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James K B Bishop - One of the best experts on this subject based on the ideXlab platform.

  • the downward flux of Biogenic Material in the ne subarctic pacific importance of algal sinking and mesozooplankton herbivory
    Deep-sea Research Part Ii-topical Studies in Oceanography, 1999
    Co-Authors: Delphine Thibault, Suzanne Roy, C S Wong, James K B Bishop
    Abstract:

    Abstract In the present study we examine factors that affect the downward flux of Biogenic carbon in the NE subarctic Pacific, one of the important high-nutrient-low-chlorophyll (HNLC) regions in the open ocean. We focus on the role of mesozooplankton, since their seasonal peaks in biomass and growth are in phase with the seasonal variations in the downward POC fluxes, whereas phytoplankton biomass is more-or-less uniform year-round. The relative importance of mesozooplankton and algal sinking was examined using the pigment composition of Material accumulated in short-term free-drifting sediment traps positioned just below the upper stratified surface layer (ca. 100–200 m). This was compared with the phytoplankton composition in the surface waters, and with the grazing activity (gut pigments and fecal pellet production rates) of the most abundant large copepods. We also examined whether the relationships between the downward flux of carbon and pelagic processes were similar in the coastal, continental margin and offshore HNLC regions of the NE subarctic Pacific, the latter represented by Ocean Station Papa (OSP). Our results show that grazing had a variable impact on the downward flux of Biogenic carbon. Carbon-transformed pheopigments (particularly pyropheophorbide a, frequently associated with copepod grazing) represented up to 13% of the total downward POC flux inshore (in May 1996) and 8–9% at OSP in May and February 1996, respectively. This flux of pheopigments was accompanied by a large potential input of fecal pellets from large copepods (as estimated from defecation rates of freshly collected animals) only in May 1996 at OSP, suggesting that pheopigments came from other sources (other herbivores, senescing algae) in February. The larger flux of pheopigments in May was probably related to the abundance of mesozooplankton at that time of the year. During summer (August 1996), both the flux of pheopigments and the potential input of fecal pellets from large copepods were negligible at OSP, consistent with more intense pelagic recycling reported in other studies. Inshore, the flux of carbon-transformed pheopigments was slightly higher than at OSP, and its contribution to the downward POC flux in May 1996 was twice that in August 1996. In contrast, the potential input of feces carbon was higher in August than in May 1996, again suggesting other sources for pheopigments found in the traps. The contribution of sinking phytoplankton to the downward Biogenic flux was negligible in summer, when prymnesiophytes (indicated by the presence of 19′-hexanoyloxyfucoxanthin) and pelagophytes (19′-butanoyloxyfucoxanthin-containing) dominated in surface offshore waters. The contribution of sinking algae was maximal (9%) in winter (February 1996) at OSP, when fucoxanthin (mainly a diatom marker) dominated the carotenoid composition in the traps and when the abundance of diatoms in surface waters showed its seasonal maximum for this station. Inshore, the low contribution of diatoms (fucoxanthin) to the sinking fluxes may have resulted from inadequate sampling (i.e. the spring bloom may have been missed). Overall, we conclude that: (a) large copepods significantly influenced the downward POC flux only during spring at OSP; (b) unidentified herbivores (e.g. salps, pteropods) producing pigmented, fast-sinking fecal Material likely had an important impact during winter; (c) algal sinking made a small contribution to the downward POC flux (maximum in winter); and (d) neither algal sinking nor mesozooplankton grazing had a significant influence on the downward flux of Biogenic Material in summer at OSP.

  • The downward flux of Biogenic Material in the NE subarctic Pacific: importance of algal sinking and mesozooplankton herbivory
    Deep-sea Research Part Ii-topical Studies in Oceanography, 1999
    Co-Authors: Delphine Thibault, Suzanne Roy, C S Wong, James K B Bishop
    Abstract:

    In the present study we examine factors that a!ect the downward #ux of Biogenic carbon in the NE subarctic Paci"c, one of the important high-nutrient-low-chlorophyll (HNLC) regions in the open ocean. We focus on the role of mesozooplankton, since their seasonal peaks in biomass and growth are in phase with the seasonal variations in the downward POC #uxes, whereas phytoplankton biomass is more-or-less uniform year-round. The relative importance of mesozooplankton and algal sinking was examined using the pigment composition of Material accumulated in short-term free-drifting sediment traps positioned just below the upper strati"ed surface layer (ca. 100}200 m). This was compared with the phytoplankton composition in the surface waters, and with the grazing activity (gut pigments and fecal pellet production rates) of the most abundant large copepods. We also examined whether the relationships between the downward #ux of carbon and pelagic processes were similar in the coastal, continental margin and o!shore HNLC regions of the NE subarctic Paci"c, the latter represented by Ocean Station Papa (OSP). Our results show that grazing had a variable impact on the downward #ux of Biogenic carbon. Carbon-transformed pheopigments (particularly pyropheophorbide a, frequently associated with copepod grazing) represented up to 13% of the total downward POC #ux inshore (in May 1996) and 8}9% at OSP in May and February 1996, respectively. This #ux of pheopigments was accompanied by a large potential input of fecal pellets from large copepods (as estimated from defecation rates of freshly collected animals) only in May 1996 at OSP, suggesting that pheopigments came from other sources (other herbivores, senescing algae) in

Delphine Thibault - One of the best experts on this subject based on the ideXlab platform.

  • the downward flux of Biogenic Material in the ne subarctic pacific importance of algal sinking and mesozooplankton herbivory
    Deep-sea Research Part Ii-topical Studies in Oceanography, 1999
    Co-Authors: Delphine Thibault, Suzanne Roy, C S Wong, James K B Bishop
    Abstract:

    Abstract In the present study we examine factors that affect the downward flux of Biogenic carbon in the NE subarctic Pacific, one of the important high-nutrient-low-chlorophyll (HNLC) regions in the open ocean. We focus on the role of mesozooplankton, since their seasonal peaks in biomass and growth are in phase with the seasonal variations in the downward POC fluxes, whereas phytoplankton biomass is more-or-less uniform year-round. The relative importance of mesozooplankton and algal sinking was examined using the pigment composition of Material accumulated in short-term free-drifting sediment traps positioned just below the upper stratified surface layer (ca. 100–200 m). This was compared with the phytoplankton composition in the surface waters, and with the grazing activity (gut pigments and fecal pellet production rates) of the most abundant large copepods. We also examined whether the relationships between the downward flux of carbon and pelagic processes were similar in the coastal, continental margin and offshore HNLC regions of the NE subarctic Pacific, the latter represented by Ocean Station Papa (OSP). Our results show that grazing had a variable impact on the downward flux of Biogenic carbon. Carbon-transformed pheopigments (particularly pyropheophorbide a, frequently associated with copepod grazing) represented up to 13% of the total downward POC flux inshore (in May 1996) and 8–9% at OSP in May and February 1996, respectively. This flux of pheopigments was accompanied by a large potential input of fecal pellets from large copepods (as estimated from defecation rates of freshly collected animals) only in May 1996 at OSP, suggesting that pheopigments came from other sources (other herbivores, senescing algae) in February. The larger flux of pheopigments in May was probably related to the abundance of mesozooplankton at that time of the year. During summer (August 1996), both the flux of pheopigments and the potential input of fecal pellets from large copepods were negligible at OSP, consistent with more intense pelagic recycling reported in other studies. Inshore, the flux of carbon-transformed pheopigments was slightly higher than at OSP, and its contribution to the downward POC flux in May 1996 was twice that in August 1996. In contrast, the potential input of feces carbon was higher in August than in May 1996, again suggesting other sources for pheopigments found in the traps. The contribution of sinking phytoplankton to the downward Biogenic flux was negligible in summer, when prymnesiophytes (indicated by the presence of 19′-hexanoyloxyfucoxanthin) and pelagophytes (19′-butanoyloxyfucoxanthin-containing) dominated in surface offshore waters. The contribution of sinking algae was maximal (9%) in winter (February 1996) at OSP, when fucoxanthin (mainly a diatom marker) dominated the carotenoid composition in the traps and when the abundance of diatoms in surface waters showed its seasonal maximum for this station. Inshore, the low contribution of diatoms (fucoxanthin) to the sinking fluxes may have resulted from inadequate sampling (i.e. the spring bloom may have been missed). Overall, we conclude that: (a) large copepods significantly influenced the downward POC flux only during spring at OSP; (b) unidentified herbivores (e.g. salps, pteropods) producing pigmented, fast-sinking fecal Material likely had an important impact during winter; (c) algal sinking made a small contribution to the downward POC flux (maximum in winter); and (d) neither algal sinking nor mesozooplankton grazing had a significant influence on the downward flux of Biogenic Material in summer at OSP.

  • The downward flux of Biogenic Material in the NE subarctic Pacific: importance of algal sinking and mesozooplankton herbivory
    Deep-sea Research Part Ii-topical Studies in Oceanography, 1999
    Co-Authors: Delphine Thibault, Suzanne Roy, C S Wong, James K B Bishop
    Abstract:

    In the present study we examine factors that a!ect the downward #ux of Biogenic carbon in the NE subarctic Paci"c, one of the important high-nutrient-low-chlorophyll (HNLC) regions in the open ocean. We focus on the role of mesozooplankton, since their seasonal peaks in biomass and growth are in phase with the seasonal variations in the downward POC #uxes, whereas phytoplankton biomass is more-or-less uniform year-round. The relative importance of mesozooplankton and algal sinking was examined using the pigment composition of Material accumulated in short-term free-drifting sediment traps positioned just below the upper strati"ed surface layer (ca. 100}200 m). This was compared with the phytoplankton composition in the surface waters, and with the grazing activity (gut pigments and fecal pellet production rates) of the most abundant large copepods. We also examined whether the relationships between the downward #ux of carbon and pelagic processes were similar in the coastal, continental margin and o!shore HNLC regions of the NE subarctic Paci"c, the latter represented by Ocean Station Papa (OSP). Our results show that grazing had a variable impact on the downward #ux of Biogenic carbon. Carbon-transformed pheopigments (particularly pyropheophorbide a, frequently associated with copepod grazing) represented up to 13% of the total downward POC #ux inshore (in May 1996) and 8}9% at OSP in May and February 1996, respectively. This #ux of pheopigments was accompanied by a large potential input of fecal pellets from large copepods (as estimated from defecation rates of freshly collected animals) only in May 1996 at OSP, suggesting that pheopigments came from other sources (other herbivores, senescing algae) in

Saulius Armalis - One of the best experts on this subject based on the ideXlab platform.

  • Wet deposition of elemental carbon in Lithuania
    Science of The Total Environment, 1999
    Co-Authors: Saulius Armalis
    Abstract:

    Elemental carbon (EC) was measured in monthly precipitation samples at 14 rural sites in Lithuania from December 1986 to June 1990. The amount of EC in the sample was determined by the light reflectance method after a procedure including the filtration through a 0.2-μm polyamide membrane filter, the chemical digestion of Biogenic Material and the dispersion of the mixture in an ultrasonic bath. Monthly elemental carbon concentrations in the precipitation samples during the measurement period at the Preila site varied from 8 to 530 μg l−1 with a volume-weighted mean of 100 μg l−1. The range of EC monthly deposition fluxes was from 0.5 to 25 mg m−2 month−1 for all the sites. The wet deposition of elemental carbon is doubled during the cold season of the year. The estimated mean value of EC washout ratio for Preila site is 97 (range 5–243). An even distribution of the elemental carbon deposition is characteristic for the rural sites in Lithuania and mean monthly deposition flux can be estimated as 6.2 mg m−2 month−1. It results in the deposition of about 4800 t of elemental carbon to the area of Lithuania annually.

  • Wet deposition of elemental carbon in Lithuania.
    The Science of the total environment, 1999
    Co-Authors: Saulius Armalis
    Abstract:

    Elemental carbon (EC) was measured in monthly precipitation samples at 14 rural sites in Lithuania from December 1986 to June 1990. The amount of EC in the sample was determined by the light reflectance method after a procedure including the filtration through a 0.2-micron polyamide membrane filter, the chemical digestion of Biogenic Material and the dispersion of the mixture in an ultrasonic bath. Monthly elemental carbon concentrations in the precipitation samples during the measurement period at the Preila site varied from 8 to 530 micrograms l-1 with a volume-weighted mean of 100 micrograms l-1. The range of EC monthly deposition fluxes was from 0.5 to 25 mg m-2 month-1 for all the sites. The wet deposition of elemental carbon is doubled during the cold season of the year. The estimated mean value of EC washout ratio for Preila site is 97 (range 5-243). An even distribution of the elemental carbon deposition is characteristic for the rural sites in Lithuania and mean monthly deposition flux can be estimated as 6.2 mg m-2 month-1. It results in the deposition of approximately 4800 t of elemental carbon to the area of Lithuania annually.

Frank E. Muller-karger - One of the best experts on this subject based on the ideXlab platform.

  • Vertical fluxes of particulate Biogenic Material through the euphotic and twilight zones in the Cariaco Basin, Venezuela
    Deep Sea Research Part I: Oceanographic Research Papers, 2012
    Co-Authors: Enrique Montes, Frank E. Muller-karger, Robert C. Thunell, David J. Hollander, Yrene Astor, Ramon Varela, Inia M. Soto, Laura Lorenzoni
    Abstract:

    Surface-tethered particle interceptor traps (PITs) were deployed at 50 and 100 m (1–3 days) on ten occasions in the Cariaco Basin between March 2007 and November 2009 to measure the settling fluxes of Biogenic particles at 50 m (the base of the euphotic zone—Ez) and 100 m. Fluxes at these two depths were compared to concurrent fluxes estimated with moored sediment traps at 150, 225 and 410 m from the CARIACO Ocean Time-Series program. We measured particulate organic carbon (POC), particulate organic nitrogen (PON), calcium carbonate, Biogenic silica and terrigenous Material concentrations in samples collected with both the drifting and moored traps. We also estimated the fluxes of foraminifera shells and coccolithophore cells at 50 and 100 m using drifting traps samples. Surface chlorophyll a and primary production observations during each sampling period were examined to quantify the relationship between the magnitude and geochemical composition of the vertical flux and overlying production. Surface chlorophyll a concentrations and primary production rates were highest during months of upwelling (2.58 � 1.35 mg m � 3 and 3.6 � 1.4 g C m � 2 d � 1 , respectively). The fluxes of POC, PON, calcite and silica measured during the upwelling season (December–May) were typically higher than during the period of non-upwelling (August–November), when surface waters are more strongly stratified. POC fluxes measured with the drifting traps (50 and 100 m) varied between 0.95 (upwelling) and 0.14 g m � 2 d � 1 (non-upwelling), compared with those from the moored traps (150, 225 and 410 m) which ranged from 0.21 to 0.01 g m � 2 d � 1 . Similarly, the fluxes of Biogenic opal in the upper 100 m ranged from 1.12 and 0.18 g m � 2 d � 1 , and those at greater depths varied from 0.27 g m � 2 d � 1 during upwelling to values near zero during stratification periods. The fluxes of POC, PON, calcite and silica in the upper 100 m decreased by an order of magnitude at the depth of the oxic–anoxic interface (4200 m). The sinking organic matter collected with the floating traps within the upper 100 m was significantly correlated with surface chlorophyll a concentrations (r¼ 0.68, po0.05) as a result of close coupling between the flux of Biogenic particles and primary production. In contrast, there was no clear relationship between surface chlorophyll/primary production and fluxes measured below 150 m depth. Published by Elsevier Ltd.

  • Varve formation in the Gulf of California: Insights from time series sediment trap sampling and remote sensing
    Quaternary Science Reviews, 1993
    Co-Authors: Robert C. Thunell, Carol J. Pride, Eric Tappa, Frank E. Muller-karger
    Abstract:

    The varved sediments that accumulate in the central Gulf of California (Guaymas and Carmen Basins) provide a record that allows for the resolution of annual to decadal-scale climate variability in this region. Time-series sediment trapping, combined with remotely sensed observations of sea surface temperature (AVHRR) and color (CZCS), have been used to examine the mechanism of varve formation in the central Gulf. SST and surface pigment concentration records for both the mainland and Baja sides of the Gulf display similar seasonal trends. High temperatures and low pigment concentrations occur synchronously on both sides of the central Gulf from June through to October. In association with the 1991/92 El Nino, warm temperatures persist in the central Gulf until December. Low SSTs typically occur from December through May, with high pigment concentrations marking the period from November through April. The summer-early fall (June–October) is a time of high terrigenous and Biogenic sediment fluxes. During this time of year, the total flux is dominated by eolian-transported lithogenic Material and dark laminae are deposited during this period. During El Nino years, high terrigenous fluxes may extend into winter. Light laminae represent deposition from November through May, during which time Biogenic Material dominates the total sediment flux. High opal fluxes beginning in November are attributed to seasonal cooling of surface water and upward mixing of nutrients. True upwelling conditions do not develop in the Gulf until late winter-spring. During this time, the total flux is still dominated by opal but the magnitude of the flux is reduced. This may be an artifact of phytoplankton grazing and not lower production rates.

Robert C. Thunell - One of the best experts on this subject based on the ideXlab platform.

  • Vertical fluxes of particulate Biogenic Material through the euphotic and twilight zones in the Cariaco Basin, Venezuela
    Deep Sea Research Part I: Oceanographic Research Papers, 2012
    Co-Authors: Enrique Montes, Frank E. Muller-karger, Robert C. Thunell, David J. Hollander, Yrene Astor, Ramon Varela, Inia M. Soto, Laura Lorenzoni
    Abstract:

    Surface-tethered particle interceptor traps (PITs) were deployed at 50 and 100 m (1–3 days) on ten occasions in the Cariaco Basin between March 2007 and November 2009 to measure the settling fluxes of Biogenic particles at 50 m (the base of the euphotic zone—Ez) and 100 m. Fluxes at these two depths were compared to concurrent fluxes estimated with moored sediment traps at 150, 225 and 410 m from the CARIACO Ocean Time-Series program. We measured particulate organic carbon (POC), particulate organic nitrogen (PON), calcium carbonate, Biogenic silica and terrigenous Material concentrations in samples collected with both the drifting and moored traps. We also estimated the fluxes of foraminifera shells and coccolithophore cells at 50 and 100 m using drifting traps samples. Surface chlorophyll a and primary production observations during each sampling period were examined to quantify the relationship between the magnitude and geochemical composition of the vertical flux and overlying production. Surface chlorophyll a concentrations and primary production rates were highest during months of upwelling (2.58 � 1.35 mg m � 3 and 3.6 � 1.4 g C m � 2 d � 1 , respectively). The fluxes of POC, PON, calcite and silica measured during the upwelling season (December–May) were typically higher than during the period of non-upwelling (August–November), when surface waters are more strongly stratified. POC fluxes measured with the drifting traps (50 and 100 m) varied between 0.95 (upwelling) and 0.14 g m � 2 d � 1 (non-upwelling), compared with those from the moored traps (150, 225 and 410 m) which ranged from 0.21 to 0.01 g m � 2 d � 1 . Similarly, the fluxes of Biogenic opal in the upper 100 m ranged from 1.12 and 0.18 g m � 2 d � 1 , and those at greater depths varied from 0.27 g m � 2 d � 1 during upwelling to values near zero during stratification periods. The fluxes of POC, PON, calcite and silica in the upper 100 m decreased by an order of magnitude at the depth of the oxic–anoxic interface (4200 m). The sinking organic matter collected with the floating traps within the upper 100 m was significantly correlated with surface chlorophyll a concentrations (r¼ 0.68, po0.05) as a result of close coupling between the flux of Biogenic particles and primary production. In contrast, there was no clear relationship between surface chlorophyll/primary production and fluxes measured below 150 m depth. Published by Elsevier Ltd.

  • Varve formation in the Gulf of California: Insights from time series sediment trap sampling and remote sensing
    Quaternary Science Reviews, 1993
    Co-Authors: Robert C. Thunell, Carol J. Pride, Eric Tappa, Frank E. Muller-karger
    Abstract:

    The varved sediments that accumulate in the central Gulf of California (Guaymas and Carmen Basins) provide a record that allows for the resolution of annual to decadal-scale climate variability in this region. Time-series sediment trapping, combined with remotely sensed observations of sea surface temperature (AVHRR) and color (CZCS), have been used to examine the mechanism of varve formation in the central Gulf. SST and surface pigment concentration records for both the mainland and Baja sides of the Gulf display similar seasonal trends. High temperatures and low pigment concentrations occur synchronously on both sides of the central Gulf from June through to October. In association with the 1991/92 El Nino, warm temperatures persist in the central Gulf until December. Low SSTs typically occur from December through May, with high pigment concentrations marking the period from November through April. The summer-early fall (June–October) is a time of high terrigenous and Biogenic sediment fluxes. During this time of year, the total flux is dominated by eolian-transported lithogenic Material and dark laminae are deposited during this period. During El Nino years, high terrigenous fluxes may extend into winter. Light laminae represent deposition from November through May, during which time Biogenic Material dominates the total sediment flux. High opal fluxes beginning in November are attributed to seasonal cooling of surface water and upward mixing of nutrients. True upwelling conditions do not develop in the Gulf until late winter-spring. During this time, the total flux is still dominated by opal but the magnitude of the flux is reduced. This may be an artifact of phytoplankton grazing and not lower production rates.