On the Estimation of Zooplankton-Mediated Active Fluxes in Oxygen Minimum Zone Regions

Kiko, Rainer; Hauss, Helena

doi:10.3389/fmars.2019.00741

Cited by 33 publications

(36 citation statements)

References 56 publications

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“…The environmental pO 2 was generally much higher than the estimated p crit for migrating euphausiids and copepods (Kiko et al, 2016, see also Figure 2). Therefore, unlike to our companion paper (Kiko and Hauss, 2019), we did not apply a correction of oxygendependent depression of metabolic activity. Daily mortality of copepods was calculated according to Hirst and Kiørboe (2002) as ln(mortality) = 0.047 * Temperature − 0.154 * ln(DW) − 2.532, thereby treating all copepods as broadcast spawners (DW = Dryweight in µg, Temperature in Celsius).…”

Section: Calculation Of Mesozooplankton Biomass Metabolic Activity mentioning

confidence: 99%

“…Global biogeochemical model studies that include some first zooplankton DVM parameterizations also suggest that the active flux can locally contribute up to 50% of the sinking flux to the mesopelagic (Bianchi et al, 2013;Aumont et al, 2018;Archibald et al, 2019), and lower oxygen concentrations in these depths by 15 µmol kg −1 (Aumont et al, 2018) up to almost 50 µmol kg −1 (Bianchi et al, 2013). However, these models do not represent the behavior of zooplankton in extreme OMZs well (Kiko and Hauss, 2019) as hypoxia threshold levels are used that are unrealistic in some regions. Feedbacks between changing oxygen levels and the role of zooplankton in the elemental cycling of oxygen and carbon are to be expected and might also impact the elemental cycling of nitrogen.…”

Section: The Role Of Zooplankton In Biogeochemical Cyclingmentioning

confidence: 99%

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Zooplankton-Mediated Fluxes in the Eastern Tropical North Atlantic

et al. 2020

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Zooplankton organisms are a central part of pelagic ecosystems. They feed on all kinds of particulate matter and their egested fecal pellets contribute substantially to the passive sinking flux to depth. Some zooplankton species also conduct diel vertical migrations (DVMs) between the surface layer (where they feed at nighttime) and midwater depth (where they hide at daytime from predation). These DVMs cause the active export of organic and inorganic matter from the surface layer as zooplankton organisms excrete, defecate, respire, die, and are preyed upon at depth. In the Eastern Tropical North Atlantic (ETNA), the daytime distribution depth of many migrators (300-600 m) coincides with an expanding and intensifying oxygen minimum zone (OMZ). We here assess the day and night-time biomass distribution of mesozooplankton with an equivalent spherical diameter of 0.39-20 mm in three regions of the ETNA, calculate the DVM-mediated fluxes and compare these to particulate matter fluxes and other biogeochemical processes. Integrated mesozooplankton biomass in the ETNA region is about twice as high at a central OMZ location (cOMZ; 11 • N, 21 • W) compared to the Cape Verde Ocean Observatory (CVOO; 17.6 • N, 24.3 • W) and an oligotrophic location at 5 • N, 23 • W (5N). An Intermediate Particle Maximum (IPM) is particularly strong at cOMZ compared to the other regions. This IPM seems to be related to DVM activity. Zooplankton DVM was found to be responsible for about 31-41% of nitrogen loss from the upper 200m of the water column. Gut flux and mortality make up about 31% of particulate matter supply to the 300-600 m depth layer at cOMZ, whereas it makes up about 32% and 41% at CVOO and 5N, respectively. Resident and migrant zooplankton are responsible for about 7-27% of the total oxygen demand at 300-600 m depth. Changes in zooplankton abundance and migration behavior due to decreasing oxygen levels at midwater depth could therefore alter the elemental cycling of oxygen and carbon in the ETNA OMZ and impact the removal of nitrogen from the surface layer.

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Section: Calculation Of Mesozooplankton Biomass Metabolic Activity mentioning

confidence: 99%

Section: The Role Of Zooplankton In Biogeochemical Cyclingmentioning

confidence: 99%

Zooplankton-Mediated Fluxes in the Eastern Tropical North Atlantic

et al. 2020

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“…For model comparison we converted the observation from nighttime hauls to dry biomass according to Lehette and Hernández-León (2009), and further to nitrogen units as suggested by Kiørboe (2013). A detailed description of the zooplankton processing is provided by Kiko and Hauss (2019). Only night observations were compared since our model does not include diel vertical migration.…”

Section: Zooplankton Validationmentioning

confidence: 99%

“…The observations, on the other hand, do not cover the whole taxonomic and size spectrum of mesozooplankton. For instance, no gelatinous organisms are accounted for, and only mesozooplankton greater than 500 µm is considered in the sampling (Kiko and Hauss, 2019), and fragile organisms, such as rhizaria, are not quantitatively sampled by nets (Biard et al, 2016). Therefore, the observations might be biased low in comparison to the model.…”

Section: Constraining the Zooplankton Compartmentmentioning

confidence: 99%

“…In reality, zooplankton is known to perform diel vertical migrations (DVM), which could increase the export flux to the deep ocean (Aumont et al, 2018;Archibald et al, 2019;Kiko and Hauss, 2019;Kiko et al, 2020). The lack of DVM could affect the export of organic matter to greater depths, and therefore the biogeochemical turnover at the surface.…”

Section: Constraining the Zooplankton Compartmentmentioning

confidence: 99%

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Zooplankton mortality effects on the plankton community of the Northern Humboldt Current System: Sensitivity of a regional biogeochemical model

Cruz¹,

Kriest²,

José³

et al. 2020

Preprint

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Abstract. Small pelagic fish off the coast of Peru in the Eastern Tropical South Pacific (ETSP) support around 10 % of the global fish catches. Their stocks fluctuate interannually due to environmental variability which can be exacerbated by fishing pressure. Because these fish are planktivorous, any change in fish abundance may directly affect the plankton and the biogeochemical system. To investigate the potential effects of variability in small pelagic fish populations on lower trophic levels, we used a coupled physical-biogeochemical model to build scenarios for the ETSP and compare these against an already published reference simulation. The scenarios mimic changes in fish predation by either increasing or decreasing mortality of the model's large and small zooplankton compartments. The results revealed that large zooplankton was the main driver of the response of the community. Its concentration increased under low mortality conditions and its prey, small zooplankton and large phytoplankton, decreased. The response was opposite, but weaker, in the high mortality scenarios. This asymmetric behaviour can be explained by the different ecological roles of large, omnivorous zooplankton, and small zooplankton, which in the model is strictly herbivorous. The response of small zooplankton depended on the antagonistic effects of mortality changes as well as the grazing pressure by large zooplankton. The results of this study provide a first insight on how the plankton ecosystem might respond if variations in fish populations were modelled explicitly.

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Testing the usefulness of optical data for zooplankton long‐term monitoring: Taxonomic composition, abundance, biomass, and size spectra from ZooScan image analysis

Cornils

Thomisch

Hase

et al. 2022

Limnology & Ocean Methods

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The pelagic ecosystem of the Arctic Ocean is threatened by severe changes such as the reduction in sea‐ice coverage and increased inflow of warmer Atlantic water. The latter is already altering the zooplankton community, highlighting the need for monitoring studies. It is therefore essential to accelerate the taxonomic identification to speed up sample analysis, and to expand the analysis to biomass and size assessments, providing data for modeling efforts. Our case study in Fram Strait illustrates that image‐based analyses with the ZooScan provide abundance data and taxonomic resolutions that are comparable to microscopic analyses and are suitable for zooplankton monitoring purposes in the Arctic. We also show that image analysis allows to differentiate developmental stages of the key species Calanus spp. and Metridia longa and, thus, to study their population dynamics. Our results emphasize that older preserved samples can be successfully reanalyzed with ZooScan. To explore the applicability of image parameters for calculating total mesozooplankton and Calanus spp. biomasses, we used (1) conversion factors (CFs) translating wet mass to dry mass (DM), and (2) length–mass (LM) relationships. For Calanus spp., the calculated biomass values yielded similar results as direct DM measurements. Total mesozooplankton biomass ranged between 1.6 and 15 (LM) or 2.4 and 21 (CF) g DM m−2, respectively, which corresponds to previous studies in Fram Strait. Ultimately, a normalized biomass size spectra analysis provides 1st insights into the mesozooplankton size structure at different depths, revealing steep slopes in the linear fit in communities influenced by Atlantic water inflow.

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On the Estimation of Zooplankton-Mediated Active Fluxes in Oxygen Minimum Zone Regions

Cited by 33 publications

References 56 publications

Zooplankton-Mediated Fluxes in the Eastern Tropical North Atlantic

Zooplankton-Mediated Fluxes in the Eastern Tropical North Atlantic

Zooplankton mortality effects on the plankton community of the Northern Humboldt Current System: Sensitivity of a regional biogeochemical model

Testing the usefulness of optical data for zooplankton long‐term monitoring: Taxonomic composition, abundance, biomass, and size spectra from ZooScan image analysis

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