related to temperature and negatively related to phytoplankton biomass, with particularly high mortality rates on the SS. The integration of our results into stage-specific recruitment rates from egg to C5 revealed that C. finmarchicus populations experience their greatest loss (mortality) during the egg–C1 transition. Loss during development to C1 was greater in the GSL than in the other regions during the period of population growth, resulting in lower recruitment success in the GSL. In autumn, C. finmarchicus showed low stage-specific daily recruitment rates on the SS at high temperatures, and low phytoplankton biomass compared with those in the GSL and on the NLS. Our findings reinforce the necessity of describing regional and seasonal patterns in mortality and survival to understand factors controlling the population dynamics of C. finmarchicus.©2009 Oxford Journals
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.
JOHNSON, C., A. LEISING, J.A. RUNGE, J.J.H. HEAD, P. PÉPIN, S. PLOURDE, E.DURBIN, 2008. Understanding Copepod Life History Patterns Through Inter-Regional Comparison of AZMP Zooplankton Data. AZMP Bull. PMZA, 7: 21-26 .
[Abstract only available in French]
Des séries temporelles de données démographiques provenant de quatre stations fixes dans lAtlantique Nord-Ouest révèlent la variabilité dans le moment dentrée et de sortie de la dormance, ou de la suspension du développement, chez des sous-populations du copépode Calanus finmarchicus. Afin de tester des hypothèses sur les signaux environnementaux contrôlant la dormance, des indicateurs basés sur les changements dans les proportions des stades de développement ont été développés. Aucun signal environnemental seul (la photopériode, la température en surface, ou la concentration de chlorophylle a moyenne en surface) na expliqué en totalité les dates dentrée et de sortie pour toutes les stations. Parmi les hypothèses mises de lavant pour expliquer la dormance chez les espèces de Calanus, nous ne pouvons éliminer lhypothèse de la fenêtre daccumulation de lipide pour linitiation de la dormance ou de «lhorloge interne» modulée par les lipides contrôlant la durée de la dormance. La prémisse de base est que les individus peuvent entrer en dormance seulement si leur historique dalimentation et de température leur permet daccumuler suffisamment de lipides pour survivre la période hivernale, muer et initier les premiers stades de maturation et de développement des gonades. Une compréhension mécaniste de la dormance est cruciale afin de modéliser et de prédire leffet du changement climatique sur les espèces dominantes de copépodes, ainsi que sur leurs prédateurs et leurs proies.
Predicting fluctuations in recruitment of commercial marine fish remains the Holy Grail of fisheries science. In previous studies, we identified statistical relationships linking Atlantic mackerel (Scomber scombrus) recruitment to regional climate, zooplankton biomass, and the production of copepod nauplii over a decade (1982-1991) that included the exceptionally strong year class of 1982. Here we tested the validity of these relationships by adding a second decade (1992-2003) of observations that includes another exceptional year class in 1999. We provide the first field-based evidence linking availability of plankton prey in the sea to early growth of larval fish and to year-class strength in a commercially exploited marine fish. Recruitment is shown to strongly depend on production of the copepod nauplii species that contribute to the diet of mackerel larvae. Both strong year classes were characterized by exceptionally high availability of these specific prey. We suggest that mackerel recruitment can be anticipated 3 years in advance based on prey availability during the first weeks of planktonic life and predict a strong year class for fish hatched in 2006.©2008 NRC Canada
JOHNSON, C.L., A. W. LEISING, J.A. RUNGE, E.J.H. HEAD, P. PEPIN, S. PLOURDE, E. G. DURBIN, 2008. Characteristics of Calanus finmarchicus dormancy patterns in the Northwest Atlantic. ICES J. Mar. Sci., 65(3): 339-350 .
Demographic time-series from four fixed stations in the Northwest Atlantic Ocean demonstrate variable timing of entry into and emergence from dormancy in subpopulations of the planktonic copepod Calanus finmarchicus. A proxy for timing of entry was established as the date each year when the proportion of the fifth copepodid stage (CV) in the subpopulation rose to half its overall climatological maximum CV proportion at that station. The proxy for timing of emergence at each station was set as the first date when adults were more than 10 % of the total abundance of copepodid stages. An alternate emergence proxy date was determined by back-calculating the spawning dates of the first early copepodid stages appearing in spring, using a stage-structured, individual-based model. No single environmental cue (photoperiod, surface temperature, or average surface-layer chlorophyll a concentration) consistently explained entry or emergence dates across all stations. Among hypotheses put forward to explain dormancy in Calanus species, we cannot eliminate the lipid accumulation window hypothesis for onset of dormancy or a lipid-modulated endogenous timer controlling dormancy duration. The fundamental premise of these hypotheses is that individuals can only enter dormancy if their food and temperature history allows them to accumulate sufficient lipid to endure overwintering, moult, and undergo early stages of gonad maturation.©2007 International Council for the Exploration of the Sea
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.
PLOURDE, S., R.G. CAMPBELL, C.J. ASHJIAN, D.A. STOCKWELL, 2005. Seasonal and regional patterns in egg production of Calanus glacialis/marshallae in the Chukchi and Beaufort Seas during spring and summer, 2002. Deep-Sea Res., Part II, 52 (24-26): 3411-3426 .
Understanding the physical and biogeochemical processes that control the exchange of biogenic carbon within and between the arctic shelves, slopes, and deep basins is a key objective of the Western Arctic Shelf-Basin Interaction program (SBI). Here, egg production (EP) of the dominant copepod Calanus glacialis/marshallae was used as an indicator of food limitation for the mesozooplankton community in the Chukchi and Beaufort Seas in spring and summer, 2002. Both C. glacialis and C. marshallae may occur in this region but the two cannot easily be differentiated visually. Four oceanographic regions were objectively identified that roughly corresponded to the different pathways in circulation of nutrient-rich Pacific water. A 'transition' region characterized by 'older' Pacific water was located at the shelfbreak and separated the nutrient-rich shelf water and the low-nutrient waters of the deep basin. The observed spatial pattern in EP in C. glacialis/marshallae in spring and summer resulted both from the different water mass environments and from the reproductive cycle of the species. EP was greater on the shelf than in the basin, corresponding to differences in body size and nitrogen condition factor (NCF) in females, while the egg viability was generally high throughout the study area. EP showed no relationship with low-chlorophyll a biomass under heavy ice-cover in spring, while a significant relationship was observed in the more open water in summer. Adult female carbon condition factor (CCF) was much higher in summer, reflecting the accumulation of lipids during the growth season. Small animals with a markedly greater NCF dominated on the shelf. The shelfbreak region contained a mixture of females from the shelf and the basin with intermediate sizes, conditions, and EP rates. The occurrence of water typical of the 'transition' shelfbreak region and elevated EP in C. glacialis/marshallae offshore on the Barrow Canyon and East Barrow sections indicated offshore transport of productive shelf water and the associated plankton community. The input of nutrient-rich Pacific water and accompanying elevated production to the northern Chukchi Sea and the Chukchi-Beaufort shelfbreak region may contribute to the reproductive success of C. glacialis/marshallae in this region.
ASHJIAN, C.J., S.M. GALLAGER, S. PLOURDE, 2005. Transport of plankton and particles between the Chukchi and Beaufort Seas during summer 2002, described using a Video Plankton Recorder. Deep-Sea Res., Part II, 52(24-26): 3259-3280 .
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