Comparison of Radiation Dose and Image Quality of Pediatric High-Resolution Chest CT Between Photon-Counting Detector CT and Energy-Integrated Detector CT: A Matched Study.

BACKGROUND. Photon-counting detector (PCD) CT has been shown to reduce radiation dose and improve image quality in adult chest CT examinations; its potential impact in pediatric CT is not well documented. OBJECTIVE. The purpose of our study was to compare radiation dose, objective image quality, and subjective image quality of PCD CT and energy-integrating detector (EID) CT in children undergoing high-resolution CT (HRCT) of the chest. METHODS. This retrospective study included 27 children (median age, 3.9 years; 10 girls, 17 boys) who underwent PCD CT between March 1, 2022, and August 31, 2022, and 27 children (median age, 4.0 years; 13 girls, 14 boys) who underwent EID CT between August 1, 2021, and January 31, 2022; all examinations comprised clinically indicated chest HRCT. The patients in the two groups were matched by age and water-equivalent diameter. Radiation dose parameters were recorded. One observer placed ROIs to measure objective parameters (lung attenuation, image noise, and SNR). Two radiologists independently assessed subjective measures (overall image quality and motion artifacts) using 5-point Likert scales (1 = highest quality). Groups were compared. RESULTS. PCD CT, in comparison with EID CT, showed lower median CTDIvol (0.41 vs 0.71 mGy, p < .001), DLP (10.2 vs 13.7 mGy × cm, p = .008), size-specific dose estimate (0.82 vs 1.34 mGy, p < .001), and tube current-exposure time product (48.0 vs 202.0 mAs, p < .001). PCD CT and EID CT showed no significant difference in right upper lobe (RUL) lung attenuation (mean, -793 vs -750 HU; p = .09), right lower lobe (RLL) lung attenuation (mean, -745 vs -716 HU; p = .23), RUL image noise (mean, 55 vs 51 HU; p = .27), RLL image noise (mean, 59 vs 57 HU; p = .48), RUL SNR (mean, -14.9 vs -15.8; p = .89), or RLL SNR (mean, -13.1 vs -13.6; p = .79). PCD CT and EID CT showed no significant difference in median overall image quality for reader 1 (1.0 vs 1.0, p = .28) or reader 2 (1.0 vs 1.0, p = .17) or median motion artifacts for reader 1 (1.0 vs 1.0, p = .07) or reader 2 (1.0 vs 1.0, p = .22). CONCLUSION. PCD CT showed significantly reduced dose levels without a significant difference in objective or subjective image quality compared with EID CT. CLINICAL IMPACT. These data expand understanding of the capabilities of PCD CT and support its routine use in children.

Imaging Course of Lung Transplantation: From Patient Selection to Postoperative Complications.

Lung transplant is increasingly performed for the treatment of end-stage lung disease. As the number of lung transplants and transplant centers continues to rise, radiologists will more frequently participate in the care of patients undergoing lung transplant, both before and after transplant. Potential donors and recipients undergo chest radiography and CT as part of their pretransplant assessment to evaluate for contraindications to transplant and to aid in surgical planning. After transplant, recipients undergo imaging during the postoperative hospitalization and also in the long-term outpatient setting. Radiologists encounter a wide variety of conditions leading to end-stage lung disease and a myriad of posttransplant complications, some of which are unique to lung transplantation. Familiarity with these pathologic conditions, including their imaging findings and their temporal relationship to the transplant, is crucial to accurate radiologic interpretation. Knowledge of the surgical techniques and expected postoperative appearance prevents confusing normal posttransplant imaging findings with complications. A basic understanding of the indications, contraindications, and surgical considerations of lung transplant aids in imaging interpretation and protocoling and also facilitates communication between radiologists and transplant physicians. Despite medical and surgical advances over the past several decades, lung transplant recipients currently have an average posttransplant life expectancy of only 6.7 years. As members of the transplant team, radiologists can help maximize patient survival and hopefully increase posttransplant life expectancy and quality of life in the coming decades. ©RSNA, 2021 An invited commentary by Bierhals is available online. Online supplemental material is available for this article.

Benthic responses to an Antarctic regime shift: food particle size and recruitment biology.

Polar ecosystems are bellwether indicators of climate change and offer insights into ecological resilience. In this study, we describe contrasting responses to an apparent regime shift of two very different benthic communities in McMurdo Sound, Antarctica. We compared species-specific patterns of benthic invertebrate abundance and size between the west (low productivity) and east (higher productivity) sides of McMurdo Sound across multiple decades (1960s-2010) to depths of 60 m. We present possible factors associated with the observed changes. A massive and unprecedented shift in sponge recruitment and growth on artificial substrata observed between the 1980s and 2010 contrasts with lack of dramatic sponge settlement and growth on natural substrata, emphasizing poorly understood sponge recruitment biology. We present observations of changes in populations of sponges, bryozoans, bivalves, and deposit-feeding invertebrates in the natural communities on both sides of the sound. Scientific data for Antarctic benthic ecosystems are scant, but we gather multiple lines of evidence to examine possible processes in regional-scale oceanography during the eight years in which the sea ice did not clear out of the southern portion of McMurdo Sound. We suggest that large icebergs blocked currents and advected plankton, allowed thicker multi-year ice, and reduced light to the benthos. This, in addition to a possible increase in iron released from rapidly melting glaciers, fundamentally shifted the quantity and quality of primary production in McMurdo Sound. A hypothesized shift from large to small food particles is consistent with increased recruitment and growth of sponges on artificial substrata, filter-feeding polychaetes, and some bryozoans, as well as reduced populations of bivalves and crinoids that favor large particles, and echinoderms Sterechinus neumayeri and Odontaster validus that predominantly feed on benthic diatoms and large phytoplankton mats that drape the seafloor after spring blooms. This response of different guilds of filter feeders to a hypothesized shift from large to small phytoplankton points to the enormous need for and potential value of holistic monitoring programs, particularly in pristine ecosystems, that could yield both fundamental ecological insights and knowledge that can be applied to critical conservation concerns as climate change continues.

Diagnostic accuracy of non-contrast magnetic resonance enterography in detecting active bowel inflammation in pediatric patients with diagnosed or suspected inflammatory bowel disease to determine necessity of gadolinium-based contrast agents.

BACKGROUND: Pediatric patients with inflammatory bowel disease (IBD) are at increased risk of gadolinium deposition given the potential need for multiple contrast-enhanced magnetic resonance enterography (MRE) exams over their lifetime. OBJECTIVE: To determine whether gadolinium-based contrast agents are necessary in assessing active bowel inflammation on MRE in pediatric patients with known or suspected IBD. MATERIALS AND METHODS: We conducted a retrospective study of 77 patients (7-18 years; 68.8% male) with known (n=58) or suspected (n=19) IBD and endoscopy with biopsy performed within 30 days of MRE without and with contrast evaluated bowel and non-bowel findings. During three visual analysis sessions, two radiologists reviewed pre-, post-, and pre-/post-contrast MRE images. A third radiologist independently reviewed 27 studies to assess inter-reader reliability. We used Cohen kappa (κ), Fleiss kappa, (κF), McNemar test, and sensitivity and specificity to compare MRE readings to combined endoscopic/histopathological findings (the reference standard). RESULTS: The pre- and pre-/post-contrast-enhanced MRE vs. combined endoscopic/histopathological results had moderate agreement (85.7%; κ 0.713, P<0.001; P-value 0.549). Compared to combined endoscopy/histopathology, pre- vs. pre-/post-contrast sensitivity (67%, confidence interval [CI] 0.53-0.79 vs. 67%, CI 0.53-0.79) and specificity (80%, CI 0.59-0.92 vs. 68%, CI 0.46-0.84) varied little (κ 0.42, P<0.001 and κ 0.32, P=0.003, respectively). The three readers had moderate agreement (85.2%; κ 0.695, P=0.001; P-value 0.625). More penetrating complications were identified following contrast administration (P-value 0.04). CONCLUSION: Use of a contrast agent does not improve the detection of active inflammation in the terminal ileum and colon compared to non-contrast MRE, although use of a contrast agent does aid in the detection of penetrating disease.

Missing Satellites Problem: Completeness Corrections to the Number of Satellite Galaxies in the Milky Way are Consistent with Cold Dark Matter Predictions.

A critical challenge to the cold dark matter (CDM) paradigm is that there are fewer satellites observed around the Milky Way than found in simulations of dark matter substructure. We show that there is a match between the observed satellite counts corrected by the detection efficiency of the Sloan Digital Sky Survey (for luminosities L≳340 L_{⊙}) and the number of luminous satellites predicted by CDM, assuming an empirical relation between stellar mass and halo mass. The "missing satellites problem," cast in terms of number counts, is thus solved. We also show that warm dark matter models with a thermal relic mass smaller than 4 keV are in tension with satellite counts, putting pressure on the sterile neutrino interpretation of recent x-ray observations. Importantly, the total number of Milky Way satellites depends sensitively on the spatial distribution of satellites, possibly leading to a "too many satellites" problem. Measurements of completely dark halos below 10^{8} M_{⊙}, achievable with substructure lensing and stellar stream perturbations, are the next frontier for tests of CDM.

Imaging of Lung Transplantation.

Lung transplantation is the only curative treatment for end-stage lung disease, which is caused by a wide variety of pathologies and encountered in a diverse range of patients. Potential recipients, as well as donors are carefully evaluated by imaging prior to transplant for contraindications to the transplant. After transplantation, recipients are imaged in the immediate, early, intermediate, and late periods for complications that may arise and require intervention. Radiography and computed tomography are the 2 most commonly used imaging modalities used to evaluate the chest after lung transplantation.

Older adults recover more marginal knowledge and use feedback more effectively than younger adults: evidence using "I don't know" vs. "I don't remember" for general knowledge questions.

Through three experiments, we examined older and younger adults' metacognitive ability to distinguish between what is not stored in the knowledge base versus merely inaccessible. Difficult materials were selected to test this ability when retrieval failures were very frequent. Of particular interest was the influence of feedback (and lack thereof) in potential new learning and recovery of marginal knowledge across age groups. Participants answered short-answer general knowledge questions, responding "I do not know" (DK) or "I do not remember" (DR) when retrieval failed. After DKs, performance on a subsequent multiple-choice (Exp. 1) and short-answer test following correct-answer feedback (Exp. 2) was lower than after DRs, supporting self-reported not remembering reflects failures of accessibility whereas not knowing captures a lack of availability. Yet, older adults showed a tendency to answer more DK questions correctly on the final tests than younger adults. Experiment 3 was a replication and extension of Experiment 2 including two groups of online participants in which one group was not provided correct answer feedback during the initial short-answer test. This allowed us to examine the degree to which any new learning and recovery of access to marginal knowledge was occurring across the age groups. Together, the findings indicate that (1) metacognitive awareness regarding underlying causes of retrieval failures is maintained across different distributions of knowledge accessibility, (2) older adults use correct answer feedback more effectively than younger adults, and (3) in the absence of feedback, older adults spontaneously recover marginal knowledge.

AAV ablates neurogenesis in the adult murine hippocampus.

Recombinant adeno-associated virus (rAAV) has been widely used as a viral vector across mammalian biology and has been shown to be safe and effective in human gene therapy. We demonstrate that neural progenitor cells (NPCs) and immature dentate granule cells (DGCs) within the adult murine hippocampus are particularly sensitive to rAAV-induced cell death. Cell loss is dose dependent and nearly complete at experimentally relevant viral titers. rAAV-induced cell death is rapid and persistent, with loss of BrdU-labeled cells within 18 hr post-injection and no evidence of recovery of adult neurogenesis at 3 months post-injection. The remaining mature DGCs appear hyperactive 4 weeks post-injection based on immediate early gene expression, consistent with previous studies investigating the effects of attenuating adult neurogenesis. In vitro application of AAV or electroporation of AAV2 inverted terminal repeats (ITRs) is sufficient to induce cell death. Efficient transduction of the dentategyrus (DG)- without ablating adult neurogenesis- can be achieved by injection of rAAV2-retro serotyped virus into CA3. rAAV2-retro results in efficient retrograde labeling of mature DGCs and permits in vivo two-photon calcium imaging of dentate activity while leaving adult neurogenesis intact. These findings expand on recent reports implicating rAAV-linked toxicity in stem cells and other cell types and suggest that future work using rAAV as an experimental tool in the DG and as a gene therapy for diseases of the central nervous system should be carefully evaluated.

Circoviruses and cycloviruses identified in Weddell seal fecal samples from McMurdo Sound, Antarctica.

Circoviridae is a family of circular single-stranded DNA viruses whose members infect a wide variety of hosts. While well characterized in avian and mammalian hosts, little is known about circoviruses associated with Antarctic animals. From 48 Weddell seal (Leptonychotes weddellii) fecal samples collected on the sea ice in McMurdo between Nov 2014 and Dec 2014, we identified and determined the genomes of novel viruses that fall within two genera of the family Circoviridae, i.e. Circovirus (n = 7) and Cyclovirus (n = 45). We named these viruses as werosea circovirus (WerCV) and werosea cyclovirus (WerCyV). The genomes of WerCV and WerCyV share ~63-64% genome-wide pairwise identity with classified circoviruses and cycloviruses, respectively. Based on the species demarcation threshold of 80% for members of the Circoviridae, the genomes of WerCV and WerCyV represent new species in their respective genera. Evidence indicated recombination in five of the 45 WerCyV genomes identified in this study. These are the first circoviruses found associated with Antarctic pinnipeds, adding to those recently identified associated with Adélie (Pygoscelis adeliae) and chinstrap penguins (P. antarcticus).

Atypical appearance of elastofibroma dorsi at thoracotomy sites: a case series and review of the literature.

Thus far, only a single case describing an atypical appearance of elastofibroma dorsi at a prior thoracotomy site has been published in the literature. We describe a series of three cases recently imaged at our institution with the same atypical appearance, in order to highlight and increase recognition of this more unusual morphology in post-operative patients.

Drivers of concentrated predation in an Antarctic marginal-ice-zone food web.

Predators impact preyscapes (3-D distribution of forage species) by consuming prey according to their abilities or by altering prey behavior as they avoid being consumed. We elucidate prey (Antarctic silverfish[Pleuragramma antarctica] and crystal krill[Euphausia chrystallorophias]) responses to predation associated with the marginal ice zone (MIZ) of the McMurdo Sound, Antarctica, polynya. Prey abundance and habitat was sampled across a 30 × 15 km area by remotely-operated vehicle, and included locations that were accessible (ice edge) or inaccessible (solid fast ice) to air-breathing predators. Prey and habitat sampling coincided with bio-logging of Adélie penguins and observations of other air-breathing predators (penguins, seals, and whales), all of which were competing for the same prey. Adélie penguins dived deeper, and more frequently, near the ice edge. Lowered abundance of krill at the ice edge indicated they were depleted or were responding to increased predation and/or higher light levels along the ice edge. Penguin diet shifted increasingly to silverfish from krill during sampling, and was correlated with the arrival of krill-eating whales. Behaviorally-mediated, high trophic transfer characterizes the McMurdo Sound MIZ, and likely other MIZs, warranting more specific consideration in food web models and conservation efforts.

Trials of new germ cell immunohistochemical stains in 93 extragonadal and metastatic germ cell tumors.

Organic cation transporter 3/4 (OCT3/4) is a transcription factor of embryonic stem cells; c-kit (CD117) is a tyrosine kinase receptor implicated in seminoma carcinogenesis. Their reactivity is well characterized in testicular, but not extragonadal and metastatic, germ cell tumors. A total of 93 germ cell tumors (41 seminoma, 22 embryonal carcinoma, 18 teratoma, and 12 yolk sac tumor) were obtained from the central nervous system (30), mediastinum (23), retroperitoneum/abdomen (31), and other locations (9). Immunohistochemical staining for c-kit, placental-like alkaline phosphatase (PLAP), OCT3/4, and new markers D2-40 and AP-2gamma was performed on seminomas; CD30 and epithelial membrane antigen were added for nonseminomas. In embryonal carcinoma, c-kit reacted in 17 of 22 cases, OCT3/4 in 18 of 22, and PLAP in 13 of 22. OCT3/4 was superior to PLAP in intensity and percent cells staining. In seminoma, OCT3/4 and D2-40 were superior to PLAP in intensity and percent cells; c-kit and AP-2gamma were superior in percent cells. D2-40 stained 23 of 24 seminomas strongly but had only weak focal reactivity in 6 of 17 embryonal carcinomas. Sensitivity and specificity were high for OCT3/4 discriminating seminoma and embryonal carcinoma, and c-kit discriminating seminoma, from other germ cell tumors. For embryonal carcinoma, OCT3/4 had higher specificity (0.94) than CD30 (0.786) owing to CD30 reactivity in 3 of 10 teratomas. Epithelial membrane antigen discriminated teratoma from other nonseminomas with a sensitivity of 1 but reacted occasionally in embryonal carcinoma (3/15) and yolk sac tumor (2/7). In conclusion, for extragonadal seminoma, OCT3/4, AP-2gamma, D2-40, and c-kit were equivalently superior to PLAP. For embryonal carcinoma, OCT3/4 was superior to PLAP and more specific than CD30. D2-40 is recommended to discriminate between seminoma and embryonal carcinoma.

Efficient Generation of CA3 Neurons from Human Pluripotent Stem Cells Enables Modeling of Hippocampal Connectivity In Vitro.

Despite widespread interest in using human induced pluripotent stem cells (hiPSCs) in neurological disease modeling, a suitable model system to study human neuronal connectivity is lacking. Here, we report a comprehensive and efficient differentiation paradigm for hiPSCs that generate multiple CA3 pyramidal neuron subtypes as detected by single-cell RNA sequencing (RNA-seq). This differentiation paradigm exhibits characteristics of neuronal network maturation, and rabies virus tracing revealed synaptic connections between stem cell-derived dentate gyrus (DG) and CA3 neurons in vitro recapitulating the neuronal connectivity within the hippocampus. Because hippocampal dysfunction has been implicated in schizophrenia, we applied DG and CA3 differentiation paradigms to schizophrenia-patient-derived hiPSCs. We detected reduced activity in DG-CA3 co-culture and deficits in spontaneous and evoked activity in CA3 neurons from schizophrenia-patient-derived hiPSCs. Our approach offers critical insights into the network activity aspects of schizophrenia and may serve as a promising tool for modeling diseases with hippocampal vulnerability. VIDEO ABSTRACT.

The role of computed tomography in following up pediatric skull fractures.

BACKGROUND: Despite the added radiation exposure and costs, the role of computed tomography (CT) in following pediatric skull fractures has not been fully evaluated. METHODS: We reviewed the radiology reports and images of the initial and follow-up head CT examinations of children with skull fractures to determine whether any interval changes in the fracture morphology and associated complications necessitate a change in clinical management. RESULTS: A total of 316 pediatric cases of skull fractures were identified, including 172 patients with and 144 without follow-up scans. At follow-up, 7% of skull fractures were unchanged, 65% healing, and 28% healed. No patient showed findings to cause a change in clinical management or a need for further medical or surgical intervention regardless of the number and patterns of the fractures or the initial intracranial complications such as intracranial hemorrhage, pneumocephalus, and traumatic brain injuries. CONCLUSIONS: Head CT may be unnecessary in following pediatric skull fractures in asymptomatic patients to avoid added radiation exposure and cost.

Diverse and highly recombinant anelloviruses associated with Weddell seals in Antarctica.

The viruses circulating among Antarctic wildlife remain largely unknown. In an effort to identify viruses associated with Weddell seals (Leptonychotes weddellii) inhabiting the Ross Sea, vaginal and nasal swabs, and faecal samples were collected between November 2014 and February 2015. In addition, a Weddell seal kidney and South Polar skua (Stercorarius maccormicki) faeces were opportunistically sampled. Using high throughput sequencing, we identified and recovered 152 anellovirus genomes that share 63-70% genome-wide identities with other pinniped anelloviruses. Genome-wide pairwise comparisons coupled with phylogenetic analysis revealed two novel anellovirus species, tentatively named torque teno Leptonychotes weddellii virus (TTLwV) -1 and -2. TTLwV-1 (n = 133, genomes encompassing 40 genotypes) is highly recombinant, whereas TTLwV-2 (n = 19, genomes encompassing three genotypes) is relatively less recombinant. This study documents ubiquitous TTLwVs among Weddell seals in Antarctica with frequent co-infection by multiple genotypes, however, the role these anelloviruses play in seal health remains unknown.

Hexabromocyclododecane flame retardant in Antarctica: Research stations as sources.

Historical persistent organic pollutants (POPs) are banned from Antarctica under international treaty; but contemporary-use POPs can enter as additives within polymer and textile products. Over their useful lives these products may release additives in-situ. Indeed, we observed 226 and 109 ng/g dry weight (dw) of the total concentrations of α-, ß- and γ-hexabromocyclododecane (HBCD) in indoor dust from McMurdo Station (U.S.) and Scott Station (New Zealand), respectively. Sewage sludge collected from wastewater treatment facilities at these stations exhibited ∑HBCD of 45 and 69 ng/g dw, respectively. Contaminants originally within the bases may exit to the local outdoor environment via wastewaters. Near McMurdo, maximum ∑HBCD levels in surficial marine sediments and aquatic biota (invertebrates and fish) were 2350 ng/g (total organic carbon basis) and 554 ng/g lipid weight, respectively. Levels declined with distance from McMurdo. Our results illustrate that Antarctic research stations serve as local HBCD sources to the pristine Antarctic environment.

Benthic changes during 10 years of organic enrichment by McMurdo Station, Antarctica.

A benthic habitat along the coast of McMurdo Station in the Ross Sea, Antarctica is enriched by sewage from the station and altered by hydrocarbons and heavy metals in an adjacent historic dumpsite. We report on 10 years of change in the benthic communities from 1988 to 1998 and compare enrichment effects at Australia's Casey Station, East Antarctica. Despite being 14 km apart, reference communities upcurrent and downcurrent of McMurdo Station remained closely similar over time, dominated in all years by a tube building polychaete, Spiophanes tcherniae. The community bordering McMurdo Station was generally a third as abundant as communities at the reference sites over the decade of sampling, although diversity was as high or higher, except in the most contaminated areas. In 1992, organic enrichment of the outfall community intensified and within the year, the opportunistic polychaetes Aphelochaeta sp., Ophryotrocha notialis, Capitella perarmata, and Leitoscoloplos kerguelensis became dominant. Since 1996, two of the three enriched communities have increased in resemblance to the reference communities. Given the observed responsiveness of the benthos to the outfall so far, further changes are anticipated within the year following implementation of sewage treatment in 2003. Organic enrichment by McMurdo Station has had a greater impact on benthic community structure than at Australia's Casey Station.

Anthropogenic disturbance and biodiversity of marine benthic communities in Antarctica: a regional comparison.

The impacts of two Antarctic stations in different regions, on marine sediment macrofaunal communities were compared: McMurdo, a very large station in the Ross Sea; and Casey, a more typical small station in East Antarctica. Community structure and diversity were compared along a gradient of anthropogenic disturbance from heavily contaminated to uncontaminated locations. We examined some of the inherent problems in comparing data from unrelated studies, such as different sampling methods, spatial and temporal scales of sampling and taxonomic uncertainty. These issues generated specific biases which were taken into account when interpreting patterns. Control sites in the two regions had very different communities but both were dominated by crustaceans. Community responses to anthropogenic disturbance (sediment contamination by metals, oils and sewage) were also different. At McMurdo the proportion of crustaceans decreased in disturbed areas and polychaetes became dominant, whereas at Casey, crustaceans increased in response to disturbance, largely through an increase in amphipods. Despite differing overall community responses there were some common elements. Ostracods, cumaceans and echinoderms were sensitive to disturbance in both regions. Capitellid, dorvelleid and orbiniid polychaetes were indicative of disturbed sites. Amphipods, isopods and tanaids had different responses at each station. Biodiversity and taxonomic distinctness were significantly lower at disturbed locations in both regions. The size of the impact, however, was not related to the level of contamination, with a larger reduction in biodiversity at Casey, the smaller, less polluted station. The impacts of small stations, with low to moderate levels of contamination, can thus be as great as those of large or heavily contaminated stations. Regional broad scale environmental influences may be important in determining the composition of communities and thus their response to disturbance, but there are some generalizations regarding responses which will aid future management of stations.

Recruitment, growth and mortality of an Antarctic hexactinellid sponge, Anoxycalyx joubini.

Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future.