Archival records of the Antarctic clam shells from Marian Cove, King George Island suggest a protective mechanism against ocean acidification.

Continuous emissions of anthropogenic CO2 are changing the atmospheric and oceanic environment. Although some species may have compensatory mechanisms to acclimatize or adapt to the changing environment, most marine organisms are negatively influenced by climate change. In this study, we aimed to understand the compensatory mechanisms of the Antarctic clam, Laternula elliptica, to climate-related stressors by using archived shells from 1995 to 2018. Principal component analysis revealed that seawater pCO2 and salinity in the Antarctic Ocean, which have increased since the 2000's, are the most influential factors on the characteristics of the shell. The periostracum thickness ratio and nitrogen on the outermost surface have increased, and the dissolution area (%) has decreased. Furthermore, the calcium content and mechanical properties of the shells have not changed. The results suggest that L. elliptica retains the mechanism of protecting the shell from high pCO2 by thickening the periostracum as a phenotype plasticity.

Corrigendum: Biogeography of southern ocean active prokaryotic communities over a large spatial scale.

[This corrects the article DOI: 10.3389/fmicb.2022.862812.].

Biogeography of Southern Ocean Active Prokaryotic Communities Over a Large Spatial Scale.

The activity of marine microorganisms depends on community composition, yet, in some oceans, less is known about the environmental and ecological processes that structure their distribution. The objective of this study was to test the effect of geographical distance and environmental parameters on prokaryotic community structure in the Southern Ocean (SO). We described the total (16S rRNA gene) and the active fraction (16S rRNA-based) of surface microbial communities over a ~6,500 km longitudinal transect in the SO. We found that the community composition of the total fraction was different from the active fraction across the zones investigated. In addition, higher α-diversity and stronger species turnover were displayed in the active community compared to the total community. Oceanospirillales, Alteromonadales, Rhodobacterales, and Flavobacteriales dominated the composition of the bacterioplankton communities; however, there were marked differences at the order level. Temperature, salinity, silicic acid, particulate organic nitrogen, and particulate organic carbon correlated with the composition of bacterioplankton communities. A strong distance-decay pattern between closer and distant communities was observed. We hypothesize that it was related to the different oceanic fronts present in the Antarctic Circumpolar Current. Our findings contribute to a better understanding of the complex arrangement that shapes the structure of bacterioplankton communities in the SO.

Association between Early Spermarche and Suicide Attempts in Boys: the Korea Youth Risk Behavior Web-based Survey.

BACKGROUND: Puberty is a biologically and psychologically unstable period, and pubertal changes differ by sex. However, most previous studies on pubertal timing and suicide have focused on girls. This study investigated the association between early spermarche and suicide attempts in boys. METHODS: We analyzed a nationally representative sample of Korean adolescents (The Korea Youth Risk Behavior Web-Based Survey, KYRBS) that included approximately 35,000 boys annually from 2011 to 2015. Pubertal timing in boys was defined by spermarche. Complex sampling logistic regression analyses were performed to evaluate the odds ratios (ORs) for suicide attempts between the early and average spermarche groups. RESULTS: The ORs for suicide attempts in boys with early spermarche were significantly higher than those in boys with average spermarche after adjustment for age, perceived stress, depressive symptoms, and suicidal ideation. The ORs from 2011 to 2015 were as follows: 1.782 (P < 0.001), 1.490 (P = 0.002), 1.693 (P < 0.001), 1.541 (P = 0.001), and 1.393 (1.024-1.895; P = 0.035), respectively. CONCLUSION: These findings suggest that early pubertal timing is a risk factor for suicide attempts in Korean boys after adjustment for depressive symptoms, perceived stress, and suicidal ideation, which have been previously reported as risk factors for suicide attempts. Therefore, careful attention should be paid to the prevention of suicide in boys who experience early spermarche in Korea.

Shift in polar benthic community structure in a fast retreating glacial area of Marian Cove, West Antarctica.

Glacier retreat is a major long-standing global issue; however, the ecological impacts of such retreats on marine organisms remain unanswered. Here, we examined changes to the polar benthic community structure of "diatoms" under current global warming in a recently retreated glacial area of Marian Cove, Antarctica. The environments and spatiotemporal assemblages of benthic diatoms surveyed in 2018-2019 significantly varied between the intertidal (tidal height of 2.5 m) and subtidal zone (10 and 30 m). A distinct floral distribution along the cove (~ 4.5 km) was characterized by the adaptive strategy of species present, with chain-forming species predominating near the glacier. The predominant chain-forming diatoms, such as Fragilaria striatula and Paralia sp., are widely distributed in the innermost cove over years, indicating sensitive responses of benthic species to the fast-evolving polar environment. The site-specific and substrate-dependent distributions of certain indicator species (e.g., F. striatula, Navicula glaciei, Cocconeis cf. pinnata) generally reflected such shifts in the benthic community. Our review revealed that the inner glacier region reflected trophic association, featured with higher diversity, abundance, and biomass of benthic diatoms and macrofauna. Overall, the polar benthic community shift observed along the cove generally represented changing environmental conditions, (in)directly linked to ice-melting due to the recent glacier retreat.

Antarctic ecosystems in transition - life between stresses and opportunities.

Important findings from the second decade of the 21st century on the impact of environmental change on biological processes in the Antarctic were synthesised by 26 international experts. Ten key messages emerged that have stakeholder-relevance and/or a high impact for the scientific community. They address (i) altered biogeochemical cycles, (ii) ocean acidification, (iii) climate change hotspots, (iv) unexpected dynamism in seabed-dwelling populations, (v) spatial range shifts, (vi) adaptation and thermal resilience, (vii) sea ice related biological fluctuations, (viii) pollution, (ix) endangered terrestrial endemism and (x) the discovery of unknown habitats. Most Antarctic biotas are exposed to multiple stresses and considered vulnerable to environmental change due to narrow tolerance ranges, rapid change, projected circumpolar impacts, low potential for timely genetic adaptation, and migration barriers. Important ecosystem functions, such as primary production and energy transfer between trophic levels, have already changed, and biodiversity patterns have shifted. A confidence assessment of the degree of 'scientific understanding' revealed an intermediate level for most of the more detailed sub-messages, indicating that process-oriented research has been successful in the past decade. Additional efforts are necessary, however, to achieve the level of robustness in scientific knowledge that is required to inform protection measures of the unique Antarctic terrestrial and marine ecosystems, and their contributions to global biodiversity and ecosystem services.

Ocean freshening and acidification differentially influence mortality and behavior of the Antarctic amphipod Gondogeneia antarctica.

The Western Antarctic Peninsula (WAP) has experienced rapid atmospheric and ocean warming over the past few decades and many marine-terminating glaciers have considerably retreated. Glacial retreat is accompanied by fresh meltwater intrusion, which may result in the freshening and acidification of coastal waters. Marian Cove (MC), on King George Island in the WAP, undergoes one of the highest rates of glacial retreat. Intertidal and shallow subtidal waters are likely more susceptible to these processes, and sensitive biological responses are expected from the organisms inhabiting this area. The gammarid amphipod Gondogeneia antarctica is one of the most abundant species in the shallow, nearshore Antarctic waters, and it occupies an essential ecological niche in the coastal marine WAP ecosystem. In this study, we tested the sensitivity of G. antarctica to lowered salinity and pH by meltwater intrusion following glacial retreat. We exposed G. antarctica to four different treatments combining two salinities (34 and 27 psu) and pH (8.0 and 7.6) levels for 26 days. Mortality, excluding cannibalized individuals, increased under low pH but decreased under low salinity conditions. Meanwhile, low salinity increased cannibalism, whereas low pH reduced food detection. Shelter use during the daytime decreased under each low salinity and pH condition, indicating that the two stressors act as disruptors of amphipod behavior. Under low salinity conditions, swimming increased during the daytime but decreased at night. Although interactions between low salinity and low pH were not observed during the experiment, the results suggest that each stressor, likely induced by glacial melting, causes altered behaviors in amphipods. These environmental factors may threaten population persistence in Marian Cove and possibly other similar glacial embayments.

Early menarche as a risk factor for suicidal ideation in girls: The Korea youth risk behavior web-based survey.

Puberty, at which point girls experience menarche, is a biologically and psychologically unstable period. This study investigated the association between early menarche and suicidal ideation in girls. This study analyzed data from approximately 35,000 girls from the Korea Youth Risk Behavior Web-Based Survey every year from 2011 to 2015. The odds ratios of suicidal ideation were compared between the early and average menarche groups. Generally, the odds ratios of suicidal ideation in girls with early menarche were significantly higher than those with average menarche.

Effects of Emotional Stability on Insomnia through Anxiety in Patients with Cataracts.

This study investigated the effect of emotional stability (ES) on insomnia through anxiety in preoperative patients with cataracts. Fifty-four subjects completed a self-questionnaire that included the Insomnia Severity Index (ISI), the International Personality Item Pool (IPIP) for ES, and the Hospital Anxiety and Depression scale (HADS). Pathway analysis was performed to analyze the mediating effects of ES, the anxiety subscale scores of the HADS, and the ISI scores. The low-ES group exhibited an insomnia severity that was significantly higher than that of the high-ES group (p=0.048). According to the pathway analysis, the significant indirect effect of ES on the ISI scores was mediated by the scores on the anxiety subscale of the HADS. Cataract patients with low ES waiting to undergo surgery have a high risk of experiencing insomnia due to anxiety. Before surgery, it is essential to identify patients' personality characteristics and provide appropriate intervention.

More Resilience in Males with Probable Bipolar Depression than Probable Unipolar Depression among Korean Conscripts.

OBJECTIVE: This study investigated whether the resilience of males with probable bipolar depression (PBD) can be strengthened and compared it to that of males with probable unipolar depression (PUD). METHODS: Prospective data for 198 participants (PBD: 66, PUD: 66, normal control: 66) were analyzed. The participants' resilience, bipolarity and severity of depressive symptoms were evaluated at baseline and after 5 weeks. Analysis of variance (ANOVA) and repeated measure ANOVA was performed for comparing resilience between three groups through a basic military training. RESULTS: The PBD group demonstrated more resilience than the PUD group at baseline. Participants with PBD became significantly more resilient than participants with PUD after 5 weeks (p<0.01, F=6.967, η2p=0.052). CONCLUSION: The study indicates that interventions that strengthen resilience need to be developed for males with PBD and that such interventions are more effective for males with PBD than PUD.

A Dynamic Energy Budget (DEB) model to describe Laternula elliptica (King, 1832) seasonal feeding and metabolism.

Antarctic marine organisms are adapted to an extreme environment, characterized by a very low but stable temperature and a strong seasonality in food availability arousing from variations in day length. Ocean organisms are particularly vulnerable to global climate change with some regions being impacted by temperature increase and changes in primary production. Climate change also affects the biotic components of marine ecosystems and has an impact on the distribution and seasonal physiology of Antarctic marine organisms. Knowledge on the impact of climate change in key species is highly important because their performance affects ecosystem functioning. To predict the effects of climate change on marine ecosystems, a holistic understanding of the life history and physiology of Antarctic key species is urgently needed. DEB (Dynamic Energy Budget) theory captures the metabolic processes of an organism through its entire life cycle as a function of temperature and food availability. The DEB model is a tool that can be used to model lifetime feeding, growth, reproduction, and their responses to changes in biotic and abiotic conditions. In this study, we estimate the DEB model parameters for the bivalve Laternula elliptica using literature-extracted and field data. The DEB model we present here aims at better understanding the biology of L. elliptica and its levels of adaptation to its habitat with a special focus on food seasonality. The model parameters describe a metabolism specifically adapted to low temperatures, with a low maintenance cost and a high capacity to uptake and mobilise energy, providing this organism with a level of energetic performance matching that of related species from temperate regions. It was also found that L. elliptica has a large energy reserve that allows enduring long periods of starvation. Additionally, we applied DEB parameters to time-series data on biological traits (organism condition, gonad growth) to describe the effect of a varying environment in food and temperature on the organism condition and energy use. The DEB model developed here for L. elliptica allowed us to improve benchmark knowledge on the ecophysiology of this key species, providing new insights in the role of food availability and temperature on its life cycle and reproduction strategy.

Relationship between School Violence and Depressive Symptoms among Multicultural Families' Offspring in South Korea.

The aim of the study was to evaluate the effect of school violence on depressive symptoms among the offspring of multicultural families in South Korea. Data from the National Survey of Multicultural Families 2012, conducted by the Korean Women's Development Institute and Statistics Korea, were used in this study. Complex samples logistic regression was performed to determine the effect of school violence on depressive mood. The survey participants were 3999 students between the ages of 9 and 24. Of the participants, 22.1% reported experiencing depressive symptoms and 9.1% reported experiencing school violence within the last year. School violence was a strong risk factor (OR=5.142, 95% CI=4.067-6.500) for depressive symptoms after adjusting for personal, familial and school factors. School violence is a serious contributor to depressive mood among the offspring of multicultural families. There is a significant need to monitor school violence among this vulnerable group.

Mediating Effect of Depressive Symptoms on the Relationship between Adult Attention Deficit Hyperactivity Disorder and Quality of Life.

OBJECTIVE: The aim of this study was to investigate whether depressive symptoms affect the relationship between adult attention deficit hyperactivity disorder (ADHD) and the quality of life (QOL) in Korean soldiers. METHODS: We evaluated past and present symptoms of adult ADHD (the Korean Adult Attention-Deficit/Hyperactivity Disorder Scale and the Wender Utah Rating Scale), depression (the Center for Epidemiological Studies Depression Scale) and QOL (the Korean version of the SmithKline Beecham 'Quality of Life' scale) in 131 soldiers during mental health screenings performed by a local mental health center. A structured equation model using AMOS 19.0 was used to evaluate the mediating effect of depression. RESULTS: In our first model (without depressive symptoms), adult ADHD significantly affected QOL (standardized regression weight=-0.51, p<0.01). After depressive symptoms were added to this model, the direct effect of adult ADHD on QOL was not significant (standardized regression weight=0.10, p=0.43). Regarding the indirect effect, adult ADHD significantly affected depression (standardized regression weight=0.78, p<0.01), and depression also affected QOL (standardized regression weight=-0.79, p<0.01). CONCLUSION: Through structural equation modeling, the complete mediation model for the influence of depressive symptoms on ADHD and QOL was confirmed. These findings indicated that it might be important to consider comorbidities, such as depression, when adult ADHD is being evaluated.

The structure of a shellfish specific GST class glutathione S-transferase from antarctic bivalve Laternula elliptica reveals novel active site architecture.

Glutathione-S-transferases have been identified in all the living species examined so far, yet little is known about their function in marine organisms. In a previous report, the recently identified GST from Antarctic bivalve Laternula elliptica (LeGST) was classified into the rho class GST, but there are several unique features of LeGST that may justify reclassification, which could represent specific shellfish GSTs. Here, we determined the crystal structure of LeGST, which is a shellfish specific class of GST. The structural analysis showed that the relatively open and wide hydrophobic H-site of the LeGST allows this GST to accommodate various substrates. These results suggest that the H-site of LeGST may be the result of adaptation to their environments as sedentary organisms.

Complete mitochondrial genome of the Arctic green sea urchin Strongylocentrotus droebachiensis (Strongylocentrotidae, Echinoidea).

The complete mitochondrial genome was obtained from the assembled genome data sequenced by next-generation sequencing technology from the Arctic green sea urchin Strongylocentrotus droebachiensis. The mitochondrial genome sequence was 15,710 bp in size, and the gene order and contents were identical with previously reported sea urchin mitochondrial genomes. Of 13 protein-coding genes (PCGs), 1 gene (Cytb) had an incomplete stop codon. The base composition of the mitogenome of Arctic S. droebachiensis showed high A+T (58.36%) and anti-G bias (14.86%) on the third position of PCGs.

Crystallization and preliminary X-ray crystallographic studies of the ice-binding protein from the Arctic [correction of Aantarctic] yeast Leucosporidium sp. AY30.

Freezing is dangerous to cellular organisms because it causes an increase in the concentration of ions and other solutes in the plasma, denatures biomolecules and ruptures cell membranes. Some cold-adapted organisms can survive at subzero temperatures by producing proteins that bind to and inhibit the growth of ice crystals. To better understand the structure and function of these proteins, the ice-binding protein from Leucosporidium sp. AY30 (LeIBP) was overexpressed, purified and crystallized. The native crystal belonged to space group P4(3)2(1)2, with unit-cell parameters a=b=98.05, c=106.13 Å. Since LeIBP lacks any cysteine or methionine residues, two leucine residues (Leu69 and Leu155) were substituted by methionine residues in order to obtain selenomethionine-substituted LeIBP for use in multiple-wavelength anomalous diffraction (MAD) phasing. The selenomethionine-substituted mutant crystallized in the same space group as the native protein.

Glutathione S-transferase as a biomarker in the Antarctic bivalve Laternula elliptica after exposure to the polychlorinated biphenyl mixture Aroclor 1254.

Glutathione S-transferases (GSTs) are a family of multifunctional enzymes involved in cellular detoxification that catalyze the attachment of electrophilic substrates to glutathione. Two classes of GSTs related to the rho and sigma classes of enzymes in Antarctic bivalves have been cloned from Laternula elliptica. The full-length cDNA of rho class GST (leGSTr) is 1530bp in length and contains an open reading frame (ORF) of 672bp encoding 223 amino acid residues. The deduced amino acid sequences of this gene have 41% and 40% identity to rho class GSTs from Ctenopharyngodon idella and Pleuronectes platessa, respectively. The sigma class GST (leGSTs) cDNA, however, is 1127bp in length and contains an ORF of 696bp encoding 231 amino acid residues. The deduced amino acid sequences share only 22% identity with sigma class GST from Xenopus laevis. The transcriptional expression of leGSTr, leGSTs, and leGSTp cloned in our previous study were examined using real-time polymerase chain reaction in response to exposure to a polychlorinated biphenyl (PCB) mixture. The expressions of these three GST transcripts were rapidly upregulated, although they showed different expression levels and patterns within each isoform. Moreover, leGSTs was the most upregulated in the gill and digestive gland in response to PCB exposure. The recombinant GSTs were highly expressed in transformed Escherichia coli, and their kinetic properties were studied with various substrates. As a result, the three classes of GSTs were found to have diverse biological functions and were responsible for different enzymatic features.

Molecular cloning, characterization, and the response of manganese superoxide dismutase from the Antarctic bivalve Laternula elliptica to PCB exposure.

Manganese superoxide dismutase (leMnSOD) cDNA was cloned from the Antarctic bivalve Laternula elliptica. The full-length cDNA of leMnSOD is 1238 bp in length and contains an open reading frame of 681 bp encoding 226 amino acid residues including a putative mitochondrial targeting peptide of 26 amino acids in the N-terminal region. The calculated molecular mass is 24.8 kDa with an estimated isoelectric point of 6.75. leMnSOD signatures from 185 to 192 (DVWEHAYY) and four conserved amino acids (H52, H11, D185, and H192) responsible for binding manganese were observed. Sequence comparison showed that leMnSOD had high levels of identity with MnSOD from Haliotis discus discus, Mizuhopecten yessoensis, and Crassostrea gigas (68%, 66%, and 59%, respectively). RT-PCR analysis revealed the presence of leMnSOD transcripts in all tissues examined. Quantitative real-time RT-PCR assay indicated that treatment with polychlorinated biphenyls (PCBs) significantly increased leMnSOD mRNA expression in an organ-, time-, and dose-dependent manner. The mRNA expression with exposure to PCBs at 0.1 and 10 ppb reached the highest level at 6 h and then recovered slightly from 6 to 48 h in the gill. In contrast, the expression of leMnSOD mRNA showed a different expression pattern related to PCB concentration in the digestive gland. The mRNA expression at 0.1 ppb PCBs increased up to 12 h and then decreased by 48 h, but increased immediately at 10 ppb PCBs. The leMnSOD was overproduced in Escherichia coli and purified. The recombinant leMnSOD showed maximum activity at pH 9.0, and it retained more than 50% of its original activity after incubation for 30 min at 40 degrees C.

Molecular characterization and induction of heat shock protein 90 in the Antarctic bivalve Laternula elliptica.

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone that plays a key role in protein synthesis, folding, denaturation prevention, and signal transduction. We cloned the complete complementary DNA (cDNA) sequence of the Laternula elliptica HSP90. The full-length cDNA was 2,823 bp in size and contained an open reading frame of 2,190 bp that was translated into 729 amino acids with a calculated molecular weight of 83.4 kDa. The deduced amino acid sequence of HSP90 showed the highest homology to Haliotis tuberculata HSP90 (83%). Reverse-transcriptase polymerase chain reaction analysis revealed the presence of HSP90 transcripts in all of the tissues examined. We also studied the transcriptional expression pattern of HSP90 exposed to thermal stress with real-time polymerase chain reaction. The relative expression level of HSP90 messenger RNA was upregulated and peaked at 12 h in the digestive gland and at 24 h in the gills, then dropped progressively.