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Arostegui MC, Muhling B, Culhane E, Dewar H, Koch SS, Braun CD. A shallow scattering layer structures the energy seascape of an open ocean predator. SCIENCE ADVANCES 2023; 9:eadi8200. [PMID: 37792940 PMCID: PMC10550225 DOI: 10.1126/sciadv.adi8200] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 09/01/2023] [Indexed: 10/06/2023]
Abstract
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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Affiliation(s)
- Martin C. Arostegui
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Barbara Muhling
- Institute of Marine Sciences, University of California, Santa Cruz, Santa Cruz, CA, USA
- Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, USA
| | - Emmett Culhane
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Heidi Dewar
- Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, USA
| | - Stephanie S. Koch
- Department of Biological Sciences, Thomas More University, Crestview Hills, KY, USA
| | - Camrin D. Braun
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
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McKnight JC, Ruesch A, Bennett K, Bronkhorst M, Balfour S, Moss SEW, Milne R, Tyack PL, Kainerstorfer JM, Hastie GD. Shining new light on sensory brain activation and physiological measurement in seals using wearable optical technology. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200224. [PMID: 34121458 PMCID: PMC8200653 DOI: 10.1098/rstb.2020.0224] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2020] [Indexed: 12/19/2022] Open
Abstract
Sensory ecology and physiology of free-ranging animals is challenging to study but underpins our understanding of decision-making in the wild. Existing non-invasive human biomedical technology offers tools that could be harnessed to address these challenges. Functional near-infrared spectroscopy (fNIRS), a wearable, non-invasive biomedical imaging technique measures oxy- and deoxyhaemoglobin concentration changes that can be used to detect localized neural activation in the brain. We tested the efficacy of fNIRS to detect cortical activation in grey seals (Halichoerus grypus) and identify regions of the cortex associated with different senses (vision, hearing and touch). The activation of specific cerebral areas in seals was detected by fNIRS in responses to light (vision), sound (hearing) and whisker stimulation (touch). Physiological parameters, including heart and breathing rate, were also extracted from the fNIRS signal, which allowed neural and physiological responses to be monitored simultaneously. This is, to our knowledge, the first time fNIRS has been used to detect cortical activation in a non-domesticated or laboratory animal. Because fNIRS is non-invasive and wearable, this study demonstrates its potential as a tool to quantitatively investigate sensory perception and brain function while simultaneously recording heart rate, tissue and arterial oxygen saturation of haemoglobin, perfusion changes and breathing rate in free-ranging animals. This article is part of the theme issue 'Measuring physiology in free-living animals (Part I)'.
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Affiliation(s)
- J. Chris McKnight
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, UK
| | - Alexander Ruesch
- Department of Biomedical Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
| | - Kimberley Bennett
- Division of Science, School of Engineering and Technology, Abertay University, Dundee, UK
| | - Mathijs Bronkhorst
- Artinis Medical Systems BV, Einsteinweg 17, 6662 PW Elst, The Netherlands
| | - Steve Balfour
- Sea Mammal Research Unit Instrumentation Group, Scottish Oceans Institute, University of St Andrews, St Andrews, UK
| | - Simon E. W. Moss
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, UK
| | - Ryan Milne
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, UK
| | - Peter L. Tyack
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, UK
| | - Jana M. Kainerstorfer
- Department of Biomedical Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
- Department of Biomedical Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213, USA
| | - Gordon D. Hastie
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, UK
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Goulet P, Guinet C, Campagna C, Campagna J, Tyack PL, Johnson M. Flash and grab: deep-diving southern elephant seals trigger anti-predator flashes in bioluminescent prey. ACTA ACUST UNITED AC 2020; 223:223/10/jeb222810. [PMID: 32430464 PMCID: PMC7322542 DOI: 10.1242/jeb.222810] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 03/31/2020] [Indexed: 11/23/2022]
Abstract
Bioluminescence, which occurs in approximately 80% of the world's mesopelagic fauna, can take the form of a low-intensity continuous glow (e.g. for counter-illumination or signalling) or fast repetitions of brighter anti-predatory flashes. The southern elephant seal (SES) is a major consumer of mesopelagic organisms, in particular the abundant myctophid fish, yet the fine-scale relationship between this predator's foraging behaviour and bioluminescent prey remains poorly understood. We hypothesised that brief, intense light emissions should be closely connected with prey strikes when the seal is targeting bioluminescent prey that reacts by emitting anti-predator flashes. To test this, we developed a biologging device containing a fast-sampling light sensor together with location and movement sensors to measure simultaneously anti-predator bioluminescent emissions and the predator's attack motions with a 20 ms resolution. Tags were deployed on female SES breeding at Kerguelen Islands and Península Valdés, Argentina. In situ light levels in combination with duration of prey capture attempts indicated that seals were targeting a variety of prey types. For some individuals, bioluminescent flashes occurred in a large proportion of prey strikes, with the timing of flashes closely connected with the predator's attack motion, suggestive of anti-predator emissions. Marked differences across individuals and location indicate that SES do exploit bioluminescent organisms but the proportion of these in the diet varies widely with location. The combination of wideband light and acceleration data provides new insight into where and when different prey types are encountered and how effectively they might be captured. Highlighted Article: Description of a new measurement method and its successful application to deep-diving elephant seals, showing that these predators attempt to catch mesopelagic prey that react with bright anti-predator flashes.
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Affiliation(s)
- Pauline Goulet
- Sea Mammal Research Unit, University of St Andrews, St Andrews, Fife KY16 8LB, UK
| | - Christophe Guinet
- Centre d'Etudes Biologiques de Chizé, CNRS, 79360 Villiers en Bois, France
| | - Claudio Campagna
- Wildlife Conservation Society, Argentina and Marine Programs, Amenábar 1595, 1426 Buenos Aires, Argentina
| | - Julieta Campagna
- Centro para el Estudio de Sistemas Marinos, CONICET, Boulevard Brown 2915, 9120 Puerto Madryn, Chubut, Argentina
| | - Peter Lloyd Tyack
- Sea Mammal Research Unit, University of St Andrews, St Andrews, Fife KY16 8LB, UK
| | - Mark Johnson
- Sea Mammal Research Unit, University of St Andrews, St Andrews, Fife KY16 8LB, UK .,Department of Biology, Aarhus University, 8000 Aarhus, Denmark
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Nowak BVR, Bowen WD, Whoriskey K, Lidgard DC, Mills Flemming JE, Iverson SJ. Foraging behaviour of a continental shelf marine predator, the grey seal ( Halichoerus grypus), is associated with in situ, subsurface oceanographic conditions. MOVEMENT ECOLOGY 2020; 8:41. [PMID: 33093960 PMCID: PMC7574573 DOI: 10.1186/s40462-020-00225-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 09/30/2020] [Indexed: 05/13/2023]
Abstract
BACKGROUND The heterogeneous oceanographic conditions of continental shelf ecosystems result in a three-dimensionally patchy distribution of prey available to upper-trophic level predators. The association of bio-physical conditions with movement patterns of large marine predators has been demonstrated in diverse taxa. However, obtaining subsurface data that are spatio-temporally relevant to the decisions made by benthically-foraging species can be challenging. METHODS Between 2009 and 2015, grey seals were captured on Sable Island, Nova Scotia, Canada during summer and fall and instrumented with high-resolution archival GPS tags. These tags recorded location data as well as depth (m), temperature (°C), and light level measurements during dives, until animals returned to the haulout site to breed. Hidden Markov models were used to predict apparent foraging along movement tracks for 79 individuals (59 females, 20 males) every 3 h. In situ measurements were used to estimate chlorophyll-a concentration (mg m- 3) and temperature within the upper-water column (50 m) and temperature and depth at the bottom of dives. As chlorophyll-a could only be estimated from 10:00 to 14:00 AST for dive depths ≥50 m, we formulated two generalized linear mixed-effects models to test the association of predicted grey seal behavioural states with oceanographic conditions and phytoplankton biomass: the first representing conditions of the upper-water column likely to influence primary productivity, and a second model including environmental conditions encountered by grey seals at the bottom of dives, when seals were more likely to be foraging. RESULTS Predicted grey seal behavioural states were associated with fine-scale chlorophyll-a concentrations and other environmental conditions they encountered across the continental shelf. In the Water Column Model, season had no influence on the probability of observing apparent foraging, but chlorophyll-a, upper-water column temperature, and sex did, with females having a greater probability of foraging than males. In the Bottom Conditions Model, again season had no influence on the probability of apparent foraging, but females were over twice as likely as males to be foraging. CONCLUSIONS The results of this study highlight the value of in situ measurements of oceanographic properties that can be collected at high temporal resolution by animal-borne data loggers. These data provide insight into how inferred behavioural decisions made by large marine predators, such as the grey seal, may be influenced by fine-scale oceanographic conditions.
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Affiliation(s)
- B. V. R. Nowak
- Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4JI Canada
| | - W. D. Bowen
- Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4JI Canada
- Population Ecology Division, Department of Fisheries and Oceans, Bedford Institute of Oceanography, Dartmouth, Nova Scotia B2Y 4A2 Canada
| | - K. Whoriskey
- Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia B3H 4JI Canada
| | - D. C. Lidgard
- Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4JI Canada
- Population Ecology Division, Department of Fisheries and Oceans, Bedford Institute of Oceanography, Dartmouth, Nova Scotia B2Y 4A2 Canada
| | - J. E. Mills Flemming
- Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia B3H 4JI Canada
| | - S. J. Iverson
- Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4JI Canada
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Abstract
Mesopelagic fish and squid occupy ocean depths extending below the photic zone and their vertical migrations represent a massive pathway moving energy and carbon through the water column. Their spatio-temporal distribution is however, difficult to map across remote regions particularly the vast Southern Ocean. This represents a key gap in understanding biogeochemical processes, marine ecosystem structure, and how changing ocean conditions will affect marine predators, which depend upon mesopelagic prey. We infer mesopelagic prey vertical distribution and relative abundance in the Indian sector of the Southern Ocean (20° to 130°E) with a novel approach using predator-derived indices. Fourteen years of southern elephant seal tracking and dive data, from the open ocean between the Antarctic Polar Front and the southern Antarctic Circumpolar Current front, clearly show that the vertical distribution of mesopelagic prey is influenced by the physical hydrographic processes that structure their habitat. Mesopelagic prey have a more restricted vertical migration and higher relative abundance closer to the surface where Circumpolar Deep Water rises to shallower depths. Combining these observations with a future projection of Southern Ocean conditions we show that changes in the coupling of surface and deep waters will potentially redistribute mesopelagic prey. These changes are small overall, but show important spatial variability: prey will increase in relative abundance to the east of the Kerguelen Plateau but decrease to the west. The consequences for deep-diving specialists such as elephant seals and whales over this time scale will likely be minor, but the changes in mesoscale vertical energy flow have implications for predators that forage within the mesopelagic zone as well as the broader pelagic ecosystem.
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