The downward flux of biogenic material in the NE subarctic Pacific: importance of algal sinking and mesozooplankton herbivory

Thibault, Delphine; Roy, S.; Wong, C. S.; Bishop, James K. B.

doi:10.1016/s0967-0645(99)00080-6

Cited by 60 publications

(63 citation statements)

References 64 publications

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“…The use of indicator pigments as tracers of phytoplankton export only accounts for the direct sinking of healthy, ungrazed cells, because grazing degrades the indicator pigments to an analytically undetectable form (Head and Harris, 1992;Strom et al, 1998;Thibault et al, 1999). Indirect export (via grazing) is thought to be an important pathway for picoplankton export in the HNLC equatorial Pacific (Richardson et al, 2004;Stukel and Landry, 2010).…”

Section: Discussionmentioning

confidence: 99%

“…Because precipitation and continental runoff exceed evaporation, a permanent halocline exists at ∼ 100 m impeding deep winter mixing. In addition, a seasonal ther- (Freeland et al, 1997;Thibault et al, 1999;Freeland, 2013;Timothy et al, 2013).…”

Section: Study Locationmentioning

confidence: 99%

“…Phytoplankton community structure exerts an important influence on the strength and efficiency of the biological pump (Michaels and Silver, 1988;Boyd and Newton, 1999;Thibault et al, 1999;Brew et al, 2009;Lomas and Moran, 2011). Small nano-and picoplankton dominate the phytoplankton community in the oligotrophic gyres and highnutrient, low-chlorophyll (HNLC) oceanographic regions.…”

Section: Introductionmentioning

confidence: 99%

“…Previous attempts to resolve the apparent paradox of low phytoplankton biomass and high nitrate concentrations at OSP concluded that a bottom-up control related to iron limitation is most important for large phytoplankton (Muggli et al, 1996;Harrison, 2006;Marchetti et al, 2006), while microzooplankton grazing exerts a strong topdown control on pico-and nanoplankton (Landry et al, 1993;Harrison et al, 1999;Rivkin et al, 1999). Primary production at the stations proximal to the coast on Line P (P4 and P12) is not iron-limited, and diatom blooms are typically observed in spring and late summer (Boyd and Harrison, 1999;Thibault et al, 1999). At the offshore stations (including OSP), the phytoplankton community is dominated by cells < 5 µm and the seasonal variability of primary production is relatively low (∼ 25 in winter and ∼ 67 mmol C m −2 d −1 in summer) (Boyd and Harrison, 1999;Thibault et al, 1999;Choi et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…Primary production at the stations proximal to the coast on Line P (P4 and P12) is not iron-limited, and diatom blooms are typically observed in spring and late summer (Boyd and Harrison, 1999;Thibault et al, 1999). At the offshore stations (including OSP), the phytoplankton community is dominated by cells < 5 µm and the seasonal variability of primary production is relatively low (∼ 25 in winter and ∼ 67 mmol C m −2 d −1 in summer) (Boyd and Harrison, 1999;Thibault et al, 1999;Choi et al, 2014). In contrast to the low variability in primary production, POC export recorded by moored sediment traps at OSP exhibits a stronger seasonal cycle with fluxes at 200 m depth ranging from ∼ 0.4 mmol C m −2 d −1 in winter to ∼ 2.4 mmol C m −2 d −1 in summer (Timothy et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Estimates of micro-, nano-, and picoplankton contributions to particle export in the northeast Pacific

et al. 2015

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Abstract. The contributions of micro-, nano-, and picoplankton to particle export were estimated from measurements of size-fractionated particulate 234 Th, organic carbon, and phytoplankton indicator pigments obtained during five cruises between 2010 and 2012 along Line P in the subarctic northeast Pacific Ocean. Sinking fluxes of particulate organic carbon (POC) and indicator pigments were calculated from 234 Th-238 U disequilibria and, during two cruises, measured by a sediment trap at Ocean Station Papa. POC fluxes at 100 m ranged from 0.65 to 7.95 mmol m −2 d −1 , similar in magnitude to previous results at Line P. Microplankton pigments dominate indicator pigment fluxes (averaging 69 ± 19 % of total pigment flux), while nanoplankton pigments comprised the majority of pigment standing stocks (averaging 64 ± 23 % of total pigment standing stocks). Indicator pigment loss rates (the ratio of pigment export flux to pigment standing stocks) point to preferential export of larger microplankton relative to smaller nano-and picoplankton. However, indicator pigments do not quantitatively trace particle export resulting from zooplankton grazing, which may be an important pathway for the export of small phytoplankton. These results have important implications for understanding the magnitude and mechanisms controlling the biological pump at Line P in particular, and more generally in oligotrophic gyres and high-nutrient, low-chlorophyll (HNLC) regions where small phytoplankton represent a major component of the autotrophic community.

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Section: Discussionmentioning

confidence: 99%

Section: Study Locationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimates of micro-, nano-, and picoplankton contributions to particle export in the northeast Pacific

et al. 2015

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Fecal pellet production by mesozooplankton in the subarctic Northeast Pacific Ocean

Stamieszkin¹,

Steinberg²,

Maas

2021

Limnology & Oceanography

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Mesozooplankton fecal pellets sinking from the sea-surface constitute an important component of the biological carbon pump, which is variable in part due to differences in zooplankton community composition on various scales. Particulate organic carbon production as fecal pellets by the entire mesozooplankton community has, until now, not been directly measured. We measured fecal pellet carbon (FPC) production rates of the mesozooplankton community separated into five size classes (0.2 to > 5.0 mm), and rates of key taxa, in the upper 100 m of the subarctic Northeast Pacific Ocean, August-September, 2018. We scaled up FPC production rates to total FPC production in the epipelagic zone, which was 2.8-fold higher at night than day due to diel vertical migration. Despite its lower total biomass, the smallest size class (0.2-0.5 mm) contributed more FPC than other size classes (up to 81.6%), due to high weight-specific FPC production rates (3.0 μgFPC mgDW −1 h −1 ). The pelagic tunicate Salpa aspera had the highest individual FPC production rate (7.5 μgFPC ind −1 h −1 ) and when present, contributed most to community FPC production (up to 82.3%). While the large copepod Neocalanus cristatus dominated the 2.0-5.0 mm fraction (up to~100% by biomass), its FPC production rate was low (0.4 μgFPC mgDW −1 h −1 ), likely due to minimal feeding and gut shrinkage preceding diapause. Comparison of FPC production with export recorded in sediment traps suggests high attenuation of smaller pellet classes in the epipelagic (86%). Our results provide direct measurements of mesozooplankton FPC production in a "low-production, low-export" region.

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Zinc and nickel isotopes in seawater from the Indian Sector of the Southern Ocean: The impact of natural iron fertilization versus Southern Ocean hydrography and biogeochemistry

2019

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The Southern Ocean is the site of 20% of global ocean carbon export, and the origin of water masses that significantly impact the chemistry of the global ocean. Much of the Southern Ocean is a high nutrient low chlorophyll (HNLC) region. Iron is the primary limiting nutrient for phytoplankton growth, and may also be an important control on the biogeochemistry of the water masses emanating from the Southern Ocean. Here we investigate the response of Zn and Ni and their isotopes to natural Fe fertilization from Southern Ocean islands, using samples collected during the KEOPS-2 (Oct-Nov 2011) program in the early austral spring near the Kerguelen plateau, Indian Sector of the Southern Ocean.Zinc and Ni concentrations show depth distributions and relationships to major nutrients that are very similar to published data from the Atlantic sector of the Southern Ocean, away from island fertilization. As in the Atlantic sector, and other regions outside the Southern Ocean, there is a slight minimum in d 66 Zn at about 100-150m depth and a slightly heavier value at the surface. At the KEOPS-2 sites, the light sub-surface Zn isotopes occur at the depth level where measured chl-a has declined to near zero. The heaviest Zn isotope values in either the Atlantic or Indian sectors occur in bottom waters, are associated with samples that show high dissolved Si relative to Zn. These latter represent possible evidence for a heavy input directly to deep water or from sediment, and the Zn-Si-d 66 Zn systematics are consistent with a source in diatom opal. Nickel concentrations show much less variation than those of Zn, with the most depleted surface value only 15-20% lower than those in upwelled deep water in the Southern Ocean. These small variations in Ni concentration are associated with no significant variability in Ni isotopes, as also previously observed in the Atlantic sector.Overall, the key feature of the dataset is the apparent absence of any significant impact of natural Fe fertilization on the distribution of Zn and Ni, with the dominant control being the station location relative to the Polar Front in both the Atlantic and Indian sectors. Zinc and Ni isotopes are invariant in surface waters, whether inside or outside the fertilised zone and whether south or north of the Polar Front.

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The downward flux of biogenic material in the NE subarctic Pacific: importance of algal sinking and mesozooplankton herbivory

Cited by 60 publications

References 64 publications

Estimates of micro-, nano-, and picoplankton contributions to particle export in the northeast Pacific

Estimates of micro-, nano-, and picoplankton contributions to particle export in the northeast Pacific

Fecal pellet production by mesozooplankton in the subarctic Northeast Pacific Ocean

Zinc and nickel isotopes in seawater from the Indian Sector of the Southern Ocean: The impact of natural iron fertilization versus Southern Ocean hydrography and biogeochemistry

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