A kleptoplastidic dinoflagellate and the tipping point between transient and fully integrated plastid endosymbiosis

Plastid endosymbiosis has been a major force in the evolution of eukaryotic cellular complexity, but how endosymbionts are integrated is still poorly understood at a mechanistic level. Dinoflagellates, an ecologically important protist lineage, represent a unique model to study this process because dinoflagellate plastids have repeatedly been reduced, lost, and replaced by new plastids, leading to a spectrum of ages and integration levels. Here we describe deep-transcriptomic analyses of the Antarctic Ross Sea dinoflagellate (RSD), which harbors long-term but temporary kleptoplasts stolen from haptophyte prey, and is closely related to dinoflagellates with fully integrated plastids derived from different haptophytes. In some members of this lineage, called the Kareniaceae, their tertiary haptophyte plastids have crossed a tipping point to stable integration, but RSD has not, and may therefore reveal the order of events leading up to endosymbiotic integration. We show that RSD has retained its ancestral secondary plastid and has partitioned functions between this plastid and the kleptoplast. It has also obtained genes for kleptoplast-targeted proteins via horizontal gene transfer (HGT) that are not derived from the kleptoplast lineage. Importantly, many of these HGTs are also found in the related species with fully integrated plastids, which provides direct evidence that genetic integration preceded organelle fixation. Finally, we find that expression of kleptoplast-targeted genes is unaffected by environmental parameters, unlike prey-encoded homologs, suggesting that kleptoplast-targeted HGTs have adapted to posttranscriptional regulation mechanisms of the host.

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A 1000-year record of Adélie penguin diets in the southern Ross Sea

Antarctic Science ◽

10.1017/s0954102002000184 ◽

2002 ◽

Vol 14 (4) ◽

pp. 327-332 ◽

Cited By ~ 33

Author(s):

MICHAEL POLITO ◽

STEVEN D. EMSLIE ◽

WILLIAM WALKER

Keyword(s):

Ross Sea ◽

Prey Selection ◽

Ice Age ◽

Adélie Penguin ◽

Pleuragramma Antarcticum ◽

Adelie Penguin ◽

Radiocarbon Dates ◽

Antarctic Silverfish ◽

The Antarctic

Non-krill prey remains were recovered from ornithogenic sediments at three active Adélie penguin colonies on Ross Island, to assess long-term dietary trends in this species. Radiocarbon dates place the age of these deposits from a maximum of 947 years ago to the present. We identified 12 taxa of fish and two of squid with the Antarctic silverfish (Pleuragramma antarcticum) as the most abundant prey species represented at all sites. In addition, silverfish have decreased in importance in Adélie penguin diet over the past 600 years, perhaps in response to climate change since the onset of the Little Ice Age, though it remains much more abundant in current penguin diet in the Ross Sea than in the Antarctic Peninsula. Other prey taxa reflect the diversity of prey selection by Adélie penguins in Antarctica.

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Mass balance of the Antarctic ice sheet 1992–2016: reconciling results from GRACE gravimetry with ICESat, ERS1/2 and Envisat altimetry

Journal of Glaciology ◽

10.1017/jog.2021.8 ◽

2021 ◽

pp. 1-27

Author(s):

H. Jay Zwally ◽

John W. Robbins ◽

Scott B. Luthcke ◽

Bryant D. Loomis ◽

Frédérique Rémy

Keyword(s):

Mass Balance ◽

Antarctic Peninsula ◽

East Antarctica ◽

Mantle Material ◽

West Antarctica ◽

Mantle Viscosity ◽

Grounding Line ◽

The Antarctic ◽

Total Gain

Abstract GRACE and ICESat Antarctic mass-balance differences are resolved utilizing their dependencies on corrections for changes in mass and volume of the same underlying mantle material forced by ice-loading changes. Modeled gravimetry corrections are 5.22 times altimetry corrections over East Antarctica (EA) and 4.51 times over West Antarctica (WA), with inferred mantle densities 4.75 and 4.11 g cm−3. Derived sensitivities (Sg, Sa) to bedrock motion enable calculation of motion (δB0) needed to equalize GRACE and ICESat mass changes during 2003–08. For EA, δB0 is −2.2 mm a−1 subsidence with mass matching at 150 Gt a−1, inland WA is −3.5 mm a−1 at 66 Gt a−1, and coastal WA is only −0.35 mm a−1 at −95 Gt a−1. WA subsidence is attributed to low mantle viscosity with faster responses to post-LGM deglaciation and to ice growth during Holocene grounding-line readvance. EA subsidence is attributed to Holocene dynamic thickening. With Antarctic Peninsula loss of −26 Gt a−1, the Antarctic total gain is 95 ± 25 Gt a−1 during 2003–08, compared to 144 ± 61 Gt a−1 from ERS1/2 during 1992–2001. Beginning in 2009, large increases in coastal WA dynamic losses overcame long-term EA and inland WA gains bringing Antarctica close to balance at −12 ± 64 Gt a−1 by 2012–16.

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Dark metabolism: a molecular insight into how the Antarctic sea‐ice diatom Fragilariopsis cylindrus survives long‐term darkness

New Phytologist ◽

10.1111/nph.15843 ◽

2019 ◽

Vol 223 (2) ◽

pp. 675-691 ◽

Cited By ~ 10

Author(s):

Fraser Kennedy ◽

Andrew Martin ◽

John P. Bowman ◽

Richard Wilson ◽

Andrew McMinn

Keyword(s):

Sea Ice ◽

Antarctic Sea Ice ◽

Fragilariopsis Cylindrus ◽

Dark Metabolism ◽

The Antarctic ◽

Insight Into

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Influence of environmental conditions on spatial distribution and abundance of early life stages of Antarctic silverfish,Pleuragramma antarcticum(Nototheniidae), in the Ross Sea

Antarctic Science ◽

10.1017/s0954102009990721 ◽

2010 ◽

Vol 22 (3) ◽

pp. 243-254 ◽

Cited By ~ 31

Author(s):

Mario La Mesa ◽

Barbara Catalano ◽

Aniello Russo ◽

Silvio Greco ◽

Marino Vacchi ◽

...

Keyword(s):

Spatial Distribution ◽

Early Life ◽

General Circulation ◽

Ross Sea ◽

Life Stages ◽

Early Life Stages ◽

Pleuragramma Antarcticum ◽

Antarctic Silverfish ◽

The Antarctic ◽

Western Ross Sea

AbstractThe Antarctic silverfishPleuragramma antarcticumBoulenger is the dominant fish species in the high Antarctic zone, playing a key role in the Ross Sea midwater shelf ecosystem. Unlike other notothenioids, it is holoplanktonic species, spending its entire life cycle in the water column. Early life stages ofP. antarcticumare generally found in the upper 200 m and their spatial distribution is largely affected by water masses and general circulation. To understand better the mechanisms involved in the geographical distribution of the Antarctic silverfish within the western Ross Sea, an analysis of abundance and distribution was carried out in relation to oceanographic conditions. Samples were collected in summer during the 1998, 2000 and 2004 Italian cruises, covering the majority of the western sector of the Ross Sea. Overall 127 stations were sampled using standard plankton nets for biological samples and CTD and XBT to record abiotic parameters. Although all surveys were in December–January, the yearly results differed in terms of relative abundance of larval developmental stages and of oceanographic characteristics. The 1997–98 samples were characterized by very low abundance overall and by the virtual absence of early larvae. In summers 1999–2000 and 2003–04 the abundance ofP. antarcticumwas one order of magnitude higher than in the earlier season. In 1999–2000 catches were mainly composed of pre-flexion larvae and late postlarvae, while in 2003–04 catches were made up of pre-flexion larvae and juveniles. In January 2000 the Ross Sea summer polynya was fully open as the pack ice was almost completely melted, whereas in January 1998 and 2004 the opening of the polynya was considerably delayed. As a consequence, a delay in phytoplankton blooms and a decrease in primary production were observed in the summer seasons 1998 and 2004 with respect to 2000. The spatial distribution of early life stages, that were confined to the continental shelf and shelf break of the Ross Sea, generally appeared to be positively influenced by transition zones (oceanographic fronts). In addition, most of catches were recorded on or in close proximity to the banks (Pennell, Mawson, Ross and Crary) that characterize the continental shelf of the Ross Sea. On the basis of present findings and literature data, a link between the general circulation in the western Ross Sea and the distribution pattern of the early life stages ofP. antarcticumhas been developed.

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Holocene sediment transport and climate variability of offshore Adélie Land, East Antarctica

10.26686/wgtn.17058101 ◽

2021 ◽

Author(s):

◽

Anna Borisovna Albot

Keyword(s):

Grain Size ◽

Sea Ice ◽

Ross Sea ◽

Size Distributions ◽

Accumulation Rates ◽

Glacial Meltwater ◽

The Core ◽

Grain Size Distributions ◽

The Antarctic ◽

Mass Accumulation Rates

Grain size analysis of the terrigenous fraction of a laminated diatom ooze dating back to 11.4 kyr recovered offshore Adélie Land, East Antarctic margin was used to examine variations in sediment transport, depositional environments and Holocene climate variability at the location. Interpretations were assisted by additional proxies of primary productivity (δ¹³CFA, BSi%), glacial meltwater input (δDFA) and subsurface temperature (TEXL₈₆). Three lithologic intervals with distinct grain size distributions were identified. At ~11.4 ka the diatom ooze has a clear glacimarine influence which gradually decreases until ~8.2 ka. During this time interval, coincident with the early Holocene warm period, sediment is inferred to have been delivered by glacial meltwater plumes and ice-bergs in a calving bay environment. It is suggested that the glaciers in Adélie Land had retreated to their present day grounding lines by 8.2 ka, and from then on sediment was delivered to the site primarily via the Antarctic Coastal and Slope Front Currents, largely through a suspended sediment load and erosion of the surrounding banks. Enhanced biogenic mass accumulation rates and primary production at 8.2 ka suggest onset of warmer climatic conditions, coincident with the mid-Holocene Climatic Optimum. At ~4.5 ka, grain size distributions show a rapid increase in mud content coincident with a transient pulse of glacial meltwater and a sudden decrease in biogenic and terrigenous mass accumulation rates. The increased mud content is inferred to have been deposited under a reduced flow regime of the Antarctic Coastal and Slope Front Currents during the Neoglacial period that followed the final stages of deglaciation in the Ross Sea. It is hypothesised here that cessation of glacial retreat in the Ross Sea and the development of the modern day Ross Sea polynya resulted in enhanced Antarctic Surface Water production which led to increased sea ice growth in the Adélie Land region. The presence of sea ice led to reduced primary production and a decrease in the maximum current strength acting to advect coarser-sized terrigenous sediment to the core site during this time. Sedimentation rates appear to have a strong correlation with the El Niño Southern Oscillation (ENSO) over the last 8.2 kyr, and are inferred to be related to changing sea ice extent and zonal wind strength. Light laminae counts (biogenic bloom events) appear to decrease in frequency during time intervals dominated by El Niño events. Spectral analysis of the greyscale values of core photographs reveals peaks in the 2-7 year band, known ENSO periods, which increase in frequency in the mid-and-late Holocene. Spectral analyses of the sand percent and natural gamma ray (NGR, a measure of clay mineral input) content of the core reveal peaks in the ~40-60, 200-300, 600, 1200-1600 and 2200-2400 year bands. The most significant of these cycles in the NGR data is in 40-60 year band may be related to internal mass balance dynamics of the Mertz Glacier or to the expansion and contraction of the Antarctic circumpolar vortex. Cycles in the 200-300 and 2200-2400 year bands are related to known periods of solar variability, which have previously been found to regulate primary productivity in Antarctic coastal waters. Cycles in the 590-625 and 1200-1600 year bands have a strong signal through the entire record and are common features of Holocene climatic records, however the origin of these cycles is still under debate between solar forcing and an independent mode of internal ocean oscillation.

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Pathways and timescales of connectivity around the Antarctic continental shelf

10.5194/egusphere-egu21-14011 ◽

2021 ◽

Author(s):

Hannah Dawson ◽

Adele Morrison ◽

Veronica Tamsitt ◽

Matthew England

Keyword(s):

Continental Shelf ◽

Ross Sea ◽

Coastal Current ◽

West Antarctica ◽

Source Regions ◽

Freshwater Forcing ◽

Antarctic Continental Shelf ◽

Antarctic Continent ◽

Antarctic Slope Current ◽

The Antarctic

The Antarctic margin is surrounded by two westward flowing currents: the Antarctic Slope Current and the Antarctic Coastal Current. The former influences key processes near the Antarctic margin by regulating the flow of heat and nutrients onto and off the continental shelf, while together they advect nutrients, biological organisms, and temperature and salinity anomalies around the coastline, providing a connective link between different shelf regions. However, the extent to which these currents transport water from one sector of the continental shelf to another, and the timescales over which this occurs, remain poorly understood. Concern that crucial water formation sites around the Antarctic coastline could respond to non-local freshwater forcing from ice shelf meltwater motivates a more thorough understanding of zonal connectivity around Antarctica. In this study, we use daily velocity fields from a global high-resolution ocean-sea ice model, combined with the Lagrangian tracking software Parcels, to investigate the pathways and timescales connecting different regions of the Antarctic continental shelf with a view to understanding the timescales of meltwater transport around the continent. Virtual particles are released over the continental shelf, poleward of the 1000 metre isobath, and are tracked for 20 years. Our results show a strong seasonal cycle connecting different sectors of the Antarctic continent, with more particles arriving further downstream during winter than during summer months. Strong advective links exist between West Antarctica and the Ross Sea while shelf geometry in some other regions acts as barriers to transport. We also highlight the varying importance of the Antarctic Slope Current and Antarctic Coastal Current in connecting different sectors of the coastline. Our results help to improve our understanding of circum-Antarctic connectivity and the timescales of meltwater transport from source regions to downstream shelf locations. Furthermore, the timescales and pathways we present provide a baseline from which to assess long-term changes in Antarctic coastal circulation due to local and remote forcing.

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International Real Estate Review

International Real Estate Review ◽

10.53383/100227 ◽

2016 ◽

Vol 19 (3) ◽

pp. 371-409

Author(s):

Yuen-Meng Wong ◽

Keyword(s):

Real Estate ◽

Interest Rates ◽

Turn Of The Millennium ◽

Market Returns ◽

Stock Market Returns ◽

Fully Integrated ◽

Empirical Tests ◽

Market Capitalisation ◽

Domestic Stock

Real estate investment trusts (REITs) are a niche alternative investment class. Since their introduction in Asia at the turn of the millennium, the REIT market in the region has experienced phenomenal growth. In particular, the Malaysia REIT (M-REIT ) market capitalisation has seen a spectacular growth of close to 20 folds from its inception in 2005 until the end of 2013. This paper chronicles the development of the M-REIT market which is rather unique as it provides a common platform for the existence of both conventional and Islamic REITs. Empirical tests are also conducted to uncover the returns characteristics of the M-REIT market. M-REIT returns are significantly correlated with domestic stock markets but only weakly correlated with changes in interest rate, with long-term proxies having a stronger impact than short-term proxies. The results from a correlation analysis are further confirmed by regression testing which shows that M-REIT returns are most significantly driven by domestic stock market returns while only mildly by changes in interest rates and not significantly driven by returns in regional REIT markets. These findings possibly imply that M-REITs (i) subscribe more to the characteristics of equity than those of bonds, (ii) are not 'pure' yield-play instruments, (iii) are often regarded as long-term investment, and (iv) may not be fully integrated with global and regional REIT markets.

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Significance of Extreme Temperament in Infancy for Clinical Status in Preschool Years

The British Journal of Psychiatry ◽

10.1192/bjp.154.4.544 ◽

1989 ◽

Vol 154 (4) ◽

pp. 544-551 ◽

Cited By ~ 22

Author(s):

Michel Maziade ◽

Jacques Thivierge ◽

Robert Côté ◽

Pierrette Boutin ◽

Hugues Bernier

Keyword(s):

Longitudinal Study ◽

Birth Cohort ◽

Clinical Status ◽

Environmental Parameters ◽

Positive Change ◽

Stability And Change ◽

Cognitive Characteristics ◽

One Year ◽

Long Term Prediction

Few, if any, of children's behavioural or cognitive characteristics assessed in the first years of life demonstrate stability until later childhood; early characteristics have so far failed to show an association with future psychopathology. This longitudinal study, from 4–8 months to 4.7 years old, focused on stability and change of extreme temperamental traits in groups of infants subselected from a large birth cohort. Persistent extreme temperament at four and eight months old did not increase stability of temperament to four years of age, relative to other children in the whole population. Sizeable change occurred, and the environmental parameters associated with negative temperamental change did not seem to be the same as those related to positive change. Boys with extreme scores were more stable, while girls appeared more prone to positive change. It is hypothesised that the direction of temperamental change in the first years could be more meaningful for long-term prediction of disorders than any one assessment of temperament taken at any one year.

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The Osservatorio Geofisico Sperimentale marine magnetic surveys in the Antarctic Seas

Annals of Geophysics ◽

10.4401/ag-3714 ◽

1999 ◽

Vol 42 (2) ◽

Author(s):

E. Lodolo ◽

F. Coren ◽

C. Zanolla

Keyword(s):

Tectonic Evolution ◽

Ross Sea ◽

Austral Summer ◽

Geological Structure ◽

Seismic Profiles ◽

Scotia Sea ◽

Geophysical Surveys ◽

Scientific Results ◽

The Antarctic ◽

Derived Data

About 40 000 km of marine magnetic and gradiometric data have been collected during eight geophysical surveys conducted since the Austral summer 1987/1988 in the circum-antarctic seas, by the research vessel OGS-Explora. For the most surveyed areas (Ross Sea, Southwestern Pacific Ocean, and Southern Scotia Sea), the analysis of the acquired data have contributed to clarify important aspects of their geological structure and tectonic evolution. The main scientific results, obtained combining other available geophysical data (multichannel seismic profiles and satellite-derived data), will be briefly illustrated.

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Are longitudinal ice-surface structures on the Antarctic Ice Sheet indicators of long-term ice-flow configuration?

Earth Surface Dynamics Discussions ◽

10.5194/esurfd-2-911-2014 ◽

2014 ◽

Vol 2 (2) ◽

pp. 911-933 ◽

Cited By ~ 1

Author(s):

N. F. Glasser ◽

S. J. A. Jennings ◽

M. J. Hambrey ◽

B. Hubbard

Keyword(s):

Flow Line ◽

Ice Sheet ◽

Surface Structures ◽

Surface Velocity ◽

Ice Flow ◽

Antarctic Ice Sheet ◽

Ice Surface ◽

Ice Stream ◽

The Antarctic

Abstract. Continent-wide mapping of longitudinal ice-surface structures on the Antarctic Ice Sheet reveals that they originate in the interior of the ice sheet and are arranged in arborescent networks fed by multiple tributaries. Longitudinal ice-surface structures can be traced continuously down-ice for distances of up to 1200 km. They are co-located with fast-flowing glaciers and ice streams that are dominated by basal sliding rates above tens of m yr-1 and are strongly guided by subglacial topography. Longitudinal ice-surface structures dominate regions of converging flow, where ice flow is subject to non-coaxial strain and simple shear. Associating these structures with the AIS' surface velocity field reveals (i) ice residence times of ~ 2500 to 18 500 years, and (ii) undeformed flow-line sets for all major flow units analysed except the Kamb Ice Stream and the Institute and Möller Ice Stream areas. Although it is unclear how long it takes for these features to form and decay, we infer that the major ice-flow and ice-velocity configuration of the ice sheet may have remained largely unchanged for several thousand years, and possibly even since the end of the last glacial cycle. This conclusion has implications for our understanding of the long-term landscape evolution of Antarctica, including large-scale patterns of glacial erosion and deposition.

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