Austral fall−winter transition of mesozooplankton assemblages and krill aggregations in an embayment west of the Antarctic Peninsula

Espinasse, Boris; Zhou, Meng; Zhu, Yiwu; Hazen, Elliott L.; Friedlaender, Ari S.; Nowacek, Douglas P.; Chu, Dezhang; Carlotti, François

doi:10.3354/meps09626

Cited by 31 publications

(30 citation statements)

References 73 publications

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“…A massive krill swarm (> 2 million t) occurred in Wilhelmina Bay and in some places reached a vertical thickness of 200 m, typically in deep water (> 400 m). The central mass of the krill layer migrated vertically at night into the upper 50 m of the water column (Espinasse et al 2012), making access to prey substantially easier for the whales during this time.…”

Section: Discussionmentioning

confidence: 99%

Extreme diel variation in the feeding behavior of humpback whales along the western Antarctic Peninsula during autumn

Friedlaender¹,

Tyson²,

Stimpert³

et al. 2013

Mar. Ecol. Prog. Ser.

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Most humpback whale Megaptera novaeangliae populations partition their time between prey-rich feeding and prey-deficient breeding/calving regions. How these whales feed and optimize the consumption of prey resources prior to long-distance migrations and fasting is largely unknown. We deployed multi-sensor tags on humpback whales around the western Antarctic Peninsula to describe their daily activity patterns late in the feeding season to test the hypothesis that feeding behavior varies over the diel cycle so as to maximize energy intake and limit energy expenditure. Dives were assigned to a behavioral state (feeding, resting, traveling, exploring) to determine hourly rates and to build an ethogram of activity patterns. Our results show a distinct diel pattern of whales feeding exclusively at night. Feeding depth was deeper around sunrise/sunset and shallower (~50 m) at night, consistent with diel vertical prey movement. Shallow feeding dives typically contained a single feeding lunge, a strategy known to increase feeding efficiency and maximize intake rates by maintaining proximity to the surface and reducing the energetic costs of deep diving. The lack of feeding during daytime may indicate prey being too deep for efficient foraging. Our results add information where currently there is a paucity of data describing how baleen whales optimize feeding behavior, specifically in relation to prey distribution and movement, to fuel their extraordinary energetic requirements necessary for growth, migration, and reproduction. Understanding behavioral patterns and predator/prey dynamics in rapidly changing marine environments, like the Antarctic Peninsula, is critical for understanding how these changes will affect ecosystem structure and function.

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Section: Discussionmentioning

confidence: 99%

Extreme diel variation in the feeding behavior of humpback whales along the western Antarctic Peninsula during autumn

Friedlaender¹,

Tyson²,

Stimpert³

et al. 2013

Mar. Ecol. Prog. Ser.

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“…Therefore, it is widely distributed worldwide and used by 60 research teams from the tropics to the poles (e.g. France (Vandromme et al, 2011); New-Caledonia (Smeti et al, 2015); Antarctica (Espinasse et al, 2012)). It is most commonly used as a computer-assisted identification system, whereby the classifier proposes identifications that are then validated by human operators for all objects.…”

Section: And the In Situ Ichthyoplankton Imagingmentioning

confidence: 99%

Imperfect automatic image classification successfully describes plankton distribution patterns

Faillettaz

Picheral

Luo

et al. 2016

Methods in Oceanography

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International audienceImaging systems were developed to explore the fine scale distributions of plankton (<10 m), but they generate huge datasets that are still a challenge to handle rapidly and accurately. So far, imaged organisms have been either classified manually or pre-classified by a computer program and later verified by human operators. In this paper, we post-process a computer-generated classification, obtained with the common ZooProcess and PlanktonIdentifier toolchain developed for the ZooScan, and test whether the same ecological conclusions can be reached with this fully automatic dataset and with a reference, manually sorted, dataset. The Random Forest classifier outputs the probabilities that each object belongs in each class and we discard the objects with uncertain predictions, i.e. under a probability threshold defined based on a 1% error rate in a self-prediction of the learning set. Keeping only well-predicted objects enabled considerable improvements in average precision, 84% for biological groups, at the cost of diminishing recall (by 39% on average). Overall, it increased accuracy by 16%. For most groups, the automatically-predicted distributions were comparable to the reference distributions and resulted in the same size-spectra. Automatically-predicted distributions also resolved ecologically-relevant patterns, such as differences in abundance across a mesoscale front or fine-scale vertical shifts between day and night. This post-processing method is tested on the classification of plankton images through Random Forest here, but is based on basic features shared by all machine learning methods and could thus be used in a broad range of applications

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“…A reduced collection efficiency of euphausiids compared to copepods could also be responsible for this mismatch, knowing that specific nets like the Multiple Opening and Closing Nets and Environment Sensing System (MOC-NESS; Wiebe et al, 1976) are needed to efficiently capture both mesozooplankton and euphausiids in the layer 0-250 m (e.g. Espinasse et al, 2012). Most studies show that zooplankton net avoidance is complex and variable; it depends on environmental conditions (e.g.…”

Section: Comparison Of Poc Flux Estimationsmentioning

confidence: 99%

The relative importance of phytoplankton aggregates and zooplankton fecal pellets to carbon export: insights from free-drifting sediment trap deployments in naturally iron-fertilised waters near the Kerguelen Plateau

et al. 2015

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Abstract. The first KErguelen Ocean and Plateau compared Study (KEOPS1), conducted in the naturally iron-fertilised Kerguelen bloom, demonstrated that fecal material was the main pathway for exporting carbon to the deep ocean during summer (January-February 2005), suggesting a limited role of direct export via phytodetrital aggregates. The KEOPS2 project reinvestigated this issue during the spring bloom initiation (October-November 2011), when zooplankton communities may exert limited grazing pressure, and further explored the link between carbon flux, export efficiency and dominant sinking particles depending upon surface plankton community structure. Sinking particles were collected in polyacrylamide gel-filled and standard free-drifting sediment traps (PPS3/3), deployed at six stations between 100 and 400 m, to examine flux composition, particle origin and their size distributions. Results revealed an important contribution of phytodetrital aggregates (49 ± 10 and 45 ± 22 % of the total number and volume of particles respectively, all stations and depths averaged). This high contribution dropped when converted to carbon content (30±16 % of total carbon, all stations and depths averaged), with cylindrical fecal pellets then representing the dominant fraction (56 ± 19 %).At 100 and 200 m depth, iron-and biomass-enriched sites exhibited the highest carbon fluxes (maxima of 180 and 84 ± 27 mg C m −2 d −1 , based on gel and PPS3/3 trap collection respectively), especially where large fecal pellets dominated Published by Copernicus Publications on behalf of the European Geosciences Union. 1008 E. C. Laurenceau-Cornec et al.: The importance of sinking particle types to carbon export over phytodetrital aggregates. Below these depths, carbon fluxes decreased (48±21 % decrease on average between 200 and 400 m), and mixed aggregates composed of phytodetritus and fecal matter dominated, suggesting an important role played by physical aggregation in deep carbon export.Export efficiencies determined from gels, PPS3/3 traps and 234 Th disequilibria (200 m carbon flux/net primary productivity) were negatively correlated to net primary productivity with observed decreases from ∼ 0.2 at low-iron sites to ∼ 0.02 at high-iron sites. Varying phytoplankton communities and grazing pressure appear to explain this negative relationship. Our work emphasises the need to consider detailed plankton communities to accurately identify the controls on carbon export efficiency, which appear to include small spatio-temporal variations in ecosystem structure.

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Austral fall−winter transition of mesozooplankton assemblages and krill aggregations in an embayment west of the Antarctic Peninsula

Cited by 31 publications

References 73 publications

Extreme diel variation in the feeding behavior of humpback whales along the western Antarctic Peninsula during autumn

Extreme diel variation in the feeding behavior of humpback whales along the western Antarctic Peninsula during autumn

Imperfect automatic image classification successfully describes plankton distribution patterns

The relative importance of phytoplankton aggregates and zooplankton fecal pellets to carbon export: insights from free-drifting sediment trap deployments in naturally iron-fertilised waters near the Kerguelen Plateau

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