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Gregory Beaugrand - One of the best experts on this subject based on the ideXlab platform.

  • Macrophysiology of Calanus finmarchicus in the North Atlantic Ocean
    Progress in Oceanography, 2011
    Co-Authors: Pierre Helaouët, Gregory Beaugrand, Philip C. Reid
    Abstract:

    Copepods represent the major part of the dry weight of the mesozooplankton in pelagic ecosystems and therefore have a central role in the secondary production of the North Atlantic Ocean. The calanoid copepod species Calanus finmarchicus is the main large copepod in subarctic waters of the North Atlantic, dominating the dry weight of the mesozooplankton in regions such as the northern North Sea and the Norwegian Sea. The objective of this work was to investigate the relationships between both the fundamental and realised niches of C. finmarchicus in order to better understand the future influence of global climate change on the abundance, the spatial distribution and the phenology of this key-structural species. Based on standardised Principal Component Analyses (PCAs), a macroecological approach was applied to determine factors affecting the spatial distribution of C. finmarchicus and to characterise its realised niche. Second, an ecophysiological model was used to calculate the Potential Egg Production Rate (PEPR) of C. finmarchicus and the centre of its fundamental niche. Relationships between the two niches were then investigated by correlation analysis. We found a close relationship between the fundamental and realised niches of C. finmarchicus at spatial, monthly and decadal scales. While the species is at the centre of its niche in the subarctic gyre, our joint macroecological and macrophysiological analyses show that it is at the edge of its niche in the North Sea, making the species in this region more vulnerable to temperature changes.

  • Future climate-driven shifts in distribution of Calanus finmarchicus
    Global Change Biology, 2010
    Co-Authors: Gabriel Reygondeau, Gregory Beaugrand
    Abstract:

    Calanus finmarchicus is a key-structural species of the North Atlantic polar biome. The species plays an important trophic role in subpolar and polar ecosystems as a grazer of phytoplankton and as a prey for higher trophic levels such as the larval stages of many fish species. Here, we used a recently developed ecological niche model to assess the ecological niche (sensu Hutchinson) of C. finmarchicus and characterize its spatial distribution. This model explained about 65% of the total variance of the observed spatial distribution inferred from an independent dataset (data of the continuous plankton recorder survey). Comparisons with other types of models (structured population and ecophysiological models) revealed a clear similarity between modeled spatial distributions at the scale of the North Atlantic. Contemporary models coupled with future projections indicated a progressive reduction of the spatial habitat of the species at the southern edge and a more pronounced one in the Georges Bank, the Scotian Shelf and the North Sea and a potential increase in abundance at the northern edge of its spatial distribution, especially in the Barents Sea. These major changes will probably lead to a major alteration of the trophodynamics of North Atlantic ecosystems affecting the trophodynamics and the biological carbon pump.

  • Water column stability and Calanus finmarchicus
    Journal of Plankton Research, 2010
    Co-Authors: Gabriel Reygondeau, Gregory Beaugrand
    Abstract:

    Many authors have suggested that the abundance of the subarctic species Calanus finmarchicus can be influenced by the structure of the water column. Unfortunately to date, such a link has never been confirmed either experimentally or statistically. By using a macroecological approach, we investigated this hypothesis and showed that it varies with the developmental staged of the species. First, we implemented a new statistical procedure, based on an exponentially weighted moving average, to identify and quantify the depth and intensity of the thermocline. We applied the technique on 1,005,619 temperature profiles over the North Atlantic Ocean and provided a mapping of these two descriptors at a seasonal scale. Second, we studied the relationships between the depth and the intensity of the thermocline and Calanus finmarchicus using a biological dataset of 99,599 sampling stations. Our results suggested that the characteristics of the water column influence the spatial distribution of C. finmarchicus. The frequency in the occurrence of this species decreases when stratification rises. Our results further revealed that the effect is more pronounced on young copepodite stages. Such findings are of interest since, in a warmer world, water stratification is expected to increase, making more likely a reduction in the abundance of this key-structural species.

  • Water column stability and Calanus finmarchicus
    Journal of Plankton Research, 2010
    Co-Authors: Gabriel Reygondeau, Gregory Beaugrand
    Abstract:

    Many authors have suggested that the abundance of the subarctic species Calanus finmarchicus can be influenced by the structure of the water column. Unfortunately, to date, such a link has never been confirmed either experimentally or statistically. By using a macroecological approach, we investigated this hypothesis and showed that it varies with the developmental stage of the species. First, we implemented a new statistical procedure, based on an exponentially weighted moving average, to identify and quantify the depth and intensity of the thermocline. We applied the technique on 1 005 619 temperature profiles over the North Atlantic Ocean and provide a mapping of these two descriptors at a seasonal scale. Second, we studied the relationships between the depth and the intensity of the thermocline and C. finmarchicus using a biological data set of 99 599 sampling stations. Our results suggested that the characteristics of the water column influence the spatial distribution of C. finmarchicus. The frequency in the occurrence of this species decreases when stratification rises. Our results further revealed that the effect is more pronounced for young copepodite stages. Such findings are of interest, since, in a warmer world, water stratification is expected to increase, making more likely a reduction in the abundance of this key species in the North Atlantic.

  • Water column stratification and Calanus finmarchicus
    Journal of Plankton Research, 2010
    Co-Authors: Gabriel Reygondeau, Gregory Beaugrand
    Abstract:

    Many authors have suggested that the abundance of the subarctic species Calanus finmarchicus can be influenced by the structure of the water column. Unfortunately, to date, such a link has never been confirmed either experimentally or statistically. By using a macroecological approach, we investigated this hypothesis and showed that it varies with the developmental stage of the species. First, we implemented a new statistical procedure, based on an exponentially weighted moving average, to identify and quantify the depth and intensity of the thermocline. We applied the technique on 1 005 619 temperature profiles over the North Atlantic Ocean and provide a mapping of these two descriptors at a seasonal scale. Second, we studied the relationships between the depth and the intensity of the thermocline and C. finmarchicus using a biological data set of 99 599 sampling stations. Our results suggested that the characteristics of the water column influence the spatial distribution of C. finmarchicus. The frequency in the occurrence of this species decreases when stratification rises. Our results further revealed that the effect is more pronounced for young copepodite stages. Such findings are of interest, since, in a warmer world, water stratification is expected to increase, making more likely a reduction in the abundance of this key species in the North Atlantic

Gabriel Reygondeau - One of the best experts on this subject based on the ideXlab platform.

  • Future climate-driven shifts in distribution of Calanus finmarchicus
    Global Change Biology, 2010
    Co-Authors: Gabriel Reygondeau, Gregory Beaugrand
    Abstract:

    Calanus finmarchicus is a key-structural species of the North Atlantic polar biome. The species plays an important trophic role in subpolar and polar ecosystems as a grazer of phytoplankton and as a prey for higher trophic levels such as the larval stages of many fish species. Here, we used a recently developed ecological niche model to assess the ecological niche (sensu Hutchinson) of C. finmarchicus and characterize its spatial distribution. This model explained about 65% of the total variance of the observed spatial distribution inferred from an independent dataset (data of the continuous plankton recorder survey). Comparisons with other types of models (structured population and ecophysiological models) revealed a clear similarity between modeled spatial distributions at the scale of the North Atlantic. Contemporary models coupled with future projections indicated a progressive reduction of the spatial habitat of the species at the southern edge and a more pronounced one in the Georges Bank, the Scotian Shelf and the North Sea and a potential increase in abundance at the northern edge of its spatial distribution, especially in the Barents Sea. These major changes will probably lead to a major alteration of the trophodynamics of North Atlantic ecosystems affecting the trophodynamics and the biological carbon pump.

  • Water column stability and Calanus finmarchicus
    Journal of Plankton Research, 2010
    Co-Authors: Gabriel Reygondeau, Gregory Beaugrand
    Abstract:

    Many authors have suggested that the abundance of the subarctic species Calanus finmarchicus can be influenced by the structure of the water column. Unfortunately to date, such a link has never been confirmed either experimentally or statistically. By using a macroecological approach, we investigated this hypothesis and showed that it varies with the developmental staged of the species. First, we implemented a new statistical procedure, based on an exponentially weighted moving average, to identify and quantify the depth and intensity of the thermocline. We applied the technique on 1,005,619 temperature profiles over the North Atlantic Ocean and provided a mapping of these two descriptors at a seasonal scale. Second, we studied the relationships between the depth and the intensity of the thermocline and Calanus finmarchicus using a biological dataset of 99,599 sampling stations. Our results suggested that the characteristics of the water column influence the spatial distribution of C. finmarchicus. The frequency in the occurrence of this species decreases when stratification rises. Our results further revealed that the effect is more pronounced on young copepodite stages. Such findings are of interest since, in a warmer world, water stratification is expected to increase, making more likely a reduction in the abundance of this key-structural species.

  • Water column stability and Calanus finmarchicus
    Journal of Plankton Research, 2010
    Co-Authors: Gabriel Reygondeau, Gregory Beaugrand
    Abstract:

    Many authors have suggested that the abundance of the subarctic species Calanus finmarchicus can be influenced by the structure of the water column. Unfortunately, to date, such a link has never been confirmed either experimentally or statistically. By using a macroecological approach, we investigated this hypothesis and showed that it varies with the developmental stage of the species. First, we implemented a new statistical procedure, based on an exponentially weighted moving average, to identify and quantify the depth and intensity of the thermocline. We applied the technique on 1 005 619 temperature profiles over the North Atlantic Ocean and provide a mapping of these two descriptors at a seasonal scale. Second, we studied the relationships between the depth and the intensity of the thermocline and C. finmarchicus using a biological data set of 99 599 sampling stations. Our results suggested that the characteristics of the water column influence the spatial distribution of C. finmarchicus. The frequency in the occurrence of this species decreases when stratification rises. Our results further revealed that the effect is more pronounced for young copepodite stages. Such findings are of interest, since, in a warmer world, water stratification is expected to increase, making more likely a reduction in the abundance of this key species in the North Atlantic.

  • Water column stratification and Calanus finmarchicus
    Journal of Plankton Research, 2010
    Co-Authors: Gabriel Reygondeau, Gregory Beaugrand
    Abstract:

    Many authors have suggested that the abundance of the subarctic species Calanus finmarchicus can be influenced by the structure of the water column. Unfortunately, to date, such a link has never been confirmed either experimentally or statistically. By using a macroecological approach, we investigated this hypothesis and showed that it varies with the developmental stage of the species. First, we implemented a new statistical procedure, based on an exponentially weighted moving average, to identify and quantify the depth and intensity of the thermocline. We applied the technique on 1 005 619 temperature profiles over the North Atlantic Ocean and provide a mapping of these two descriptors at a seasonal scale. Second, we studied the relationships between the depth and the intensity of the thermocline and C. finmarchicus using a biological data set of 99 599 sampling stations. Our results suggested that the characteristics of the water column influence the spatial distribution of C. finmarchicus. The frequency in the occurrence of this species decreases when stratification rises. Our results further revealed that the effect is more pronounced for young copepodite stages. Such findings are of interest, since, in a warmer world, water stratification is expected to increase, making more likely a reduction in the abundance of this key species in the North Atlantic

Kurt S. Tande - One of the best experts on this subject based on the ideXlab platform.

  • clinical safety evaluation of marine oil derived from Calanus finmarchicus
    Regulatory Toxicology and Pharmacology, 2016
    Co-Authors: Kurt S. Tande, Trung D Vo, Barry Lynch
    Abstract:

    Marine oils are rich in polyunsaturated fatty acids (PUFAs), including docosahexaenoic and eicosapentaenoic acid. These PUFAs are associated with health benefits and additional sustainable sources of marine oils are desirable. One of the source organisms is Calanus finmarchicus, a copepod endemic to the North Atlantic. PUFAs in the lipid fraction of this organism are largely in the form of wax esters. To assess the safety of these wax esters as a source of PUFAs, a randomized, double-blinded, placebo-controlled clinical trial was conducted whereby 64 subjects consumed 2 g Calanus oil in capsule form daily for a period of one year. A group of 53 subjects consumed placebo capsules. At baseline, 6-, and 12-months, series of evaluations were conducted, including: vital signs, clinical chemistry and hematological evaluations, and adverse event reporting. Food intake and physical exercise were controlled by means of a questionnaire. There were no effects on Calanus oil treatment on any of the safety parameters measured. A slight increase in the incidence of eczema was reported in the Calanus oil group, but the response was minor in nature, not statistically significant after controlling for multiple comparisons, and could not be attributed to treatment.

  • cannibalism by female Calanus finmarchicus on naupliar stages
    Marine Ecology Progress Series, 2006
    Co-Authors: Sunnje Linnea Basedow, Kurt S. Tande
    Abstract:

    Cannibalism has been assumed to strongly affect population dynamics of the calanoid copepod Calanus spp. during the pre-bloom phase. We hypothesised that Calanus finmarchicus females cannibalise on nauplii until there is enough phytoplankton available to fulfil their energy demands. We tested this experimentally by exposing females to different concentrations of algae Thalassiosira weissflogii (0.08 to 22.58 µg chlorophyll a l -1 ) and nauplii (stages NI and NII, 0 to 20 nauplii l -1 ). Clearance rates on algae and on nauplii were high (221 and 689 ml ind. -1 d -1 , respec- tively), but were independent of algal concentration. Females ingested naupliar carbon at a higher proportion than was available, even when naupliar carbon accounted for <5% of the totally available carbon. Predation rates on nauplii increased linearly and significantly (p < 0.001) with increasing nauplii abundance. Compared with literature values, predation rates were considerably higher (up to 10 nauplii ind. -1 d -1 ) than predation rates of the sibling species C. helgolandicus and C. pacificus on their nauplii, and also higher than predation rates of the omnivorous copepod Metridia lucens on Calanus sp. nauplii. Based on our data, we estimated that as much as 20% d -1 of the nauplii popula- tion may be preyed on by adult females. Thus, during the pre-bloom period when abundance of nau- plii is small and that of females is large, cannibalism may prevent recruitment to the G1 population.

  • A model study of demography and spatial distribution of Calanus finmarchicus at the Norwegian coast
    Deep-sea Research Part Ii-topical Studies in Oceanography, 2000
    Co-Authors: O.p. Pedersen, Kurt S. Tande, Dag Slagstad
    Abstract:

    Abstract For calanoid copepods living in an advective environment, any predictive life history model relies on our comprehension of the significance of advection and environmental parameters. To study the propagation of an initial population of Calanus finmarchicus with respect to spatial distribution and stage development throughout time, we have developed a lagrangian particle-tracking model. The advection of the population is driven by a physical component, while a biological model describes vertical migration and stage development. The physical model is composed of large- and small-scale current fields, while the biological model reflects our current understanding of vertical migration and spawning behavior resolved spatially. The results indicate that the population is distributed along the major current branches in the Norwegian Sea, with fractions entering the Barents Sea, West-Spitsbergen and the Norwegian Shelf. A part of the population spends their entire life progression in the oceanic realm, with relatively low rate of advection. The stage progression shows that C. finmarchicus developing in the oceanic region has a late spawning period compared to the fraction of the population residing in the near coastal regions. The life history of Calanus finmarchicus in Norwegian waters is considered to deviate between one and three generations per year. In the shelf region, Lofoten is often referred to as the northernmost area where a two-generation cycle occurs. Our two-generation simulations are compared with field data obtained from the OMEX study site, and the results indicate that the two-generation cycle is a very plausible explanation to the obtained data. The spawning regions of G2 are both oceanic regions in close vicinity to the Norwegian Atlantic Current flowing along the shelf break, and the mid-Norwegian shelf.

  • Sex change and female dimorphism in Calanus finmarchicus
    Marine Ecology Progress Series, 1999
    Co-Authors: Camilla Svensen, Kurt S. Tande
    Abstract:

    Adult females were examined from November until spring in northern Norway (30" N) to determine the fraction with the quadrithek and the fraction with the trithek setal pattern on the antennule. The quadrithek (Q) pattern is a male characteristic in which odd numbered, proximal segments carry 2 aesthetascs and 2 setae; the trithek (T) pattern has 1 aesthetics on all antennular segments. The frequency of quadrithek females (%Q = 100 X [Q/T]) varied with season. It peaked at 38% in February, declining to 25 % in March. Higher proportions appeared early, consistently between years, i.e. higher proportions were found among the first females emerging from the stock of resting copepodids. In light of the hypothesis of Fleminger (1985; Mar Biol 88:273-294) that females w t h the quadrithek pattern result from sex switching by genetic males, we tested whether %Q in newly moulted females could be altered by separate exposure of the maturing CVs to adult males or females. The experiments were run with specimens from Gratsund during the last 3 wk prior to moulting of CVs in the field. Of females not exposed to adults as CVs, 35% had quadrithek patterns, while those exposed to adult males or females produced 33 and 37% quadritheks respectively. In these experiments, presence of adult Calanus finmarchicus (Gunnerus) did not influence the proportion of females with male characteristics. No evidence for sex specific pheromones was found and therefore the stimulus for sex change was not revealed. A possible influence of the environment on C. finmarchicus sex determination (ESD) is suggested and discussed.

Jeffrey A. Runge - One of the best experts on this subject based on the ideXlab platform.

  • Biogeography of key mesozooplankton species in the North Atlantic and egg production of Calanus finmarchicus
    Earth System Science Data, 2015
    Co-Authors: Webjørn Melle, Jeffrey A. Runge, Stéphane Plourde, Catherine L. Johnson, Erica J. H. Head, Sigrun Jonasdottir, Claudia Castellani, James J. Pierson, Priscilla Licandro, Cecilie Broms
    Abstract:

    Abstract. Here we present a new, pan-North-Atlantic compilation of data on key mesozooplankton species, including the most important copepod, Calanus finmarchicus. Distributional data of eight representative zooplankton taxa, from recent (2000–2009) Continuous Plankton Recorder data, are presented, along with basin-scale data of the phytoplankton colour index. Then we present a compilation of data on C. finmarchicus, including observations of abundance, demography, egg production and female size, with accompanying data on temperature and chlorophyll. This is a contribution by Canadian, European and US scientists and their institutions: http://doi.pangaea.de/10.1594/PANGAEA.820732 , http://doi.pangaea.de/10.1594/PANGAEA.824423 , http://doi.pangaea.de/10.1594/PANGAEA.828393 (please also see Melle et al., 2013; Castellani and Licandro, 2013; Jonasdottir et al., 2014).

  • The impact of increasing temperatures on dormancy duration in Calanus finmarchicus
    Journal of Plankton Research, 2013
    Co-Authors: James J. Pierson, Andrew W. Leising, Harold P. Batchelder, Whitley J. Saumweber, Jeffrey A. Runge
    Abstract:

    Dormancy is a key life history trait of planktonic calanoid copepods in the genus Calanus. Empirical evidence suggests that duration of dormancy is controlled by ambient temperature driving lipid metabolism in individuals. Here, we use the temperature-dependent metabolic rates of overwintering individuals to show that increasing temperatures, associated with global climate change over the next several decades, may reduce dormancy duration for the north Atlantic species C. finmarchicus by up to 40 days. Our calculations are based on comparing predicted dormancy duration for individuals of a given size at specific temperatures to dormancy duration at warmer temperatures and smaller size. We also provide corrections to the relationship of dormancy duration described by Saumweber and Durbin [Estimating potential diapause duration in Calanus finmarchicus. Deep Sea Res. Pt. II., 53, 2597‐2617.]. Our calculations indicate that changing temperatures in the sea may lead to phenological shifts in life histories of C. finmarchicus and congeners, which may have implications for planktonic food web and trophic dynamics.

  • Characteristics of Calanus finmarchicus dormancy patterns in the Northwest Atlantic
    ICES Journal of Marine Science, 2007
    Co-Authors: Catherine L. Johnson, Jeffrey A. Runge, Stéphane Plourde, Andrew W. Leising, Erica J. H. Head, Pierre Pepin, Edward G. Durbin
    Abstract:

    Johnson, C. L., Leising, A. W., Runge, J. A., Head, E. J. H., Pepin, P., Plourde, S., and Durbin, E. G. 2008. Characteristics of Calanus finmarchicus dormancy patterns in the Northwest Atlantic. - ICES Journal of Marine Science, 65: 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.

  • A revised methodology for prediction of egg production Calanus finmarchicus from preserved samples
    Journal of Plankton Research, 2003
    Co-Authors: Barbara Niehoff, Jeffrey A. Runge
    Abstract:

    We describe here a refinement of the method for the estimation of egg production rates of the planktonic copepod, Calanus finmarchicus, from formaldehyde-preserved samples. We present criteria for classing pre-spawned clutches as either high, intermediate or low in number. The method allows reproductive assessment of preserved females without the need for staining and is capable of accurate asssessments in food-limited environments.

  • SHORT COMMUNICATION A revised methodology for prediction of egg production Calanus finmarchicus from preserved samples
    2003
    Co-Authors: Barbara Niehoff, Jeffrey A. Runge, Hole Oceanographic, Alfred Wegener
    Abstract:

    We describe here a refinement of the method for the estimation of egg production rates of the planktonic copepod, Calanus finmarchicus, from formaldehyde-preserved samples. We present criteria for classifying pre-spawned clutches as either high, intermediate or low in number. The method allows reproductive assessment of preserved females without the need for staining and is capable of accurate asssessments in food-limited environments.

Eilif Gaard - One of the best experts on this subject based on the ideXlab platform.

  • Wax-ester mobilization by female Calanus finmarchicus (Gunnerus) during spring ascendance and advection to the Faroe Shelf
    ICES Journal of Marine Science, 2008
    Co-Authors: Matias L. Madsen, Eilif Gaard, Benni Winding Hansen
    Abstract:

    Madsen, M. L., Gaard, E., and Hansen, B. W. 2008. Wax-ester mobilization by female Calanus finmarchicus (Gunnerus) during spring ascendance and advection to the Faroe Shelf. - ICES Journal of Marine Science, 65: 1112-1121.Time of ascendance and initiation of reproduction in Calanus finmarchicus is closely correlated with the phytoplankton spring bloom. However, significant egg production can take place before the bloom, fuelled by mobilizing stored wax-ester lipids. Calanus finmarchicus from stations on the Faroe Shelf were compared with specimens collected off the shelf. Biological parameters such as gut contents, egg production, developmental stage, and lipid content were determined and correlated with phytoplankton concentration and spatial distribution along two transects in late April 2003 across the shelf northeast and southwest of the Faroe Islands. Grazing by C. finmarchicus on phytoplankton was significantly lower northeast of the Faroe plateau. However, the egg production was generally high for a pre-bloom situation, with significantly higher rates of egg production on the shelf than off it, along both transects. Wax-ester content of female C. finmarchicus was significantly higher and more variable at off-shelf stations than on the shelf (

  • Abundance, feeding and reproduction of Calanus finmarchicus in the Irminger Sea and on the northern Mid-Atlantic Ridge in June
    Deep-sea Research Part Ii-topical Studies in Oceanography, 2007
    Co-Authors: Astthor Gislason, Eilif Gaard, Høgni Debes, Tone Falkenhaug
    Abstract:

    Abstract Measurements of hydrography, chlorophyll a, abundance, egg production rates and gut fluorescence of Calanus finmarchicus were made on the northern Mid-Atlantic Ridge, along a north–south transect extending from Iceland to the Azores (∼60–44°N, 25–35°W) in June 2004. In addition, similar data were sampled in the Irminger Sea and on the Reykjanes Ridge in June 2003. The results show marked differences in abundance, phytoplankton ingestion rates and egg production rates from north to south. C. finmarchicus was most abundant in the central Irminger Sea (∼80,000–160,000 individuals m−2, 0–100 m), with abundance declining drastically (

  • Egg production of Calanus finmarchicus—A basin-scale study
    Deep-sea Research Part Ii-topical Studies in Oceanography, 2007
    Co-Authors: Erling Kaare Stenevik, Astthor Gislason, Eilif Gaard, Irina Prokopchuk, Webjørn Melle, Cecilie Broms, Bjørnar Ellertsen
    Abstract:

    Egg production of Calanus finmarchicus was studied during joint basin-scale surveys in April-June 2003 in the Norwegian Sea. Surveys covered the whole Norwegian Sea and were conducted from Norwegian, Icelandic and Faroese research vessels. Stations were classified as being in pre-bloom, bloom or post-bloom phase according to levels of chlorophyll a and nitrate. Individual egg production rates and population egg production rates were calculated and compared between areas. Both individual egg production rates (eggs female -1 day -1 ) and population egg production rates (eggs m -2 day -1 ) were significantly higher in bloom areas compared with pre-bloom and post-bloom areas. However, when integrated over an estimated duration of the three phases, the time-integrated egg production (eggs m -2 ) in most years was highest in the pre-bloom phase, and this was explained by the longer duration of this phase compared with the two other phases.

  • Variations in the advection of Calanus finmarchicus onto the Faroe Shelf
    ICES Journal of Marine Science, 2000
    Co-Authors: Eilif Gaard, B. Hansen
    Abstract:

    The copepod Calanus finmarchicus is a dominant factor in the marine ecosystem on the Faroe Plateau, but its abundance is highly variable. Interannual differences of about one order of magnitude in Calanus abundance were observed on the shelf in spring and summer. In winter, C. finmarchicus is scarcely found on the Faroe Plateau, but during spring and summer it is imported from offshore by advection. Variations in the numbers of imported overwintered C. finmarchicus on the shelf in April are much larger than in the offshore waters feeding the area, and variability in inflow rates is likely the major explanation. Independent estimates of flushing rates for the shelf water exhibit variations of a similar order of magnitude as the interannual variations in the biomass of C. finmarchicus on the shelf. Prolonged windstress, especially from the southwest, increases the flushing rate, and there is some observational evidence of a relationship between C. finmarchicus abundance on the shelf and water inflow.

  • Life cycle, abundance and transport of Calanus finmarchicus in Faroese waters
    Ophelia, 1996
    Co-Authors: Eilif Gaard
    Abstract:

    Abstract Calanus finmarchicus is the dominant copepod in the open ocean around the Faroe Islands. Measurements from 1990-93 showed that C. finmarchicus in the Atlantic Water outside the Faroe Shelf has two annual generations.The overwintering individuals migrate towards the surface in March-April and their spawning usually peaks in May.The majority of the individuals of this generation reaches stage CV in mid-summer.Some of the overwintering individuals remain in the upper layer and a small number of them spawn again in late summer.To the north of the Iceland-Faroes Front, C. finmarchicus has only one generation the overwintering individuals of which migrate towards the surface later than in the Atlantic Water and have their peak spawning in June.The individuals of this generation reach stages CIV and CV in August-September, when they migrate downwards.The phytoplankton biomasses in spring were higher north of the Iceland-Faroes Front than south of it.Therefore the delay of maturation and spawning north o...