Artículos de revistas: "Southern high latitude marine ecosystems"

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Paterson, J. Terrill, Jay J. Rotella, Kevin R. Arrigo y Robert A. Garrott. "Tight coupling of primary production and marine mammal reproduction in the Southern Ocean". Proceedings of the Royal Society B: Biological Sciences 282, n.º 1806 (7 de mayo de 2015): 20143137. http://dx.doi.org/10.1098/rspb.2014.3137.

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Polynyas are areas of open water surrounded by sea ice and are important sources of primary production in high-latitude marine ecosystems. The magnitude of annual primary production in polynyas is controlled by the amount of exposure to solar radiation and sensitivity to changes in sea-ice extent. The degree of coupling between primary production and production by upper trophic-level consumers in these environments is not well understood, which prevents reliable predictions about population trajectories for species at higher trophic levels under potential future climate scenarios. In this study, we find a strong, positive relationship between annual primary production in an Antarctic polynya and pup production by ice-dependent Weddell seals. The timing of the relationship suggests reproductive effort increases to take advantage of high primary production occurring in the months after the birth pulse. Though the proximate causal mechanism is unknown, our results indicate tight coupling between organisms at disparate trophic levels on a short timescale, deepen our understanding of marine ecosystem processes, and raise interesting questions about why such coupling exists and what implications it has for understanding high-latitude ecosystems.

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Arfianti, T. y MJ Costello. "Global biogeography of marine amphipod crustaceans: latitude, regionalization, and beta diversity". Marine Ecology Progress Series 638 (19 de marzo de 2020): 83–94. http://dx.doi.org/10.3354/meps13272.

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Studying the biogeography of amphipod crustaceans is of interest because they play an important role at lower trophic levels in ecosystems. Because they lack a planktonic larval stage, it has been hypothesized that marine benthic amphipod crustaceans may have short dispersal distances, high endemicity, and spatial turnover in species composition, and consequently high global species richness. In this study, we examined over 400000 distribution records of 4876 amphipod species, and identified 12 regions of endemicity. The number and percent of endemic species peaked at 30°-35°S and coincided with 3 of these regions of high endemicity: Australia, New Zealand, and southern Africa. Pelagic species of marine amphipod crustaceans were more cosmopolitan than benthic species. The latitudinal patterns of richness (alpha, gamma, and ES50) and species turnover were at least bimodal. Most occurrence records and greater alpha and gamma richness were in mid-latitudes, reflecting sampling bias. Both ES50 and beta diversity had similar richness in the tropics, mid-latitudes, and on the Antarctic shelf around 70°S. These 2 indices exhibited a sharp dip in the deep Southern Ocean at 55°S. ES50 peaked at 30°-35°S and a small dip was apparent near the equator at 5°-10°N. Beta diversity was driven mostly by turnover rather than nestedness. These findings support the need for conservation in each realm of species endemicity—and for amphipods, particularly in Antarctica and the coastal mid-latitudes (30°-35°S) of the Southern Hemisphere.

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3

Contreras, L., J. Pross, P. K. Bijl, R. B. O'Hara, J. I. Raine, A. Sluijs y H. Brinkhuis. "Southern high-latitude terrestrial climate change during the Paleocene–Eocene derived from a marine pollen record (ODP Site 1172, East Tasman Plateau)". Climate of the Past Discussions 10, n.º 1 (20 de enero de 2014): 291–340. http://dx.doi.org/10.5194/cpd-10-291-2014.

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Abstract. Reconstructing the early Paleogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Paleogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Paleocene to the early Eocene (60.7–54.2 Ma) based on a sporomorph record from Ocean Drilling Program (ODP) Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Paleocene to early Eocene, with each type representing different temperature conditions: (i) warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Paleocene; (ii) cool-temperate forests dominated by southern beech (Nothofagus) and araucarians across the middle/late Paleocene transition interval (~59.5 to ~59.0 Ma); and (iii) paratropical forests rich in ferns that were established during and in the wake of the Paleocene–Eocene Thermal Maximum (PETM). The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e., palms and cycads) across the middle/late Paleocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the comparison of our season-specific climate estimates for the sporomorph assemblages from ODP Site 1172 with the TEX86L- and TEX86H-based temperature data suggests a warm-season bias of both calibrations for the early Paleogene of the high southern latitudes.

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4

Contreras, L., J. Pross, P. K. Bijl, R. B. O'Hara, J. I. Raine, A. Sluijs y H. Brinkhuis. "Southern high-latitude terrestrial climate change during the Palaeocene–Eocene derived from a marine pollen record (ODP Site 1172, East Tasman Plateau)". Climate of the Past 10, n.º 4 (24 de julio de 2014): 1401–20. http://dx.doi.org/10.5194/cp-10-1401-2014.

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Abstract. Reconstructing the early Palaeogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Palaeogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Palaeocene to the early Eocene (60.7–54.2 Ma) based on a sporomorph record from Ocean Drilling Program (ODP) Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Palaeocene to early Eocene, with each type representing different temperature conditions: (i) warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Palaeocene (excluding the middle/late Palaeocene transition); (ii) cool-temperate forests dominated by southern beech (Nothofagus) and araucarians that transiently prevailed across the middle/late Palaeocene transition interval (~ 59.5 to ~ 59.0 Ma); and (iii) paratropical forests rich in ferns that were established during and in the wake of the Palaeocene–Eocene Thermal Maximum (PETM). The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e. palms and cycads) across the middle/late Palaeocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the comparison of our season-specific climate estimates for the sporomorph assemblages from ODP Site 1172 with the TEX86L- and TEX86H-based temperature data suggests a warm bias of both calibrations for the early Palaeogene of the high southern latitudes.

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5

Son, Min Ho, Chung Il Lee, Joo Myun Park, Hyun Jung Kim, Ralf Riedel, Inseo Hwang, Young-Nam Kim y Hae Kun Jung. "The Northward Habitat Expansion of the Korean Top Shell Turbo sazae (Gastropoda: Vetigastropoda: Turbinidae) in the Korean Peninsula: Effects of Increasing Water Temperature". Journal of Marine Science and Engineering 8, n.º 10 (7 de octubre de 2020): 782. http://dx.doi.org/10.3390/jmse8100782.

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Recent global climate change often leads to poleward expansions of habitat range of marine organisms in response to increasing water temperature at high latitude. This study investigated latitudinal distribution patterns of Turbo sazae from 2009 to 2018 along the southern and eastern coasts of Korea to verify whether gradual increases in seawater temperature in the East Sea/Sea of Japan (hereafter East/Japan Sea) accelerate changes in the geographic distribution of T. sazae. Between 2009 and 2018, underwater SCUBA surveys were conducted at 19 subtidal rocky shore habitats from the southern and eastern coast of the Korean Peninsula, including Jeju Island. Additionally, long-term seawater temperature records over the last 40 years (between 1980s and 2010s) from the East/Japan Sea were analyzed to verify how changes of water temperature corresponded to geographical distributions of T. sazae. The habitat range of T. sazae was found to have extended from latitude 34°02′ N to latitude 37°06′ N from 2009 to 2018. Although seawater temperature has gradually increased since the 1990s in the East/Japan Sea, habitat expansion was particularly evident during the rapid rise of coastal seawater temperature in the 2010s. Because the strong northward expansion of the Tsushima Current can accelerate the rise of seawater temperature in the East/Japan Sea, studies of the effects of climate change on marine ecosystems of the Korean Peninsula should include data from monitoring the dynamics of the Tsushima Current.

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6

Beltran, Roxanne S., A. Marm Kilpatrick, Greg A. Breed, Taiki Adachi, Akinori Takahashi, Yasuhiko Naito, Patrick W. Robinson, Walker O. Smith, Amy L. Kirkham y Jennifer M. Burns. "Seasonal resource pulses and the foraging depth of a Southern Ocean top predator". Proceedings of the Royal Society B: Biological Sciences 288, n.º 1947 (17 de marzo de 2021): 20202817. http://dx.doi.org/10.1098/rspb.2020.2817.

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Seasonal resource pulses can have enormous impacts on species interactions. In marine ecosystems, air-breathing predators often drive their prey to deeper waters. However, it is unclear how ephemeral resource pulses such as near-surface phytoplankton blooms alter the vertical trade-off between predation avoidance and resource availability in consumers, and how these changes cascade to the diving behaviour of top predators. We integrated data on Weddell seal diving behaviour, diet stable isotopes, feeding success and mass gain to examine shifts in vertical foraging throughout ice break-out and the resulting phytoplankton bloom each year. We also tested hypotheses about the likely location of phytoplankton bloom origination (advected or produced in situ where seals foraged) based on sea ice break-out phenology and advection rates from several locations within 150 km of the seal colony. In early summer, seals foraged at deeper depths resulting in lower feeding rates and mass gain. As sea ice extent decreased throughout the summer, seals foraged at shallower depths and benefited from more efficient energy intake. Changes in diving depth were not due to seasonal shifts in seal diets or horizontal space use and instead may reflect a change in the vertical distribution of prey. Correspondence between the timing of seal shallowing and the resource pulse was variable from year to year and could not be readily explained by our existing understanding of the ocean and ice dynamics. Phytoplankton advection occurred faster than ice break-out, and seal dive shallowing occurred substantially earlier than local break-out. While there remains much to be learned about the marine ecosystem, it appears that an increase in prey abundance and accessibility via shallower distributions during the resource pulse could synchronize life-history phenology across trophic levels in this high-latitude ecosystem.

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7

Loeb, Valerie J., Eileen E. Hofmann, John M. Klinck, Osmund Holm-Hansen y Warren B. White. "ENSO and variability of the Antarctic Peninsula pelagic marine ecosystem". Antarctic Science 21, n.º 2 (19 de noviembre de 2008): 135–48. http://dx.doi.org/10.1017/s0954102008001636.

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AbstractThe West Antarctic Peninsula region is an important source of Antarctic krill (Euphausia superba) in the Southern Ocean. From 1980–2004 abundance and concentration of phytoplankton and zooplankton, krill reproductive and recruitment success and seasonal sea ice extent here were significantly correlated with the atmospheric Southern Oscillation Index and exhibited three- to five-year frequencies characteristic of El Niño–Southern Oscillation (ENSO) variability. This linkage was associated with movements of the Southern Antarctic Circumpolar Current Front and Boundary, a changing influence of Antarctic Circumpolar Current and Weddell Sea waters, and eastward versus westward flow and mixing processes that are consistent with forcing by the Antarctic Dipole high-latitude climate mode. Identification of hydrographic processes underlying ecosystem variability presented here were derived primarily from multi-disciplinary data collected during 1990–2004, a period with relatively stable year-to-year sea ice conditions. These results differ from the overwhelming importance of seasonal sea ice development previously established using 1980–1996 data, a period marked by a major decrease in sea ice from the Antarctic Peninsula region in the late 1980s. These newer results reveal the more subtle consequences of ENSO variability on biological responses. They highlight the necessity of internally consistent long-term multidisciplinary datasets for understanding ecosystem variability and ultimately for establishing well-founded ecosystem management. Furthermore, natural environmental variability associated with interannual- and decadal-scale changes in ENSO forcing must be considered when assessing impacts of climate warming in the Antarctic Peninsula–Weddell Sea region.

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Steneck, Robert S., Michael H. Graham, Bruce J. Bourque, Debbie Corbett, Jon M. Erlandson, James A. Estes y Mia J. Tegner. "Kelp forest ecosystems: biodiversity, stability, resilience and future". Environmental Conservation 29, n.º 4 (diciembre de 2002): 436–59. http://dx.doi.org/10.1017/s0376892902000322.

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Kelp forests are phyletically diverse, structurally complex and highly productive components of coldwater rocky marine coastlines. This paper reviews the conditions in which kelp forests develop globally and where, why and at what rate they become deforested. The ecology and long archaeological history of kelp forests are examined through case studies from southern California, the Aleutian Islands and the western North Atlantic, well-studied locations that represent the widest possible range in kelp forest biodiversity. Global distribution of kelp forests is physiologically constrained by light at high latitudes and by nutrients, warm temperatures and other macrophytes at low latitudes. Within mid-latitude belts (roughly 40–60° latitude in both hemispheres) well-developed kelp forests are most threatened by herbivory, usually from sea urchins. Overfishing and extirpation of highly valued vertebrate apex predators often triggered herbivore population increases, leading to widespread kelp deforestation. Such deforestations have the most profound and lasting impacts on species-depauperate systems, such as those in Alaska and the western North Atlantic. Globally urchin-induced deforestation has been increasing over the past 2–3 decades. Continued fishing down of coastal food webs has resulted in shifting harvesting targets from apex predators to their invertebrate prey, including kelp-grazing herbivores. The recent global expansion of sea urchin harvesting has led to the widespread extirpation of this herbivore, and kelp forests have returned in some locations but, for the first time, these forests are devoid of vertebrate apex predators. In the western North Atlantic, large predatory crabs have recently filled this void and they have become the new apex predator in this system. Similar shifts from fish- to crab-dominance may have occurred in coastal zones of the United Kingdom and Japan, where large predatory finfish were extirpated long ago. Three North American case studies of kelp forests were examined to determine their long history with humans and project the status of future kelp forests to the year 2025. Fishing impacts on kelp forest systems have been both profound and much longer in duration than previously thought. Archaeological data suggest that coastal peoples exploited kelp forest organisms for thousands of years, occasionally resulting in localized losses of apex predators, outbreaks of sea urchin populations and probably small-scale deforestation. Over the past two centuries, commercial exploitation for export led to the extirpation of sea urchin predators, such as the sea otter in the North Pacific and predatory fishes like the cod in the North Atlantic. The large-scale removal of predators for export markets increased sea urchin abundances and promoted the decline of kelp forests over vast areas. Despite southern California having one of the longest known associations with coastal kelp forests, widespread deforestation is rare. It is possible that functional redundancies among predators and herbivores make this most diverse system most stable. Such biodiverse kelp forests may also resist invasion from non-native species. In the species-depauperate western North Atlantic, introduced algal competitors carpet the benthos and threaten future kelp dominance. There, other non-native herbivores and predators have become established and dominant components of this system. Climate changes have had measurable impacts on kelp forest ecosystems and efforts to control the emission of greenhouse gasses should be a global priority. However, overfishing appears to be the greatest manageable threat to kelp forest ecosystems over the 2025 time horizon. Management should focus on minimizing fishing impacts and restoring populations of functionally important species in these systems.

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Rodgers, K. B., J. Lin y T. L. Frölicher. "Emergence of multiple ocean ecosystem drivers in a large ensemble suite with an Earth system model". Biogeosciences 12, n.º 11 (3 de junio de 2015): 3301–20. http://dx.doi.org/10.5194/bg-12-3301-2015.

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Abstract. Marine ecosystems are increasingly stressed by human-induced changes. Marine ecosystem drivers that contribute to stressing ecosystems – including warming, acidification, deoxygenation and perturbations to biological productivity – can co-occur in space and time, but detecting their trends is complicated by the presence of noise associated with natural variability in the climate system. Here we use large initial-condition ensemble simulations with an Earth system model under a historical/RCP8.5 (representative concentration pathway 8.5) scenario over 1950–2100 to consider emergence characteristics for the four individual and combined drivers. Using a 1-standard-deviation (67% confidence) threshold of signal to noise to define emergence with a 30-year trend window, we show that ocean acidification emerges much earlier than other drivers, namely during the 20th century over most of the global ocean. For biological productivity, the anthropogenic signal does not emerge from the noise over most of the global ocean before the end of the 21st century. The early emergence pattern for sea surface temperature in low latitudes is reversed from that of subsurface oxygen inventories, where emergence occurs earlier in the Southern Ocean. For the combined multiple-driver field, 41% of the global ocean exhibits emergence for the 2005–2014 period, and 63% for the 2075–2084 period. The combined multiple-driver field reveals emergence patterns by the end of this century that are relatively high over much of the Southern Ocean, North Pacific, and Atlantic, but relatively low over the tropics and the South Pacific. For the case of two drivers, the tropics including habitats of coral reefs emerges earliest, with this driven by the joint effects of acidification and warming. It is precisely in the regions with pronounced emergence characteristics where marine ecosystems may be expected to be pushed outside of their comfort zone determined by the degree of natural background variability to which they are adapted. The results underscore the importance of sustained multi-decadal observing systems for monitoring multiple ecosystems drivers.

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Murray, Alison E. y Joseph J. Grzymski. "Diversity and genomics of Antarctic marine micro-organisms". Philosophical Transactions of the Royal Society B: Biological Sciences 362, n.º 1488 (21 de mayo de 2007): 2259–71. http://dx.doi.org/10.1098/rstb.2006.1944.

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Marine bacterioplanktons are thought to play a vital role in Southern Ocean ecology and ecosystem function, as they do in other ocean systems. However, our understanding of phylogenetic diversity, genome-enabled capabilities and specific adaptations to this persistently cold environment is limited. Bacterioplankton community composition shifts significantly over the annual cycle as sea ice melts and phytoplankton bloom. Microbial diversity in sea ice is better known than that of the plankton, where culture collections do not appear to represent organisms detected with molecular surveys. Broad phylogenetic groupings of Antarctic bacterioplankton such as the marine group I Crenarchaeota, α-Proteobacteria ( Roseobacter -related and SAR-11 clusters), γ-Proteobacteria (both cultivated and uncultivated groups) and Bacteriodetes-affiliated organisms in Southern Ocean waters are in common with other ocean systems. Antarctic SSU rRNA gene phylotypes are typically affiliated with other polar sequences. Some species such as Polaribacter irgensii and currently uncultivated γ-Proteobacteria (Ant4D3 and Ant10A4) may flourish in Antarctic waters, though further studies are needed to address diversity on a larger scale. Insights from initial genomics studies on both cultivated organisms and genomes accessed through shotgun cloning of environmental samples suggest that there are many unique features of these organisms that facilitate survival in high-latitude, persistently cold environments.

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Dorschel, B., J. Gutt, D. Piepenburg, M. Schröder y J. E. Arndt. "The influence of the geomorphological and sedimentological settings on the distribution of epibenthic assemblages on a flat topped hill on the over-deepened shelf of the western Weddell Sea (Southern Ocean)". Biogeosciences 11, n.º 14 (21 de julio de 2014): 3797–817. http://dx.doi.org/10.5194/bg-11-3797-2014.

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Abstract. Epibenthos communities play an important role in the marine ecosystems of the Weddell Sea. Information on the factors controlling their structure and distribution are, however, still rare. In particular, the interactions between environmental factors and biotic assemblages are not fully understood. Nachtigaller Hill, a newly discovered seabed structure on the over-deepened shelf of the northwest Weddell Sea (Southern Ocean), offers a unique site to study these interactions in a high-latitude Antarctic setting. Based on high-resolution bathymetry and georeferenced biological data, the effect of the terrain and related environmental parameters on the epibenthos was assessed. At Nachtigaller Hill, both geomorphological and biological data showed complex distribution patterns, reflecting local processes such as iceberg scouring and locally amplified bottom currents. This variability was also generally reflected in the variable epibenthos distribution patterns although statistical analyses did not show strong correlations between the selected environmental parameters and species abundances. By analysing the interactions between environmental and biological patterns, this study provides crucial information towards a better understanding of the factors and processes that drive epibenthos communities on the shelves of the Weddell Sea and probably also on other Antarctic shelves.

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12

Dorschel, B., J. Gutt, D. Piepenburg, M. Schröder y J. E. Arndt. "The influence of the geo-morphological and sedimentological settings on the distribution of epibenthic assemblages on a flat topped hill on the over-deepened shelf of the Western Weddell Sea". Biogeosciences Discussions 11, n.º 1 (23 de enero de 2014): 1631–72. http://dx.doi.org/10.5194/bgd-11-1631-2014.

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Abstract. Epibenthos communities play an important role in the marine ecosystems of the Weddell Sea. Information on the factors controlling their structure and distribution are, however, still rare. Especially the interactions between environmental factors and biotic assemblages are not fully understood. Nachtigaller Hill, a newly discovered seabed structure on the over-deepened shelf of the Northwest Weddell Sea (Southern Ocean), offers a unique site to study these interactions in a high-latitude Antarctic setting. Based on high-resolution bathymetry, geo-referenced biological data, the effect of the terrain and related environmental parameters on the epibenthos was assessed. At Nachtigaller Hill, both geo-morphological and biological data showed complex distribution patterns, reflecting local processes such as iceberg scouring and locally amplified bottom currents. This variability is also generally reflected in the variable epibenthos distribution patterns although statistical analyses did not show strong correlations between the selected environmental parameters and species abundances. By analysing the interactions between environmental and biological patterns, this study provides crucial information towards a better understanding of the factors and processes that drive epibenthos communities on the shelves of the Weddell Sea and probably also on other Antarctic shelves.

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13

Crame, J. Alistair. "Evolution of taxonomic diversity gradients in the marine realm: evidence from the composition of Recent bivalve faunas". Paleobiology 26, n.º 2 (2000): 188–214. http://dx.doi.org/10.1666/0094-8373(2000)026<0188:eotdgi>2.0.co;2.

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A major new inventory of living marine Bivalvia (Mollusca) is based on 29 regional faunas. These again pick out strong latitudinal and longitudinal gradients in taxonomic diversity, but there are indications that the patterns are not so regular as previously thought. There are signs of asymmetry between the Northern and Southern Hemisphere latitudinal gradients, with the former tending to be more regular than the latter. Northern gradients are also characterized by a marked inflection at approximately 30°N, and the three Australian provinces seem to form a distinct “hot-spot” in the Southern Hemisphere. The larger of the two tropical high-diversity foci (the southern China-Indonesia-NE Australia one) appears to be much more nearly arcuate in plan view than oval and is closely associated with the world's richest development of coral reefs.A taxonomic and stratigraphic analysis reveals that the steepest latitudinal gradients are associated with the youngest bivalve clades. The most striking pattern is that shown by the heteroconchs, an essentially infaunal taxon that radiated extensively throughout the Cenozoic era. Steep gradients are also characteristic of the relatively young anomalodesmatan and arcoid clades and, somewhat surprisingly, the predominantly epifaunal pteriomorphs. Although the latter taxon falls within an older (i.e., “late Paleozoic-Jurassic”) group of clades, it is apparent that certain elements within it (and in particular the Pectinidae) radiated extensively in the latest Mesozoic-Cenozoic. A small but significant component of the later stages of the adaptive radiation of the Bivalvia comprised epifaunal taxa.The presence of the steepest latitudinal gradients in the youngest clades provides further evidence that the Tropics have served as a major center of evolutionary innovation. Even though some sort of retraction mechanism cannot be completely ruled out, these gradients are most likely the product of primary radiations. Clade history can be an important determinant of contemporary large-scale biodiversity patterns. The markedly lower diversity of some bivalve clades, such as the heteroconchs, in the high-latitude and polar regions may simply reflect the fact that they are not yet fully established there. In a way that is reminiscent of the onshore-offshore radiation of certain benthic marine invertebrate taxa, it may take periods of tens or even hundreds of millions of years for bivalve clades to disseminate fully across the earth's surface.The persistent spread of taxa from low- to high-latitude regions should perhaps come as no great surprise, as the tropical ocean is very much older than either of the polar ones. The late Cretaceous-Cenozoic evolutionary radiation of the Bivalvia was accompanied by a marked deterioration in global climates, and many new groups have yet to be fully assimilated into cool- and cold-water benthic ecosystems.

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Rodgers, K. B., J. Lin y T. L. Frölicher. "Emergence of multiple ocean ecosystem drivers in a large ensemble suite with an earth system model". Biogeosciences Discussions 11, n.º 12 (21 de diciembre de 2014): 18189–227. http://dx.doi.org/10.5194/bgd-11-18189-2014.

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Abstract. Marine ecosystems are increasingly impacted by human-induced changes. Ocean ecosystem drivers – including warming, acidification, deoxygenation and perturbations to biological productivity – can co-occur in space and time, but detecting their trends is complicated by the presence of noise associated with natural variability in the climate system. Here we use Large Initial-Condition Ensemble Simulations with a comprehensive Earth System Model under a historical/RCP8.5 pathway over 1950–2100 to consider emergence characteristics for the four individual and combined drivers. Using a one-standard deviation (67% confidence) threshold of signal-to-noise to define emergence with a 30 yr trend window, we show that ocean acidification emerges much earlier than other drivers, namely during the 20th century over most of the global ocean. For biological productivity, the anthropogenic signal does not emerge from the noise over most of the global ocean before the end of the 21st century. The early emergence pattern for sea surface temperature in low latitudes is reversed from that of subsurface oxygen inventories, where emergence occurs earlier in the Southern Ocean. For the combined multiple-driver field, 41% of the global ocean exhibits emergence for the 2005–2014 period, and 63% for the 2075–2084 period. The combined multiple-driver field reveals emergence patterns by the end of this century that are relatively high over much of the Southern Ocean, North Pacific, and Atlantic, but relatively low over the tropics and the South Pacific. In regions with pronounced emergence characteristics, marine ecosystems can be expected to be pushed outside of their comfort zone determined by the degree of natural background variability to which they are adapted. The results here thus have implications not only for optimization of the ocean observing system, but also for risk assessment and mitigation strategies.

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15

Trathan, P. N., J. Forcada y E. J. Murphy. "Environmental forcing and Southern Ocean marine predator populations: effects of climate change and variability". Philosophical Transactions of the Royal Society B: Biological Sciences 362, n.º 1488 (24 de mayo de 2007): 2351–65. http://dx.doi.org/10.1098/rstb.2006.1953.

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The Southern Ocean is a major component within the global ocean and climate system and potentially the location where the most rapid climate change is most likely to happen, particularly in the high-latitude polar regions. In these regions, even small temperature changes can potentially lead to major environmental perturbations. Climate change is likely to be regional and may be expressed in various ways, including alterations to climate and weather patterns across a variety of time-scales that include changes to the long interdecadal background signals such as the development of the El Niño–Southern Oscillation (ENSO). Oscillating climate signals such as ENSO potentially provide a unique opportunity to explore how biological communities respond to change. This approach is based on the premise that biological responses to shorter-term sub-decadal climate variability signals are potentially the best predictor of biological responses over longer time-scales. Around the Southern Ocean, marine predator populations show periodicity in breeding performance and productivity, with relationships with the environment driven by physical forcing from the ENSO region in the Pacific. Wherever examined, these relationships are congruent with mid-trophic-level processes that are also correlated with environmental variability. The short-term changes to ecosystem structure and function observed during ENSO events herald potential long-term changes that may ensue following regional climate change. For example, in the South Atlantic, failure of Antarctic krill recruitment will inevitably foreshadow recruitment failures in a range of higher trophic-level marine predators. Where predator species are not able to accommodate by switching to other prey species, population-level changes will follow. The Southern Ocean, though oceanographically interconnected, is not a single ecosystem and different areas are dominated by different food webs. Where species occupy different positions in different regional food webs, there is the potential to make predictions about future change scenarios.

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Le Grix, Natacha, Jakob Zscheischler, Keith B. Rodgers, Ryohei Yamaguchi y Thomas L. Frölicher. "Hotspots and drivers of compound marine heatwaves and low net primary production extremes". Biogeosciences 19, n.º 24 (16 de diciembre de 2022): 5807–35. http://dx.doi.org/10.5194/bg-19-5807-2022.

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Abstract. Extreme events can severely impact marine organisms and ecosystems. Of particular concern are multivariate compound events, namely when conditions are simultaneously extreme for multiple ocean ecosystem stressors. In 2013–2015 for example, an extensive marine heatwave (MHW), known as the Blob, co-occurred locally with extremely low net primary productivity (NPPX) and negatively impacted marine life in the northeast Pacific. Yet, little is known about the characteristics and drivers of such multivariate compound MHW–NPPX events. Using five different satellite-derived net primary productivity (NPP) estimates and large-ensemble-simulation output of two widely used and comprehensive Earth system models, the Geophysical Fluid Dynamics Laboratory (GFDL) ESM2M-LE and Community Earth System Model version 2 (CESM2-LE), we assess the present-day distribution of compound MHW–NPPX events and investigate their potential drivers on the global scale. The satellite-based estimates and both models reveal hotspots of frequent compound events in the center of the equatorial Pacific and in the subtropical Indian Ocean, where their occurrence is at least 3 times higher (more than 10 d yr−1) than if MHWs (temperature above the seasonally varying 90th-percentile threshold) and NPPX events (NPP below the seasonally varying 10th-percentile threshold) were to occur independently. However, the models show disparities in the northern high latitudes, where compound events are rare in the satellite-based estimates and GFDL ESM2M-LE (less than 3 d yr−1) but relatively frequent in CESM2-LE. In the Southern Ocean south of 60∘ S, low agreement between the observation-based estimates makes it difficult to determine which of the two models better simulates MHW–NPPX events. The frequency patterns can be explained by the drivers of compound events, which vary among the two models and phytoplankton types. In the low latitudes, MHWs are associated with enhanced nutrient limitation on phytoplankton growth, which results in frequent compound MHW–NPPX events in both models. In the high latitudes, NPPX events in GFDL ESM2M-LE are driven by enhanced light limitation, which rarely co-occurs with MHWs, resulting in rare compound events. In contrast, in CESM2-LE, NPPX events in the high latitudes are driven by reduced nutrient supply that often co-occurs with MHWs, moderates phytoplankton growth, and causes biomass to decrease. Compound MHW–NPPX events are associated with a relative shift towards larger phytoplankton in most regions, except in the eastern equatorial Pacific in both models, as well as in the northern high latitudes and between 35 and 50∘ S in CESM2-LE, where the models suggest a shift towards smaller phytoplankton, with potential repercussions on marine ecosystems. Overall, our analysis reveals that the likelihood of compound MHW–NPPX events is contingent on model representation of the factors limiting phytoplankton production. This identifies an important need for improved process understanding in Earth system models used for predicting and projecting compound MHW–NPPX events and their impacts.

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17

Song, Yangjinan y Xianqing Lv. "Study of Phytoplankton Biomass and Environmental Drivers in and around the Ross Sea Marine Protected Area". Journal of Marine Science and Engineering 11, n.º 4 (30 de marzo de 2023): 747. http://dx.doi.org/10.3390/jmse11040747.

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The Southern Ocean plays a vital role in the global climate system and the life cycle of high-latitude marine life. Phytoplankton is an important source of primary productivity in this ecosystem. Its future changes could affect Southern Ocean geochemistry, carbon export, and higher trophic organisms. To better protect Antarctica, three different marine protected areas (MPA) have been established in the Ross Sea region. Because time-continuous and regionally complete data are difficult to obtain in this region, we obtained data from ocean model outputs to understand the spatiotemporal variability of phytoplankton biomass in this region. This study explored the correlation between phytoplankton biomass and key environmental factors. Phytoplankton biomass peaks in February as temperatures rise and sea ice melts. Correlations also vary between different protected areas. The correlation between biomass, nitrate, and salinity in the Krill Research Zone (KRZ) area was significantly different from other protected areas. In addition, in the context of global warming, Antarctica lacks temperature perception. The model results show a downward trend in temperature and an increase in sea ice coverage in the western Ross Sea that other studies have also pointed to. How phytoplankton biomass will change in protected areas in the future is a question worth considering. Finally, the study simply simulates future regional trends by comparing the biomass distribution in hot years to average years. This will increase our knowledge of the polar system.

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18

Mendoza-Segura, Clara, Emilio Fernández y Pedro Beca-Carretero. "Predicted Changes in the Biogeographical Range of Gracilaria vermiculophylla under Present and Future Climate Scenarios". Journal of Marine Science and Engineering 11, n.º 2 (7 de febrero de 2023): 367. http://dx.doi.org/10.3390/jmse11020367.

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Global change effects have favoured the introduction of new species in marine ecosystems in recent years. Gracilaria vermiculophylla, a red seaweed native from the north-eastern Pacific, has successfully colonised large regions in the Northern Hemisphere. In this research, we implemented species distribution models (SDMs) to (i) examine which were the most important environmental factors defining the presence of G. vermiculophylla at a global scale, and (ii) determine the potential current and future distribution of G. vermiculophylla based on two climate scenarios (representative concentration pathways (RCP 2.6 and RCP 8.5)). Our results suggest that temperature and salinity were the most important variables explaining the distribution of the target species. Additionally, the SDMs for present climate settings showed a potential wider distribution than is recorded to date. In addition, a subtle habitat expansion of 2.9° into higher latitudes was reported under the RCP 2.6 scenario by the end of this century. The high-carbon-emission scenario (RCP 8.5) delivered a potential large habitat expansion (6.0°), even reaching arctic latitudes, and a remarkable habitat loss of 11° in its southern distribution range. SMDs also forecasted suitable areas for this species in the Southern Hemisphere, pointing toward a potential global expansion in the coming decades.

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19

Mays, Chris, Vivi Vajda, Tracy D. Frank, Christopher R. Fielding, Robert S. Nicoll, Allen P. Tevyaw y Stephen McLoughlin. "Refined Permian–Triassic floristic timeline reveals early collapse and delayed recovery of south polar terrestrial ecosystems". GSA Bulletin 132, n.º 7-8 (14 de noviembre de 2019): 1489–513. http://dx.doi.org/10.1130/b35355.1.

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Abstract The collapse of late Permian (Lopingian) Gondwanan floras, characterized by the extinction of glossopterid gymnosperms, heralded the end of one of the most enduring and extensive biomes in Earth’s history. The Sydney Basin, Australia, hosts a near-continuous, age-constrained succession of high southern paleolatitude (∼65–75°S) terrestrial strata spanning the end-Permian extinction (EPE) interval. Sedimentological, stable carbon isotopic, palynological, and macrofloral data were collected from two cored coal-exploration wells and correlated. Six palynostratigraphic zones, supported by ordination analyses, were identified within the uppermost Permian to Lower Triassic succession, corresponding to discrete vegetation stages before, during, and after the EPE interval. Collapse of the glossopterid biome marked the onset of the terrestrial EPE and may have significantly predated the marine mass extinctions and conodont-defined Permian–Triassic Boundary. Apart from extinction of the dominant Permian plant taxa, the EPE was characterized by a reduction in primary productivity, and the immediate aftermath was marked by high abundances of opportunistic fungi, algae, and ferns. This transition is coeval with the onset of a gradual global decrease in δ13Corg and the primary extrusive phase of Siberian Traps Large Igneous Province magmatism. The dominant gymnosperm groups of the Gondwanan Mesozoic (peltasperms, conifers, and corystosperms) all appeared soon after the collapse but remained rare throughout the immediate post-EPE succession. Faltering recovery was due to a succession of rapid and severe climatic stressors until at least the late Early Triassic. Immediately prior to the Smithian–Spathian boundary (ca. 249 Ma), indices of increased weathering, thick redbeds, and abundant pleuromeian lycophytes likely signify marked climate change and intensification of the Gondwanan monsoon climate system. This is the first record of the Smithian–Spathian floral overturn event in high southern latitudes.

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20

Savenko, O. y A. Friedlaender. "New sightings of the Southern right whales in West Antarctic Peninsula waters". Ukrainian Antarctic Journal 20, n.º 1(24) (2022): 104–12. http://dx.doi.org/10.33275/1727-7485.1.2022.693.

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Southern right whales (SRW) in the southwest Atlantic are recognized as slowly recovering after the massive population decline induced by harvesting. SRWs spend summer months in high-latitude feeding grounds and migrate to mid-latitude wintering grounds in autumn, where breeding occurs. Only a few sightings are known for the Antarctic waters as far south as 64° S. The West Antarctic Peninsula is a biologically productive area experiencing marine ecosystem transformations caused by climate changing at one of the fastest rates on Earth. The continental shelf of this region is important for krill stocks — a key prey source for SRW. The purpose of the present study was to reveal the austral summer and autumn presence of the SRWs in the waters of the West Antarctic Peninsula. In May—June 2009, vessel observations were made during a National Science Foundation research cruise. In March 2014, opportunistic surveys were conducted by researchers using the tour vessel as a platform of opportunity. During late March and April of 2018, January — July 2019 and March — April 2020, regular boat-based observations and vessel surveys were conducted in frames of the XXIII and XXIV Ukrainian Antarctic Expeditions, based at the Ukrainian Antarctic Akademik Vernadsky station. In our study we discuss four sightings of SRWs occurred at south of 64° S (2), and 65° S (2). On May 7, 2009, a single adult foraging SRW was sighted in Wilhelmina Bay. On March 22, 2014, an adult SRW was resting with two adult humpback whales in the northern part of the Lemaire Channel. On April 7, 2018, one SRW was sighted in a group with four humpback whales, and intensive interspecies social interactions happened. The last encounter of the SRW happened on April 24, 2020, in Gerlache Strait, near the southeastern coast of the Brabant Island — a single adult right whale was noticed while travelling. Results of our study indicate the autumn presence of some SRWs in the West Antarctic Peninsula waters — on the edge of the southern limit of known distribution for the species.

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21

Wang, S., D. Bailey, K. Lindsay, J. K. Moore y M. Holland. "Impact of sea ice on the marine iron cycle and phytoplankton productivity". Biogeosciences 11, n.º 17 (8 de septiembre de 2014): 4713–31. http://dx.doi.org/10.5194/bg-11-4713-2014.

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Abstract. Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes, the iron cycle is closely related to the dynamics of sea ice. In recent decades, Arctic sea ice cover has been declining rapidly and Antarctic sea ice has exhibited large regional trends. A significant reduction of sea ice in both hemispheres is projected in future climate scenarios. In order to adequately study the effect of sea ice on the polar iron cycle, sea ice bearing iron was incorporated in the Community Earth System Model (CESM). Sea ice acts as a reservoir for iron during winter and releases the trace metal to the surface ocean in spring and summer. Simulated iron concentrations in sea ice generally agree with observations in regions where iron concentrations are relatively low. The maximum iron concentrations simulated in Arctic and Antarctic sea ice are much lower than observed, which is likely due to underestimation of iron inputs to sea ice or missing mechanisms. The largest iron source to sea ice is suspended sediments, contributing fluxes of iron of 2.2 × 108 mol Fe month−1 in the Arctic and 4.1 × 106 mol Fe month−1 in the Southern Ocean during summer. As a result of the iron flux from ice, iron concentrations increase significantly in the Arctic. Iron released from melting ice increases phytoplankton production in spring and summer and shifts phytoplankton community composition in the Southern Ocean. Results for the period of 1998 to 2007 indicate that a reduction of sea ice in the Southern Ocean will have a negative influence on phytoplankton production. Iron transport by sea ice appears to be an important process bringing iron to the central Arctic. The impact of ice to ocean iron fluxes on marine ecosystems is negligible in the current Arctic Ocean, as iron is not typically the growth-limiting nutrient. However, it may become a more important factor in the future, particularly in the central Arctic, as iron concentrations will decrease with declining sea ice cover and transport.

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22

Wang, S., D. Bailey, K. Lindsay, K. Moore y M. Holland. "Impacts of sea ice on the marine iron cycle and phytoplankton productivity". Biogeosciences Discussions 11, n.º 2 (11 de febrero de 2014): 2383–418. http://dx.doi.org/10.5194/bgd-11-2383-2014.

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Abstract. Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes, the iron cycle is closely related to sea ice. In recent decades, Arctic sea ice cover has been declining rapidly and Antarctic sea ice has exhibited large regional trends. A significant reduction of sea ice in both hemispheres is projected in future climate scenarios. To study impacts of sea ice on the iron cycle, iron sequestration in ice is incorporated to the Biogeochemical Elemental Cycling (BEC) model. Sea ice acts as a reservoir of iron during winter and releases iron to the surface ocean in spring and summer. Simulated iron concentrations in sea ice generally agree with observations, in regions where iron concentrations are lower. The maximum iron concentrations simulated in the Arctic sea ice and the Antarctic sea ice are 192 nM and 134 nM, respectively. These values are much lower than observed, which is likely due to missing biological processes in sea ice. The largest iron source to sea ice is suspended sediments, contributing fluxes of iron of 2.2 × 108 mol Fe month−1 to the Arctic and 4.1 × 106 mol Fe month−1 to the Southern Ocean during summer. As a result of the iron flux from ice, iron concentrations increase significantly in the Arctic. Iron released from melting ice increases phytoplankton production in spring and summer and shifts phytoplankton community composition in the Southern Ocean. Simulation results for the period of 1998 to 2007 indicate that a reduction of sea ice in the Southern Ocean will have a negative influence on phytoplankton production. Iron transport by sea ice appears to be an important process bringing iron to the central Arctic. Impacts of iron fluxes from ice to ocean on marine ecosystems are negligible in the current Arctic Ocean, as iron is not typically the growth-limiting nutrient. However, it may become a more important factor in the future, particularly in the central Arctic, as iron concentrations will decrease with declining sea ice cover and transport.

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23

Weller, Gunter. "Regional impacts of climate change in the Arctic and Antarctic". Annals of Glaciology 27 (1998): 543–52. http://dx.doi.org/10.3189/1998aog27-1-543-552.

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Regional assessments of impacts due to global climate change are a high priority in the international programs on global-change research. in the polar regions, climate models indicate an amplification of global greenhouse warming, but there are large differences between the results of various models, and uncertainties about the magnitude and timing of the expected changes. Also, the observed high-latitude climate trends over the past few decades are much more regional and patchy than predicted by the models. As a first step in assessing possible climate impacts, model results are compared with observations of changes in temperature, precipitation, sea-ice extent, the permafrost regime and other cryospheric parameters. While considerable uncertainties remain in the long-term prediction of change, there is some agreement between model results and observed trends by season on shorter time-scales, The warming observed over the land masses of the Arctic over the past few decades is matched by corresponding observed decreases in snow cover the glacier mass, balances, by thawing of the permafrost, and to a lesser degree by reductions in sea-ice extent. in Antarctica, warming in the Antarctic Peninsula and Ross Sea regions is associated with large decreases in ice-shelf areas and reduced ice thicknesses on the lakes in the McMurdo Dry Valleys. Major future impacts due to global greenhouse warming are likely to include permafrost thawing on and and its consequences for ecosystems and humans; changes in the productivity of marine ecosystems in the Arctic and Southern Ocean: economic impacts on fisheries, petroleum and other human activities; and social impacts on northern indigenous populations. Some of these impacts will have positive ramifications, but most are likely to be detrimental. While uncertainties exist about the future, climate change in the polar regions during the past few decades can be shown to have had major impacts already which will become much mole pronounced if present trends continue.

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Brown, Kristy, Jacquomo Monk, Joel Williams, Andrew Carroll, David Harasti y Neville Barrett. "Depth and benthic habitat influence shallow and mesophotic predatory fishes on a remote, high-latitude coral reef". PLOS ONE 17, n.º 3 (24 de marzo de 2022): e0265067. http://dx.doi.org/10.1371/journal.pone.0265067.

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Predatory fishes on coral reefs continue to decline globally despite playing key roles in ecosystem functioning. Remote atolls and platform reefs provide potential refugia for predator populations, but quantitative information on their spatial distribution is required to establish accurate baselines for ongoing monitoring and conservation management. Current knowledge of predatory fish populations has been derived from targeted shallow diver-based surveys (<15 m). However, the spatial distribution and extent of predatory fishes on outer mesophotic shelf environments has remained under described. Middleton Reef is a remote, high-latitude, oceanic platform reef that is located within a no-take area in the Lord Howe Marine Park off eastern Australia. Here we used baited remote underwater stereo video to sample predatory fishes across lagoon and outer shelf habitats from depths 0–100 m, extending knowledge on use of mesophotic depths and habitats. Many predatory fish demonstrated clear depth and habitat associations over this depth range. Carcharhinid sharks and Carangid fishes were the most abundant predators sampled on Middleton Reef, with five predatory fishes accounting for over 90% of the predator fish biomass. Notably, Galapagos shark (Carcharhinus galapagensis) and the protected black rockcod (Epinephelus daemelii) dominated the predator fish assemblage. A higher richness of predator fish species was sampled on reef areas north and south of the lagoon. The more exposed southern aspect of the reef supported a different suite of predator fish across mesophotic habitats relative to the assemblage recorded in the north and lagoonal habitats, a pattern potentially driven by differences in hard coral cover. Biomass of predatory fishes in the more sheltered north habitats was twice that of other areas, predominantly driven by high abundances of Galapagos shark. This work adds to the growing body of literature highlighting the conservation value of isolated oceanic reefs and the need to ensure that lagoon, shallow and mesophotic habitats in these systems are adequately protected, as they support vulnerable ecologically and economically important predator fish assemblages.

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McBride, Margaret M., Padmini Dalpadado, Kenneth F. Drinkwater, Olav Rune Godø, Alistair J. Hobday, Anne B. Hollowed, Trond Kristiansen et al. "Krill, climate, and contrasting future scenarios for Arctic and Antarctic fisheries". ICES Journal of Marine Science 71, n.º 7 (28 de marzo de 2014): 1934–55. http://dx.doi.org/10.1093/icesjms/fsu002.

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Abstract Arctic and Antarctic marine systems have in common high latitudes, large seasonal changes in light levels, cold air and sea temperatures, and sea ice. In other ways, however, they are strikingly different, including their: age, extent, geological structure, ice stability, and foodweb structure. Both regions contain very rapidly warming areas and climate impacts have been reported, as have dramatic future projections. However, the combined effects of a changing climate on oceanographic processes and foodweb dynamics are likely to influence their future fisheries in very different ways. Differences in the life-history strategies of the key zooplankton species (Antarctic krill in the Southern Ocean and Calanus copepods in the Arctic) will likely affect future productivity of fishery species and fisheries. To explore future scenarios for each region, this paper: (i) considers differing characteristics (including geographic, physical, and biological) that define polar marine ecosystems and reviews known and projected impacts of climate change on key zooplankton species that may impact fished species; (ii) summarizes existing fishery resources; (iii) synthesizes this information to generate future scenarios for fisheries; and (iv) considers the implications for future fisheries management. Published studies suggest that if an increase in open water during summer in Arctic and Subarctic seas results in increased primary and secondary production, biomass may increase for some important commercial fish stocks and new mixes of species may become targeted. In contrast, published studies suggest that in the Southern Ocean the potential for existing species to adapt is mixed and that the potential for the invasion of large and highly productive pelagic finfish species appears low. Thus, future Southern Ocean fisheries may largely be dependent on existing species. It is clear from this review that new management approaches will be needed that account for the changing dynamics in these regions under climate change.

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Malviya, Shruti, Eleonora Scalco, Stéphane Audic, Flora Vincent, Alaguraj Veluchamy, Julie Poulain, Patrick Wincker et al. "Insights into global diatom distribution and diversity in the world’s ocean". Proceedings of the National Academy of Sciences 113, n.º 11 (29 de febrero de 2016): E1516—E1525. http://dx.doi.org/10.1073/pnas.1509523113.

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Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of ∼12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 size-fractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron. We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.

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Mora-Soto, Alejandra, Mauricio Palacios, Erasmo Macaya, Iván Gómez, Pirjo Huovinen, Alejandro Pérez-Matus, Mary Young et al. "A High-Resolution Global Map of Giant Kelp (Macrocystis pyrifera) Forests and Intertidal Green Algae (Ulvophyceae) with Sentinel-2 Imagery". Remote Sensing 12, n.º 4 (20 de febrero de 2020): 694. http://dx.doi.org/10.3390/rs12040694.

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Giant kelp (Macrocystis pyrifera) is the most widely distributed kelp species on the planet, constituting one of the richest and most productive ecosystems on Earth, but detailed information on its distribution is entirely missing in some marine ecoregions, especially in the high latitudes of the Southern Hemisphere. Here, we present an algorithm based on a series of filter thresholds to detect giant kelp employing Sentinel-2 imagery. Given the overlap between the reflectances of giant kelp and intertidal green algae (Ulvophyceae), the latter are also detected on shallow rocky intertidal areas. The kelp filter algorithm was applied separately to vegetation indices, the Floating Algae Index (FAI), the Normalised Difference Vegetation Index (NDVI), and a novel formula (the Kelp Difference, KD). Training data from previously surveyed kelp forests and other coastal and ocean features were used to identify reflectance threshold values. This procedure was validated with independent field data collected with UAV imagery at a high spatial resolution and point-georeferenced sites at a low spatial resolution. When comparing UAV with Sentinel data (high-resolution validation), an average overall accuracy ≥ 0.88 and Cohen’s kappa ≥ 0.64 coefficients were found in all three indices for canopies reaching the surface with extensions greater than 1 hectare, with the KD showing the highest average kappa score (0.66). Measurements between previously surveyed georeferenced points and remotely-sensed kelp grid cells (low-resolution validation) showed that 66% of the georeferenced points had grid cells indicating kelp presence within a linear distance of 300 m. We employed the KD in our kelp filter algorithm to estimate the global extent of giant kelp and intertidal green algae per marine ecoregion and province, producing a high-resolution global map of giant kelp and intertidal green algae, powered by Google Earth Engine.

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Vedenin, Andrey A., Eteri I. Musaeva, Daria N. Zasko y Alexander L. Vereshchaka. "Zooplankton communities in the Drake Passage through environmental boundaries: a snapshot of 2010, early spring". PeerJ 7 (7 de noviembre de 2019): e7994. http://dx.doi.org/10.7717/peerj.7994.

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Background Spatial distribution of zooplankton communities influenced by various environmental factors is always important for understanding pelagic ecosystems. The area of the Drake Passage (Southern Ocean) is of particular interest owing to the high spatial and temporal variability of hydrological parameters affecting marine fauna. This study provides a survey of zooplankton composition and spatial distribution along a transect in the Drake Passage sampled during the 31th Cruise of RV “Akademik Sergey Vavilov” in November, 2010. The main aim was to trace the main regularities in spatial zooplankton structure and its relationships with the environmental parameters. Methodology A total of 43 vertical hauls from the surface to 1,000 m depth were made at 13 stations using the Juday plankton net. 60 taxa were recorded, abundance and biomass of each were assessed. Environmental parameters including temperature, salinity, depth, horizontal distance between stations and surface chlorophyll concentration were tested as environmental factors possibly explaining plankton distribution. Results Higher zooplankton abundance and biomass with lower diversity were observed near the Polar Front. Cluster analysis revealed five different groups of zooplankton samples, four of which were arranged mostly by depth. Along the transect within the 1,000 m depth range, the qualitative taxonomical composition differed significantly with depth and to some extent differed also among horizontal hydrological regimes, while the quantitative structure of the communities (abundance of taxa) was mainly determined by depth. Plankton assemblages within the upper 300-m layer depended on hydrological fronts. Abundance of dominant taxa as well as total zooplankton abundance showed a clear correlation with depth, salinity and surface chlorophyll concentration. Some taxa also showed correlations with temperature and latitude. Between the stations the similarity in zooplankton structure was clearly dependent on the distance among them which indicates an importance of latitudinal gradient. Surface chlorophyll concentration was not correlated with zooplankton biomass, which can be explained by the uncompleted seasonal migrations of zooplankton from deeper waters in early spring.

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Laufkötter, C., M. Vogt, N. Gruber, M. Aita-Noguchi, O. Aumont, L. Bopp, E. Buitenhuis et al. "Drivers and uncertainties of future global marine primary production in marine ecosystem models". Biogeosciences 12, n.º 23 (7 de diciembre de 2015): 6955–84. http://dx.doi.org/10.5194/bg-12-6955-2015.

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Abstract. Past model studies have projected a global decrease in marine net primary production (NPP) over the 21st century, but these studies focused on the multi-model mean rather than on the large inter-model differences. Here, we analyze model-simulated changes in NPP for the 21st century under IPCC's high-emission scenario RCP8.5. We use a suite of nine coupled carbon–climate Earth system models with embedded marine ecosystem models and focus on the spread between the different models and the underlying reasons. Globally, NPP decreases in five out of the nine models over the course of the 21st century, while three show no significant trend and one even simulates an increase. The largest model spread occurs in the low latitudes (between 30° S and 30° N), with individual models simulating relative changes between −25 and +40 %. Of the seven models diagnosing a net decrease in NPP in the low latitudes, only three simulate this to be a consequence of the classical interpretation, i.e., a stronger nutrient limitation due to increased stratification leading to reduced phytoplankton growth. In the other four, warming-induced increases in phytoplankton growth outbalance the stronger nutrient limitation. However, temperature-driven increases in grazing and other loss processes cause a net decrease in phytoplankton biomass and reduce NPP despite higher growth rates. One model projects a strong increase in NPP in the low latitudes, caused by an intensification of the microbial loop, while NPP in the remaining model changes by less than 0.5 %. While models consistently project increases NPP in the Southern Ocean, the regional inter-model range is also very substantial. In most models, this increase in NPP is driven by temperature, but it is also modulated by changes in light, macronutrients and iron as well as grazing. Overall, current projections of future changes in global marine NPP are subject to large uncertainties and necessitate a dedicated and sustained effort to improve the models and the concepts and data that guide their development.

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Laufkötter, C., M. Vogt, N. Gruber, M. Aita-Noguchi, O. Aumont, L. Bopp, E. Buitenhuis et al. "Drivers and uncertainties of future global marine primary production in marine ecosystem models". Biogeosciences Discussions 12, n.º 4 (27 de febrero de 2015): 3731–824. http://dx.doi.org/10.5194/bgd-12-3731-2015.

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Abstract. Past model studies have projected a global decrease in marine net primary production (NPP) over the 21st century, but these studies focused on the multi-model mean and mostly ignored the large inter-model differences. Here, we analyze model simulated changes of NPP for the 21st century under IPCC's high emission scenario RCP8.5 using a suite of nine coupled carbon–climate Earth System Models with embedded marine ecosystem models with a focus on the spread between the different models and the underlying reasons. Globally, five out of the nine models show a decrease in NPP over the course of the 21st century, while three show no significant trend and one even simulates an increase. The largest model spread occurs in the low latitudes (between 30° S and 30° N), with individual models simulating relative changes between −25 and +40%. In this region, the inter-quartile range of the differences between the 2012–2031 average and the 2081–2100 average is up to 3 mol C m-2 yr-1. These large differences in future change mirror large differences in present day NPP. Of the seven models diagnosing a net decrease in NPP in the low latitudes, only three simulate this to be a consequence of the classical interpretation, i.e., a stronger nutrient limitation due to increased stratification and reduced upwelling. In the other four, warming-induced increases in phytoplankton growth outbalance the stronger nutrient limitation. However, temperature-driven increases in grazing and other loss processes cause a net decrease in phytoplankton biomass and reduces NPP despite higher growth rates. One model projects a strong increase in NPP in the low latitudes, caused by an intensification of the microbial loop, while the remaining model simulates changes of less than 0.5%. While there is more consistency in the modeled increase in NPP in the Southern Ocean, the regional inter-model range is also very substantial. In most models, this increase in NPP is driven by temperature, but is also modulated by changes in light, macronutrients and iron as well as grazing. Overall, current projections of future changes in global marine NPP are subject to large uncertainties and necessitate a dedicated and sustained effort to improve the models and the concepts and data that guide their development.

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Mace, Gerald G., Sally Benson, Ruhi Humphries, Peter M. Gombert y Elizabeth Sterner. "Natural marine cloud brightening in the Southern Ocean". Atmospheric Chemistry and Physics 23, n.º 2 (1 de febrero de 2023): 1677–85. http://dx.doi.org/10.5194/acp-23-1677-2023.

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Abstract. The number of cloud droplets per unit volume (Nd) is a fundamentally important property of marine boundary layer (MBL) liquid clouds that, at constant liquid water path, exerts considerable controls on albedo. Past work has shown that regional Nd has a direct correlation to marine primary productivity (PP) because of the role of seasonally varying, biogenically derived precursor gases in modulating secondary aerosol properties. These linkages are thought to be observable over the high-latitude oceans, where strong seasonal variability in aerosol and meteorology covary in mostly pristine environments. Here, we examine Nd variability derived from 5 years of MODIS Level 2-derived cloud properties in a broad region of the summer eastern Southern Ocean and adjacent marginal seas. We demonstrate latitudinal, longitudinal and temporal gradients in Nd that are strongly correlated with the passage of air masses over high-PP waters that are mostly concentrated along the Antarctic Shelf poleward of 60∘ S. We find that the albedo of MBL clouds in the latitudes south of 60∘ S is significantly higher than similar liquid water path (LWP) clouds north of this latitude.

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Bednaršek, N., J. Možina, M. Vogt, C. O'Brien y G. A. Tarling. "The global distribution of pteropods and their contribution to carbonate and carbon biomass in the modern ocean". Earth System Science Data 4, n.º 1 (10 de diciembre de 2012): 167–86. http://dx.doi.org/10.5194/essd-4-167-2012.

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Abstract. Pteropods are a group of holoplanktonic gastropods for which global biomass distribution patterns remain poorly described. The aim of this study was to collect and synthesise existing pteropod (Gymnosomata, Thecosomata and Pseudothecosomata) abundance and biomass data, in order to evaluate the global distribution of pteropod carbon biomass, with a particular emphasis on temporal and spatial patterns. We collected 25 939 data points from several online databases and 41 scientific articles. These data points corresponded to observations from 15 134 stations, where 93% of observations were of shelled pteropods (Thecosomata) and 7% of non-shelled pteropods (Gymnosomata). The biomass data has been gridded onto a 360 × 180° grid, with a vertical resolution of 33 depth levels. Both the raw data file and the gridded data in NetCDF format can be downloaded from PANGAEA, doi:10.1594/PANGAEA.777387. Data were collected between 1950–2010, with sampling depths ranging from 0–2000 m. Pteropod biomass data was either extracted directly or derived through converting abundance to biomass with pteropod-specific length to carbon biomass conversion algorithms. In the Northern Hemisphere (NH), the data were distributed quite evenly throughout the year, whereas sampling in the Southern Hemisphere (SH) was biased towards winter and summer values. 86% of all biomass values were located in the NH, most (37%) within the latitudinal band of 30–60° N. The range of global biomass values spanned over four orders of magnitude, with mean and median (non-zero) biomass values of 4.6 mg C m−3 (SD = 62.5) and 0.015 mg C m−3, respectively. The highest mean biomass was located in the SH within the 70–80° S latitudinal band (39.71 mg C m−3, SD = 93.00), while the highest median biomass was in the NH, between 40–50° S (0.06 mg C m−3, SD = 79.94). Shelled pteropods constituted a mean global carbonate biomass of 23.17 mg CaCO3 m−3 (based on non-zero records). Total biomass values were lowest in the equatorial regions and equally high at both poles. Pteropods were found at least to depths of 1000 m, with the highest biomass values located in the surface layer (0–10 m) and gradually decreasing with depth, with values in excess of 100 mg C m−3 only found above 200 m depth. Tropical species tended to concentrate at greater depths than temperate or high-latitude species. Global biomass levels in the NH were relatively invariant over the seasonal cycle, but more seasonally variable in the SH. The collected database provides a valuable tool for modellers for the study of marine ecosystem processes and global biogeochemical cycles. By extrapolating regional biomass to a global scale, we established global pteropod biomass to add up to 500 Tg C.

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33

Huber, Brian T., Maria Rose Petrizzo y Kenneth G. MacLeod. "Planktonic Foraminiferal Endemism at Southern High Latitudes Following the Terminal Cretaceous Extinction". Journal of Foraminiferal Research 50, n.º 4 (1 de octubre de 2020): 382–402. http://dx.doi.org/10.2113/gsjfr.50.4.382.

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Abstract Austral planktonic foraminiferal assemblages from immediately above the Cretaceous/Paleogene (K/Pg) boundary at Ocean Drilling Program Hole 690C (Maud Rise, Weddell Sea) and International Ocean Drilling Program Hole U1514C (southeast Indian Ocean) show a much different record of post-extinction recovery than anywhere outside the circum-Antarctic region. Species of Woodringina and Parvularugoglobigerina, genera with well-documented evolutionary successions within the early Danian P0 and Pα biozones at tropical/subtropical and mid-latitude localities, are absent from southern high latitude sequences. This study proposes new criteria for biostratigraphic correlation of the lowermost Danian Antarctic Paleocene AP0 and AP1 Zones using stratophenetic observations from Scanning Electron Microscope images of lower Danian planktonic foraminifera at deep-sea sites in the southern South Atlantic and southern Indian Ocean. The small but distinctive species Turborotalita nikolasi (Koutsoukos) is a highly reliable index species for the lowermost Danian as it consistently occurs immediately above the K/Pg boundary at multiple southern high latitude sites, which is consistent with its distribution at middle and low latitudes. Also useful for cross-latitude correlation is Parasubbotina neanika n. sp., which first appears within the lowermost Danian worldwide. The geographic distribution of the New Zealand species Antarcticella pauciloculata (Jenkins) and Zeauvigerina waiparaensis (Jenkins), as well as Eoglobigerina maudrisensis n. sp. from just above the K/Pg in the southern South Atlantic and southern Indian Ocean, helps define the extent of the Austral Biogeographic Province and provides evidence for marine communication via marine seaways across Antarctica. While An. pauciloculata was previously considered a benthic species, new stable isotope evidence demonstrates that it lived a planktonic mode of life. It is possible this species evolved from a benthic ancestor and that the benthic to planktonic transition occurred through an intermediate tychopelagic lifestyle at a time when calcareous plankton were less abundant as a result of the terminal Cretaceous mass extinction.

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34

Moline, Mark A., Nina J. Karnovsky, Zachary Brown, George J. Divoky, Thomas K. Frazer, Charles A. Jacoby, Joseph J. Torres y William R. Fraser. "High Latitude Changes in Ice Dynamics and Their Impact on Polar Marine Ecosystems". Annals of the New York Academy of Sciences 1134, n.º 1 (junio de 2008): 267–319. http://dx.doi.org/10.1196/annals.1439.010.

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35

Hunt, George L., Kenneth F. Drinkwater, Kevin Arrigo, Jørgen Berge, Kendra L. Daly, Seth Danielson, Malin Daase et al. "Advection in polar and sub-polar environments: Impacts on high latitude marine ecosystems". Progress in Oceanography 149 (diciembre de 2016): 40–81. http://dx.doi.org/10.1016/j.pocean.2016.10.004.

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36

Colombo, Stefanie M., Alexander Wacker, Christopher C. Parrish, Martin J. Kainz y Michael T. Arts. "A fundamental dichotomy in long-chain polyunsaturated fatty acid abundance between and within marine and terrestrial ecosystems". Environmental Reviews 25, n.º 2 (junio de 2017): 163–74. http://dx.doi.org/10.1139/er-2016-0062.

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Polyunsaturated fatty acids (PUFA), especially long-chain (i.e., ≥20 carbons) polyunsaturated fatty acids (LC-PUFA), are fundamental to the health and survival of marine and terrestrial organisms. Therefore, it is imperative that we gain a better understanding of their origin, abundance, and transfer between and within these ecosystems. We evaluated the natural variation in PUFA distribution and abundance that exists between and within these ecosystems by amassing and analyzing, using multivariate and analysis of variance (ANOVA) methods, >3000 fatty acid (FA) profiles from marine and terrestrial organisms. There was a clear dichotomy in LC-PUFA abundance between organisms in marine and terrestrial ecosystems, mainly driven by the C18 PUFA in terrestrial organisms and omega-3 (n-3) LC-PUFA in marine organisms. The PUFA content of an organism depended on both its biome (marine vs terrestrial) and taxonomic group. Within the marine biome, the PUFA content varied among taxonomic groups. PUFA content of marine organisms was dependent on both geographic zone (i.e., latitude, and thus broadly related to temperature) and trophic level (a function of diet). The contents of n-3 LC-PUFA were higher in polar and temperate marine organisms than those from the tropics. Therefore, we conclude that, on a per capita basis, high latitude marine organisms provide a disproportionately large global share of these essential nutrients to consumers, including terrestrial predators. Our analysis also hints at how climate change, and other anthropogenic stressors, might act to negatively impact the global distribution and abundance of n-3 LC-PUFA within marine ecosystems and on the terrestrial consumers that depend on these subsidies.

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37

Brandt, A., J. A. Crame, H. Polz y M. R. A. Thomson. "Late Jurassic tethyan ancestry of Recent southern high-latitude marine isopods (Crustacea, Malacostraca)". Palaeontology 42, n.º 4 (agosto de 1999): 663–75. http://dx.doi.org/10.1111/1475-4983.00090.

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38

Carballeira, Rafael y Xabier Pontevedra-Pombal. "Diatoms in Paleoenvironmental Studies of Peatlands". Quaternary 3, n.º 2 (1 de abril de 2020): 10. http://dx.doi.org/10.3390/quat3020010.

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The great diversity of diatoms in aquatic ecosystems and their close relationship with water chemistry make them one of the most informative and widely used biological proxies in paleoenvironmental studies of wetlands, except for peatland ecosystems. Currently, significant controversy still exists over the preservation of diatoms in peat. However, considerable evidence indicates that diatoms remain in good condition in minerotrophic peatlands, and they have been successfully used in paleoenvironmental studies in high-latitude regions and especially in Southern Europe.

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39

Whalen, Matthew A., Ross D. B. Whippo, John J. Stachowicz, Paul H. York, Erin Aiello, Teresa Alcoverro, Andrew H. Altieri et al. "Climate drives the geography of marine consumption by changing predator communities". Proceedings of the National Academy of Sciences 117, n.º 45 (26 de octubre de 2020): 28160–66. http://dx.doi.org/10.1073/pnas.2005255117.

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The global distribution of primary production and consumption by humans (fisheries) is well-documented, but we have no map linking the central ecological process of consumption within food webs to temperature and other ecological drivers. Using standardized assays that span 105° of latitude on four continents, we show that rates of bait consumption by generalist predators in shallow marine ecosystems are tightly linked to both temperature and the composition of consumer assemblages. Unexpectedly, rates of consumption peaked at midlatitudes (25 to 35°) in both Northern and Southern Hemispheres across both seagrass and unvegetated sediment habitats. This pattern contrasts with terrestrial systems, where biotic interactions reportedly weaken away from the equator, but it parallels an emerging pattern of a subtropical peak in marine biodiversity. The higher consumption at midlatitudes was closely related to the type of consumers present, which explained rates of consumption better than consumer density, biomass, species diversity, or habitat. Indeed, the apparent effect of temperature on consumption was mostly driven by temperature-associated turnover in consumer community composition. Our findings reinforce the key influence of climate warming on altered species composition and highlight its implications for the functioning of Earth’s ecosystems.

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40

Lamy, Frank, Dierk Hebbeln y Gerold Wefer. "High-Resolution Marine Record of Climatic Change in Mid-latitude Chile during the Last 28,000 Years Based on Terrigenous Sediment Parameters". Quaternary Research 51, n.º 1 (enero de 1999): 83–93. http://dx.doi.org/10.1006/qres.1998.2010.

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AbstractMarine sediment cores from the continental slope off mid-latitude Chile (33°S) were studied with regard to grain-size distributions and clay mineral composition. The data provide a 28,000-yr14C accelerator mass spectrometry-dated record of variations in the terrigenous sediment supply reflecting modifications of weathering conditions and sediment source areas in the continental hinterland. These variations can be interpreted in terms of the paleoclimatic evolution of mid-latitude Chile and are compared to existing terrestrial records. Glacial climates (28,000–18,000 cal yr B.P.) were generally cold–humid with a cold–semiarid interval between 26,000 and 22,000 cal yr B.P. The deglaciation was characterized by a trend toward more arid conditions. During the middle Holocene (8000–4000 cal yr B.P.), comparatively stable climatic conditions prevailed with increased aridity in the Coastal Range. The late Holocene (4000–0 cal yr B.P.) was marked by more variable paleoclimates with generally more humid conditions. Variations of rainfall in mid-latitude Chile are most likely controlled by shifts of the latitudinal position of the Southern Westerlies. Compared to the Holocene, the southern westerly wind belt was located significantly farther north during the last glacial maximum. Less important variations of the latitudinal position of the Southern Westerlies also occurred on shorter time scales.

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41

Holst, T., A. Arneth, S. Hayward, A. Ekberg, M. Mastepanov, M. Jackowicz-Korczynski, T. Friborg, P. M. Crill y K. Bäckstrand. "BVOC ecosystem flux measurements at a high latitude wetland site". Atmospheric Chemistry and Physics Discussions 8, n.º 6 (18 de diciembre de 2008): 21129–69. http://dx.doi.org/10.5194/acpd-8-21129-2008.

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Abstract. In this study, we present summertime concentrations and fluxes of biogenic volatile organic compounds (BVOCs) measured at a sub-arctic wetland in northern Sweden using a disjunct eddy-covariance (DEC) technique based on a proton transfer reaction mass spectrometer (PTR-MS). The vegetation at the site was dominated by Sphagnum, Carex and Eriophorum spp. The performance of the DEC system was assessed by comparing H3O+-ion cluster formed with water molecules (H3O+(H2O) at m37) with water vapour concentration measurements made using an adjacent humidity sensor, and from a comparison of sensible heat fluxes for high frequency and DEC data obtained from the sonic anemometer. These analyses showed no significant PTR-MS sensor drift over a period of several weeks and only a small flux-loss due to high-frequency spectrum omissions. This loss was within the range expected from other studies and the theoretical considerations. Standardised (20°C and 1000 μmol m−2 s−1 PAR) summer isoprene emission rates of 323 μg C m−2 (ground area) h−1 were comparable with findings from more southern boreal forests, and fen-like ecosystems. On a diel scale, measured fluxes indicated a stronger temperature dependence when compared with emissions from temperate or (sub)tropical ecosystems. For the first time, to our knowledge, we report ecosystem methanol fluxes from a sub-arctic ecosystem. Maximum daytime emission fluxes were around 270 μg m−2 h−1 (ca. 100 μg C m−2 h-1) and measurements indicated some nocturnal deposition. The measurements reported here covered a period of 50 days (1 August to 19 September 2006), approximately one half of the growing season at the site, and allowed to investigate the effect of vegetation senescence on daily BVOC fluxes and on their temperature and light responses. Long-term measurements of BVOC are still lacking for nearly all ecosystems and only a very few studies about seasonal or even interannual variation of BVOC emissions have been published so far, particularly for northern ecosystems. The results presented here will be useful for testing process understanding obtained in laboratory studies and for model evaluation, improving our understanding of biogeochemical cycles in a region which is likely to be sensitive to climate change and currently undergoes rapid changes due to global warming.

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42

Bell, Phil R., Federico Fanti, Mark T. Mitchell y Philip J. Currie. "Marine reptiles (Plesiosauria and Mosasauridae) from the Puskwaskau Formation (Santonian–Campanian), west-central Alberta". Journal of Paleontology 88, n.º 1 (enero de 2014): 187–94. http://dx.doi.org/10.1666/13-043.

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Plesiosaurs and mosasaurs are identified from the Puskwaskau Formation of west-central Alberta, Canada. These deposits record the final stages during which the Western Interior Seaway remained open to the Boreal Sea to the North and therefore are important for determining the ranges of high-latitude marine reptiles. Polycotylid and elasmosaurid plesiosaurs shared these waters with russellosaurine (including plioplatecarpine) mosasaurs suggesting a diverse ecology of large-bodied marine predators occupied these high-latitude waters in the early Campanian. This locality, situated at 65°N paleolatitude, helps link the poorly known faunas from northern Canada with the better-known faunas from central and southern North America. Rare articulated material from the Puskwaskau Formation urges further investigation of this poorly explored unit.

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43

Varela, Augusto Nicolás, María Sol Raigemborn, Patricio Emmanuel Santamarina, Sabrina Lizzoli, Thierry Adatte y Ulrich Heimhofer. "Carbon Isotopic Signature and Organic Matter Composition of Cenomanian High-Latitude Paleosols of Southern Patagonia". Geosciences 11, n.º 9 (8 de septiembre de 2021): 378. http://dx.doi.org/10.3390/geosciences11090378.

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The Cenomanian Mata Amarilla Formation (MAF) in southern Patagonia (~55° S paleolatitude, Austral-Magallanes Basin, Argentina) is composed mainly of stacked fluvial deposits with intercalated paleosols, which document Cenomanian environments at high-paleolatitudes in the Southern Hemisphere. We performed a multiproxy study of the paleosols and sediments of the MAF in order to (1) understand the composition of the soil- and sediment-derived organic matter (OM), (2) apply carbon isotope stratigraphy as a tool to correlate patterns obtained from the MAF with existing marine and non-marine δ13Corg records worldwide, and (3) investigate the relationship between variations in spore-pollen assemblages of the MAF and the climatic conditions prevailing in the Cenomanian Southern Hemisphere. An integrated dataset was generated, including total organic carbon content, Rock-Eval pyrolysis data, stable isotope (δ13Corg) composition, and palynological data, combined with published paleosol-derived mean annual temperatures and mean annual precipitations. The results indicated that the OM preserved in the MAF paleosols allowed its use as a chemostratigraphic tool. The MAF δ13Corg curve showed the rather stable pattern characteristic for the Early to Late Cenomanian interval. The absence of the major positive carbon isotope excursion associated with oceanic anoxic event 2 provided an upper limit for the stratigraphic range of the MAF. The palynological data suggested the development of fern prairies during warmer and moister periods at the expense of the background gymnosperm-dominated forests. Overall, the multiproxy record provided new insights into the long-term environmental conditions during the Cenomanian in the high latitudes of the Southern Hemisphere.

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44

Douglas, Marianne S. V. "Environmental Change at High Latitudes". Paleontological Society Papers 13 (octubre de 2007): 169–79. http://dx.doi.org/10.1017/s1089332600001522.

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Paleolimnological techniques have been used successfully to reconstruct environmental change in the Arctic and Antarctic. Diatoms are powerful indicators of environmental change because their community composition responds to changes in environmental conditions. As more regional diatom calibrations throughout the high latitude regions are achieved, the autecology of diatom taxa can be quantified and transfer functions for the driving environmental variables developed. In most instances, environmental variables related to physical, chemical, and climate-related characteristics are the main drivers affecting diatom distribution across polar aquatic bodies. A decline in ice cover and increase in growing season length results in an increase in diatom diversity as well as increased productivity, and increased thermal stratification in lakes (vs. shallow ponds). Because the siliceous cell wall preserves well in sediments, diatoms are among the most commonly used organisms used in paleolimnological analyses. Polar latitudes are experiencing amplification of the current global warming trend and as such, analyses of diatoms from high latitude lake and pond sediments are revealing the timing and extent of these trends. Diatom-based paleolimnological analyses are also being used to track the environmental impact of excess nutrient additions to lakes. Similar findings have also been reported from marine ecosystems.

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45

Verwega, Maria-Theresia, Christopher J. Somes, Markus Schartau, Robyn Elizabeth Tuerena, Anne Lorrain, Andreas Oschlies y Thomas Slawig. "Description of a global marine particulate organic carbon-13 isotope data set". Earth System Science Data 13, n.º 10 (26 de octubre de 2021): 4861–80. http://dx.doi.org/10.5194/essd-13-4861-2021.

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Abstract. Marine particulate organic carbon stable isotope ratios (δ13CPOC) provide insights into understanding carbon cycling through the atmosphere, ocean and biosphere. They have for example been used to trace the input of anthropogenic carbon in the marine ecosystem due to the distinct isotopically light signature of anthropogenic emissions. However, δ13CPOC is also significantly altered during photosynthesis by phytoplankton, which complicates its interpretation. For such purposes, robust spatio-temporal coverage of δ13CPOC observations is essential. We collected all such available data sets and merged and homogenized them to provide the largest available marine δ13CPOC data set (https://doi.org/10.1594/PANGAEA.929931; Verwega et al., 2021). The data set consists of 4732 data points covering all major ocean basins beginning in the 1960s. We describe the compiled raw data, compare different observational methods, and provide key insights in the temporal and spatial distribution that is consistent with previously observed large-scale patterns. The main different sample collection methods (bottle, intake, net, trap) are generally consistent with each other when comparing within regions. An analysis of 1990s median δ13CPOC values in a meridional section across the best-covered Atlantic Ocean shows relatively high values (≥-22 ‰) in the low latitudes (<30∘) trending towards lower values in the Arctic Ocean (∼-24 ‰) and Southern Ocean (≤-28 ‰). The temporal trend since the 1960s shows a decrease in the median δ13CPOC by more than 3 ‰ in all basins except for the Southern Ocean, which shows a weaker trend but contains relatively poor multi-decadal coverage.

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46

Barnes, D. K. A., M. A. Collins, P. Brickle, P. Fretwell, H. J. Griffiths, D. Herbert, O. T. Hogg y C. J. Sands. "The need to implement the Convention on Biological Diversity at the high latitude site, South Georgia". Antarctic Science 23, n.º 4 (5 de abril de 2011): 323–31. http://dx.doi.org/10.1017/s0954102011000253.

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AbstractThe multilateral failure to apply the Convention on Biological Diversity (CBD) by the target year 2010 was headline news as are the accelerating climatic changes which dictate its urgency. Some ecosystems that are vulnerable to anthropogenic change have few species listed as endangered because too little is known about their biota. The highest vulnerability may correspond to where hotspots of species endemism, range limits and physiological sensitivity overlap with areas of most rapid physical change. The old, large and remote archipelago of South Georgia is one such location. Sea-surface temperatures around South Georgia are amongst the most rapidly warming reported. Furthermore oceanographic projections are highlighting the region as extremely vulnerable to ocean acidification. We outline the first polar Darwin Initiative project and the technical advances in generating an interactive and fully integrated georeferenced map of marine biodiversity, seabed topography and physical oceanography at South Georgia. Mapping marine mega and macro-faunal biodiversity onto multiple physical variables has rarely been attempted. This should provide a new tool in assessing the processes driving biological variability, the importance of marine areas in terms of ecosystem services, the threats and vulnerabilities of Polar Regions and should greatly aid implementation of the CBD.

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47

Laufkötter, Charlotte, Meike Vogt, Nicolas Gruber, Olivier Aumont, Laurent Bopp, Scott C. Doney, John P. Dunne et al. "Projected decreases in future marine export production: the role of the carbon flux through the upper ocean ecosystem". Biogeosciences 13, n.º 13 (14 de julio de 2016): 4023–47. http://dx.doi.org/10.5194/bg-13-4023-2016.

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Abstract. Accurate projections of marine particle export production (EP) are crucial for predicting the response of the marine carbon cycle to climate change, yet models show a wide range in both global EP and their responses to climate change. This is, in part, due to EP being the net result of a series of processes, starting with net primary production (NPP) in the sunlit upper ocean, followed by the formation of particulate organic matter and the subsequent sinking and remineralisation of these particles, with each of these processes responding differently to changes in environmental conditions. Here, we compare future projections in EP over the 21st century, generated by four marine ecosystem models under the high emission scenario Representative Concentration Pathways (RCP) 8.5 of the Intergovernmental Panel on Climate Change (IPCC), and determine the processes driving these changes. The models simulate small to modest decreases in global EP between −1 and −12 %. Models differ greatly with regard to the drivers causing these changes. Among them, the formation of particles is the most uncertain process with models not agreeing on either magnitude or the direction of change. The removal of the sinking particles by remineralisation is simulated to increase in the low and intermediate latitudes in three models, driven by either warming-induced increases in remineralisation or slower particle sinking, and show insignificant changes in the remaining model. Changes in ecosystem structure, particularly the relative role of diatoms matters as well, as diatoms produce larger and denser particles that sink faster and are partly protected from remineralisation. Also this controlling factor is afflicted with high uncertainties, particularly since the models differ already substantially with regard to both the initial (present-day) distribution of diatoms (between 11–94 % in the Southern Ocean) and the diatom contribution to particle formation (0.6–3.8 times higher than their contribution to biomass). As a consequence, changes in diatom concentration are a strong driver for EP changes in some models but of low significance in others. Observational and experimental constraints on ecosystem structure and how the fixed carbon is routed through the ecosystem to produce export production are urgently needed in order to improve current generation ecosystem models and their ability to project future changes.

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48

Laufkötter, C., M. Vogt, N. Gruber, O. Aumont, L. Bopp, S. C. Doney, J. P. Dunne et al. "Projected decreases in future marine export production: the role of the carbon flux through the upper ocean ecosystem". Biogeosciences Discussions 12, n.º 23 (14 de diciembre de 2015): 19941–98. http://dx.doi.org/10.5194/bgd-12-19941-2015.

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Abstract. Accurate projections of marine particle export production (EP) are crucial for predicting the response of the marine carbon cycle to climate change, yet models show a wide range in both global EP and their responses to climate change. This is, in part, due to EP being the net result of a series of processes, starting with net primary production (NPP) in the sunlit upper ocean, followed by the formation of particulate organic matter and the subsequent sinking and remineralization of these particles, with each of these processes responding differently to changes in environmental conditions. Here, we compare future projections in EP over the 21st century, generated by four marine ecosystem models under IPCC's high emission scenario RCP8.5, and determine the processes driving these changes. The models simulate small to modest decreases in global EP between −1 and −12 %. Models differ greatly with regard to the drivers causing these changes. Among them, the formation of particles is the most uncertain process with models not agreeing on either magnitude or the direction of change. The removal of the sinking particles by remineralization is simulated to increase in the low and intermediate latitudes in three models, driven by either warming-induced increases in remineralization or slower particle sinking, and show insignificant changes in the remaining model. Changes in ecosystem structure, particularly the relative role of diatoms matters as well, as diatoms produce larger and denser particles that sink faster and are partly protected from remineralization. Also this controlling factor is afflicted with high uncertainties, particularly since the models differ already substantially with regard to both the initial (present-day) distribution of diatoms (between 11–94 % in the Southern Ocean) and the diatom contribution to particle formation (0.6–3.8 times lower/higher than their contribution to biomass). As a consequence, changes in diatom concentration are a strong driver for EP changes in some models but of low significance in others. Observational and experimental constraints on ecosystem structure and how the fixed carbon is routed through the ecosystem to produce export production are urgently needed in order to improve current generation ecosystem models and their ability to project future changes.

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49

Jones, Miranda C. y William W. L. Cheung. "Multi-model ensemble projections of climate change effects on global marine biodiversity". ICES Journal of Marine Science 72, n.º 3 (10 de octubre de 2014): 741–52. http://dx.doi.org/10.1093/icesjms/fsu172.

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Abstract Species distribution models (SDMs) are important tools to explore the effects of future global changes in biodiversity. Previous studies show that variability is introduced into projected distributions through alternative datasets and modelling procedures. However, a multi-model approach to assess biogeographic shifts at the global scale is still rarely applied, particularly in the marine environment. Here, we apply three commonly used SDMs (AquaMaps, Maxent, and the Dynamic Bioclimate Envelope Model) to assess the global patterns of change in species richness, invasion, and extinction intensity in the world oceans. We make species-specific projections of distribution shift using each SDM, subsequently aggregating them to calculate indices of change across a set of 802 species of exploited marine fish and invertebrates. Results indicate an average poleward latitudinal shift across species and SDMs at a rate of 15.5 and 25.6 km decade−1 for a low and high emissions climate change scenario, respectively. Predicted distribution shifts resulted in hotspots of local invasion intensity in high latitude regions, while local extinctions were concentrated near the equator. Specifically, between 10°N and 10°S, we predicted that, on average, 6.5 species would become locally extinct per 0.5° latitude under the climate change emissions scenario Representative Concentration Pathway 8.5. Average invasions were predicted to be 2.0 species per 0.5° latitude in the Arctic Ocean and 1.5 species per 0.5° latitude in the Southern Ocean. These averaged global hotspots of invasion and local extinction intensity are robust to the different SDM used and coincide with high levels of agreement.

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50

C. Young, Euan. "Conservation values, research and New Zealand's responsibilities for the Southern Ocean Islands and Antarctica". Pacific Conservation Biology 2, n.º 1 (1995): 99. http://dx.doi.org/10.1071/pc950099.

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New Zealand has direct responsibility for the conservation and protection of five subantarctic island groups (Snares, Bounty, Antipodes, Auckland and Campbell), all of which are protected within National reserves. New Zealand also claims the Ross Dependency in Antarctica sharing conservation responsibility with others within the Antarctic Treaty regime. The subantarctic islands' ecosystems are of interest for their range of species, for their dependence on marine nutrients, for their vulnerability to introduction by alien species, and for illustrating the outcomes of independent evolutionary experiments. Each is characterized by a unique assemblage of plant and animal species, of which the diversity of oceanic birds (especially their albatrosses, petrels and penguins) and of the changes with latitude of their vegetation cover is internationally regarded. They form an interesting contrast to the sparse biota of the Balleny Islands and continental Antarctica. The fauna and flora on these subantarctic islands are now substantially catalogued and the impact of alien species in part understood, but ecological studies have been hampered by isolation and difficult access. Ecological research is needed to ensure that management strategies for each island are well founded on an understanding of their individual ecosystems. By way of contrast, ecological research has flourished in Antarctica with many long-term programmes. This difference is attributed to the way research is promoted and supported in the two regions.

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