Impact of sociodemographic status and sex on chronic rhinosinusitis and olfaction in people with cystic fibrosis.

BACKGROUND: Sociodemographic status (SDS) including race/ethnicity and socioeconomic status as approximated by education, income, and insurance status impact pulmonary disease in people with cystic fibrosis (PwCF). The relationship between SDS and chronic rhinosinusitis (CRS) remains understudied. METHODS: In a prospective, multi-institutional study, adult PwCF completed the 22-Question SinoNasal Outcome Test (SNOT-22), Smell Identification Test (SIT), Questionnaire of Olfactory Disorder Negative Statements (QOD-NS), and Cystic Fibrosis Questionnaire-Revised (CFQ-R). Lund-Kennedy scores, sinus computed tomography, and clinical data were collected. Data were analyzed across race/ethnicity, sex, and socioeconomic factors using multivariate regression. RESULTS: Seventy-three PwCF participated with a mean age of 34.7 ± 10.9 years and 49 (67.1%) were female. Linear regression identified that elexacaftor/tezacaftor/ivacaftor (ETI) use (ß = â€’4.09, 95% confidence interval [CI] [‒6.08, ‒2.11], p < 0.001), female sex (ß = â€’2.14, 95% CI [‒4.11, ‒0.17], p = 0.034), and increasing age (ß = â€’0.14, 95% CI [‒0.22, ‒0.05], p = 0.003) were associated with lower/better endoscopy scores. Private health insurance (ß = 17.76, 95% CI [5.20, 30.32], p = 0.006) and >16 educational years (ß = 13.50, 95% CI [2.21, 24.80], p = 0.020) were associated with higher baseline percent predicted forced expiratory volume in one second (ppFEV1). Medicaid/Medicare insurance was associated with worse endoscopy scores, CFQ-R respiratory scores, and ppFEV1 (all p < 0.017), and Hispanic/Latino ethnicity was associated with worse SNOT-22 scores (p = 0.047), prior to adjustment for other cofactors. No other SDS factors were associated with SNOT-22, QOD-NS, or SIT scores. CONCLUSIONS: Differences in objective measures of CRS severity exist among PwCF related to sex, age, and ETI use. Variant status and race did not influence patient-reported CRS severity measures or olfaction in this study. Understanding how these factors impact response to treatment may improve care disparities among PwCF. CLINICAL TRIALS: NCT04469439.

Sociodemographic Factors Associated with Emergent Eye-Related Emergency Department Visits: A Multicenter Analysis.

OBJECTIVE: To compare sociodemographic factors in patients presenting to the emergency department (ED) with emergent and non-emergent eye-related concerns. DESIGN: Cross-sectional multicenter study. SUBJECTS: 60,677 patients with eye-related concerns who visited EDs at Bascom Palmer Eye Institute, Wills Eye Hospital, Massachusetts Eye and Ear, and Johns Hopkins Hospital/Wilmer Eye Institute from January 1st, 2019 until December 31st, 2019. METHODS: Descriptive statistics were performed using STATA 17. MAIN OUTCOME MEASURES: 1) Sociodemographic factors associated with emergent diagnoses, 2) Visit patterns across ED settings (i.e. standard ED vs eye ED), and 3) the most common emergent and non-emergent diagnoses. RESULTS: A total of 60,677 eye-related ED encounters were included in the study, including 22,434 at Bascom Palmer Eye Institute, 16,124 at Wills Eye Hospital, 15,487 at Massachusetts Eye and Ear, and 6,632 at Johns Hopkins Hospital/Wilmer Eye Institute. Most patients had non-emergent diagnoses (56.7%). Males (OR 1.85, 95% CI 1.79-1.92) were more likely to have an emergent diagnosis than females. Patients with private/employer-based insurance (OR 0.88, 95% CI 0.81-0.96), Medicare (OR 0.80, 95% CI 0.72-0.87), and Medicaid (OR 0.81, 95% CI 0.74-0.89) were all less likely to have an emergent diagnosis than uninsured patients. Those with veteran/military insurance (OR 1.08, 95% CI 0.87-1.34) were equally likely to have an emergent diagnosis compared to uninsured patients. Non-White Hispanic patients (OR 1.26, 95% CI 1.12-1.42) were more likely to present with an emergent condition than White patients. Patient seen in the standard ED setting were more likely to have emergent diagnoses than those who visited standalone eye EDs (P < 0.001). The most common emergent diagnoses were corneal abrasion (12.97%), extraocular foreign body (7.61%), and corneal ulcer (7.06%). The most common non-emergent diagnoses were dry eye (7.90%), posterior vitreous detachment (7.76%), and chalazion (6.57%). CONCLUSIONS: ED setting was associated with the acuity of patient diagnoses. Lack of insurance coverage and non-White Hispanic race/ethnicity were associated with emergent eye-related ED visits. Improving access to ophthalmic care in these populations may reduce the incidence of preventable eye emergencies related to untreated chronic conditions. This combined with measures to redirect non-emergent issues to outpatient clinics may alleviate ED overload.

Streamlining large-scale oceanic biomonitoring using passive eDNA samplers integrated into vessel's continuous pump underway seawater systems.

Passive samplers are enabling the scaling of environmental DNA (eDNA) biomonitoring in our oceans, by circumventing the time-consuming process of water filtration. Designing a novel passive sampler that does not require extensive sample handling time and can be connected to ocean-going vessels without impeding normal underway activities has potential to rapidly upscale global biomonitoring efforts onboard the world's oceanic fleet. Here, we demonstrate the utility of an artificial sponge sampler connected to the continuous pump underway seawater system as a means to enable oceanic biomonitoring. We compared the performance of this passive sampling protocol with standard water filtration at six locations during a research voyage from New Zealand to Antarctica in early 2023. Eukaryote metabarcoding of the mitochondrial COI gene revealed no significant difference in phylogenetic α-diversity between sampling methods and both methods delineated a progressive reduction in number of Zero-Radius Operational Taxonomic Units (ZOTUs) with increased latitudes. While both sampling methods revealed comparable trends in geographical community compositions, distinct clusters were identified for passive samplers and water filtration at each location. Additionally, greater variability between replicates was observed for passive samplers, resulting in an increased estimated level of replication needed to recover 90 % of the biodiversity. Furthermore, traditional water filtration failed to detect three phyla observed by passive samplers and extrapolation analysis estimated passive samplers recover a larger number of ZOTUs compared to water filtration for all six locations. Our results demonstrate the potential of this passive eDNA sampler protocol and highlight areas where this emerging technology could be improved, thereby enabling large-scale offshore marine eDNA biomonitoring by leveraging the world's oceanic fleet without interfering with onboard activities.

A multi-center analysis of visual outcomes following open globe injury.

The purpose of this study was to examine how demographics, etiology, and clinical examination findings are related to visual outcomes in subjects with open globe injury (OGI) across a large and generalizable sample. A retrospective cohort analysis was performed using data collected from the electronic medical records of four tertiary university centers for subjects with OGI presenting from 2018 to 2021. Demographic information, injury mechanisms, clinical exam findings, visual acuity (VA) at presentation and most recent follow-up were recorded. In subjects with bilateral OGIs, only right eyes were included. A modified ocular trauma score (OTS) using presenting VA, the presence of perforating injury, OGI, and afferent pupillary defect was calculated. The risk of subjects' demographic characteristics, ocular trauma etiology, clinical findings and modified OTS on the presence of monocular blindness at follow-up were assessed using univariable and multivariable regression models. 1426 eyes were identified. The mean age was 48.3 years (SD: ± 22.4 years) and the majority of subjects were men (N = 1069, 75.0%). Univariable analysis demonstrated that subjects of Black race were 66% (OR: 1.66 [1.25-2.20]; P < 0.001) more likely to have monocular blindness relative to White race at follow-up. OTS Class 1 was the strongest predictor of blindness (OR: 38.35 [21.33-68.93]; P < 0.001). Based on multivariable analysis, lower OTS category (OTS Class 1 OR: 23.88 [16.44-45.85]; P < 0.001) moderately predicted visual outcomes (R2 = 0.275, P < 0.001). OGI has many risks of poor visual outcome across patient groups that vary by demographic category, mechanism of injury, and clinical presentation. Our findings validate that a modified OTS remains a strong predictor of visual prognosis following OGI in a large and generalizable sample.

Developing, characterizing and modeling CRISPR-based point-of-use pathogen diagnostics.

Recent years have seen intense interest in the development of point-of-care nucleic acid diagnostic technologies to address the scaling limitations of laboratory-based approaches. Chief among these are combinations of isothermal amplification approaches with CRISPR-based detection and readouts of target products. Here, we contribute to the growing body of rapid, programmable point-of-care pathogen tests by developing and optimizing a one-pot NASBA-Cas13a nucleic acid detection assay. This test uses the isothermal amplification technique NASBA to amplify target viral nucleic acids, followed by Cas13a-based detection of amplified sequences. We first demonstrate an in-house formulation of NASBA that enables optimization of individual NASBA components. We then present design rules for NASBA primer sets and LbuCas13a guide RNAs for fast and sensitive detection of SARS-CoV-2 viral RNA fragments, resulting in 20 - 200 aM sensitivity without any specialized equipment. Finally, we explore the combination of high-throughput assay condition screening with mechanistic ordinary differential equation modeling of the reaction scheme to gain a deeper understanding of the NASBA-Cas13a system. This work presents a framework for developing a mechanistic understanding of reaction performance and optimization that uses both experiments and modeling, which we anticipate will be useful in developing future nucleic acid detection technologies.

Cognitive profile, neuroimaging and fluid biomarkers in post-acute COVID-19 syndrome.

We aimed to characterize the cognitive profile of post-acute COVID-19 syndrome (PACS) patients with cognitive complaints, exploring the influence of biological and psychological factors. Participants with confirmed SARS-CoV-2 infection and cognitive complaints ≥ 8 weeks post-acute phase were included. A comprehensive neuropsychological battery (NPS) and health questionnaires were administered at inclusion and at 1, 3 and 6 months. Blood samples were collected at each visit, MRI scan at baseline and at 6 months, and, optionally, cerebrospinal fluid. Cognitive features were analyzed in relation to clinical, neuroimaging, and biochemical markers at inclusion and follow-up. Forty-nine participants, with a mean time from symptom onset of 10.4 months, showed attention-executive function (69%) and verbal memory (39%) impairment. Apathy (64%), moderate-severe anxiety (57%), and severe fatigue (35%) were prevalent. Visual memory (8%) correlated with total gray matter (GM) and subcortical GM volume. Neuronal damage and inflammation markers were within normal limits. Over time, cognitive test scores, depression, apathy, anxiety scores, MRI indexes, and fluid biomarkers remained stable, although fewer participants (50% vs. 75.5%; p = 0.012) exhibited abnormal cognitive evaluations at follow-up. Altered attention/executive and verbal memory, common in PACS, persisted in most subjects without association with structural abnormalities, elevated cytokines, or neuronal damage markers.

Mechanism of chaperone coordination during cotranslational protein folding in bacteria.

Protein folding is assisted by molecular chaperones that bind nascent polypeptides during mRNA translation. Several structurally distinct classes of chaperones promote de novo folding, suggesting that their activities are coordinated at the ribosome. We used biochemical reconstitution and structural proteomics to explore the molecular basis for cotranslational chaperone action in bacteria. We found that chaperone binding is disfavored close to the ribosome, allowing folding to precede chaperone recruitment. Trigger factor recognizes compact folding intermediates that expose an extensive unfolded surface, and dictates DnaJ access to nascent chains. DnaJ uses a large surface to bind structurally diverse intermediates and recruits DnaK to sequence-diverse solvent-accessible sites. Neither Trigger factor, DnaJ, nor DnaK destabilize cotranslational folding intermediates. Instead, the chaperones collaborate to protect incipient structure in the nascent polypeptide well beyond the ribosome exit tunnel. Our findings show how the chaperone network selects and modulates cotranslational folding intermediates.

Not just binary: embracing the complexity of nuclear division dynamics.

Cell division presents a challenge for eukaryotic cells: how can chromosomes effectively segregate within the confines of a membranous nuclear compartment? Different organisms have evolved diverse solutions by modulating the degree of nuclear compartmentalization, ranging from complete nuclear envelope breakdown to complete maintenance of nuclear compartmentalization via nuclear envelope expansion. Many intermediate forms exist between these extremes, suggesting that nuclear dynamics during cell division are surprisingly plastic. In this review, we highlight the evolutionary diversity of nuclear divisions, focusing on two defining characteristics: (1) chromosome compartmentalization and (2) nucleocytoplasmic transport. Further, we highlight recent evidence that nuclear behavior during division can vary within different cellular contexts in the same organism. The variation observed within and between organisms underscores the dynamic evolution of nuclear divisions tailored to specific contexts and cellular requirements. In-depth investigation of diverse nuclear divisions will enhance our understanding of the nucleus, both in physiological and pathological states.

Long-distance movement dynamics shape host microbiome richness and turnover.

Host-associated microbial communities are shaped by host migratory movements. These movements can have contrasting impacts on microbiota, and understanding such patterns can provide insight into the ecological processes that contribute to community diversity. Furthermore, long-distance movements to new environments are anticipated to occur with increasing frequency due to host distribution shifts resulting from climate change. Understanding how hosts transport their microbiota with them could be of importance when examining biological invasions. Although microbial community shifts are well-documented, the underlying mechanisms that lead to the restructuring of these communities remain relatively unexplored. Using literature and ecological simulations, we develop a framework to elucidate the major factors that lead to community change. We group host movements into two types-regular (repeated/cyclical migratory movements, as found in many birds and mammals) and irregular (stochastic/infrequent movements that do not occur on a cyclical basis, as found in many insects and plants). Ecological simulations and prior research suggest that movement type and frequency, alongside environmental exposure (e.g. internal/external microbiota) are key considerations for understanding movement-associated community changes. From our framework, we derive a series of testable hypotheses, and suggest means to test them, to facilitate future research into host movement and microbial community dynamics.

Free-Radical Deoxygenative Amination of Alcohols via Copper Metallaphotoredox Catalysis.

Alcohols are among the most abundant chemical feedstocks, yet they remain vastly underutilized as coupling partners in transition metal catalysis. Herein, we describe a copper metallaphotoredox manifold for the open shell deoxygenative coupling of alcohols with N-nucleophiles to forge C(sp3)-N bonds, a linkage of high value in pharmaceutical agents that is challenging to access via conventional cross-coupling techniques. N-heterocyclic carbene (NHC)-mediated conversion of alcohols into the corresponding alkyl radicals followed by copper-catalyzed C-N coupling renders this platform successful for a broad range of structurally unbiased alcohols and 18 classes of N-nucleophiles.

Liver and pancreatic-targeted interleukin-22 as a therapeutic for metabolic dysfunction-associated steatohepatitis.

Metabolic dysfunction-associated steatohepatitis (MASH) is the most prevalent cause of liver disease worldwide, with a single approved therapeutic. Previous research has shown that interleukin-22 (IL-22) can suppress ß-cell stress, reduce local islet inflammation, restore appropriate insulin production, reverse hyperglycemia, and ameliorate insulin resistance in preclinical models of diabetes. In clinical trials long-acting forms of IL-22 have led to increased proliferation in the skin and intestine, where the IL-22RA1 receptor is highly expressed. To maximise beneficial effects whilst reducing the risk of epithelial proliferation and cancer, we designed short-acting IL-22-bispecific biologic drugs that successfully targeted the liver and pancreas. Here we show 10-fold lower doses of these bispecific biologics exceed the beneficial effects of native IL-22 in multiple preclinical models of MASH, without off-target effects. Treatment restores glycemic control, markedly reduces hepatic steatosis, inflammation, and fibrogenesis. These short-acting IL-22-bispecific targeted biologics are a promising new therapeutic approach for MASH.

Pancreatic beta-cell IL-22 receptor deficiency induces age-dependent dysregulation of insulin biosynthesis and systemic glucose homeostasis.

The IL-22RA1 receptor is highly expressed in the pancreas, and exogenous IL-22 has been shown to reduce endoplasmic reticulum and oxidative stress in human pancreatic islets and promote secretion of high-quality insulin from beta-cells. However, the endogenous role of IL-22RA1 signaling on these cells remains unclear. Here, we show that antibody neutralisation of IL-22RA1 in cultured human islets leads to impaired insulin quality and increased cellular stress. Through the generation of mice lacking IL-22ra1 specifically on pancreatic alpha- or beta-cells, we demonstrate that ablation of murine beta-cell IL-22ra1 leads to similar decreases in insulin secretion, quality and islet regeneration, whilst increasing islet cellular stress, inflammation and MHC II expression. These changes in insulin secretion led to impaired glucose tolerance, a finding more pronounced in female animals compared to males. Our findings attribute a regulatory role for endogenous pancreatic beta-cell IL-22ra1 in insulin secretion, islet regeneration, inflammation/cellular stress and appropriate systemic metabolic regulation.

POLARIS: A phase 2 trial of encorafenib plus binimetinib evaluating high-dose and standard-dose regimens in patients with BRAF V600-mutant melanoma with brain metastasis.

Background: POLARIS (phase 2 [ph2]; NCT03911869) evaluated encorafenib (BRAF inhibitor) in combination with binimetinib (MEK1/2 inhibitor) in BRAF/MEK inhibitor-naïve patients with BRAF V600-mutant melanoma with asymptomatic brain metastases. Methods: The safety lead-in (SLI) assessed tolerability for high-dose encorafenib 300 mg twice daily (BID) plus binimetinib 45 mg BID. If the high dose was tolerable in ph2, patients would be randomized to receive high or standard dose (encorafenib 450 mg once daily [QD] plus binimetinib 45 mg BID). Otherwise, standard dose was evaluated as the recommended ph2 dose (RP2D). Patients who tolerated standard dosing during Cycle 1 could be dose escalated to encorafenib 600 mg QD plus binimetinib 45 mg BID in Cycle 2. Safety, efficacy, and pharmacokinetics were examined. Results: RP2D was standard encorafenib dosing, as >33% of evaluable SLI patients (3/9) had dose-limiting toxicities. Overall, of 13 safety-evaluable patients (10 SLI, 3 ph2), 9 had prior immunotherapy. There were 9 treatment-related adverse events in the SLI and 3 in ph2. Of the SLI efficacy-evaluable patients (n = 10), 1 achieved complete response and 5 achieved partial responses (PR); the brain metastasis response rate (BMRR) was 60% (95% CI: 26.2, 87.8). In ph2, 2 of 3 patients achieved PR (BMRR, 67% [95% CI: 9.4, 99.2]). Repeated encorafenib 300 mg BID dosing did not increase steady-state exposure compared with historical 450 mg QD data. Conclusions: Despite small patient numbers due to early trial termination, BMRR appeared similar between the SLI and ph2, and the ph2 safety profile appeared consistent with previous reports of standard-dose encorafenib in combination with binimetinib.

Enhanced Molecular Response in Myeloproliferative Neoplasms with Complete JAK2V617F Inhibition.

SUMMARY: Dunbar, Bowman, and colleagues present here a novel genetic mouse model with inducible and reversible expression of the JAK2V617F mutation in the endogenous locus. Results from this study clearly demonstrate an absolute requirement for myeloproliferative neoplasm-initiating cells for this mutation in their survival and imply that more efficacious inhibitors could be curative for these patients even in the setting of additional cooperating mutations. See related article by Dunbar et al., p. 737 (8).

A toolbox to engineer the highly productive cyanobacterium Synechococcus sp. PCC 11901.

Synechococcus sp. PCC 11901 (PCC 11901) is a fast-growing marine cyanobacterial strain that has a capacity for sustained biomass accumulation to very high cell densities, comparable to that achieved by commercially relevant heterotrophic organisms. However, genetic tools to engineer PCC 11901 for biotechnology applications are limited. Here we describe a suite of tools based on the CyanoGate MoClo system to unlock the engineering potential of PCC 11901. First, we characterised neutral sites suitable for stable genomic integration that do not affect growth even at high cell densities. Second, we tested a suite of constitutive promoters, terminators, and inducible promoters including a 2,4-diacetylphloroglucinol (DAPG)-inducible PhlF repressor system, which has not previously been demonstrated in cyanobacteria, and showed tight regulation and a 228-fold dynamic range of induction. Lastly, we developed a DAPG-inducible dCas9-based CRISPR interference (CRISPRi) system and a modular method to generate markerless mutants using CRISPR-Cas12a. Based on our findings, PCC 11901 is highly responsive to CRISPRi-based repression and showed high efficiencies for single insertion (31-81%) and multiplex double insertion (25%) genome editing with Cas12a. We envision that these tools will lay the foundations for the adoption of PCC 11901 as a robust model strain for engineering biology and green biotechnology.

The welfare of ill and injured feedlot cattle: a review of the literature and implications for managing feedlot hospital and chronic pens.

By definition, ill and injured animals are on the negative valence of animal welfare. For beef cattle kept in feedlot settings, advances in cattle health management have resulted in a greater understanding and prevention of illness and injury. However, the management of cattle once they become ill and injured is an understudied area, and there are gaps in knowledge that could inform evidence-based decision-making and strengthen welfare for this population. The aim of this review is to provide a comprehensive overview of the acquired knowledge regarding ill and injured feedlot cattle welfare, focusing on existing knowledge gaps and implications for hospital and chronic pen management and welfare assurance. Ill and injured feedlot cattle consist of acutely impaired animals with short-term health conditions that resolve with treatment and chronically impaired animals with long-term health conditions that may be difficult to treat. A literature search identified 110 articles that mentioned welfare and ill and injured feedlot cattle, but the population of interest in most of these articles was healthy cattle, not ill and injured cattle. Articles about managing ill and injured cattle in specialized hospital (n = 12) or chronic (n = 2) pens were even more sparse. Results from this literature search will be used to outline the understanding of acutely and chronically ill and injured feedlot cattle, including common dispositions and welfare considerations, behavior during convalescence, and strategies for identifying and managing ill and injured cattle. Finally, by working through specific ailments common in commercial feedlot environments, we illustrate how the Five Domains Model can be used to explore feelings and experiences and subsequent welfare state of individual ill or injured feedlot cattle. Using this approach and our knowledge of current industry practices, we identify relevant animal-based outcomes and critical research questions to strengthen knowledge in this area. A better understanding of this overlooked topic will inform future research and the development of evidence-based guidelines to help producers care for this vulnerable population.

Mapping medically relevant RNA isoform diversity in the aged human frontal cortex with deep long-read RNA-seq.

Determining whether the RNA isoforms from medically relevant genes have distinct functions could facilitate direct targeting of RNA isoforms for disease treatment. Here, as a step toward this goal for neurological diseases, we sequenced 12 postmortem, aged human frontal cortices (6 Alzheimer disease cases and 6 controls; 50% female) using one Oxford Nanopore PromethION flow cell per sample. We identified 1,917 medically relevant genes expressing multiple isoforms in the frontal cortex where 1,018 had multiple isoforms with different protein-coding sequences. Of these 1,018 genes, 57 are implicated in brain-related diseases including major depression, schizophrenia, Parkinson's disease and Alzheimer disease. Our study also uncovered 53 new RNA isoforms in medically relevant genes, including several where the new isoform was one of the most highly expressed for that gene. We also reported on five mitochondrially encoded, spliced RNA isoforms. We found 99 differentially expressed RNA isoforms between cases with Alzheimer disease and controls.

Managing risk of infectious disease transmission at religious mass gatherings: Insights from survey, COVID-19 PCR, and antibody tests from Arbaeen walkers in 2020.

BACKGROUND: Arbaeen in Iraq has been one of the largest mass gatherings during the COVID-19 pandemic with 14.5 million attendees in 2020. We set out to assess the prevalence of current or past COVID-19 among 2020 Arbaeen participants, and establish associations between COVID-19 test results, symptoms, and known recent exposure. METHODS: This was a cross-sectional study involving participants who joined Arbaeen walk in Iraq in October 2020. COVID-19 PCR and/or rapid antibody test were conducted among consented participants. A short questionnaire was administered. Rapid antibody testing was done onsite. Nasal and throat swab samples were transferred to the laboratory for PCR testing. RESULTS: A total of 835 (88.3% male; 11.7% female) participants were recruited. The most common symptom overall was cough (9.6%) followed by sore throat, fever, and loss of taste/smell (6.6%, 5.5%, and 5.0%, respectively). One in five (20.3%) participants reported close contact with a confirmed COVID-19 case in the past 14 days. Of the 237 participants with a PCR test, 18 (7.6%) were positive. Of the 765 participants with rapid antibody test, 19.3% tested positive for IgM, 39.3% for IgG, and 16.4% for both. Approximately 40% of the participants had evidence of current or past COVID-19 infection based on antibody and PCR. CONCLUSIONS: The almost 1 in 10 COVID-19 cases within such a multimillion person gathering, illustrates the difficulty in limiting the participation of infectious individuals in religious mass gatherings. There is a pressing need to explore measures to reduce the risk of transmission of infectious diseases at major mass gathering events.

Kelp holdfast microclimates buffer invertebrate inhabitants from extreme temperatures.

Climate change is altering environmental conditions, with microclimates providing small-scale refuges within otherwise challenging environments. Durvillaea (southern bull kelp; rimurapa) is a genus of large intertidal fucoid algae, and some species harbour diverse invertebrate communities in their holdfasts. We hypothesised that animal-excavated Durvillaea holdfasts provide a thermal refuge for epibiont species, and tested this hypothesis using the exemplar species D. poha. Using a southern Aotearoa New Zealand population as a case-study, we found extreme temperatures outside the holdfast were 4.4 °C higher in summer and 6.9 °C lower in winter than inside the holdfast. A microclimate model of the holdfasts was built and used to forecast microclimates under 2100 conditions. Temperatures are predicted to increase by 2-3 °C, which may exceed the tolerances of D. poha. However, if D. poha or a similar congeneric persists, temperatures inside holdfasts will remain less extreme than the external environment. The thermal tolerances of two Durvillaea-associated invertebrates, the trochid gastropod Cantharidus antipodum and the amphipod Parawaldeckia kidderi, were also assessed; C. antipodum, but not P. kidderi, displayed metabolic depression at temperatures above and below those inside holdfasts, suggesting that they would be vulnerable outside the holdfast and with future warming. Microclimates, such as those within D. poha holdfasts or holdfasts of similar species, will therefore be important refuges for the survival of species both at the northern (retreating edge) and southern (expanding edge) limits of their distributions.