Compositional Differences in the Habitat-Forming Bryozoan Communities of the Antarctic Shelf

In some areas of the Antarctic shelf, bryozoans are abundant, acting as ecosystem engineers creating secondary structures with wide benthic coverage and harboring numerous other species. As the combined forces of global warming and ocean acidification threaten these habitats, we measured the composition of habitat-forming bryozoan communities using two techniques for imaging the sea floor, a YoYo-camera system and the AWI Ocean Floor Observation System (OFOS). YoYo-camera transects of the Bellingshausen, Amundsen, and Ross Seas were conducted during a research cruise on the R/V Nathaniel B. Palmer in 2013. OFOS transects included sites in the northern Palmer Archipelago where it borders the Scotia Sea and the Weddell Sea as part of the DynAMO project during the PS81 and PS96 cruises of R/V Polarstern in 2013 and 2015-16, respectively. Areas of bryozoan colonies were measured from the sea floor images using machine-learning algorithms available through the Trainable Weka Segmentation plugin developed for FIJI software. Habitat-forming bryozoan communities in the Palmer Archipelago and Ross Sea were largely composed of anascan flustrid species with finely mineralized skeletons, and to a lesser extent by other ascophoran lepraliomorph and umbonulomorph species having more robustly mineralized skeletons. Although habitat-forming bryozoan communities in the shallower (200 m) sites of the Weddell Sea also contained flustrid species, percent area and composition of flustrid bryozoans declined with increasing depth. Lepraliomorph and umbonulomorph bryozoan morphotypes were more abundant in the Weddell Sea, maintaining their relative percent area and increasing their percent composition between 200 − 400 m. Moreover, our analyses of species composition based on externally gathered datasets show similar trends among sites, depths, and degrees of colony mineralization to our seabed imaging study. Variation present in the bryozoan species compositions of the Amundsen and Bellingshausen Seas suggest that these areas potentially represent divergent bryozoan communities requiring further validation via remote imaging surveys. Overall, compositional differences among Antarctic habitat-forming bryozoan communities are likely influenced by the combined effects of seasonal ice scour and carbonate chemistry, which in an increasingly acidified and warming ocean may put the communities of the eastern Weddell Sea at greater risk

Determinants of thoughts of death or suicide in depressed older persons

<p>Background: In depressed persons, thoughts of death and suicide are assumed to represent different degrees of a construct: suicidality. However, this can be questioned in older persons facing physical and social losses. Thoughts of death in depressed older persons are hardly examined in the absence of suicidal ideation. Furthermore, most depression instruments do not discriminate suicidal ideation from thoughts of death only. We examined whether determinants of thoughts of death differ from determinants of suicidal ideation in late life depression.</p><p>Methods: Past month's thoughts of death and suicidal ideation were assessed with the Composite International Diagnostic Interview in 378 depressed older persons (>60 years of age). Multinomial logistic regression analyses adjusted for age and depression severity were used to identify socio-demographic, lifestyle, clinical and somatic determinants of past month's thoughts of death, and suicidal ideation.</p><p>Results: Compared with patients without thoughts of death or suicide (n = 267), patients reporting thoughts of death but no suicidal ideation (n = 74) were older (OR (95% confidence interval) = 1.04 (1.00-1.08)) and more severely depressed (OR = 1.06 (1.04-1.08)), whereas patients with suicidal ideation (n = 37) were also more severely depressed (OR = 1.09 (1.06-1.13)), but not older. This latter group was further characterized by more psychiatric comorbidity (dysthymia OR = 2.28 (1.08-4.85)), panic disorder (OR = 2.27 (1.00-518)), at-risk alcohol use (OR = 4.10 (1.42-11.90)), lifetime suicide attempts (OR = 3.37 (1.46-7.75)), loneliness (OR = 1.24 (1.07-1.43)), and recent life events (OR = 3.14 (1.48-6.67)).</p><p>Conclusions: In depressed older persons thoughts of death and suicide differ in relevant demographic, social, and clinical characteristics, suggesting that the risks and consequences of the two conditions differ.</p>