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1
Dornan, Tracey, Sophie Fielding, Ryan A. Saunders, and Martin J. Genner. "Swimbladder morphology masks Southern Ocean mesopelagic fish biomass." Proceedings of the Royal Society B: Biological Sciences 286, no. 1903 (May 29, 2019): 20190353. http://dx.doi.org/10.1098/rspb.2019.0353.
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Within the twilight of the oceanic mesopelagic realm, 200–1000 m below sea level, are potentially vast resources of fish. Collectively, these mesopelagic fishes are the most abundant vertebrates on Earth, and this global fish community plays a vital role in the function of oceanic ecosystems. The biomass of these fishes has recently been estimated using acoustic survey methods, which rely on echosounder-generated signals being reflected from gas-filled swimbladders and detected by transducers on vessels. Here, we use X-ray computed tomography scans to demonstrate that several of the most abundant species of mesopelagic fish in the Southern Ocean lack gas-filled swimbladders. We also show using catch data from survey trawls that the fish community switches from fish possessing gas-filled swimbladders to those lacking swimbladders as latitude increases towards the Antarctic continent. Thus, the acoustic surveys that repeatedly show a decrease in mesopelagic fish biomass towards polar environments systematically overlook a large proportion of fish species that dominate polar seas. Importantly, this includes lanternfish species that are key prey items for top predators in the region, including king penguins and elephant seals. This latitudinal community switch, from gas to non-gas dominance, has considerable implications for acoustic biomass estimation, ecosystem modelling and long-term monitoring of species at risk from climate change and potential exploitation.
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Benoit-Bird, Kelly J., and Whitlow W. L. Au. "Spatial dynamics of a nearshore, micronekton sound-scattering layer." ICES Journal of Marine Science 60, no. 4 (January 1, 2003): 899–913. http://dx.doi.org/10.1016/s1054-3139(03)00092-4.
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AbstractIn the Hawaiian Islands, there is a distinct resident community of micronekton, distributed along a narrow band where the upper underwater slopes of the islands meet the oceanic, mesopelagic environment. This mesopelagic boundary community serves as an important food resource to many animals. The goal of this work was to examine spatial heterogeneity of the Hawaiian mesopelagic boundary biomass at a range of scales, in the context of its diel vertical and horizontal migrations. A modified echosounder was used to sample the coasts of three Hawaiian Islands, permitting a range of scales from several meters to several kilometers to be assessed rapidly. The Hawaiian mesopelagic boundary community fits the hierarchical model of patch structure with patches within patches that are part of a larger-scale matrix of patches. Large differences in the overall distribution patterns of the mesopelagic boundary community exist along with a wide range of overall mesopelagic-animal densities. High animal-density locations have boundary-community layers with a large (kilometers) horizontal extent, and low animal-density locations have small (tens of meters), discrete patches. Higher animal-density locations are also more complex than low-density sites, with more levels of patchiness within the same range of spatial scales. Both time of day and distance from shore significantly affected the geometric and density characteristics as well as the distribution of aggregations within the boundary layer. Horizontal and vertical structures of the mesopelagic boundary community are also coupled. In high-density sites, there is strong vertical layering in acoustic-scattering strength while in low-density sites vertical acoustic structure is absent. The differences observed in the distribution of the mesopelagic boundary community at different levels of overall mesopelagic-animal density suggest biological forcing as the dominant mechanism. A description of heterogeneity in the mesopelagic boundary community in Hawaii is the first step in understanding its importance to both neritic and oceanic ecosystems and its potential for linking these two systems.
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Davison, Peter C., J. Anthony Koslow, and Rudy J. Kloser. "Acoustic biomass estimation of mesopelagic fish: backscattering from individuals, populations, and communities." ICES Journal of Marine Science 72, no. 5 (February 19, 2015): 1413–24. http://dx.doi.org/10.1093/icesjms/fsv023.
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Abstract Acoustic survey methods are useful to estimate the distribution, abundance, and biomass of mesopelagic fish, a key component of open ocean ecosystems. However, mesopelagic fish pose several challenges for acoustic biomass estimation based on their small size, wide depth range, mixed aggregations, and length-dependent acoustic reflectance, which differentiate them from the larger epipelagic and neritic fish for which these methods were developed. Foremost, there is a strong effect of depth on swimbladder resonance, so acoustic surveys of mesopelagic fish must incorporate depth-stratification. Additionally, the 1–3 cm juveniles of many species are not only more abundant, but can also be stronger acoustic backscatterers than the larger adults that comprise most of the biomass. The dominant species in terms of biomass may thus be weak acoustic backscatters. Failure to properly incorporate depth, the full size distribution, and certain less-abundant species into mesopelagic acoustic analyses could lead to errors in estimated biomass of up to three orders of magnitude. Thus, thorough validation, or “ground-truthing ”, of the species composition, depth structure, population size distribution, capture efficiency of the sampling device, and acoustic properties of the fish present is critical for credible acoustic estimates of mesopelagic fish biomass. This is not insurmountable, but requires more ancillary data than is usually collected.
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Belcher, Anna, Kathryn Cook, Daniel Bondyale-Juez, Gabriele Stowasser, Sophie Fielding, Ryan A. Saunders, Daniel J. Mayor, and Geraint A. Tarling. "Respiration of mesopelagic fish: a comparison of respiratory electron transport system (ETS) measurements and allometrically calculated rates in the Southern Ocean and Benguela Current." ICES Journal of Marine Science 77, no. 5 (March 14, 2020): 1672–84. http://dx.doi.org/10.1093/icesjms/fsaa031.
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Abstract Mesopelagic fish are an important component of marine ecosystems, and their contribution to marine biogeochemical cycles is becoming increasingly recognized. However, major uncertainties remain in the rates at which they remineralize organic matter. We present respiration rate estimates of mesopelagic fish from two oceanographically contrasting regions: the Scotia Sea and the Benguela Current. Respiration rates were estimated by measuring the enzyme activities of the electron transport system. Regression analysis of respiration with wet mass highlights regional and inter-specific differences. The mean respiration rates of all mesopelagic fish sampled were 593.6 and 354.9 µl O2 individual−1 h−1 in the Scotia Sea and Benguela Current, respectively. Global allometric models performed poorly in colder regions compared with our observations, underestimating respiratory flux in the Scotia Sea by 67–88%. This may reflect that most data used to fit such models are derived from temperate and subtropical regions. We recommend caution when applying globally derived allometric models to regional data, particularly in cold (<5°C) temperature environments where empirical data are limited. More mesopelagic fish respiration rate measurements are required, particularly in polar regions, to increase the accuracy with which we can assess their importance in marine biogeochemical cycles.
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Benoit-Bird, Kelly J., and Margaret A. McManus. "Bottom-up regulation of a pelagic community through spatial aggregations." Biology Letters 8, no. 5 (May 2, 2012): 813–16. http://dx.doi.org/10.1098/rsbl.2012.0232.
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The importance of spatial pattern in ecosystems has long been recognized. However, incorporating patchiness into our understanding of forces regulating ecosystems has proved challenging. We used a combination of continuously sampling moored sensors, complemented by shipboard sampling, to measure the temporal variation, abundance and vertical distribution of four trophic levels in Hawaii's near shore pelagic ecosystem. Using an analysis approach from trophic dynamics, we found that the frequency and intensity of spatial aggregations—rather than total biomass—in each step of a food chain involving phytoplankton, copepods, mesopelagic micronekton and spinner dolphins ( Stenella longirostris ) were the most significant predictors of variation in adjacent trophic levels. Patches of organisms had impacts disproportionate to the biomass of organisms within them. Our results are in accordance with resource limitation—mediated by patch dynamics—regulating structure at each trophic step in this ecosystem, as well as the foraging behaviour of the top predator. Because of their high degree of heterogeneity, ecosystem-level effects of patchiness such as this may be common in many pelagic marine systems.
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TIERNEY, MEGAN, MARK A. HINDELL, and SIMON GOLDSWORTHY. "Energy content of mesopelagic fish from Macquarie Island." Antarctic Science 14, no. 3 (September 2002): 225–30. http://dx.doi.org/10.1017/s0954102002000020.
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The water and calorific content of fifteen species of mesopelagic sub-Antarctic fish from Macquarie Island were determined. Mean percent water content was 69–82%. Calorific content was highly variable between species, especially in the Myctophidae, where it ranged between 22.6–59.3 kJ·g−1 dry weight. The water and calorific content varied with size class within a species, with the smallest size classes generally having the lowest water content but highest calorific content. These values will be useful for future assessment of energetic transfer between trophic levels and energetic modelling of Southern Ocean ecosystems.
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Halanych, Kenneth, Cameron Ainsworth, Erik Cordes, Richard Dodge, Markus Huettel, Irving Mendelssohn, Steven Murawski, et al. "Effects of Petroleum By-Products and Dispersants on Ecosystems." Oceanography 34, no. 1 (March 1, 2021): 152–63. http://dx.doi.org/10.5670/oceanog.2021.123.
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Gulf of Mexico (GOM) ecosystems are interconnected by numerous physical and biological processes. After the Deepwater Horizon (DWH) disaster, these ecological processes facilitated dispersal of oil-spill toxicants or were damaged and broken. A considerable portion of post-DWH research focused on higher levels of biological organization (i.e., populations, communities, and ecosystems) spanning at least four environments (onshore, coastal, open ocean, and deep benthos). Damage wrought by the oil spill and mitigation efforts varied considerably across ecosystems. Whereas all systems show prolonged impacts because of cascading effects that impacted functional connections within and between communities, deep-sea and mesopelagic environments were particularly hard hit and have shown less resilience than shallow environments. In some environments, such as marshes or the deep-sea benthos, products from the spill are still biologically accessible. Some shallow ecosystems show signs of recovery, and populations of some species show resilience; however, a return to a “pre-spill” state is questionable. Importantly, habitats in which large amounts of energy flow through the ecosystem (marshes, coastal regions) recovered more quickly than low energy habitats (deep-sea benthos). Functional interactions between Gulf of Mexico systems are more complex and widespread than generally recognized. Moreover, ecosystems in the Gulf are subject to multiple stressors that can combine to impart greater, and less predictable, impacts. To help mitigate the effects of future insults, we identified four salient areas of research that should be addressed for each of the major environments within the GOM: establishing monitoring systems; quantifying coupling between GOM ecosystems; developing criteria for assessing the “vulnerability” and “resilience” of species, communities, and ecosystems; and developing holistic predictive modeling.
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Golikov, Alexey V., Filipe R. Ceia, Hendrik J. T. Hoving, José P. Queirós, Rushan M. Sabirov, Martin E. Blicher, Anna M. Larionova, Wojciech Walkusz, Denis V. Zakharov, and José C. Xavier. "Life History of the Arctic Squid Gonatus fabricii (Cephalopoda: Oegopsida) Reconstructed by Analysis of Individual Ontogenetic Stable Isotopic Trajectories." Animals 12, no. 24 (December 15, 2022): 3548. http://dx.doi.org/10.3390/ani12243548.
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Cephalopods are important in Arctic marine ecosystems as predators and prey, but knowledge of their life cycles is poor. Consequently, they are under-represented in the Arctic ecosystems assessment models. One important parameter is the change in ecological role (habitat and diet) associated with individual ontogenies. Here, the life history of Gonatus fabricii, the most abundant Arctic cephalopod, is reconstructed by the analysis of individual ontogenetic trajectories of stable isotopes (δ13C and δ15N) in archival hard body structures. This approach allows the prediction of the exact mantle length (ML) and mass when the species changes its ecological role. Our results show that the life history of G. fabricii is divided into four stages, each having a distinct ecology: (1) epipelagic squid (ML < 20 mm), preying mostly on copepods; (2) epi- and occasionally mesopelagic squid (ML 20–50 mm), preying on larger crustaceans, fish, and cephalopods; (3) meso- and bathypelagic squid (ML > 50 mm), preying mainly on fish and cephalopods; and (4) non-feeding bathypelagic gelatinous females (ML > 200 mm). Existing Arctic ecosystem models do not reflect the different ecological roles of G. fabricii correctly, and the novel data provided here are a necessary baseline for Arctic ecosystem modelling and forecasting.
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Reid, S. B., J. Hirota, R. E. Young, and L. E. Hallacher. "Mesopelagic-boundary community in Hawaii: Micronekton at the interface between neritic and oceanic ecosystems." Marine Biology 109, no. 3 (October 1991): 427–40. http://dx.doi.org/10.1007/bf01313508.
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Alt, Katharina G., Thomas Kuhn, Julian Münster, Regina Klapper, Judith Kochmann, and Sven Klimpel. "Mesopredatory fishes from the subtropical upwelling region off NW-Africa characterised by their parasite fauna." PeerJ 6 (August 8, 2018): e5339. http://dx.doi.org/10.7717/peerj.5339.
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Eastern boundary upwelling provides the conditions for high marine productivity in the Canary Current System off NW-Africa. Despite its considerable importance to fisheries, knowledge on this marine ecosystem is only limited. Here, parasites were used as indicators to gain insight into the host ecology and food web of two pelagic fish species, the commercially important species Trichiurus lepturus Linnaeus, 1758, and Nealotus tripes Johnson, 1865. Fish specimens of T. lepturus (n = 104) and N. tripes (n = 91), sampled from the Canary Current System off the Senegalese coast and Cape Verde Islands, were examined, collecting data on their biometrics, diet and parasitisation. In this study, the first parasitological data on N. tripes are presented. T. lepturus mainly preyed on small pelagic Crustacea and the diet of N. tripes was dominated by small mesopelagic Teleostei. Both host species were infested by mostly generalist parasites. The parasite fauna of T. lepturus consisted of at least nine different species belonging to six taxonomic groups, with a less diverse fauna of ectoparasites and cestodes in comparison to studies in other coastal ecosystems (Brazil Current and Kuriosho Current). The zoonotic nematode Anisakis pegreffii occurred in 23% of the samples and could pose a risk regarding food safety. The parasite fauna of N. tripes was composed of at least thirteen species from seven different taxonomic groups. Its most common parasites were digenean ovigerous metacercariae, larval cestodes and a monogenean species (Diclidophoridae). The observed patterns of parasitisation in both host species indicate their trophic relationships and are typical for mesopredators from the subtropical epi- and mesopelagic. The parasite fauna, containing few dominant species with a high abundance, represents the typical species composition of an eastern boundary upwelling ecosystem.
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Real, Enric, Ainhoa Bernal, Beatriz Morales-Nin, Balbina Molí, Itziar Alvarez, and M. Pilar Olivar. "Growth patterns of the lanternfish Ceratoscopelus maderensis in the western Mediterranean Sea." Scientia Marina 85, no. 2 (June 11, 2021): 71–80. http://dx.doi.org/10.3989/scimar.05106.007.
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The age and growth patterns of the mesopelagic fish Ceratoscopelus maderensis (family Myctophidae) of the western Mediterranean Sea were described throughout its entire life cycle (from larvae to adult stages) using the sagittae otoliths of 59 individuals collected in December 2009. Three characteristic zones were identified along the cross-section of the sagittae (larval, metamorphic and juvenile-adult zones). Assuming growth rings as daily increments, the age of the analysed individuals (from 3.5 to 64 mm standard length [SL]) would range from 7 to 332 days. The relationship between the number of increments and the fish SL was fitted to a von Bertalanffy growth model (SL=70.5899Å~(1–exp(–0.0501(t+2.6705))). The growth pattern of C. maderensis in the western Mediterranean Sea was similar to that reported for this species in the northeast Atlantic Ocean. Though from a body size of 40-45 mm SL, growth rates declined more slowly in individuals from the western Mediterranean Sea, growth differences between these individuals and those from the northeast Atlantic Ocean were not statistically significant. This study provides new insights into the age and growth patterns of one of the most abundant mesopelagic fish species in the Mediterranean Sea that have clear implications for the study and management of marine ecosystems.
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Gajigan, Andrian P., Aletta T. Yñiguez, Cesar L. Villanoy, Maria Lourdes San Diego-McGlone, Gil S. Jacinto, and Cecilia Conaco. "Diversity and community structure of marine microbes around the Benham Rise underwater plateau, northeastern Philippines." PeerJ 6 (May 16, 2018): e4781. http://dx.doi.org/10.7717/peerj.4781.
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Microbes are central to the structuring and functioning of marine ecosystems. Given the remarkable diversity of the ocean microbiome, uncovering marine microbial taxa remains a fundamental challenge in microbial ecology. However, there has been little effort, thus far, to describe the diversity of marine microorganisms in the region of high marine biodiversity around the Philippines. Here, we present data on the taxonomic diversity of bacteria and archaea in Benham Rise, Philippines, Western Pacific Ocean, using 16S V4 rRNA gene sequencing. The major bacterial and archaeal phyla identified in the Benham Rise are Proteobacteria, Cyanobacteria, Actinobacteria, Bacteroidetes, Marinimicrobia, Thaumarchaeota and, Euryarchaeota. The upper mesopelagic layer exhibited greater microbial diversity and richness compared to surface waters. Vertical zonation of the microbial community is evident and may be attributed to physical stratification of the water column acting as a dispersal barrier. Canonical Correspondence Analysis (CCA) recapitulated previously known associations of taxa and physicochemical parameters in the environment, such as the association of oligotrophic clades with low nutrient surface water and deep water clades that have the capacity to oxidize ammonia or nitrite at the upper mesopelagic layer. These findings provide foundational information on the diversity of marine microbes in Philippine waters. Further studies are warranted to gain a more comprehensive picture of microbial diversity within the region.
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Yao, Weiqi, Adina Paytan, and Ulrich G. Wortmann. "Large-scale ocean deoxygenation during the Paleocene-Eocene Thermal Maximum." Science 361, no. 6404 (July 19, 2018): 804–6. http://dx.doi.org/10.1126/science.aar8658.
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The consequences of global warming for fisheries are not well understood, but the geological record demonstrates that carbon cycle perturbations are frequently associated with ocean deoxygenation. Of particular interest is the Paleocene-Eocene Thermal Maximum (PETM), where the carbon dioxide input into the atmosphere was similar to the IPCC RCP8.5 emission scenario. Here we present sulfur-isotope data that record a positive 1 per mil excursion during the PETM. Modeling suggests that large parts of the ocean must have become sulfidic. The toxicity of hydrogen sulfide will render two of the largest and least explored ecosystems on Earth, the mesopelagic and bathypelagic zones, uninhabitable by multicellular organisms. This will affect many marine species whose ecozones stretch into the deep ocean.
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Shima, Jeffrey S., Craig W. Osenberg, Suzanne H. Alonzo, Erik G. Noonburg, and Stephen E. Swearer. "How moonlight shapes environments, life histories, and ecological interactions on coral reefs." Emerging Topics in Life Sciences 6, no. 1 (January 12, 2022): 45–56. http://dx.doi.org/10.1042/etls20210237.
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The lunar cycle drives variation in nocturnal brightness. For the epipelagic larvae of coral reef organisms, nocturnal illumination may have widespread and underappreciated consequences. At sea, the onset of darkness coincides with an influx of mesopelagic organisms to shallow water (i.e. ‘diel vertical migrants’) that include predators (e.g. lanternfishes) and prey (zooplankton) of zooplanktivorous coral reef larvae. Moonlight generally suppresses this influx, but lunar periodicity in the timing and intensity of nocturnal brightness may affect vertically migrating predators and prey differently. A major turnover of species occurs at sunset on the reef, with diurnal species seeking shelter and nocturnal species emerging to hunt. The hunting ability of nocturnal reef-based predators is aided by the light of the moon. Consequently, variation in nocturnal illumination is likely to shape the timing of reproduction, larval development, and settlement for many coral reef organisms. This synthesis underscores the potential importance of trophic linkages between coral reefs and adjacent pelagic ecosystems, facilitated by the diel migrations of mesopelagic organisms and the ontogenetic migrations of coral reef larvae. Research is needed to better understand the effects of lunar cycles on life-history strategies, and the potentially disruptive effects of light pollution, turbidity, and climate-driven changes to nocturnal cloud cover. These underappreciated threats may alter patterns of nocturnal illumination that have shaped the evolutionary history of many coral reef organisms, with consequences for larval survival and population replenishment that could rival or exceed other effects arising from climate change.
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Davesne, Donald. "A fossil unicorn crestfish (Teleostei, Lampridiformes, Lophotidae) from the Eocene of Iran." PeerJ 5 (June 28, 2017): e3381. http://dx.doi.org/10.7717/peerj.3381.
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Lophotidae, or crestfishes, is a family of rare deep-sea teleosts characterised by an enlarged horn-like crest on the forehead. They are poorly represented in the fossil record, by only three described taxa. One specimen attributed to Lophotidae has been described from the pelagic fauna of the middle-late Eocene Zagros Basin, Iran. Originally considered as a specimen of the fossil lophotid †Protolophotus, it is proposed hereby as a new genus and species †Babelichthys olneyi, gen. et sp. nov., differs from the other fossil lophotids by its relatively long and strongly projecting crest, suggesting a close relationship with the modern unicorn crestfish,Eumecichthys. This new taxon increases the diversity of the deep-sea teleost fauna to which it belongs, improving our understanding of the taxonomic composition of the early Cenozoic mesopelagic ecosystems.
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Azzaro, Maurizio, Theodore T. Packard, Luis Salvador Monticelli, Giovanna Maimone, Alessandro Ciro Rappazzo, Filippo Azzaro, Federica Grilli, Ermanno Crisafi, and Rosabruna La Ferla. "Microbial metabolic rates in the Ross Sea: the ABIOCLEAR Project." Nature Conservation 34 (May 3, 2019): 441–75. http://dx.doi.org/10.3897/natureconservation.34.30631.
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The Ross Sea is one of the most productive areas of the Southern Ocean and includes several functionally different marine ecosystems. With the aim of identifying signs and patterns of microbial response to current climate change, seawater microbial populations were sampled at different depths, from surface to the bottom, at two Ross Sea mooring areas southeast of Victoria Land in Antarctica. This oceanographic experiment, the XX Italian Antarctic Expedition, 2004-05, was carried out in the framework of the ABIOCLEAR project as part of LTER-Italy. Here, microbial biogeochemical rates of respiration, carbon dioxide production, total community heterotrophic energy production, prokaryotic heterotrophic activity, production (by3H-leucine uptake) and prokaryotic biomass (by image analysis) were determined throughout the water column. As ancillary parameters, chlorophylla, adenosine-triphosphate concentrations, temperature and salinity were measured and reported. Microbial metabolism was highly variable amongst stations and depths. In epi- and mesopelagic zones, respiratory rates varied between 52.4–437.0 and 6.3–271.5 nanol O2l-1h-1; prokaryotic heterotrophic production varied between 0.46–29.5 and 0.3–6.11 nanog C l-1h-1; and prokaryotic biomass varied between 0.8–24.5 and 1.1–9.0 µg C l-1, respectively. The average heterotrophic energy production ranged between 570 and 103 mJ l-1h-1in upper and deeper layers, respectively. In the epipelagic layer, the Prokaryotic Carbon Demand and Prokaryotic Growth Efficiency averaged 9 times higher and 2 times lower, respectively, than in the mesopelagic one. The distribution of plankton metabolism and organic matter degradation was mainly related to the different hydrological and trophic conditions. In comparison with previous research, the Ross Sea results, here, evidenced a relatively impoverished oligotrophic microbial community, throughout the water column.
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Schwarzhans, Werner, and Giorgio Carnevale. "The rise to dominance of lanternfishes (Teleostei: Myctophidae) in the oceanic ecosystems: a paleontological perspective." Paleobiology 47, no. 3 (March 19, 2021): 446–63. http://dx.doi.org/10.1017/pab.2021.2.
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AbstractLanternfishes currently represent one of the dominant groups of mesopelagic fishes in terms of abundance, biomass, and diversity. Their otolith record dominates pelagic sediments below 200 m in dredges, especially during the entire Neogene. Here we provide an analysis of their diversity and rise to dominance primarily based on their otolith record. The earliest unambiguous fossil myctophids are known based on otoliths from the late Paleocene and early Eocene. During their early evolutionary history, myctophids were likely not adapted to a high oceanic lifestyle but occurred over shelf and upper-slope regions, where they were locally abundant during the middle Eocene. A distinct upscaling in otolith size is observed in the early Oligocene, which also marks their earliest occurrence in bathyal sediments. We interpret this transition to be related to the change from a halothermal deep-ocean circulation to a thermohaline regime and the associated cooling of the deep ocean and rearrangement of nutrient and silica supply. The early Oligocene myctophid size acme shows a remarkable congruence with diatom abundance, the main food resource for the zooplankton and thus for myctophids and whales. The warmer late Oligocene to early middle Miocene period was characterized by an increase in disparity of myctophids but with a reduction in their otolith sizes. A second and persisting secular pulse in myctophid diversity (particularly within the genus Diaphus) and increase in size begins with the “biogenic bloom” in the late Miocene, paralleled with diatom abundance and mysticete gigantism.
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Haddock, Steven H. D., and C. Anela Choy. "Life in the Midwater: The Ecology of Deep Pelagic Animals." Annual Review of Marine Science 16, no. 1 (January 17, 2024): 383–416. http://dx.doi.org/10.1146/annurev-marine-031623-095435.
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The water column of the deep ocean is dark, cold, low in food, and under crushing pressures, yet it is full of diverse life. Due to its enormous volume, this mesopelagic zone is home to some of the most abundant animals on the planet. Rather than struggling to survive, they thrive—owing to a broad set of adaptations for feeding, behavior, and physiology. Our understanding of these adaptations is constrained by the tools available for exploring the deep sea, but this tool kit is expanding along with technological advances. Each time we apply a new method to the depths, we gain surprising insights about genetics, ecology, behavior, physiology, diversity, and the dynamics of change. These discoveries show structure within the seemingly uniform habitat, limits to the seemingly inexhaustible resources, and vulnerability in the seemingly impervious environment. To understand midwater ecology, we need to reimagine the rules that govern terrestrial ecosystems. By spending more time at depth—with whatever tools are available—we can fill the knowledge gaps and better link ecology to the environment throughout the water column.
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Grassian, Benjamin D., Chris Roman, Joseph Warren, and David Casagrande. "High resolution measurements of the epi- and mesopelagic ocean by a profiling vehicle equipped with environmental sensors and a broadband echosounder." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A150. http://dx.doi.org/10.1121/10.0010936.
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Collecting detailed surveys of the physical and biological heterogeneity in the epi and mesopelagic ocean is critical to describe the ecosystems within these vast and three-dimensional habitats. Common ocean sampling platforms (e.g., net systems, moored and shipboard sensors) are often unable to resolve marine biota at scales comparable to the variability existing in their physical environment. We have integrated a dual-frequency split-beam echosounder (Simrad EK80 with 70 and 200 kHz transducers) into the Wire Flyer profiling vehicle to achieve concurrent hydrographic and acoustic sections in environments between 0 and 1000 m. The Wire Flyer provides high-resolution repeat profiling (0–2.5 m/s vertical velocity, ∼1 km horizontal repeats) within specified water column depth bands typically spanning 300–400 m. This system can provide acoustic backscatter data at depths unavailable to shipboard surveys and can be operated in tandem with shipboard echosounders to provide overlapping acoustic coverage with concurrent hydrographic sections near the surface. The side-looking transducer orientation samples orthogonal to the vehicle's profiling survey path provide a direct measurement of horizontal heterogeneity. The collected data have proven the system’s capacity to resolve migrating layers, biological patches, and single targets in the horizontal, rising gas plumes, and scattering layer distributions tightly coupled to submesoscale environmental features.
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Kwon, Eun Young, Curtis Deutsch, Shang-Ping Xie, Sunke Schmidtko, and Yang-Ki Cho. "The North Pacific Oxygen Uptake Rates over the Past Half Century." Journal of Climate 29, no. 1 (December 22, 2015): 61–76. http://dx.doi.org/10.1175/jcli-d-14-00157.1.
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Abstract The transport of dissolved oxygen (O2) from the surface ocean into the interior is a critical process sustaining aerobic life in mesopelagic ecosystems, but its rates and sensitivity to climate variations are poorly understood. Using a circulation model constrained to historical variability by assimilation of observations, the study shows that the North Pacific thermocline effectively takes up O2 primarily by expanding the area through which O2-rich mixed layer water is detrained into the thermocline. The outcrop area during the critical winter season varies in concert with the Pacific decadal oscillation (PDO). When the central North Pacific Ocean is in a cold phase, the winter outcrop window for the central mode water class (CMW; a neutral density range of γ = 25.6–26.6) expands southward, allowing more O2-rich surface water to enter the ocean’s interior. An increase in volume flux of water to the CMW density class is partly compensated by a reduced supply to the shallower densities of subtropical mode water (γ = 24.0–25.5). The thermocline has become better oxygenated since the 1980s partly because of strong O2 uptake. Positive O2 anomalies appear first near the outcrop and subsequently downstream in the subtropical gyre. In contrast to the O2 variations within the ventilated thermocline, observed O2 in intermediate water (density range of γ = 26.7–27.2) shows a declining trend over the past half century, a trend not explained by the open ocean water mass formation rate.
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Hallett, Chris S., and Ross K. Daley. "Feeding ecology of the southern lanternshark (Etmopterus baxteri) and the brown lanternshark (E. unicolor) off southeastern Australia." ICES Journal of Marine Science 68, no. 1 (September 8, 2010): 157–65. http://dx.doi.org/10.1093/icesjms/fsq143.
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Abstract Hallett, C. S., and Daley, R. K. 2011. Feeding ecology of the southern lanternshark (Etmopterus baxteri) and the brown lanternshark (E. unicolor) off southeastern Australia. – ICES Journal of Marine Science, 68: 157–165. Little is known about the ecological interactions between bycatch species and orange roughy (Hoplostethus atlanticus) within exploited slope and seamount communities off Tasmania. The diet of Etmopterus baxteri and E. unicolor, two important bycatch species of these fisheries, is described using four indices [percentage frequency of occurrence, percentage by number, percentage by weight, and percentage by the index of relative importance (%IRI)] calculated for broad prey categories, individual prey taxa, and functional prey groups. The identifiable diet of E. unicolor was dominated by benthic cephalopods (96%IRI), whereas benthic teleost prey, notably orange roughy (43%IRI), dominated the diet of E. baxteri. Similar trophic mechanisms appear to support aggregations of orange roughy and Etmopterus spp. off Tasmania; they feed on demersal species and mesopelagic or vertically migrating nekton advected laterally onto the mid-slope. The importance of teleost prey in the diet of E. baxteri apparently increases with shark length, whereas crustaceans become less important, which is a similar diet shift to that of orange roughy. Etmopterus baxteri is both a potential competitor and predator of orange roughy in these ecosystems. Fishery managers need to understand and consider the complex trophic interactions between orange roughy, sharks, and other exploited species in managing recently reopened deep-water fisheries off southeastern Australia.
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Agustí, Susana, Jeffrey W. Krause, Israel A. Marquez, Paul Wassmann, Svein Kristiansen, and Carlos M. Duarte. "Arctic (Svalbard islands) active and exported diatom stocks and cell health status." Biogeosciences 17, no. 1 (January 3, 2020): 35–45. http://dx.doi.org/10.5194/bg-17-35-2020.
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Abstract. Diatoms tend to dominate the Arctic spring phytoplankton bloom, a key event in the ecosystem including a rapid decline in surface-water pCO2. While a mass sedimentation event of diatoms at the bloom terminus is commonly observed, there are few reports on the status of diatoms' health during Arctic blooms and its possible role on sedimentary fluxes. Thus, we examine the idea that the major diatom-sinking event which occurs at the end of the regional bloom is driven by physiologically deteriorated cells. Here we quantify, using the Bottle-Net, Arctic diatom stocks below and above the photic zone and assess their cell health status. The communities were sampled around the Svalbard islands and encompassed pre- to post-bloom conditions. A mean of 24.2±6.7 % SE (standard error) of the total water column (max. 415 m) diatom standing stock was found below the photic zone, indicating significant diatom sedimentation. The fraction of living diatom cells in the photic zone averaged 59.4±6.3 % but showed the highest mean percentages (72.0 %) in stations supporting active blooms. In contrast, populations below the photic layer were dominated by dead cells (20.8±4.9 % living cells). The percentage of diatoms' standing stock found below the photic layer was negatively related to the percentage of living diatoms in the surface, indicating that healthy populations remained in the surface layer. Shipboard manipulation experiments demonstrated that (1) dead diatom cells sank faster than living cells, and (2) diatom cell mortality increased in darkness, showing an average half-life among diatom groups of 1.025±0.075 d. The results conform to a conceptual model where diatoms grow during the bloom until resources are depleted and supports a link between diatom cell health status (affected by multiple factors) and sedimentation fluxes in the Arctic. Healthy Arctic phytoplankton communities remained at the photic layer, whereas the physiologically compromised (e.g., dying) communities exported a large fraction of the biomass to the aphotic zone, fueling carbon sequestration to the mesopelagic and material to benthic ecosystems.
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Cocco, V., F. Joos, M. Steinacher, T. L. Frölicher, L. Bopp, J. Dunne, M. Gehlen, et al. "Oxygen and indicators of stress for marine life in multi-model global warming projections." Biogeosciences 10, no. 3 (March 19, 2013): 1849–68. http://dx.doi.org/10.5194/bg-10-1849-2013.
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Abstract. Decadal-to-century scale trends for a range of marine environmental variables in the upper mesopelagic layer (UML, 100–600 m) are investigated using results from seven Earth System Models forced by a high greenhouse gas emission scenario. The models as a class represent the observation-based distribution of oxygen (O2) and carbon dioxide (CO2), albeit major mismatches between observation-based and simulated values remain for individual models. By year 2100 all models project an increase in SST between 2 °C and 3 °C, and a decrease in the pH and in the saturation state of water with respect to calcium carbonate minerals in the UML. A decrease in the total ocean inventory of dissolved oxygen by 2% to 4% is projected by the range of models. Projected O2 changes in the UML show a complex pattern with both increasing and decreasing trends reflecting the subtle balance of different competing factors such as circulation, production, remineralization, and temperature changes. Projected changes in the total volume of hypoxic and suboxic waters remain relatively small in all models. A widespread increase of CO2 in the UML is projected. The median of the CO2 distribution between 100 and 600m shifts from 0.1–0.2 mol m−3 in year 1990 to 0.2–0.4 mol m−3 in year 2100, primarily as a result of the invasion of anthropogenic carbon from the atmosphere. The co-occurrence of changes in a range of environmental variables indicates the need to further investigate their synergistic impacts on marine ecosystems and Earth System feedbacks.
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Lembke-Jene, Lester, Ralf Tiedemann, Dirk Nürnberg, Xun Gong, and Gerrit Lohmann. "Rapid shift and millennial-scale variations in Holocene North Pacific Intermediate Water ventilation." Proceedings of the National Academy of Sciences 115, no. 21 (May 7, 2018): 5365–70. http://dx.doi.org/10.1073/pnas.1714754115.
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The Pacific hosts the largest oxygen minimum zones (OMZs) in the world ocean, which are thought to intensify and expand under future climate change, with significant consequences for marine ecosystems, biogeochemical cycles, and fisheries. At present, no deep ventilation occurs in the North Pacific due to a persistent halocline, but relatively better-oxygenated subsurface North Pacific Intermediate Water (NPIW) mitigates OMZ development in lower latitudes. Over the past decades, instrumental data show decreasing oxygenation in NPIW; however, long-term variations in middepth ventilation are potentially large, obscuring anthropogenic influences against millennial-scale natural background shifts. Here, we use paleoceanographic proxy evidence from the Okhotsk Sea, the foremost North Pacific ventilation region, to show that its modern oxygenated pattern is a relatively recent feature, with little to no ventilation before six thousand years ago, constituting an apparent Early–Middle Holocene (EMH) threshold or “tipping point.” Complementary paleomodeling results likewise indicate a warmer, saltier EMH NPIW, different from its modern conditions. During the EMH, the Okhotsk Sea switched from a modern oxygenation source to a sink, through a combination of sea ice loss, higher water temperatures, and remineralization rates, inhibiting ventilation. We estimate a strongly decreased EMH NPIW oxygenation of ∼30 to 50%, and increased middepth Pacific nutrient concentrations and carbon storage. Our results (i) imply that under past or future warmer-than-present conditions, oceanic biogeochemical feedback mechanisms may change or even switch direction, and (ii) provide constraints on the high-latitude North Pacific’s influence on mesopelagic ventilation dynamics, with consequences for large oceanic regions.
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Casenove, David, Taichiro Goto, and Jean Vannier. "Relation between anatomy and lifestyles in Recent and Early Cambrian chaetognaths." Paleobiology 37, no. 4 (2011): 563–76. http://dx.doi.org/10.1666/10030.1.
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The Burgess Shale-type Lagerstätten of the Early Cambrian Maotianshan Shale record an apparently sudden conquest of pelagic niches by ten phyla of metazoans. One of these phyla is Chaetognatha, a group of predatory marine worms. Given their role as major predators in modern planktonic ecosystems, the chaetognaths discovered in the Maotianshan Shale (Yunnan Province, South China) suggest that the pelagos at the time was already quite complex. Modern chaetognaths, however, can be divided into benthic and pelagic forms; the pelagic nature of Eognathacantha ercainella should therefore be validated by strong morphological evidence.Knowing that planktonic animals present morphological adaptations that increase their buoyancy, we studied the drag produced during the active phase of chaetognath locomotion for the modern forms Paraspadella gotoi (benthic) and Sagitta elegans (pelagic). By using a motion model developed by Jordan in 1992, we could calculate the resistive force produced by the undulatory movement of chaetognaths' bodies.This mechanistic approach evaluates the effect of three motion parameters (relative speed, total length, and tail ratio) on the drag force produced during locomotion. Our results show that the increase of size contributes to higher drag while the shorter tail of the pelagic form balances this effect by reducing the wetted surface subject to friction. For chaetognaths, therefore, a bigger body (both in length and width) and a shorter tail indicate a pelagic lifestyle, a finding that can be applied to the study of the fossil Eognathacantha ercainella. A discriminant analysis can confirm that the Early Cambrian chaetognath presents a pelagic morphology with similarities to modern bathypelagic and mesopelagic species.
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Votier, S. C., R. B. Sherley, K. L. Scales, K. Camphuysen, and R. A. Phillips. "An overview of the impacts of fishing on seabirds, including identifying future research directions." ICES Journal of Marine Science 80, no. 9 (November 1, 2023): 2380–92. http://dx.doi.org/10.1093/icesjms/fsad173.
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Abstract Knowledge of fisheries impacts, past and present, is essential for understanding the ecology and conservation of seabirds, but in a rapidly changing world, knowledge and research directions require updating. In this Introduction and in the articles in this Themed Set “Impacts of fishing on seabirds”, we update our understanding of how fishing impacts seabird communities and identify areas for future research. Despite awareness of the problems and mitigation efforts for >20 years, fisheries still negatively impact seabirds via the effects of bycatch, competition, and discards. Bycatch continues to kill hundreds of thousands of seabirds annually, with negative population-level consequences. Fisheries for forage fish (e.g. anchovy, sandeel, and krill) negatively impact seabirds by competing for the same stocks. Historically, discards supplemented seabird diets, benefitting some species but also increasing bycatch rates and altering seabird community composition. However, declining discard production has led to potentially deleterious diet switches, but reduced bycatch rates. To improve research into these problems, we make the following recommendations: (1) improve data collection on seabird–vessel interaction and bycatch rates, on fishing effort and vessel movements (especially small-scale fleets), and on mitigation compliance, (2) counter the current bias towards temperate and high-latitude ecosystems, larger-bodied species and particular life stages or times of year (e.g. adults during breeding), and (3) advance our currently poor understanding of combined effects of fisheries and other threats (e.g. climate change, offshore renewables). In addition, research is required on under-studied aspects of fishing impacts: consequences for depleted sub-surface predators, impacts of illegal, unreported and unregulated fishing, artisanal and emerging fisheries, such as those targeting mesopelagic fish, have received insufficient research attention. Some of these shortfalls can be overcome with new tools (e.g. electronic monitoring, remote sensing, artificial intelligence, and big data) but quantifying and addressing fishing impacts on seabirds requires greater research investment at appropriate spatio-temporal scales, and more inclusive dialogue from grassroots to national and international levels to improve governance as fishing industries continue to evolve.
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Adachi, Taiki, Akinori Takahashi, Daniel P. Costa, Patrick W. Robinson, Luis A. Hückstädt, Sarah H. Peterson, Rachel R. Holser, Roxanne S. Beltran, Theresa R. Keates, and Yasuhiko Naito. "Forced into an ecological corner: Round-the-clock deep foraging on small prey by elephant seals." Science Advances 7, no. 20 (May 2021): eabg3628. http://dx.doi.org/10.1126/sciadv.abg3628.
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Small mesopelagic fishes dominate the world’s total fish biomass, yet their ecological importance as prey for large marine animals is poorly understood. To reveal the little-known ecosystem dynamics, we identified prey, measured feeding events, and quantified the daily energy balance of 48 deep-diving elephant seals throughout their oceanic migrations by leveraging innovative technologies: animal-borne smart accelerometers and video cameras. Seals only attained positive energy balance after feeding 1000 to 2000 times per day on small fishes, which required continuous deep diving (80 to 100% of each day). Interspecies allometry suggests that female elephant seals have exceptional diving abilities relative to their body size, enabling them to exploit a unique foraging niche on small but abundant mesopelagic fish. This unique foraging niche requires extreme round-the-clock deep diving, limiting the behavioral plasticity of elephant seals to a changing mesopelagic ecosystem.
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Kock, Karl-Hermann. "Fishing and conservation in southern waters Karl-Hermann Kock." Polar Record 30, no. 172 (January 1994): 3–22. http://dx.doi.org/10.1017/s0032247400020994.
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AbstractIn the Southern Ocean, fishing for finfish began in 1969/70 and for krill in 1972/73. The Soviet Union was the most important fishing nation, taking 80–90% of the entire catch. More than 3 million tonnes of finfish wereharvested prior to 1992/93, most of the catch coming from around South Georgia and lies Kerguelen. After 15 years of exploitation, most fish stocks were heavily depleted. The krill catch from the Southern Ocean has been 4.9 million tonnes to date. More than 90% of this catch has originated from the Atlantic sector. 50–90% is taken from the foraging range of land-based predators during the critical period of their breeding cycle when they raise their young. This creates the potential for direct competition between krill fisheries and krill-dependent predators. Potential impacts of krill and finfishing on the ecosystems of the Southern Ocean range from endangering recruitment due to the by-catch of juvenile fish in the krill fishery to incidental mortality of birds during longline operations and the entanglement of seals in fragments of discarded or lost fishing gear.Most fish stocks had already been over-exploited before the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) came into force in 1982. Stringent conservation measures to halt the further decline of the stocks have been implemented only since 1989. There is evidence that some fish stocks have started to recover recently. Precautionary catch limits for krill of 1.5 million tonnes for the Atlantic sector (Statistical Area 48), and of 390, 000 tonnes for Statistical Division 58. 4.2 in the Indian sector, were set in 1991 and 1992, respectively. CCAMLR has implemented a number of conservation measures to safeguard other components of the marine ecosystems from fishing. CCAMLR adopted a system of inspection in 1989/90 and a scheme of international scientific observation in 1992. It is too early to judge the efficacy of these enforcement and data-gathering programmes.There is a growing recognition in CCAMLR of the need for preventati ve measures in circumstances of biological uncertainty. The development of multi-species management models appears to be remote at present. The way forward is likely to be a single-species model for the krill fishery, which needs to take implicit account of the demands of natural predators, particularly at small scales. If demersal fish stocks are able to recover to their maximum sustainable yield level, the fishery potential of the Southern Ocean is likely to be much larger than current catches. The fishery potential of krill and mesopelagic lanternfish is likely to exceed that of demersal fish stocks by an order of magnitude. By contrast with the 1970s and 1980s, when most fisheries were subsidized, economic considerations and market demands will be the primary determinants of the development of fishing in southern waters during the 1990s.
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Anderson, Thomas R., Adrian P. Martin, Richard S. Lampitt, Clive N. Trueman, Stephanie A. Henson, and Daniel J. Mayor. "Quantifying carbon fluxes from primary production to mesopelagic fish using a simple food web model." ICES Journal of Marine Science 76, no. 3 (January 5, 2018): 690–701. http://dx.doi.org/10.1093/icesjms/fsx234.
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Abstract An ecosystem-based flow analysis model was used to study carbon transfer from primary production (PP) to mesopelagic fish via three groups of copepods: detritivores that access sinking particles, vertical migrators, and species that reside in the surface ocean. The model was parameterized for 40°S to 40°N in the world ocean such that results can be compared with recent estimates of mesopelagic fish biomass in this latitudinal range, based on field studies using acoustic technologies, of ∼13 Gt (wet weight). Mesopelagic fish production was predicted to be 0.32% of PP which, assuming fish longevity of 1.5 years, gives rise to predicted mesopelagic fish biomass of 2.4 Gt. Model ensembles were run to analyse the uncertainty of this estimate, with results showing predicted biomass >10 Gt in only 8% of the simulations. The work emphasizes the importance of migrating animals in transferring carbon from the surface ocean to the mesopelagic zone. It also highlights how little is known about the physiological ecology of mesopelagic fish, trophic pathways within the mesopelagic food web, and how these link to PP in the surface ocean. A deeper understanding of these interacting factors is required before the potential for utilizing mesopelagic fish as a harvestable resource can be robustly assessed.
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Hidalgo, Manuel, and Howard I. Browman. "Developing the knowledge base needed to sustainably manage mesopelagic resources." ICES Journal of Marine Science 76, no. 3 (May 1, 2019): 609–15. http://dx.doi.org/10.1093/icesjms/fsz067.
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Abstract Recent estimates suggest that the mesopelagic zone could contain a total fish biomass of 2-19.5 gigatonnes, roughly equivalent to 100 times the annual catch of all existing fisheries. In addition to the possibility of direct consumption of mesopelagic species, there is interest in their use for fishmeal, as a source of dietary supplements for humans, and to bio-prospect pharmaceuticals. All of this, and the demands for a global food supply that can feed an ever-growing population, has driven interest in the mesopelagic. Thus, accurate quantification of the biomass of mesopelagic resources, their nutritional and genetic composition, their links to other components of the food web, to other oceanic realms and to biological and chemical oceanographic processes and cycles, are the focus of growing research activity. This information is needed to ensure the sustainable management of these resources. In this introduction, we summarize the contributions included in this theme set and provide some “food for thought” on the state-of-the-art in research on the mesopelagic, including identifying the knowledge that must be generated to support its sustainable management (e.g. the effect that extracting significant biomass might have on the pelagic ecosystem and the flow of material and energy through it).
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Davison, Peter, Ana Lara-Lopez, and J. Anthony Koslow. "Mesopelagic fish biomass in the southern California current ecosystem." Deep Sea Research Part II: Topical Studies in Oceanography 112 (February 2015): 129–42. http://dx.doi.org/10.1016/j.dsr2.2014.10.007.
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O'Driscoll, Richard L., Stéphane Gauthier, and Jennifer A. Devine. "Acoustic estimates of mesopelagic fish: as clear as day and night?" ICES Journal of Marine Science 66, no. 6 (February 12, 2009): 1310–17. http://dx.doi.org/10.1093/icesjms/fsp015.
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Abstract O'Driscoll, R. L., Gauthier, S., and Devine, J. A. 2009. Acoustic estimates of mesopelagic fish: as clear as day and night? – ICES Journal of Marine Science, 66: 1310–1317. The pelagic ecosystem on the Chatham Rise east of New Zealand has been monitored annually using acoustic surveys since 2001. Most of the acoustic backscatter comes from diurnally migrating mesopelagic fish, which are the major prey of hoki (Macruronus novaezelandiae) and other valuable commercial species. Mesopelagic schools and layers typically occur at 100–400 m depth during the day and migrate above 200 m depth at night. Previous acoustic estimates of the biomass of mesopelagic fish on the Chatham Rise were based only on night-time estimates from the upper 200 m and may significantly underestimate actual biomass. Paired day–night comparisons found that an estimated 20% of the total daytime backscatter migrates to depths of 0–14 m at night, where it is too shallow to be detected by hull-mounted acoustic instruments. In contrast, there is a positive bias associated with acoustic estimates of mesopelagic organisms during the day because they can occur close to the bottom mixed with demersal fish. Two alternative approaches for estimating biomass of diurnally migrating mesopelagic species are suggested. The first applies a correction based on the estimated proportion of backscatter migrating into the surface deadzone to night-time estimates of backscatter in the upper 200 m. The second uses night-time estimates of demersal backscatter, which remains deeper than 200 m at night, to correct daytime estimates of total backscatter. Both methods gave similar estimates of abundance and demonstrated that there was no statistically significant trend in mesopelagic fish biomass on the Chatham Rise over the past seven years.
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Prellezo, Raúl. "Exploring the economic viability of a mesopelagic fishery in the Bay of Biscay." ICES Journal of Marine Science 76, no. 3 (January 24, 2018): 771–79. http://dx.doi.org/10.1093/icesjms/fsy001.
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Abstract The study analyses the economic viability of the mesopelagic fish exploitation. Operating characteristics of the selected bottom-trawl fleet operating in the Bay of Biscay were analysed on a trip basis, from the technical, financial and market perspectives. The results show that, while this activity is technically possible, it cannot be considered a viable financial alternative to the existing commercial fisheries. However, the landing obligation of the European Union Common Fisheries Policy, to become fully operational in 2019, provides an economic incentive in the form of alternative trips. The fishing effort is to be limited by this regulation. Thus, the discouraging opportunity costs of fishing mesopelagic species might be alleviated by the effort limitation. Additionally, the existing markets might expand, and new opportunities for commercial fisheries of mesopelagic species might be created. The sustainability of exploitation and its impact on the ecosystem services associated with these species should be considered in their management.
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Terrado, R., WF Vincent, and C. Lovejoy. "Mesopelagic protists: diversity and succession in a coastal Arctic ecosystem." Aquatic Microbial Ecology 56 (July 9, 2009): 25–39. http://dx.doi.org/10.3354/ame01327.
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Sato, Mei, and Kelly J. Benoit-Bird. "Heterogeneity of deep scattering layer shapes the Bahamian mesopelagic ecosystem." Journal of the Acoustical Society of America 140, no. 4 (October 2016): 3243. http://dx.doi.org/10.1121/1.4970259.
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Jacquet, S. H. M., F. Dehairs, A. J. Cavagna, F. Planchon, L. Monin, L. André, I. Closset, and D. Cardinal. "Early season mesopelagic carbon remineralization and transfer efficiency in the naturally iron-fertilized Kerguelen area." Biogeosciences Discussions 11, no. 6 (June 16, 2014): 9035–69. http://dx.doi.org/10.5194/bgd-11-9035-2014.
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Abstract. We report on the zonal variability of mesopelagic particulate organic carbon) remineralization and deep carbon transfer potential during the Kerguelen Ocean and Plateau compared Study 2 expedition (KEOPS 2; October–November 2011) in an area of the Polar Front supporting recurrent massive blooms from natural Fe fertilization. Mesopelagic carbon remineralization was assessed using the excess, non-lithogenic particulate barium (Baxs) inventories in mesopelagic waters and compared with surface primary and export productions. Results for this early season study are compared with results obtained earlier (2005; KEOPS 1) for the same area during summer. For the Kerguelen plateau (A3 site) we observe a similar functioning of the mesopelagic ecosystem during both seasons (spring and summer), with less that 30% of carbon exported from the upper 150 m being remineralized in the mesopelagic column (150–400 m). For deeper stations (> 2000 m) located on the margin, inside a Polar Front meander, as well as in the vicinity of the Polar Front, east of Kerguelen, remineralization in the upper 400 m in general represents > 30% of carbon export, but when considering the upper 800 m, in some cases, the entire flux of exported carbon is remineralized. It appears that above the plateau (A3 site) mesopelagic remineralization is not a major barrier to the transfer of organic matter to the sea-floor (close to 500 m). There the efficiency of carbon sequestration into the bottom waters (> 400 m) reached up to 87% of the carbon exported from the upper 150 m. In contrast, at the deeper locations mesopelagic remineralization clearly limits the sequestration of carbon to depths > 400 m. For sites at the margin of the plateau (station E-4W) and the Polar front (station F-L), mesopelagic remineralization even exceeds upper 150 m export, resulting in a null sequestration efficiency to depths > 800 m. In the Polar Front meander, where successive stations form a time series, the capacity of the meander to transfer carbon to depth > 800 m is highly variable (0 to 73 %). The highest carbon transfer efficiencies in the meander are furthermore coupled to intense and complete deep (> 800 m) remineralization, resulting again in a close to zero deep (> 2000 m) carbon sequestration efficiency there.
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Lomas, M. W., D. K. Steinberg, T. Dickey, C. A. Carlson, N. B. Nelson, R. H. Condon, and N. R. Bates. "Increased ocean carbon export in the Sargasso Sea is countered by its enhanced mesopelagic attenuation." Biogeosciences Discussions 6, no. 5 (October 6, 2009): 9547–82. http://dx.doi.org/10.5194/bgd-6-9547-2009.
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Abstract. Photosynthetic CO2 uptake by oceanic phytoplankton and subsequent export of particulate organic carbon (POC) to the ocean interior comprises a globally significant biological carbon pump, controlled in part by the composition of the planktonic community. The strength and efficiency of this pump depends upon the balance of particle production in the euphotic zone and remineralization of those particles in the mesopelagic (defined here as depths between 150 and 300 m), but how these processes respond to climate-driven changes in the physical environment is not completely understood. In the Sargasso Sea, from 1996–2007, we have observed a decade-long >50% increase in euphotic zone integrated autotrophic biomass (estimated from chlorophyll TChl-a from the surface ocean, prokaryotic phytoplankton, primary production and shallow (150 m) POC export coinciding with a shift in the mean phase of the winter North Atlantic Oscillation (NAO) from consistently positive to neutral but variable. During this same period mesopelagic POC flux attenuation has doubled such that carbon sequestration below 300 m, the maximum winter/spring ventilation depth, has not changed. The increased mesopelagic POC attenuation appears mediated by changes in plankton community composition and metabolic activity in both the euphotic and mesopelagic zones which are counter to extant hypotheses regarding inter-relationships between phytoplankton community composition, productivity and carbon export, and have significant impacts on how the Sargasso Sea ecosystem, at least, is modeled. Moreover, these time-series observations suggest that processes in the euphotic zone and mesopelagic are tightly coupled and should be considered together in future research.
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Lomas, M. W., D. K. Steinberg, T. Dickey, C. A. Carlson, N. B. Nelson, R. H. Condon, and N. R. Bates. "Increased ocean carbon export in the Sargasso Sea linked to climate variability is countered by its enhanced mesopelagic attenuation." Biogeosciences 7, no. 1 (January 5, 2010): 57–70. http://dx.doi.org/10.5194/bg-7-57-2010.
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Abstract. Photosynthetic CO2 uptake by oceanic phytoplankton and subsequent export of particulate organic carbon (POC) to the ocean interior comprises a globally significant biological carbon pump, controlled in part by the composition of the planktonic community. The strength and efficiency of this pump depends upon the balance of particle production in the euphotic zone and remineralization of those particles in the mesopelagic (defined here as depths between 150 and 300 m), but how these processes respond to climate-driven changes in the physical environment is not completely understood. In the Sargasso Sea, from ~1996–2007, we have observed a decade-long >50% increase in euphotic zone integrated autotrophic biomass (estimated from chlorophyll TChl-α), prokaryotic phytoplankton, primary production and shallow (150 m) POC export coinciding with a shift in the mean phase of the winter North Atlantic Oscillation (NAO) from consistently positive to neutral but variable. During this same period mesopelagic POC flux attenuation has doubled such that carbon sequestration below 300 m, the maximum winter/spring ventilation depth, has not changed. The increased mesopelagic POC attenuation appears mediated by changes in plankton community composition and metabolic activity in both the euphotic and mesopelagic zones. These changes are counter to extant hypotheses regarding inter-relationships between phytoplankton community composition, productivity and carbon export, and have significant impacts on how the Sargasso Sea ecosystem, at least, is modeled. Moreover, these time-series observations suggest that processes in the euphotic zone and mesopelagic are tightly coupled and should be considered together in future research.
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López -Chávez, O., G. Aceves -Medina, R. J. Saldierna -Martínez, S. P. Jiménez -Rosenberg, J. P. Murad -Serrano, A. Marín -Gutiérrez, and O. Hernández - Hernández. "CHANGES IN SPECIES COMPOSITION AND ABUNDANCE OF FISH LARVAE FROM THE GULF OF TEHUANTEPEC, MEXICO." CICIMAR Oceánides 27, no. 2 (December 4, 2012): 1. http://dx.doi.org/10.37543/oceanides.v27i2.112.
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The larval fish abundance and species composition of the Gulf of Tehuantepec are described based on the analysis of samples obtained from oblique zooplankton tows during summer 2007 and spring 2008. Changes in species composition and abundance between both periods were also described. A total of 145 taxa were obtained from which 73 were identified to species level, 43 to genus and 29 to family. The larval fish assemblage of the Gulf of Tehuantepec showed distinctive characteristics from other regions of the American Pacific, such as: A) a dominance of coastal-pelagic species (mainly Bregmaceros bathymaster); B) high diversity and abundance of shallow demersal species even along the oceanic stations of the study area; and C) a low proportion of mesopelagic species, an unusual condition in areas with narrow continental shelf. The diversity estimations suggest that Gulf of Tehuantepec is one of the most diverse ecosystems of the American Pacific, even as compared with other regions considered of highest diversity such as the Gulf of California. The high abundance, as well as the presence of the larval, juvenile and adult stages of B. bathymaster, suggests the importance of this region as a reproductive, nursery and recruitment for this species. Cambios en la composición de especies y abundancia de larvas de peces en el Golfo de Tehuantepec, México Se describen la composición de especies y abundancia de larvas de peces del Golfo de Tehuantepec a partir del análisis de muestras obtenidas en arrastres oblicuos de zooplancton. Así mismo, se describen los cambios en composición y abundancia entre un periodo de verano y uno de primavera. Se obtuvieron 145 taxa de los que 73 se identificaron a nivel especie, 43 a género y 29 a familia. La comunidad de larvas de peces del Golfo de Tehuantepec mostró rasgos distintivos de otras regiones similares del Pacífico Americano, tales como: A) dominancia de especies pelágico-costeras (particularmente Bregmaceros bathymaster); B) alta diversidad y abundancia de especies demersales someras aún en las estaciones mas oceánicas del área de estudio; y C) una proporción menor de especies de peces mesopelágicos, condición poco común en áreas con plataforma continental estrecha. Las estimaciones de diversidad ubican al Golfo de Tehuantepec como uno de los ecosistemas más diversos del Pacífico americano, aún comparándolo con regiones consideradas de alta diversidad a nivel mundial como es el caso del Golfo de California. La abundancia y la presencia de estadios larvales, juveniles y adultos de B. bathymaster reflejan la importancia de esta zona como área de reproducción, crianza y reclutamiento de esta especie.
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López -Chávez, O., G. Aceves -Medina, R. J. Saldierna -Martínez, S. P. Jiménez -Rosenberg, J. P. Murad -Serrano, A. Marín -Gutiérrez, and O. Hernández - Hernández. "CHANGES IN SPECIES COMPOSITION AND ABUNDANCE OF FISH LARVAE FROM THE GULF OF TEHUANTEPEC, MEXICO." CICIMAR Oceánides 27, no. 2 (December 4, 2012): 1. http://dx.doi.org/10.37543/oceanides.v27i2.112.
Full textAbstract:
The larval fish abundance and species composition of the Gulf of Tehuantepec are described based on the analysis of samples obtained from oblique zooplankton tows during summer 2007 and spring 2008. Changes in species composition and abundance between both periods were also described. A total of 145 taxa were obtained from which 73 were identified to species level, 43 to genus and 29 to family. The larval fish assemblage of the Gulf of Tehuantepec showed distinctive characteristics from other regions of the American Pacific, such as: A) a dominance of coastal-pelagic species (mainly Bregmaceros bathymaster); B) high diversity and abundance of shallow demersal species even along the oceanic stations of the study area; and C) a low proportion of mesopelagic species, an unusual condition in areas with narrow continental shelf. The diversity estimations suggest that Gulf of Tehuantepec is one of the most diverse ecosystems of the American Pacific, even as compared with other regions considered of highest diversity such as the Gulf of California. The high abundance, as well as the presence of the larval, juvenile and adult stages of B. bathymaster, suggests the importance of this region as a reproductive, nursery and recruitment for this species. Cambios en la composición de especies y abundancia de larvas de peces en el Golfo de Tehuantepec, México Se describen la composición de especies y abundancia de larvas de peces del Golfo de Tehuantepec a partir del análisis de muestras obtenidas en arrastres oblicuos de zooplancton. Así mismo, se describen los cambios en composición y abundancia entre un periodo de verano y uno de primavera. Se obtuvieron 145 taxa de los que 73 se identificaron a nivel especie, 43 a género y 29 a familia. La comunidad de larvas de peces del Golfo de Tehuantepec mostró rasgos distintivos de otras regiones similares del Pacífico Americano, tales como: A) dominancia de especies pelágico-costeras (particularmente Bregmaceros bathymaster); B) alta diversidad y abundancia de especies demersales someras aún en las estaciones mas oceánicas del área de estudio; y C) una proporción menor de especies de peces mesopelágicos, condición poco común en áreas con plataforma continental estrecha. Las estimaciones de diversidad ubican al Golfo de Tehuantepec como uno de los ecosistemas más diversos del Pacífico americano, aún comparándolo con regiones consideradas de alta diversidad a nivel mundial como es el caso del Golfo de California. La abundancia y la presencia de estadios larvales, juveniles y adultos de B. bathymaster reflejan la importancia de esta zona como área de reproducción, crianza y reclutamiento de esta especie.
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Sato, M., and KJ Benoit-Bird. "Spatial variability of deep scattering layers shapes the Bahamian mesopelagic ecosystem." Marine Ecology Progress Series 580 (September 29, 2017): 69–82. http://dx.doi.org/10.3354/meps12295.
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Jacquet, S. H. M., F. Dehairs, D. Lefèvre, A. J. Cavagna, F. Planchon, U. Christaki, L. Monin, L. André, I. Closset, and D. Cardinal. "Early spring mesopelagic carbon remineralization and transfer efficiency in the naturally iron-fertilized Kerguelen area." Biogeosciences 12, no. 6 (March 17, 2015): 1713–31. http://dx.doi.org/10.5194/bg-12-1713-2015.
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Abstract. We report on the zonal variability of mesopelagic particulate organic carbon remineralization and deep carbon transfer potential during the Kerguelen Ocean and Plateau compared Study 2 expedition (KEOPS 2; October–November 2011) in an area of the polar front supporting recurrent massive blooms from natural Fe fertilization. Mesopelagic carbon remineralization (MR) was assessed using the excess, non-lithogenic particulate barium (Baxs) inventories in mesopelagic waters and compared with bacterial production (BP), surface primary production (PP) and export production (EP). Results for this early season study are compared with the results obtained during a previous study (2005; KEOPS 1) for the same area at a later stage of the phytoplankton bloom. Our results reveal the patchiness of the seasonal advancement and of the establishment of remineralization processes between the plateau (A3) and polar front sites during KEOPS 2. For the Kerguelen plateau (A3 site) we observe a similar functioning of the mesopelagic ecosystem during both seasons (spring and summer), with low and rather stable remineralization fluxes in the mesopelagic column (150–400 m). The shallow water column (~500 m), the lateral advection, the zooplankton grazing pressure and the pulsed nature of the particulate organic carbon (POC) transfer at A3 seem to drive the extent of MR processes on the plateau. For deeper stations (>2000 m) located on the margin, inside a polar front meander, as well as in the vicinity of the polar front, east of Kerguelen, remineralization in the upper 400 m in general represents a larger part of surface carbon export. However, when considering the upper 800 m, in some cases, the entire flux of exported carbon is remineralized. In the polar front meander, where successive stations form a time series, two successive events of particle transfer were evidenced by remineralization rates: a first mesopelagic and deep transfer from a past bloom before the cruise, and a second transfer expanding at mesopelagic layers during the cruise. Regarding the deep carbon transfer efficiency, it appeared that above the plateau (A3 site) the mesopelagic remineralization was not a major barrier to the transfer of organic matter to the seafloor (close to 500 m). There, the efficiency of carbon transfer to the bottom waters (>400 m) as assessed by PP, EP and MR fluxes comparisons reached up to 87% of the carbon exported from the upper 150 m. In contrast, at the deeper locations, mesopelagic remineralization clearly limited the transfer of carbon to depths of >400 m. For sites at the margin of the plateau (station E-4W) and the polar front (station F-L), mesopelagic remineralization even exceeded upper 150 m export, resulting in a zero transfer efficiency to depths >800 m. In the polar front meander (time series), the capacity of the meander to transfer carbon to depth >800 m was highly variable (0 to 73%). The highest carbon transfer efficiencies in the meander are furthermore coupled to intense and complete deep (>800 m) remineralization, resulting again in a near-zero, deep (>2000 m) carbon sequestration efficiency there.
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Peters, Katharina J., Sarah J. Bury, Bethany Hinton, Emma L. Betty, Déborah Casano-Bally, Guido J. Parra, and Karen A. Stockin. "Too Close for Comfort? Isotopic Niche Segregation in New Zealand’s Odontocetes." Biology 11, no. 8 (August 5, 2022): 1179. http://dx.doi.org/10.3390/biology11081179.
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Species occurring in sympatry and relying on similar and limited resources may partition resource use to avoid overlap and interspecific competition. Aotearoa, New Zealand hosts an extraordinarily rich marine megafauna, including 50% of the world’s cetacean species. In this study, we used carbon and nitrogen stable isotopes as ecological tracers to investigate isotopic niche overlap between 21 odontocete (toothed whale) species inhabiting neritic, mesopelagic, and bathypelagic waters. Results showed a clear niche separation for the bathypelagic Gray’s beaked whales (Mesoplodon grayi) and sperm whales (Physeter macrocephalus), but high isotopic niche overlap and potential interspecific competition for neritic and mesopelagic species. For these species, competition could be reduced via temporal or finer-scale spatial segregation or differences in foraging behaviour. This study represents the first insights into the coexistence of odontocetes in a biodiverse hotspot. The data presented here provide a critical baseline to a system already ongoing ecosystem change via ocean warming and subsequent effects on prey abundance and distributions.
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Vik, Dean R., Simon Roux, Jennifer R. Brum, Ben Bolduc, Joanne B. Emerson, Cory C. Padilla, Frank J. Stewart, and Matthew B. Sullivan. "Putative archaeal viruses from the mesopelagic ocean." PeerJ 5 (June 15, 2017): e3428. http://dx.doi.org/10.7717/peerj.3428.
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Oceanic viruses that infect bacteria, or phages, are known to modulate host diversity, metabolisms, and biogeochemical cycling, while the viruses that infect marine Archaea remain understudied despite the critical ecosystem roles played by their hosts. Here we introduce “MArVD”, for Metagenomic Archaeal Virus Detector, an annotation tool designed to identify putative archaeal virus contigs in metagenomic datasets. MArVD is made publicly available through the online iVirus analytical platform. Benchmarking analysis of MArVD showed it to be >99% accurate and 100% sensitive in identifying the 127 known archaeal viruses among the 12,499 viruses in the VirSorter curated dataset. Application of MArVD to 10 viral metagenomes from two depth profiles in the Eastern Tropical North Pacific (ETNP) oxygen minimum zone revealed 43 new putative archaeal virus genomes and large genome fragments ranging in size from 10 to 31 kb. Network-based classifications, which were consistent with marker gene phylogenies where available, suggested that these putative archaeal virus contigs represented six novel candidate genera. Ecological analyses, via fragment recruitment and ordination, revealed that the diversity and relative abundances of these putative archaeal viruses were correlated with oxygen concentration and temperature along two OMZ-spanning depth profiles, presumably due to structuring of the host Archaea community. Peak viral diversity and abundances were found in surface waters, whereThermoplasmata16S rRNA genes are prevalent, suggesting these archaea as hosts in the surface habitats. Together these findings provide a baseline for identifying archaeal viruses in sequence datasets, and an initial picture of the ecology of such viruses in non-extreme environments.
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Dall'Olmo, Giorgio, James Dingle, Luca Polimene, Robert J. W. Brewin, and Hervé Claustre. "Substantial energy input to the mesopelagic ecosystem from the seasonal mixed-layer pump." Nature Geoscience 9, no. 11 (September 26, 2016): 820–23. http://dx.doi.org/10.1038/ngeo2818.
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Chilvers, B. L. "Stable isotope signatures of whisker and blood serum confirm foraging strategies for female New Zealand sea lions (Phocarctos hookeri) derived from telemetry." Canadian Journal of Zoology 95, no. 12 (December 2017): 955–63. http://dx.doi.org/10.1139/cjz-2016-0299.
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Recognizing the individual variability of foraging behaviour of marine predators is important for understanding their role in the marine ecosystem and identifying how species may respond to environmental variability or human impacts. This research examines stable isotope signatures (δ13C and δ15N) of blood serum and whiskers from 22 female New Zealand sea lions (Phocarctos hookeri (Gray, 1844)) to determine if the isotopic composition of serum reflects foraging strategy, and whether serum and proximal whisker growth have similar signatures, therefore indicating the isotopic composition of whiskers also reflects the foraging strategy diet at the time of their growth. Female New Zealand sea lions are known to have two distinct foraging strategies (mesopelagic or benthic ecotypes), shown to be habitual within and between years. Females who are known to be mesopelagic foragers have higher overlap and are at greater risk of harmful interactions with fisheries. This research found that the two foraging strategies identified from telemetry are also associated with different δ13C and δ15N isotopic values from blood serum and whiskers. Therefore, stable isotope analysis could be used to determine the proportion of the female population that are likely to be exposed to the detrimental direct and indirect interactions with fisheries.
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Madigan, Daniel J., Aaron B. Carlisle, Luke D. Gardner, Nishad Jayasundara, Fiorenza Micheli, Kurt M. Schaefer, Daniel W. Fuller, and Barbara A. Block. "Assessing niche width of endothermic fish from genes to ecosystem." Proceedings of the National Academy of Sciences 112, no. 27 (June 22, 2015): 8350–55. http://dx.doi.org/10.1073/pnas.1500524112.
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Endothermy in vertebrates has been postulated to confer physiological and ecological advantages. In endothermic fish, niche expansion into cooler waters is correlated with specific physiological traits and is hypothesized to lead to greater foraging success and increased fitness. Using the seasonal co-occurrence of three tuna species in the eastern Pacific Ocean as a model system, we used cardiac gene expression data (as a proxy for thermal tolerance to low temperatures), archival tag data, and diet analyses to examine the vertical niche expansion hypothesis for endothermy in situ. Yellowfin, albacore, and Pacific bluefin tuna (PBFT) in the California Current system used more surface, mesopelagic, and deep waters, respectively. Expression of cardiac genes for calcium cycling increased in PBFT and coincided with broader vertical and thermal niche utilization. However, the PBFT diet was less diverse and focused on energy-rich forage fishes but did not show the greatest energy gains. Ecosystem-based management strategies for tunas should thus consider species-specific differences in physiology and foraging specialization.
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Thorrold, Simon R., Allan Adams, Ann Bucklin, Ken Buesseler, Godi Fischer, Annette Govindarajan, Porter Hoagland, et al. "Twilight Zone Observation Network: A Distributed Observation Network for Sustained, Real-Time Interrogation of the Ocean's Twilight Zone." Marine Technology Society Journal 55, no. 3 (May 1, 2021): 92–93. http://dx.doi.org/10.4031/mtsj.55.3.46.
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Abstract The ocean's twilight zone (TZ) is a vast, globe-spanning region of the ocean. Home to myriad fishes and invertebrates, mid-water fishes alone may constitute 10 times more biomass than all current ocean wild-caught fisheries combined. Life in the TZ supports ocean food webs and plays a critical role in carbon capture and sequestration. Yet the ecological roles that mesopelagic animals play in the ocean remain enigmatic. This knowledge gap has stymied efforts to determine the effects that extraction of mesopelagic biomass by industrial fisheries, or alterations due to climate shifts, may have on ecosystem services provided by the open ocean. We propose to develop a scalable, distributed observation network to provide sustained interrogation of the TZ in the northwest Atlantic. The network will leverage a “tool-chest” of emerging and enabling technologies including autonomous, unmanned surface and underwater vehicles and swarms of low-cost “smart” floats. Connectivity among in-water assets will allow rapid assimilation of data streams to inform adaptive sampling efforts. The TZ observation network will demonstrate a bold new step towards the goal of continuously observing vast regions of the deep ocean, significantly improving TZ biomass estimates and understanding of the TZ's role in supporting ocean food webs and sequestering carbon.
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Delpech, Audrey, Anna Conchon, Olivier Titaud, and Patrick Lehodey. "Influence of oceanic conditions in the energy transfer efficiency estimation of a micronekton model." Biogeosciences 17, no. 4 (February 18, 2020): 833–50. http://dx.doi.org/10.5194/bg-17-833-2020.
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Abstract. Micronekton – small marine pelagic organisms around 1–10 cm in size – are a key component of the ocean ecosystem, as they constitute the main source of forage for all larger predators. Moreover, the mesopelagic component of micronekton that undergoes diel vertical migration (DVM) likely plays a key role in the transfer and storage of CO2 in the deep ocean: this is known as the “biological pump”. SEAPODYM-MTL is a spatially explicit dynamical model of micronekton. It simulates six functional groups of vertically migrant (DVM) and nonmigrant (no DVM) micronekton, in the epipelagic and mesopelagic layers. Coefficients of energy transfer efficiency between primary production and each group are unknown, but they are essential as they control the production of micronekton biomass. Since these coefficients are not directly measurable, a data assimilation method is used to estimate them. In this study, Observing System Simulation Experiments (OSSEs) are used at a global scale to explore the response of oceanic regions regarding energy transfer coefficient estimation. In our experiments, we obtained different results for spatially distinct sampling regions based on their prevailing ocean conditions. According to our study, ideal sampling areas are warm and productive waters associated with weak surface currents like the eastern side of tropical oceans. These regions are found to reduce the error of estimated coefficients by 20 % compared to cold and more dynamic sampling regions.
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Braun, Camrin D., Peter Gaube, Tane H. Sinclair-Taylor, Gregory B. Skomal, and Simon R. Thorrold. "Mesoscale eddies release pelagic sharks from thermal constraints to foraging in the ocean twilight zone." Proceedings of the National Academy of Sciences 116, no. 35 (August 6, 2019): 17187–92. http://dx.doi.org/10.1073/pnas.1903067116.
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Mesoscale eddies are critical components of the ocean’s “internal weather” system. Mixing and stirring by eddies exerts significant control on biogeochemical fluxes in the open ocean, and eddies may trap distinctive plankton communities that remain coherent for months and can be transported hundreds to thousands of kilometers. Debate regarding how and why predators use fronts and eddies, for example as a migratory cue, enhanced forage opportunities, or preferred thermal habitat, has been ongoing since the 1950s. The influence of eddies on the behavior of large pelagic fishes, however, remains largely unexplored. Here, we reconstruct movements of a pelagic predator, the blue shark (Prionace glauca), in the Gulf Stream region using electronic tags, earth-observing satellites, and data-assimilating ocean forecasting models. Based on >2,000 tracking days and nearly 500,000 high-resolution time series measurements collected by 15 instrumented individuals, we show that blue sharks seek out the interiors of anticyclonic eddies where they dive deep while foraging. Our observations counter the existing paradigm that anticyclonic eddies are unproductive ocean “deserts” and suggest anomalously warm temperatures in these features connect surface-oriented predators to the most abundant fish community on the planet in the mesopelagic. These results also shed light on the ecosystem services provided by mesopelagic prey. Careful consideration will be needed before biomass extraction from the ocean twilight zone to avoid interrupting a key link between planktonic production and top predators. Moreover, robust associations between targeted fish species and oceanographic features increase the prospects for effective dynamic ocean management.