Zooplankton and Micronekton Active Flux Across the Tropical and Subtropical Atlantic Ocean

Hernández‐León, Santiago; Olivar, M. Pilar; Puelles, María Luz Fernández de; Bode, Antonio; Castellón, A.; López-Pérez, C.; Tuset, Víctor M.; González-Gordillo, J. Ignacio

doi:10.3389/fmars.2019.00535

Cited by 61 publications

(73 citation statements)

References 61 publications

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“…M h can be multiplied by the number of hours spent at depth to obtain individual contribution to downward flux attributed to natural mortality. For comparison, we also calculate mortality from growth as in Hernández-León et al (2019). Assuming our systems are in steady-state, growth should be approximately equivalent to mortality.…”

Section: Mortalitymentioning

confidence: 99%

“…While this is the best available correction for our data, it should be noted that our sampling approach differs slightly from that of Koslow et al (1997) in terms of tow speed (1 vs. 1.5 m/s), net dimension (157.5 vs. 105 m 2 ), and mesh size (200 mm tapering to 10 mm at the codend vs. 100 mm tapering to 10 mm at the codend), which may influence the overall net efficiency. Thus, we also apply a more conservative correction for net efficiency of 50% for comparison with other studies in the literature (i.e., Hernández-León et al, 2019). All conversions are shown in Supplementary Table S8.…”

Section: Vertical Migration and Active Carbon Transportmentioning

confidence: 99%

“…In some cases, the contribution of decapods to downward carbon transport may even exceed that of myctophids in mesoscale eddies. Hernández-León et al (2019) reported that decapods coincided with sharp oxygen minimum zones (OMZs) in the subtropical Atlantic Ocean. In our study, the B-CCE exhibited a sharp decline in oxygen at the base of the MLD (∼100 m), in this case the migratory biomass of decapods exceeded that of myctophids.…”

Section: Vertical Migration and Active Carbon Transportmentioning

confidence: 99%

“…This study simply represents a starting point, as stomiid predation on mesopelagic fish alone is estimated to range from 58 to 230% (Clarke, 1982;Hopkins et al, 1996;Davison et al, 2013). Thus, we provide a direct comparison with our values and the approach taken in Hernández-León et al (2019), which assumes that the system is in steady-state and thus mortality is approximately equivalent to growth ( Table 5). Our results demonstrate that vastly different estimates of mortality flux can be obtained by the two different approaches, and that one is not consistently more conservative than the other.…”

Section: Uncertainty and Limitationsmentioning

confidence: 99%

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Mesozooplankton and Micronekton Active Carbon Transport in Contrasting Eddies

et al. 2020

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were sampled along the eastern coast of Australia. Depth stratified mesozooplankton and micronekton were collected using a Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) and an International Young Gadoid Pelagic Trawl (IYGPT) equipped with an opening/closing codend. Sampling was undertaken at the center and edge of a frontal cold-core eddy (F-CCE Center and Edge) in 2015, and at the center of a cold-core eddy (B-CCE) and two warmcore eddies (R-WCE and WCE) in 2017. We assess the diel vertical structure, biomass, and downward active carbon transport by mesozooplankton and micronekton in eddies. Total water column mesozooplankton and micronekton biomass did not vary substantially across water masses, while the extent and depth of diel vertical migration did. Using in situ measurements of temperature and measurements of mesozooplankton and micronekton abundance and biomass, we estimated the contribution of respiration, dissolved organic carbon (DOC) excretion, gut flux, and mortality to total downward active carbon transport in each water mass. Overall, active carbon transport by mesozooplankton and micronekton below the mixed layer varied substantially across water masses. We corrected estimates of micronekton migratory biomass and active carbon transport assuming 50% net efficiency. In the R-WCE mesozooplankton remained within the mixed layer during the day and night; only 50% of the total micronekton population migrated below the mixed layer contributing to carbon transport, equating to 2.89 mg C m −2 d −1. Mesozooplankton actively transported 16.1 and 8.0 mg C m −2 d −1 at the F-CCE Center and Edge, respectively. Mesozooplankton and micronekton active carbon transport in the B-CCE were 5.4 and 0.74 mg C m −2 d −1 , and in the WCE 88 and 13.4 mg C m −2 d −1. Differences in carbon export were dependent on food availability, temperature, time spent migrating, and mixed layer depth. These findings suggest that under certain conditions mesoscale eddies can act as important carbon sinks.

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Section: Mortalitymentioning

confidence: 99%

Section: Vertical Migration and Active Carbon Transportmentioning

confidence: 99%

Section: Vertical Migration and Active Carbon Transportmentioning

confidence: 99%

Section: Uncertainty and Limitationsmentioning

confidence: 99%

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Mesozooplankton and Micronekton Active Carbon Transport in Contrasting Eddies

et al. 2020

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“…Hansen and Visser (2016) estimated that across the North Atlantic active transport by mesozooplankton may constitute 27% of total export. In addition to zooplankton, vertical migrations by micronekton can also lead to significant export fluxes (Angel and Pugh, 2010; Davison et al, 2013; Hernandez-Leon et al). Using biomass estimates and metabolic relationships, Davison et al (2013) found micronekton contributions of 22 – 24 mg C m −2 d −1 (or 15% - 17% of estimated passive export) in the northeast Pacific.…”

Section: Discussionmentioning

confidence: 99%

The Importance of Mesozooplankton Diel Vertical Migration for Sustaining a Mesopelagic Food Web

Kelly

Davison

Goericke

et al. 2019

Preprint

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We used extensive ecological and biogeochemical measurements obtained from quasi-Lagrangian experiments during two California Current Ecosystem Long-Term Ecosystem Research cruises to analyze carbon fluxes between the epipelagic and mesopelagic zones using a linear inverse ecosystem model (LIEM). Measurement constraints on the model include 14C primary productivity, dilution-based microzooplankton grazing rates, gut pigment-based mesozooplankton grazing rates (on multiple zooplankton size classes), 234Th:238U disequilibrium and sediment trap measured carbon export, and metabolic requirements of micronekton, zooplankton, and bacteria. A likelihood approach (Markov Chain Monte Carlo) was used to estimate the resulting flow uncertainties from a sample of potential flux networks. Results highlight the importance of mesozooplankton active transport (i.e., diel vertical migration) for supplying the carbon demand of mesopelagic organisms and sequestering carbon dioxide from the atmosphere. In nine water parcels ranging from a coastal bloom to offshore oligotrophic conditions, mesozooplankton active transport accounted for 18% - 84% (median: 42%) of the total carbon supply to the mesopelagic, with gravitational settling of POC (12% - 55%; median: 37%) and subduction (2% - 32%; median: 14%) providing the majority of the remainder. Vertically migrating zooplankton contributed to downward carbon flux through respiration and excretion at depth and via consumption loses to predatory zooplankton and mesopelagic fish (e.g. myctophids and gonostomatids). Sensitivity analyses showed that the results of the LIEM were robust to changes in nekton metabolic demands, rates of bacterial production, and mesozooplankton gross growth efficiency. This analysis suggests that prior estimates of zooplankton active transport based on conservative estimates of standard (rather than active) metabolism should be revisited. Contribution to the Field Understanding the flows of carbon within the ocean is important for predicting how global climate will shift; yet even after decades of research, the magnitude with which the ocean sequesters carbon is highly uncertain. One reason behind this uncertainty is that a variety of mechanisms control the balance between carbon input and carbon output within the ocean. The topic of this work is to inspect the role of biological organisms in physically transferring organic carbon from the surface to the deep ocean. As opposed to other mechanisms—such as sinking particles, the biological transfer of carbon is difficult to measure directly and is often quite variable, leading to large uncertainties. Here we use an extensive set of in situ observations off the coast of southern California to model the flow of carbon through the ecosystem. The model determined that in our study area nearly half of the total transfer of carbon from the surface ocean to deep was carried out by zooplankton that swim up to the surface each night to feed. This finding has direct implications for global carbon budgets, which of...

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Toward a better understanding of fish‐based contribution to ocean carbon flux

Saba

Burd

Dunne

et al. 2021

Limnology & Oceanography

134

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Fishes are the dominant vertebrates in the ocean, yet we know little of their contribution to carbon export flux at regional to global scales. We synthesize the existing information on fish-based carbon flux in coastal and pelagic waters, identify gaps and challenges in measuring this flux and approaches to address them, and recommend research priorities. Based on our synthesis of passive (fecal pellet sinking) and active (migratory) flux of fishes, we estimated that fishes contribute an average (AE standard deviation) of about 16.1% (AE 13%) to total carbon flux out of the euphotic zone. Using the mean value of model-generated global carbon flux estimates, this equates to an annual flux of 1.5 AE 1.2 Pg C yr −1 . High variability in estimations of the fish-based contribution to total carbon flux among previous field studies and reported here highlight significant methodological variations and observational gaps in our present knowledge. Community-adopted methodological standards, improved and more frequent measurements of biomass and passive and active fluxes of fishes, and stronger linkages between observations and models will decrease uncertainty, increase our confidence in the estimation of fish-based carbon flux, and enable identification of controlling factors to account for spatial and temporal variability. Better constraints on this key component of the biological pump will provide a baseline for understanding how ongoing climate change and harvest will affect the role fishes play in carbon flux. * Estimated from DVM fish standing stock in and out of 500 m, an assumed daily ration of 10% body weight, 50% assimilation efficiency, and 5% fecal carbon content. † Uncorrected for capture efficiency. ‡ Estimated from midwater fish standing stock and daily consumption rate assuming an egestion rate of 20% food intake. §Values reported here include only data where anchovy fecal pellets were present in sediment traps (in 12 out of 20 free-drifting sediment trap sampling deployments in fall of 1977 and fall of 1978). ¶ Assumes 14% capture efficiency. ** Maximum respiratory carbon flux as day-time net catches have not been corrected for capture efficiency. † † Value estimated as the geometric mean from the ranges reported in the study. ‡ ‡ Assumes 50% capture efficiency. § § Assumes 14% capture efficiency for Matsuda-Oozeki-Hu trawls and an additional 6% capture efficiency for Isaacs-Kidd midwater trawls. ¶ ¶ Calculated from Davison et al. 2013 (table 9), comparing Vertical Migrant (VM) export and Fish-Mediated Export (FME; vertical migrant + nonmigrant export) to passive POC flux measured from sediment traps at 150 m). ***Estimated from assuming total fish export flux is equivalent to 100% (fecal) plus 180% (excretory) plus 50% (mortality) of the fish standing stock (11.9-66 mg C m −2).**Atmospheric Arpege weather forecast model coupled with geochemical Hamburg ocean carbon cycle model. † † Ecosystem model that consists of several compartments and tracks elements, including carbon, for the biota and detrital pools....

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Zooplankton and Micronekton Active Flux Across the Tropical and Subtropical Atlantic Ocean

Cited by 61 publications

References 61 publications

Mesozooplankton and Micronekton Active Carbon Transport in Contrasting Eddies

Mesozooplankton and Micronekton Active Carbon Transport in Contrasting Eddies

The Importance of Mesozooplankton Diel Vertical Migration for Sustaining a Mesopelagic Food Web

Toward a better understanding of fish‐based contribution to ocean carbon flux

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