32 research outputs found
Global distributions of microzooplankton abundance and biomass - Gridded data product (NetCDF) - Contribution to the MAREDAT World Ocean Atlas of Plankton Functional Types
No full textMicrozooplankton database. Originally published in: Buitenhuis, Erik, Richard Rivkin, Sévrine Sailley, Corinne Le Quéré (2010) Biogeochemical fluxes through microzooplankton. Global Biogeochemical Cycles Vol. 24, GB4015, doi:10.1029/2009GB003601
This new version has had some mistakes corrected
Data base on heterotrophic dinoflagellates grazing and growth rate as a function of size, prey size and type compiled from the literature
No full textMicrozooplankton (the 20 to 200 µm size class of zooplankton) is recognised as an important part of marine pelagic ecosystems. In terms of biomass and abundance heterotrophic dinoflagellates are one of the important groups of organism in microzooplankton. However, their rates - grazing and growth - , feeding behaviour and prey preferences are poorly known and understood. A set of data was assembled in order to derive a better understanding of heterotrophic dinoflagellates rates, in response to parameters such as prey concentration, prey type (size and species), temperature and their own size. With these objectives, literature was searched for laboratory experiments with information on one or more of these parameters effect studied. The criteria for selection and inclusion in the database included:
(i) controlled laboratory experiment with a known dinoflagellate feeding on a known prey;
(ii) presence of ancillary information about experimental conditions, used organisms - cell volume, cell dimensions, and carbon content. Rates and ancillary information were measured in units that meet the experimenter need, creating a need to harmonize the data units after collection. In addition different units can link to different mechanisms (carbon to nutritive quality of the prey, volume to size limits).
As a result, grazing rates are thus available as pg C dinoflagellate-1 h-1, µm3 dinoflagellate-1 h-1 and prey cell dinoflagellate-1 h-1; clearance rate was calculated if not given and growth rate is expressed as the growth rate per day
Parameterisation of Microprotozooplankton Grazing and Growth: From data analysis to simulations in ecosystem model coupled to general circulation-biogeochemical model.
No full textIn the context of global warming and climate change Biogeochemical Ocean General Circulation Models (BOGCM) are hard pressed to provide clear and realistic answers as to how ecosystems and the carbon cycle are affected. Ecosystem models have developed from the NPZ type (Nutrient-Plankton-Zooplankton) towards the use of several plankton functional types (PFTs) to enhance the prediction of ecosystem feedback on climate change. PFTs are selected on their impact on biogeochemical cycles. Zooplankton PFTs, for example, are mostly defined by size. Microzooplankton, one of these size classes, is a group of interest due to a high biomass and growth rates which allow these organisms to follow fluctuations in prey concentration. Furthermore, they are known to graze ~40-75% of particulate primary production in the surface ocean, against ~10-15% for the mesozooplankton. As a size class, microzooplankton includes several organisms pelagic ciliates, heterotrophic dinoflagellates, foraminifera, metazoans larva and copepods nauplii with different feeding modes, food preferences, grazing and growth rates. Ciliates and heterotrophic dinoflagellates are the main microzooplankton organisms. Although they are both protozoans, their feeding behaviour and preferred prey size have a substantial difference. In order to assess their differences, results from laboratory experiments were compiled from the literature a total of 342 for ciliates and 161 for dinoflagellates. It emerged that both organisms have a growth and a grazing threshold, also both grazing and growth rates depends on organism size and the size ratio with their prey (size expressed as diameter, volume or carbon content). Ciliates exhibit an increase of their maximal grazing rate past the optimal prey:ciliate ratio of 1:10. Dinoflagellates have a maximal grazing rate which increases to a prey:dinoflagellate ratio of 2:1, then continues to increase past this value, with a marked preference for diatoms over other possible prey types. As both ciliates and heterotrophic dinoflagellates have different size ratios with their prey, they will target different prey types. Moreover, both have different functional responses to fluctuations in prey concentration. Ciliates, with a higher threshold concentration and lower half-saturation concentration, will commence grazing later than dinoflagellates, but reach their maximal rates faster. They differ further from dinoflagellates with a higher maximal grazing rate and a lower metabolism. Parameterisation for a microzooplankton, ciliates and heterotrophic dinoflagellates PFTs were obtained from the data and used in a BOGCM. The 12 PFTs have a different impact on the ecosystem and biogeochemical cycles. The dinoflagellate PFT reduces the export and alters the distribution area of high primary production. The ciliate PFT has a similar impact to that of microzooplankton. It is doubtful that the microzooplankton PFT in itself correctly represents ciliates and heterotrophic dinoflagellates. Consequently a separation of both organisms in future models is recommanded to provide a better representation of the ecosystem and its response to climate change
Habitat partitioning in Antarctic krill: Spawning hotspots and nursery areas
No full textAntarctic krill, Euphausia superba, have a circumpolar distribution but are concentrated within the south-west Atlantic sector, where they support a unique food web and a commercial fishery. Within this sector, our first goal was to produce quantitative distribution maps of all six ontogenetic life stages of krill (eggs, nauplii plus metanauplii, calyptopes, furcilia, juveniles, and adults), based on a compilation of all available post 1970s data. Using these maps, we then examined firstly whether “hotspots” of egg production and early stage nursery occurred, and secondly whether the available habitat was partitioned between the successive life stages during the austral summer and autumn, when krill densities can be high. To address these questions, we compiled larval krill density records and extracted data spanning 41 years (1976–2016) from the existing KRILLBASE-abundance and KRILLBASE-length-frequency databases. Although adult males and females of spawning age were widely distributed, the distribution of eggs, nauplii and metanauplii indicates that spawning is most intense over the shelf and shelf slope. This contrasts with the distributions of calyptope and furcilia larvae, which were concentrated further offshore, mainly in the Southern Scotia Sea. Juveniles, however, were strongly concentrated over shelves along the Scotia Arc. Simple environmental analyses based on water depth and mean water temperature suggest that krill associate with different habitats over the course of their life cycle. From the early to late part of the austral season, juvenile distribution moves from ocean to shelf, opposite in direction to that for adults. Such habitat partitioning may reduce intraspecific competition for food, which has been suggested to occur when densities are exceptionally high during years of strong recruitment. It also prevents any potential cannibalism by adults on younger stages. Understanding the location of krill spawning and juvenile development in relation to potentially overlapping fishing activities is needed to protect the health of the south-west Atlantic sector ecosystem
Parameterisation of microzooplankon grazing and growth: from data analysis to simulations in ecosystems model coupled to general circulation-biogeochemical model.
No full textData compilation of dinoflagellates growth rate, grazing rate and gross gowth efficiency from field and labratory experiments
No full textThe present data compilation includes dinoflagellates growth rate, grazing rate and gross growth efficiency determined either in the field or in laboratory experiments. From the existing literature, we synthesized all data that we could find on dinoflagellates. Some sources might be missing but none were purposefully ignored. We did not include autotrophic dinoflagellates in the database, but mixotrophic organisms may have been included. This is due to the large uncertainty about which taxa are mixotrophic, heterotrophic or symbiont bearing. Field data on microzooplankton grazing are mostly comprised of grazing rate using the dilution technique with a 24h incubation period. Laboratory grazing and growth data are focused on pelagic ciliates and heterotrophic dinoflagellates. The experiment measured grazing or growth as a function of prey concentration or at saturating prey concentration (maximal grazing rate). When considering every single data point available (each measured rate for a defined predator-prey pair and a certain prey concentration) there is a total of 801 data points for the dinoflagellates, counting experiments that measured growth and grazing simultaneously as 1 data point
Abnahme- und Wachstumsparametrisierung von Mikroprotozooplankton : Von der Datenanalyse zu Simulationen in mit biogeochemische Zirkulationsmodellen gekoppelten Ökosystemen
No full textIn the context of global warming and climate change Biogeochemical Ocean General Circulation Models (BOGCM) are hard pressed to provide clear and realistic answers as to how ecosystems and the carbon cycle are affected. Ecosystem models have developed from the NPZ type (Nutrient-Plankton-Zooplankton) towards the use of several plankton functional types (PFTs) to enhance the prediction of ecosystem feedback on climate change. PFTs are selected on their impact on biogeochemical cycles. Zooplankton PFTs, for example, are mostly defined by size. Microzooplankton, one of these size classes, is a group of interest due to a high biomass and growth rates which allow these organisms to follow fluctuations in prey concentration. Furthermore, they are known to graze ~40-75% of particulate primary production in the surface ocean, against ~10-15% for the mesozooplankton. As a size class, microzooplankton includes several organisms pelagic ciliates, heterotrophic dinoflagellates, foraminifera, metazoans larva and copepods nauplii with different feeding modes, food preferences, grazing and growth rates. Ciliates and heterotrophic dinoflagellates are the main microzooplankton organisms. Although they are both protozoans, their feeding behaviour and preferred prey size have a substantial difference. In order to assess their differences, results from laboratory experiments were compiled from the literature a total of 342 for ciliates and 161 for dinoflagellates. It emerged that both organisms have a growth and a grazing threshold, also both grazing and growth rates depends on organism size and the size ratio with their prey (size expressed as diameter, volume or carbon content). Ciliates exhibit an increase of their maximal grazing rate past the optimal prey:ciliate ratio of 1:10. Dinoflagellates have a maximal grazing rate which increases to a prey:dinoflagellate ratio of 2:1, then continues to increase past this value, with a marked preference for diatoms over other possible prey types. As both ciliates and heterotrophic dinoflagellates have different size ratios with their prey, they will target different prey types. Moreover, both have different functional responses to fluctuations in prey concentration. Ciliates, with a higher threshold concentration and lower half-saturation concentration, will commence grazing later than dinoflagellates, but reach their maximal rates faster. They differ further from dinoflagellates with a higher maximal grazing rate and a lower metabolism. Parameterisation for a microzooplankton, ciliates and heterotrophic dinoflagellates PFTs were obtained from the data and used in a BOGCM. The 12 PFTs have a different impact on the ecosystem and biogeochemical cycles. The dinoflagellate PFT reduces the export and alters the distribution area of high primary production. The ciliate PFT has a similar impact to that of microzooplankton. It is doubtful that the microzooplankton PFT in itself correctly represents ciliates and heterotrophic dinoflagellates. Consequently a separation of both organisms in future models is recommanded to provide a better representation of the ecosystem and its response to climate change
Temperature-induced hatch failure and nauplii malformation in Antarctic krill
No full textAntarctic krill inhabit areas of the Southern Ocean that can exceed 4.0C, yet they preferentially inhabit regions with temperatures of -1.5 to 1.5C. Successful embryonic development and hatching are key to their life cycle, but despite the rapid climatic warming seen across their main spawning areas, the effects of elevated temperatures on embryogenesis, hatching success, and nauplii malformations are unknown. We incubated 24,483 krill embryos in two independent experiments to investigate the hypothesis that temperatures exceeding 1.5C have a negative impact on hatching success and increase the numbers of malformed nauplii. Field experiments were on krill collected from near the northern, warm limit of their range and embryos incubated soon after capture, while laboratory experiments were on embryos from krill acclimated to laboratory conditions. The hatching success of embryo batches varied enormously, from 0 to 98% (mean 27%). Both field and laboratory experiments showed that hatching success decreased markedly above 3.0C. Our field experiments also showed an approximate doubling of the percentage of malformed nauplii at elevated temperatures, reaching 50% at 5.0C. At 3.0C or below, however, temperature was not the main factor driving the large variation in embryo hatching success. Our observations of highly variable and often low success of hatching to healthy nauplii suggest that indices of reproductive potential of female krill relate poorly to the subsequent production of viable krill larvae and may help to explain spatial discrepancies between the distribution of the spawning stock and larval distribution
Data compilation of ciliates growth rate, grazing rate and gross gowth efficiency from field and labratory experiments
No full textThe present data compilation includes ciliates growth rate, grazing rate and gross growth efficiency determined either in the field or in laboratory experiments. From the existing literature, we synthesized all data that we could find on cilliate. Some sources might be missing but none were purposefully ignored. Field data on microzooplankton grazing are mostly comprised of grazing rate using the dilution technique with a 24h incubation period. Laboratory grazing and growth data are focused on pelagic ciliates and heterotrophic dinoflagellates. The experiment measured grazing or growth as a function of prey concentration or at saturating prey concentration (maximal grazing rate). When considering every single data point available (each measured rate for a defined predator-prey pair and a certain prey concentration) there is a total of 1485 data points for the ciliates, counting experiments that measured growth and grazing simultaneously as 1 data point
Data base on pelagic ciliates grazing and growth rate as a function of size, prey size and type compiled from the literature
No full textMicrozooplankton (the 20 to 200 µm size class of zooplankton) is recognised as an important part of marine pelagic ecosystems. In terms of biomass and abundance pelagic ciliates are one of the important groups of organism in microzooplankton. However, their rates - grazing and growth - , feeding behaviour and prey preferences are poorly known and understood. A set of data was assembled in order to derive a better understanding of pelagic ciliates rates, in response to parameters such as prey concentration, prey type (size and species), temperature and their own size. With these objectives, literature was searched for laboratory experiments with information on one or more of these parameters effect studied. The criteria for selection and inclusion in the database included:
(i) controlled laboratory experiment with a known ciliates feeding on a known prey;
(ii) presence of ancillary information about experimental conditions, used organisms - cell volume, cell dimensions, and carbon content. Rates and ancillary information were measured in units that meet the experimenter need, creating a need to harmonize the data units after collection. In addition different units can link to different mechanisms (carbon to nutritive quality of the prey, volume to size limits).
As a result, grazing rates are thus available as pg C/(ciliate*h), µm**3/(ciliate*h) and prey cell/(ciliate*h); clearance rate was calculated if not given and growth rate is expressed as the growth rate per day
