Glacial fjord environment and ecosystem reconstructed from sediments deposited in Bowdoin Fjord, northwestern Greenland.

The Tenth Symposium on Polar Science/Ordinary sessions: [OG] Polar Geosciences, Wed. 4 Dec. / 3F Seminar room, National Institute of Polar Researc

Signaling pathway for phagocyte priming upon encounter with apoptotic cells

The phagocytic elimination of cells undergoing apoptosis is an evolutionarily conserved innate immune mechanism for eliminating unnecessary cells. Previous studies showed an increase in the level of engulfment receptors in phagocytes after the phagocytosis of apoptotic cells, which leads to the enhancement of their phagocytic activity. However, precise mechanisms underlying this phenomenon require further clarification. We found that the pre-incubation of a Drosophila phagocyte cell line with the fragments of apoptotic cells enhanced the subsequent phagocytosis of apoptotic cells, accompanied by an augmented expression of the engulfment receptors Draper and integrin αPS3. The DNA-binding activity of the transcription repressor Tailless was transiently raised in those phagocytes, depending on two partially overlapping signal-transduction pathways for the induction of phagocytosis as well as the occurrence of engulfment. The RNAi knockdown of tailless in phagocytes abrogated the enhancement of both phagocytosis and engulfment receptor expression. Furthermore, the hemocytespecific RNAi of tailless reduced apoptotic cell clearance in Drosophila embryos. Taken together, we propose the following mechanism for the activation of Drosophila phagocytes after an encounter with apoptotic cells: two partially overlapping signal-transduction pathways for phagocytosis are initiated; transcription repressor Tailless is activated; expression of engulfment receptors is stimulated; and phagocytic activity is enhanced. This phenomenon most likely ensures the phagocytic elimination of apoptotic cells by stimulated phagocytes and is thus considered as a mechanism to prime phagocytes in innate immunity. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.Embargo Period 12 month

Meltwater Discharge From Marine-Terminating Glaciers Drives Biogeochemical Conditions in a Greenlandic Fjord

An increasing body of work has shown the potential impacts of subglacial discharge from marine-terminating glaciers on the marine environment around Greenland. Upwelling of nutrients associated with rising buoyant plumes near the front of marine-terminating glaciers plays a key role in maintaining the high productivity of connected fjords. The response of protist communities to subglacial discharges into fjords nevertheless remains poorly understood. Here we show data of water properties, nutrients, and protist communities during two summers in 2018 and 2019 in a Greenlandic fjord system fed by marine-terminating glaciers. This study included the period of intense summer melting of the Greenland Ice Sheet in 2019. The data revealed high nutrient concentrations in 2019 that were attributed to intensified upwelling of nutrients and dissolved iron into the subsurface layer. The source of the iron and the nutrients was subglacial discharge and deep fjord water, respectively. Intense glacial discharges in 2019 mitigated nitrate and phosphate limitations of phytoplankton in the fjord and resulted in an increase of chlorophyll a in the subsurface layer and growth of large diatoms. Heterotrophic protists such as dinoflagellates, tintinnids, and nanoflagellates were more abundant in the summer of 2019. We concluded that nutrient upwelling by subglacial discharges was the major driver of the structure of lower trophic levels in fjord ecosystems. We hypothesize that the more intense melting of glaciers and related increase in subglacial discharge will enhance nutrient upwelling, and increased summer productivity in fjords until the glaciers retreat and terminate on land

Increasing dust emission from ice free terrain in southeastern Greenland since 2000

Mineral dust plays a key role in both local and global climates. At high latitudes, atmospheric dust can affect icenuclei formation, and surface dust can reduce the albedo as well as increase subsequent ice melting. As a proxy for past climate, mineral dust is preserved in ice cores, but few studies have examined deposited dust in ice cores during the Anthropocene, especially after 2000. We measured dust concentrations in an ice core at the southeastern dome in Greenland (SE-Dome), and reconstructed the annual and seasonal dust fluxes during 1960-2014. We find the annual average flux during 1960-2014 to be 34.8 ± 13.5 mg m- 2 yr-1, a value about twice that of ice cores further inland. The more recent part of that period, 2000-2014, has the higher annual flux of 46.6 ± 16.2 mg m- 2 yr-1. The annual and autumn dust fluxes highly correlate with air temperature in Tasiilaq (r = 0.61 and 0.50, respectively), a coastal location in southeastern Greenland. Our results suggest that the local dust emissions at the coastal region are increasing due to a decreasing seasonal snow-cover area arising from coastal Greenland warming after 2000

[Dataset]SE-Dome dust aerosols(Amino2020)_2020

Mineral dust plays a key role in both local and global climates. At high latitudes, atmospheric dust can affect icenuclei formation, and surface dust can reduce the albedo as well as increase subsequent ice melting. As a proxy for past climate, mineral dust is preserved in ice cores, but few studies have examined deposited dust in ice cores during the Anthropocene, especially after 2000. We measured dust concentrations in an ice core at the southeastern dome in Greenland (SE-Dome), and reconstructed the annual and seasonal dust fluxes during 1960-2014. We find the annual average flux during 1960-2014 to be 34.8 ± 13.5 mg m- 2 yr-1, a value about twice that of ice cores further inland. The more recent part of that period, 2000-2014, has the higher annual flux of 46.6 ± 16.2 mg m- 2 yr-1. The annual and autumn dust fluxes highly correlate with air temperature in Tasiilaq (r = 0.61 and 0.50, respectively), a coastal location in southeastern Greenland. Our results suggest that the local dust emissions at the coastal region are increasing due to a decreasing seasonal snow-cover area arising from coastal Greenland warming after 2000

Reconstruction of sea ice concentration in northern Baffin Bay using deuterium excess in a coastal ice core from the northwestern Greenland Ice Sheet

Variations in the conditions of sea ice in the northern part of Baffin Bay and North Open Water polynya influence human activity in northwestern Greenland through oceanic circulation and heat balance between air and sea. To evaluate the impact of variations in sea ice conditions on the surrounding environment, it is important to understand the mechanism of sea ice variations over long periods. In this study, we estimated the age of the SIGMA‐A ice core collected northwestern Greenland Ice Sheet and researched the relationship between annual or seasonal deuterium excess (d‐excess) and seasonal sea ice concentration. We found that a temporal variation in the spring d‐excess in the ice core negatively correlated significantly with that of sea ice concentration in February–April in northern Baffin Bay from 1979–2005 (r = −0.61, p < 0.001). Using this relationship, we reconstructed the temporal variations in sea ice concentrations for 100 years from the ice core drilled in the northwestern Greenland Ice Sheet. The sea ice concentration in the early twentieth century was lower than that in the present. The decrease in sea ice concentration was consistent with analytical results for marine sediments obtained from Baffin Bay. We also suggested that the sea ice concentration was controlled by atmospheric conditions from the 1920s to 1940s based on examinations of correlations with the North Atlantic Oscillation index and air temperature in Ilulissat and by oceanographic conditions from 1945–1955, 1959–1969, and 1982–1992 based on the Atlantic Multidecadal Oscillation index and meridional heat transport to western Greenland

Maternal Renal Dysfunction in Late Pregnancy in Twin and Singleton Pregnancies: Retrospective Study

This study aimed to evaluate the differences in the impact on maternal renal function between singleton and twin pregnancies in the second half of pregnancy. It retrospectively enrolled 1711 pregnant women consisting of 1547 singleton pregnancies and 164 twin pregnancies from Japanese Red Cross Aichi Medical Center Nagoya Daiichi Hospital from January 2019 to June 2021. Patients underwent renal function tests (serum blood urea nitrogen, creatinine, and estimated glomerular filtration rate (eGFR)) at least one month before delivery. The main outcome measure was maternal renal dysfunction, defined as a serum creatinine level above 0.8 mg/dL. The serum creatinine level was significantly higher and the eGFR was significantly lower in twin than in singleton pregnancies (p p < 0.01). Multivariate analysis revealed that twin pregnancy (odds ratio (OR) 3.38), nulliparity (OR 2.31), and preeclampsia (OR 3.64) were significant risk factors for maternal renal dysfunction. Maternal renal dysfunction was observed in 13 twin pregnancies, all of which recovered to within normal limits during the early months of the postpartum period. Twin pregnancy is a significant risk factor for maternal renal dysfunction; renal function should be carefully monitored in twin pregnancies