Impact of sea-ice dynamics on the spatial distribution of diatom resting stages in sediments of the Pacific Arctic region

Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(7), (2021): e2021JC017223, https://doi.org/10.1029/2021JC017223.The Pacific Arctic region is characterized by seasonal sea-ice, the spatial extent and duration of which varies considerably. In this region, diatoms are the dominant phytoplankton group during spring and summer. To facilitate survival during periods that are less favorable for growth, many diatom species produce resting stages that settle to the seafloor and can serve as a potential inoculum for subsequent blooms. Since diatom assemblage composition is closely related to sea-ice dynamics, detailed studies of biophysical interactions are fundamental to understanding the lower trophic levels of ecosystems in the Pacific Arctic. One way to explore this relationship is by comparing the distribution and abundance of diatom resting stages with patterns of sea-ice coverage. In this study, we quantified viable diatom resting stages in sediments collected during summer and autumn 2018 and explored their relationship to sea-ice extent during the previous winter and spring. Diatom assemblages were clearly dependent on the variable timing of the sea-ice retreat and accompanying light conditions. In areas where sea-ice retreated earlier, open-water species such as Chaetoceros spp. and Thalassiosira spp. were abundant. In contrast, proportional abundances of Attheya spp. and pennate diatom species that are commonly observed in sea-ice were higher in areas where diatoms experienced higher light levels and longer day length in/under the sea-ice. This study demonstrates that sea-ice dynamics are an important determinant of diatom species composition and distribution in the Pacific Arctic region.This work was conducted by the Arctic Challenge for Sustainability (ArCS) project, Arctic Challenge for Sustainability II (ArCSII) project and ArCS program for overseas visits by young researchers. In addition, this work was partly supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number JP20J20410 and JP21H02263. We thank Anderson laboratory members for their support of our study at WHOI, and also thank Robert Pickart, Leah McRaven, and Jacqueline Grebmeier for their support and assistance on the Healy cruises. Funding for DA, EF, and MR was provided by the NOAA Arctic Research Program through the Cooperative Institute for the North Atlantic Region (CINAR Award NA14OAR4320158), by the NOAA ECOHAB Program (NA20NOS4780195) and by the National Science Foundation Office of Polar Programs (OPP-1823002). This is ECOHAB contribution number ECO986.2021-12-1

ニホンゴガクシュウ ニ オケル ヒハンセイ・ソウゾウセイ ノ イクセイ ヘノ ココロミ-「キョウカショ カキカエ」プロジェクト-

本稿では、クリティカル・リテラシーの概念がどのように日本語教育の教室活動に取り入れられるのかを、米国東部の大学における中級前半のコースで行われた実践を基に考察する。 外国語学習を通してものごとをクリティカル(批判的)に考える力を養うことは、外国語教育の目標の1つである。 批判的思考能力は 学習者の言語レベルに関わらず、言語運用能力を伸ばすのにかかせない要素である。なぜなら、自分の考えを自分の言葉で表現するためには、教師や教科書が提示する「知識」を単に受け入れるだけでは不十分であり、様々な情報を自らの知識や経験を基に分析・批判する力が必要だからである。 筆者は日本語学習にクリティカル・リテラシー活動を取り入れる試みとして、教科書の読み物の1つを書きかえるというプロジェクトを実施した。プロジェクトで使われたのは日本の学校制度についての読み物で、日本の教育制度の説明の後、アメリカの大学に関する記述がある。学習者は各自関連資料を集めて得た知識を教科書の読み物の内容と比較・分析し、クラス全体で話し合った後、それを基に協働で教科書の読み物をウィキを利用して書きかえるという作業を行った。この学習者が書き換えた読み物は、今後教科書に採用されることを目標としている。 本稿では、まずクリティカル・リテラシーの基本的概念を概観し、「教科書書きかえ」プロジェクトの作業手順を紹介する。そして、データ(話し合いの内容、書きかえたテキスト、アンケートによる学習者の意見等)を基に、その結果と可能性を報告・考察する。This paper discusses how principles of critical literacy can be incorporated into a Japanese language classroom by examining a project carried out in an intermediate-level Japanese class at a university in the eastern United States. One of the goals of foreign language education is to develop the learner\u27s ability to think critically through the learning of a foreign language. In order for learners to express their thoughts in their own words, it is insufficient to simply accept "knowledge" presented by the teacher and in the textbooks; learners are required to have the ability to critically analyze a variety of information based on their knowledge and experience. Thus, regardless of the language level of the learner, critical thinking skills are essential to further language proficiency. In an effort to incorporate critical literacy practices into Japanese language learning, a project was carried out in which learners revise one of the chapters in a textbook. The chapter used in the project is titled "Japan\u27s Educational System." The chapter provides basic information about the educational system in Japan and a description of universities in the United States. Learners who participated in the project researched and collected information related to the topic and analyzed the content of the chapter in the textbook by comparing it to the information they gathered. Then, they discussed the findings in class and collaboratively revised the original text in the textbook using Wiki, which allows users to modify a text in collaboration online. The goal is to have the revised texts adopted by the textbook in the future. In this paper, first, the key principles of critical literacy are introduced, followed by a description of the procedures of the textbook revision project. Then, the findings will be discussed based on the analysis of data such as in-class discussions, the revised texts, and the learners\u27reactions to the project

14-3-3 proteins stabilize LGI1-ADAM22 levels to regulate seizure thresholds in mice

新たなてんかん治療戦略を提案 --脳の過剰興奮を阻止するタンパク質ADAM22の量が鍵--. 京都大学プレスリリース. 2021-12-15.What percentage of the protein function is required to prevent disease symptoms is a fundamental question in genetic disorders. Decreased transsynaptic LGI1-ADAM22 protein complexes, because of their mutations or autoantibodies, cause epilepsy and amnesia. However, it remains unclear how LGI1-ADAM22 levels are regulated and how much LGI1-ADAM22 function is required. Here, by genetic and structural analysis, we demonstrate that quantitative dual phosphorylation of ADAM22 by protein kinase A (PKA) mediates high-affinity binding of ADAM22 to dimerized 14-3-3. This interaction protects LGI1-ADAM22 from endocytosis-dependent degradation. Accordingly, forskolin-induced PKA activation increases ADAM22 levels. Leveraging a series of ADAM22 and LGI1 hypomorphic mice, we find that ∼50% of LGI1 and ∼10% of ADAM22 levels are sufficient to prevent lethal epilepsy. Furthermore, ADAM22 function is required in excitatory and inhibitory neurons. These results suggest strategies to increase LGI1-ADAM22 complexes over the required levels by targeting PKA or 14-3-3 for epilepsy treatment

Evidence for massive and recurrent toxic blooms of Alexandrium catenella in the Alaskan Arctic

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Anderson, D. M., Fachon, E., Pickart, R. S., Lin, P., Fischer, A. D., Richlen, M. L., Uva, V., Brosnahan, M. L., McRaven, L., Bahr, F., Lefebvre, K., Grebmeier, J. M., Danielson, S. L., Lyu, Y., & Fukai, Y. Evidence for massive and recurrent toxic blooms of Alexandrium catenella in the Alaskan Arctic. Proceedings of the National Academy of Sciences of the United States of America, 118(41) (2021): e2107387118, https://doi.org/10.1073/pnas.2107387118.Among the organisms that spread into and flourish in Arctic waters with rising temperatures and sea ice loss are toxic algae, a group of harmful algal bloom species that produce potent biotoxins. Alexandrium catenella, a cyst-forming dinoflagellate that causes paralytic shellfish poisoning worldwide, has been a significant threat to human health in southeastern Alaska for centuries. It is known to be transported into Arctic regions in waters transiting northward through the Bering Strait, yet there is little recognition of this organism as a human health concern north of the Strait. Here, we describe an exceptionally large A. catenella benthic cyst bed and hydrographic conditions across the Chukchi Sea that support germination and development of recurrent, locally originating and self-seeding blooms. Two prominent cyst accumulation zones result from deposition promoted by weak circulation. Cyst concentrations are among the highest reported globally for this species, and the cyst bed is at least 6× larger in area than any other. These extraordinary accumulations are attributed to repeated inputs from advected southern blooms and to localized cyst formation and deposition. Over the past two decades, warming has likely increased the magnitude of the germination flux twofold and advanced the timing of cell inoculation into the euphotic zone by 20 d. Conditions are also now favorable for bloom development in surface waters. The region is poised to support annually recurrent A. catenella blooms that are massive in scale, posing a significant and worrisome threat to public and ecosystem health in Alaskan Arctic communities where economies are subsistence based.Funding for D.M.A., R.S.P., E.F., P.L., A.D.F., V.U., M.L.B., L.M., F.B., and M.L.R. was provided by grants from the NSF Office of Polar Programs (Grants OPP-1823002 and OPP-1733564) and the National Ocanic and Atmospheric Administration (NOAA) Arctic Research program (through the Cooperative Institute for the North Atlantic Region [CINAR; Grants NA14OAR4320158 and NA19OAR4320074]), for J.M.G. through CINAR 22309.07 UMCES (University of Maryland Center for Environmental Science), and for D.M.A. and K.L. through NOAA’s Center for Coastal and Ocean Studies Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) Program (NA20NOS4780195). Funding for D.M.A., M.L.R., M.L.B., E.F., V.U., and A.D.F. was also provided by NSF (Grant OCE-1840381) and NIH (Grant 1P01-ES028938-01) through the Woods Hole Center for Oceans and Human Health. S.L.D. was supported by North Pacific Research Board IERP Grants A91-99a and A91-00a. This is IERP publication ArcticIERP-41 and ECOHAB Contribution No. ECO983

Ryugu’s nucleosynthetic heritage from the outskirts of the Solar System

Little is known about the origin of the spectral diversity of asteroids and what it says about conditions in the protoplanetary disk. Here, we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids. Growth and migration of the giant planets destabilized nearby planetesimals and ejected some inward to be implanted into the Main Belt. In this framework, most carbonaceous chondrites may have originated from regions around the birthplaces of Jupiter and Saturn, while the distinct isotopic composition of CI chondrites and Ryugu may reflect their formation further away in the disk, owing their presence in the inner Solar System to excitation by Uranus and Neptune

Water circulation in Ryugu asteroid affected the distribution of nucleosynthetic isotope anomalies in returned sample

Studies of material returned from Cb asteroid Ryugu have revealed considerable mineralogical and chemical heterogeneity, stemming primarily from brecciation and aqueous alteration. Isotopic anomalies could have also been affected by delivery of exogenous clasts and aqueous mobilization of soluble elements. Here, we show that isotopic anomalies for mildly soluble Cr are highly variable in Ryugu and CI chondrites, whereas those of Ti are relatively uniform. This variation in Cr isotope ratios is most likely due to physicochemical fractionation between 54Cr-rich presolar nanoparticles and Cr-bearing secondary minerals at the millimeter-scale in the bulk samples, likely due to extensive aqueous alteration in their parent bodies that occurred 5:2þ11::84 Ma after Solar System birth. In contrast, Ti isotopes were marginally affected by this process. Our results show that isotopic heterogeneities in asteroids are not all nebular or accretionary in nature but can also reflect element redistribution by water

On the origin and evolution of the asteroid Ryugu: A comprehensive geochemical perspective

Presented here are the observations and interpretations from a comprehensive analysis of 16 representative particles returned from the C-type asteroid Ryugu by the Hayabusa2 mission. On average Ryugu particles consist of 50% phyllosilicate matrix, 41% porosity and 9% minor phases, including organic matter. The abundances of 70 elements from the particles are in close agreement with those of CI chondrites. Bulk Ryugu particles show higher δ18O, Δ17O, and ε54Cr values than CI chondrites. As such, Ryugu sampled the most primitive and least-thermally processed protosolar nebula reservoirs. Such a finding is consistent with multi-scale H-C-N isotopic compositions that are compatible with an origin for Ryugu organic matter within both the protosolar nebula and the interstellar medium. The analytical data obtained here, suggests that complex soluble organic matter formed during aqueous alteration on the Ryugu progenitor planetesimal (several 10’s of km), <2.6 Myr after CAI formation. Subsequently, the Ryugu progenitor planetesimal was fragmented and evolved into the current asteroid Ryugu through sublimation

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ‘‘Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample

Volatile and organic-rich C-type asteroids may have been one of the main sources of Earth’s water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but the meteorite record is biased: only the strongest types survive atmospheric entry and are then modified by interaction with the terrestrial environment. Here we present the results of a detailed bulk and microanalytical study of pristine Ryugu particles, brought to Earth by the Hayabusa2 spacecraft. Ryugu particles display a close compositional match with the chemically unfractionated, but aqueously altered, CI (Ivuna-type) chondrites, which are widely used as a proxy for the bulk Solar System composition. The sample shows an intricate spatial relationship between aliphatic-rich organics and phyllosilicates and indicates maximum temperatures of ~30 °C during aqueous alteration. We find that heavy hydrogen and nitrogen abundances are consistent with an outer Solar System origin. Ryugu particles are the most uncontaminated and unfractionated extraterrestrial materials studied so far, and provide the best available match to the bulk Solar System composition

A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu

Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through a collective process called space weathering. The return of samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory study of space-weathering signatures on the most abundant type of inner solar system body: a C-type asteroid, composed of materials largely unchanged since the formation of the Solar System. Weathered Ryugu grains show areas of surface amorphization and partial melting of phyllosilicates, in which reduction from Fe3+ to Fe2+ and dehydration developed. Space weathering probably contributed to dehydration by dehydroxylation of Ryugu surface phyllosilicates that had already lost interlayer water molecules and to weakening of the 2.7 µm hydroxyl (–OH) band in reflectance spectra. For C-type asteroids in general, this indicates that a weak 2.7 µm band can signify space-weathering-induced surface dehydration, rather than bulk volatile loss