Global decline of pelagic fauna in a warmer ocean

Ariza, Alejandro; Lengaigne, Matthieu; Menkès, Christophe E.; Lebourges‐Dhaussy, Anne; Receveur, Aurore; Gorguès, Thomas; Habasque, Jérémie; Gutiérrez, Mariano; Maury, Olivier; Bertrand, Arnaud

doi:10.1038/s41558-022-01479-2

Cited by 35 publications

(9 citation statements)

References 67 publications

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“…We were unable to directly quantify foraging at depth, and therefore, the absolute value of deep resources to these predators remains unknown. However, our results suggest that mesopelagic forage species contribute significantly to the energy budgets of pelagic predators and highlight the need for additional research to better characterize the ecological value of this connectivity, particularly in light of climate-induced changes to midwater ecosystems ( 70 , 71 ) and planned harvest of mesopelagic resources ( 72 , 73 ). Despite extensive diet data supporting the importance of mesopelagic prey for a suite of predator taxa [reviewed in ref.…”

Section: Discussionmentioning

confidence: 83%

“…Better accounting is needed to more accurately quantify the potentially significant role of predators and the impacts of associated fisheries for predators ( 75 ) and prey ( 72 , 73 ) in the marine carbon cycle. Together, the overlap in ongoing fishing effort and pelagic predator distributions ( 76 ), expected climate-induced changes in pelagic ecosystems ( 70 , 71 , 77 ), and the potential extraction of mesopelagic biomass ( 72 , 73 ) suggest that this critical link may be in jeopardy.…”

Section: Discussionmentioning

confidence: 99%

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Linking vertical movements of large pelagic predators with distribution patterns of biomass in the open ocean

Braun,

Della Penna,

Arostegui

et al. 2023

Proc. Natl. Acad. Sci. U.S.A.

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Many predator species make regular excursions from near-surface waters to the twilight (200 to 1,000 m) and midnight (1,000 to 3,000 m) zones of the deep pelagic ocean. While the occurrence of significant vertical movements into the deep ocean has evolved independently across taxonomic groups, the functional role(s) and ecological significance of these movements remain poorly understood. Here, we integrate results from satellite tagging efforts with model predictions of deep prey layers in the North Atlantic Ocean to determine whether prey distributions are correlated with vertical habitat use across 12 species of predators. Using 3D movement data for 344 individuals who traversed nearly 1.5 million km of pelagic ocean in > 42,000 d, we found that nearly every tagged predator frequented the twilight zone and many made regular trips to the midnight zone. Using a predictive model, we found clear alignment of predator depth use with the expected location of deep pelagic prey for at least half of the predator species. We compared high-resolution predator data with shipboard acoustics and selected representative matches that highlight the opportunities and challenges in the analysis and synthesis of these data. While not all observed behavior was consistent with estimated prey availability at depth, our results suggest that deep pelagic biomass likely has high ecological value for a suite of commercially important predators in the open ocean. Careful consideration of the disruption to ecosystem services provided by pelagic food webs is needed before the potential costs and benefits of proceeding with extractive activities in the deep ocean can be evaluated.

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Section: Discussionmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Linking vertical movements of large pelagic predators with distribution patterns of biomass in the open ocean

Braun,

Della Penna,

Arostegui

et al. 2023

Proc. Natl. Acad. Sci. U.S.A.

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“…Thus, acute sensory capabilities lead SES to have a much larger ecological footprint and therefore exercise far greater top–down control over Southern Ocean food webs than they would as reactive predators. But even this robust foraging strategy is susceptible to large-scale changes in prey abundance and community structure due to industrial mesopelagic trawling and climate change ( 39 ).…”

Section: Discussionmentioning

confidence: 99%

Large sensory volumes enable Southern elephant seals to exploit sparse deep-sea prey

Chevallay,

Goulet,

Madsen

et al. 2023

Proc. Natl. Acad. Sci. U.S.A.

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The ability of echolocating toothed whales to detect and classify prey at long ranges enables efficient searching and stalking of sparse prey in these time-limited dives. However, nonecholocating deep-diving seals such as elephant seals appear to have much less sensory advantage over their prey. Both elephant seals and their prey rely on visual and hydrodynamic cues that may be detectable only at short ranges in the deep ocean, leading us to hypothesize that elephant seals must adopt a less efficient reactive mode of hunting that requires high prey densities. To test that hypothesis, we deployed high-resolution sonar and movement tags on 25 females to record simultaneous predator and prey behavior during foraging interactions. We demonstrate that elephant seals have a sensory advantage over their prey that allows them to potentially detect prey 5 to 10 s before striking. The corresponding prey detection ranges of 7 to 17 m enable stealthy approaches and prey-specific capture tactics. In comparison, prey react at a median range of 0.7 m, close to the neck extension range of striking elephant seals. Estimated search swathes of 150 to 900 m 2 explain how elephant seals can locate up to 2,000 prey while swimming more than 100 km per day. This efficient search capability allows elephant seals to subsist on prey densities that are consonant with the deep scattering layer resources estimated by hydroacoustic surveys but which are two orders of magnitude lower than the prey densities needed by a reactive hunter.

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“…Given burgeoning interest in scattering layer fisheries ( 66 ), predictions for climate change to cause a global decline of scattering layer fauna ( 67 ), and scattering layer research being predominantly focused on the globally distributed primary DSL ( 16 , 17 ), increased effort is needed to understand the ecology and biogeography of the SSL in the mid-latitudes. The occurrence of an SSL in multiple subtropical gyres ( 20 , 40 ), the oligotrophic Red Sea ( 68 ), and elsewhere under specific oligotrophic conditions ( 19 ), merits investigation to determine whether high light penetration driving the DSL(s) deeper increases ecological niche availability via vertical segregation.…”

Section: Discussionmentioning

confidence: 99%

A shallow scattering layer structures the energy seascape of an open ocean predator

Arostegui,

Muhling,

Culhane

et al. 2023

Sci. Adv.

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Large predators frequent the open ocean where subsurface light drives visually based trophic interactions. However, we lack knowledge on how predators achieve energy balance in the unproductive open ocean where prey biomass is minimal in well-lit surface waters but high in dim midwaters in the form of scattering layers. We use an interdisciplinary approach to assess how the bioenergetics of scattering layer forays by a model predator vary across biomes. We show that the mean metabolic cost rate of daytime deep foraging dives to scattering layers decreases as much as 26% from coastal to pelagic biomes. The more favorable energetics offshore are enabled by the addition of a shallow scattering layer that, if not present, would otherwise necessitate costlier dives to deeper layers. The unprecedented importance of this shallow scattering layer challenges assumptions that the globally ubiquitous primary deep scattering layer constitutes the only mesopelagic resource regularly targeted by apex predators.

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Global decline of pelagic fauna in a warmer ocean

Cited by 35 publications

References 67 publications

Linking vertical movements of large pelagic predators with distribution patterns of biomass in the open ocean

Linking vertical movements of large pelagic predators with distribution patterns of biomass in the open ocean

Large sensory volumes enable Southern elephant seals to exploit sparse deep-sea prey

A shallow scattering layer structures the energy seascape of an open ocean predator

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