Effects of coralline algal diffusion boundary layers on growth of newly settled sea urchins: implications for ocean acidification conditions

Macroalgae are able to modify their local environment via biological processes, thereby creating a diffusive boundary layer (DBL) where the chemical and physical environment differs from the overlying bulk seawater. In slow flow environments, the DBL has the potential to modulate effects of reduced seawater pH associated with ocean acidification (OA). OA poses a major threat to marine ecosystems and particularly to calcifying organisms. While implications for macroalgae and corals in the DBL have been studied, the effects on invertebrates settling and inhabiting the DBL are not well understood. This study examines the oxygen and pH conditions within coralline algal DBLs that change as a result of irradiance, flow and bulk seawater pH, in order to understand the effects of these variable conditions on growth of juvenile sea urchins in the DBL. Oxygen concentrations, used as a proxy for pH based on previous research, were measured above crustose coralline algal surfaces to determine DBL thickness and pH levels within the DBL. Newly settled juvenile sea urchins Pseudechinus huttoni were subsequently grown in these conditions for up to 11 days. Morphological measurements (test diameter and spine length) and scanning electron microscopy were used to examine growth and calcification of sea urchins. Seawater pH levels above CCA varied as a result of irradiance, flow and bulk seawater pH. In static flow, CCA increased pH at its surface up to approximately 0.8 units above the overlying bulk seawater in the light, but only decreased pH up to nearly 0.09 units below bulk seawater in the dark. DBLs were thickest at zero or slow flow (1 cm s-1) in the light. pH levels in the DBL varied from approximately pHT 7.4 to 8.6, but there was no strong effect of these varying pH levels within the DBL on post-settlement growth of P. huttoni juveniles. Life in the diffusion boundary has allowed juveniles to adapt to grow and calcify in naturally fluctuating pH environments. This finding supports observations seen in other juvenile sea urchins, and is significant because it indicates that the early post-settlement stage may not be as sensitive to OA as the larval stage, where negative effects have been previously documented. Life in thick diffusion boundary layers above CCA in slow-flow fjord environments may have increased tolerance of juvenile P. huttoni to reduced bulk seawater pH, thereby conferring greater resilience to future ocean acidification conditions

Desperate planktotrophs : decreased settlement selectivity with age in competent eastern oyster Crassostrea virginica larvae

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 599 (2018): 93-106, doi:10.3354/meps12653.For larvae of benthic marine invertebrate species, settlement from planktonic to benthic life is a critical transition. The “desperate larva” concept describes the tendency of larvae to accept suboptimal settlement habitats as they age. We quantified swimming behavior in planktotrophic larvae of the eastern oyster, Crassostrea virginica, to determine whether settlement behaviors, such as swimming downward and remaining on the bottom, increased with age and whether these ontogenetic changes were more apparent in larvae exposed to suboptimal conditions than to preferred conditions (settlement cue absent or present, respectively). In two experiments, the proportion of competent larvae remaining near the bottom of experimental flasks (indicating settlement) increased with larval age, but only in larvae that were not exposed to the settlement cue. This result is consistent with the hypothesis that larvae encountering suboptimal habitat become “desperate” (i.e. more likely to settle) as they age. Exploratory behaviors, such as upward swimming, meandering, or helices, were expected to decrease with age, especially in the absence of the settlement cue, but this pattern was detected in only one of the five swimming metrics tested (helices in downward swimming larvae). Surprisingly, pre-competent larvae exhibited settlement behavior when exposed to the cue, raising the question of whether a response at this stage would have positive or negative consequences. Acceptance of suboptimal settlement habitats by aging larvae may increase the resilience of a species by allowing populations to persist in variable environmental conditions.Funding was provided by NSF grant OCE-0850419, NOAA Sea Grant NA14OAR4170074, grants from WHOI Coastal Ocean Institute, discretionary WHOI funds, a WHOI Ocean Life Fellowship to LSM, a WHOI Summer Student Fellowship to EH, and a WHOI Postdoctoral Scholarship to KSM

Who Would Have Thought It?: Space and Hybridity in Chicana Literature and Literary Humanitarianism and the Short Story: Understanding How Genre and Ethics Intersect in "The Gold Vanity Set"

Postcolonial studies demand new ways of understanding identity and have developed concepts such as hybridity to address the needs of identities that resist stringent classifications. For Chicana literature, authors like Gloria Anzaldúa have emphasized the mestiza, or the hybridized identity, giving new meaning to what it means to live on the border. However, this hybridized border identity cannot exist without first acknowledging the theoretical and spatial aspects of the border. This essay argues that the hybridized border identity and the geographic border location are elements of identity that must exist simultaneously. A prime example of a text that positions the hybridized identity in relation to geographical contextualization is Who Would Have Thought It? by Mexican-American regionalist writer, Maria Amparo Ruiz de Burton. In Ruiz de Burton's text, various forms of hybridity develop as the lines between North/South/West, citizen/foreigner, white/black/Mexican, rich/poor, and public/private blur. It is through the various regional spaces of New England, New York, Washington D.C, and Mexico that these hybridities develop, illustrating how an emphasis upon geographical locations can clarify the hybridized identity within a physical location. Critical debate has arisen over the ethics of readers' approaches to texts about social injustices and human suffering. Scholars like Joseph Slaughter have asserted that an ethical approach to reading demands an exploration of the relationship between the reader and a text's suffering characters. Slaughter argues that to create the most effective empathy between reader and textual subject, readers should position themselves not as the sufferer but instead as "the humanitarian, the subject position of one who already recognizes the human dignity of the wounded and attempts to relieve the suffering." I extend Slaughter's idea one step further and assert that the reader should not only be conscious of his or her relationship to the sufferer, but also of his or her relationship to the text that tells the sufferer's story. In evaluating the latter relationship, an exploration of preconceived notions about form is critical. Specifically, interrogating assumptions about literary form can ultimately result in a more ethical interpretation of texts pertaining to human suffering and social injustices. In exploring assumptions about literary form, I rely upon a genre whose very definition is based on form, the short story, a genre bears the weight of structural ideals such as brevity, totality, character development, and limited temporality. When one breaks down these assumptions, a greater reflective space, fewer representational characters, and a resistance to textual "mastery" can develop, stimulating a more ethical connection between the reader and the short story's characters. I locate my exploration of short story reading in a work by Mexican-American writer, Maria Cristina Mena, entitled "The Gold Vanity Set." On the surface, this particular story follows the many conventions of the short story form; however, these conventions also work against themselves, creating a stereotypical portrayal of indigenous Mexicans that simultaneously voices concerns about the oppression of this group. The ambiguous portrayal of this subaltern group makes "The Gold Vanity Set" a valuable story to consider when exploring ethical reading, for awareness of assumptions about form helps readers make sense of Mena's textual ambiguity. My goal is not to propose a moral code for reading, but instead to explore the various ways that one might achieve a more ethical relationship to the text through the deconstruction of literary assumptions that can impede the realization of human rights and social justice for subaltern groups

Emergency Law Responses and Conflict-Affected States in Transition

This post looks at emergency law responses to the Covid-19 pandemic in conflict-affected states in transition. While some type of emergency response to Covid-19 has been used in most states, we suggest that conflict ‘fault lines’ can mean that emergency law responses have a capacity to undermine transitions. We suggest four key areas of concern: 1. How emergency law has impacted on efforts to build the rule of law as a mechanism of transition; 2. The impact on timing of elections and governmental succession; 3. The impact on relationships between the central state and divided groups in sub-state regions; and 4. The impact on militarisation of the state. Whether or not these issues operate to trigger wider conflict fault lines is inherently linked to histories of conflict, and differ in terms of relevance from one setting to the next. This piece identifies and illustrates the ways in which Covid-19 emergency responses can impact on these areas of concern, and suggests policy responses to ensure the continuation of the transition post-Covid-19. These are based on the deliberations at the Seventh Edinburgh Dialogue on Post-Conflict Constitution-Building, held in December 2020. The Edinburgh Dialogues are the result of a partnership between International IDEA, the University of Edinburgh’s Political Settlements Research Programme, and the Edinburgh Centre for Constitutional Law

Effects of coralline algal diffusion boundary layers on growth of newly settled sea urchins: implications for ocean acidification conditions

Macroalgae are able to modify their local environment via biological processes, thereby creating a diffusive boundary layer (DBL) where the chemical and physical environment differs from the overlying bulk seawater. In slow flow environments, the DBL has the potential to modulate effects of reduced seawater pH associated with ocean acidification (OA). OA poses a major threat to marine ecosystems and particularly to calcifying organisms. While implications for macroalgae and corals in the DBL have been studied, the effects on invertebrates settling and inhabiting the DBL are not well understood. This study examines the oxygen and pH conditions within coralline algal DBLs that change as a result of irradiance, flow and bulk seawater pH, in order to understand the effects of these variable conditions on growth of juvenile sea urchins in the DBL. Oxygen concentrations, used as a proxy for pH based on previous research, were measured above crustose coralline algal surfaces to determine DBL thickness and pH levels within the DBL. Newly settled juvenile sea urchins Pseudechinus huttoni were subsequently grown in these conditions for up to 11 days. Morphological measurements (test diameter and spine length) and scanning electron microscopy were used to examine growth and calcification of sea urchins. Seawater pH levels above CCA varied as a result of irradiance, flow and bulk seawater pH. In static flow, CCA increased pH at its surface up to approximately 0.8 units above the overlying bulk seawater in the light, but only decreased pH up to nearly 0.09 units below bulk seawater in the dark. DBLs were thickest at zero or slow flow (1 cm s-1) in the light. pH levels in the DBL varied from approximately pHT 7.4 to 8.6, but there was no strong effect of these varying pH levels within the DBL on post-settlement growth of P. huttoni juveniles. Life in the diffusion boundary has allowed juveniles to adapt to grow and calcify in naturally fluctuating pH environments. This finding supports observations seen in other juvenile sea urchins, and is significant because it indicates that the early post-settlement stage may not be as sensitive to OA as the larval stage, where negative effects have been previously documented. Life in thick diffusion boundary layers above CCA in slow-flow fjord environments may have increased tolerance of juvenile P. huttoni to reduced bulk seawater pH, thereby conferring greater resilience to future ocean acidification conditions

Using trained dogs and organic semi-conducting sensors to identify asymptomatic and mild SARS-CoV-2 infections: an observational study

Background A rapid, accurate, non-invasive diagnostic screen is needed to identify people with SARS-CoV-2 infection. We investigated whether organic semi-conducting (OSC) sensors and trained dogs could distinguish between people infected with asymptomatic or mild symptoms, and uninfected individuals, and the impact of screening at ports-of-entry. Methods Odour samples were collected from adults, and SARS-CoV-2 infection status confirmed using RT-PCR. OSC sensors captured the volatile organic compound (VOC) profile of odour samples. Trained dogs were tested in a double-blind trial to determine their ability to detect differences in VOCs between infected and uninfected individuals, with sensitivity and specificity as the primary outcome. Mathematical modelling was used to investigate the impact of bio-detection dogs for screening. Results About, 3921 adults were enrolled in the study and odour samples collected from 1097 SARS-CoV-2 infected and 2031 uninfected individuals. OSC sensors were able to distinguish between SARS-CoV-2 infected individuals and uninfected, with sensitivity from 98% (95% CI 95–100) to 100% and specificity from 99% (95% CI 97–100) to 100%. Six dogs were able to distinguish between samples with sensitivity ranging from 82% (95% CI 76–87) to 94% (95% CI 89–98) and specificity ranging from 76% (95% CI 70–82) to 92% (95% CI 88–96). Mathematical modelling suggests that dog screening plus a confirmatory PCR test could detect up to 89% of SARS-CoV-2 infections, averting up to 2.2 times as much transmission compared to isolation of symptomatic individuals only. Conclusions People infected with SARS-CoV-2, with asymptomatic or mild symptoms, have a distinct odour that can be identified by sensors and trained dogs with a high degree of accuracy. Odour-based diagnostics using sensors and/or dogs may prove a rapid and effective tool for screening large numbers of people

Evolution over Time of Ventilatory Management and Outcome of Patients with Neurologic Disease∗

OBJECTIVES: To describe the changes in ventilator management over time in patients with neurologic disease at ICU admission and to estimate factors associated with 28-day hospital mortality. DESIGN: Secondary analysis of three prospective, observational, multicenter studies. SETTING: Cohort studies conducted in 2004, 2010, and 2016. PATIENTS: Adult patients who received mechanical ventilation for more than 12 hours. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Among the 20,929 patients enrolled, we included 4,152 (20%) mechanically ventilated patients due to different neurologic diseases. Hemorrhagic stroke and brain trauma were the most common pathologies associated with the need for mechanical ventilation. Although volume-cycled ventilation remained the preferred ventilation mode, there was a significant (p < 0.001) increment in the use of pressure support ventilation. The proportion of patients receiving a protective lung ventilation strategy was increased over time: 47% in 2004, 63% in 2010, and 65% in 2016 (p < 0.001), as well as the duration of protective ventilation strategies: 406 days per 1,000 mechanical ventilation days in 2004, 523 days per 1,000 mechanical ventilation days in 2010, and 585 days per 1,000 mechanical ventilation days in 2016 (p < 0.001). There were no differences in the length of stay in the ICU, mortality in the ICU, and mortality in hospital from 2004 to 2016. Independent risk factors for 28-day mortality were age greater than 75 years, Simplified Acute Physiology Score II greater than 50, the occurrence of organ dysfunction within first 48 hours after brain injury, and specific neurologic diseases such as hemorrhagic stroke, ischemic stroke, and brain trauma. CONCLUSIONS: More lung-protective ventilatory strategies have been implemented over years in neurologic patients with no effect on pulmonary complications or on survival. We found several prognostic factors on mortality such as advanced age, the severity of the disease, organ dysfunctions, and the etiology of neurologic disease