Infectious Esophagitis in Children.

Infectious esophagitis is the third most common cause of esophagitis after gastroesophageal reflux disease and eosinophilic esophagitis (EoE) and should always be considered in the differential of patients with dysphagia and odynophagia. The most common organisms causing disease are candida, Herpes simplex virus (HSV) and cytomegalovirus (CMV). It is well recognized that an impaired local or systemic immune system is a risk factor for disease; however, esophageal dysmotility and disruptions in esophageal homeostasis and the esophageal milieu are likely to represent additional risk factors in disease pathogenesis.

Electronic health record-integrated approach for collection of patient-reported outcome measures: a retrospective evaluation.

BACKGROUND: The integration of Patient Reported Outcome Measures (PROMs) into clinical care presents many challenges for health systems. PROMs provide quantitative data regarding patient-reported health status. However, the most effective model for collecting PROMs has not been established. Therefore the purpose of this study is to report the development and preliminary evaluation of the standardized collection of PROMs within a department of orthopedic surgery at a large academic health center. METHODS: We utilized the Users' Guide to Integrating Patient-Reported Outcomes in Electronic Health Records by Gensheimer et al., 2018 as a framework to describe the development of PROMs collection initiative. We framed our initiative by operationalizing the three aspects of PROM collection development: Planning, Selection, and Engagement. Next, we performed a preliminary evaluation of our initiative by assessing the response rate of patients completing PROMs (no. of PROMs completed/no. of PROMs administered) across the entire department (18 clinics), ambulatory clinics only (14 clinics), and hospital-based clinics only (4 clinics). Lastly, we reported on the mean response rates for the top 5 and bottom 5 orthopaedic providers to describe the variability across providers. RESULTS: We described the development of a fully-integrated, population health based implementation strategy leveraging the existing resources of our local EHR to maximize clinical utility of PROMs and routine collection. We collected a large volume of PROMs over a 13 month period (n = 10,951) across 18 clinical sites, 7 clinical specialties and over 100 providers. The response rates varied across the department, ranging from 29 to 42%, depending on active status for the portal to the electronic health record (MyChart). The highest single provider mean response rate was 52%, and the lowest provider rate was 13%. Rates were similar between hospital-based (26%) and ambulatory clinics (29%). CONCLUSIONS: We found that our standardized PROMs collection initiative, informed by Gensheimer et al., achieved scope and scale, but faced challenges in achieving a high response rate commensurate with existing literature. However, most studies reported a targeted recruitment strategy within a narrow clinical population. Further research is needed to elucidate the trade-off between scalability and response rates in PROM collection initiatives.

Deep learning-based algorithm for assessment of knee osteoarthritis severity in radiographs matches performance of radiologists.

A fully-automated deep learning algorithm matched performance of radiologists in assessment of knee osteoarthritis severity in radiographs using the Kellgren-Lawrence grading system. PURPOSE: To develop an automated deep learning-based algorithm that jointly uses Posterior-Anterior (PA) and Lateral (LAT) views of knee radiographs to assess knee osteoarthritis severity according to the Kellgren-Lawrence grading system. MATERIALS AND METHODS: We used a dataset of 9739 exams from 2802 patients from Multicenter Osteoarthritis Study (MOST). The dataset was divided into a training set of 2040 patients, a validation set of 259 patients and a test set of 503 patients. A novel deep learning-based method was utilized for assessment of knee OA in two steps: (1) localization of knee joints in the images, (2) classification according to the KL grading system. Our method used both PA and LAT views as the input to the model. The scores generated by the algorithm were compared to the grades provided in the MOST dataset for the entire test set as well as grades provided by 5 radiologists at our institution for a subset of the test set. RESULTS: The model obtained a multi-class accuracy of 71.90% on the entire test set when compared to the ratings provided in the MOST dataset. The quadratic weighted Kappa coefficient for this set was 0.9066. The average quadratic weighted Kappa between all pairs of radiologists from our institution who took part in the study was 0.748. The average quadratic-weighted Kappa between the algorithm and the radiologists at our institution was 0.769. CONCLUSION: The proposed model performed demonstrated equivalency of KL classification to MSK radiologists, but clearly superior reproducibility. Our model also agreed with radiologists at our institution to the same extent as the radiologists with each other. The algorithm could be used to provide reproducible assessment of knee osteoarthritis severity.

Stream Dissolved Organic Matter in Permafrost Regions Shows Surprising Compositional Similarities but Negative Priming and Nutrient Effects.

Permafrost degradation is delivering bioavailable dissolved organic matter (DOM) and inorganic nutrients to surface water networks. While these permafrost subsidies represent a small portion of total fluvial DOM and nutrient fluxes, they could influence food webs and net ecosystem carbon balance via priming or nutrient effects that destabilize background DOM. We investigated how addition of biolabile carbon (acetate) and inorganic nutrients (nitrogen and phosphorus) affected DOM decomposition with 28-day incubations. We incubated late-summer stream water from 23 locations nested in seven northern or high-altitude regions in Asia, Europe, and North America. DOM loss ranged from 3% to 52%, showing a variety of longitudinal patterns within stream networks. DOM optical properties varied widely, but DOM showed compositional similarity based on Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Addition of acetate and nutrients decreased bulk DOM mineralization (i.e., negative priming), with more negative effects on biodegradable DOM but neutral or positive effects on stable DOM. Unexpectedly, acetate and nutrients triggered breakdown of colored DOM (CDOM), with median decreases of 1.6% in the control and 22% in the amended treatment. Additionally, the uptake of added acetate was strongly limited by nutrient availability across sites. These findings suggest that biolabile DOM and nutrients released from degrading permafrost may decrease background DOM mineralization but alter stoichiometry and light conditions in receiving waterbodies. We conclude that priming and nutrient effects are coupled in northern aquatic ecosystems and that quantifying two-way interactions between DOM properties and environmental conditions could resolve conflicting observations about the drivers of DOM in permafrost zone waterways.

Tundra wildfire triggers sustained lateral nutrient loss in Alaskan Arctic.

Climate change is creating widespread ecosystem disturbance across the permafrost zone, including a rapid increase in the extent and severity of tundra wildfire. The expansion of this previously rare disturbance has unknown consequences for lateral nutrient flux from terrestrial to aquatic environments. Lateral loss of nutrients could reduce carbon uptake and slow recovery of already nutrient-limited tundra ecosystems. To investigate the effects of tundra wildfire on lateral nutrient export, we analyzed water chemistry in and around the 10-year-old  Anaktuvuk River fire scar in northern Alaska. We collected water samples from 21 burned and 21 unburned watersheds during snowmelt, at peak growing season, and after plant senescence in 2017 and 2018. After a decade of ecosystem recovery, aboveground biomass had recovered in burned watersheds, but overall carbon and nitrogen remained ~20% lower, and the active layer remained ~10% deeper. Despite lower organic matter stocks, dissolved organic nutrients were substantially elevated in burned watersheds, with higher flow-weighted concentrations of organic carbon (25% higher), organic nitrogen (59% higher), organic phosphorus (65% higher), and organic sulfur (47% higher). Geochemical proxies indicated greater interaction with mineral soils in watersheds with surface subsidence, but optical analysis and isotopes suggested that recent plant growth, not mineral soil, was the main source of organic nutrients in burned watersheds. Burned and unburned watersheds had similar δ15 N-NO3 - , indicating that exported nitrogen was of preburn origin (i.e., not recently fixed). Lateral nitrogen flux from burned watersheds was 2- to 10-fold higher than rates of background nitrogen fixation and atmospheric deposition estimated in this area. These findings indicate that wildfire in Arctic tundra can destabilize nitrogen, phosphorus, and sulfur previously stored in permafrost via plant uptake and leaching. This plant-mediated nutrient loss could exacerbate terrestrial nutrient limitation after disturbance or serve as an important nutrient release mechanism during succession.

Clinician Knowledge of Societal Guidelines on Management of Gastrointestinal Complications in Esophageal Atresia.

OBJECTIVES: The aim of this study was to assess whether clinicians approached the management of children with esophageal atresia (EA) in accordance with the 2016 European Society of Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN)/North American Society of Paediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN) guidelines on the management of gastrointestinal and nutritional complications in this cohort. METHODS: We invited expert physicians and surgeons closely involved in the care of children with EA (members of the International network on esophageal atresia [INoEA], ESPGHAN EA working group, French national EA registry, European pediatric surgical association (EUPSA), and European rare disease reference network [ERNICA]) to participate in an anonymous online survey containing 15 multiple choice questions concerning the management of gastrointestinal and nutritional complications in children with EA. Questions were based on the management of gastroesophageal reflux disease (GERD) dysphagia, cyanotic spells, feeding and nutrition, anastamotic strictures, and transition to adult care as detailed in the 2016 guidelines. RESULTS: Median concordance with ESPGHAN/NASPHAN EA Guidelines was 69% (16-100%, SD 16%) across all responders. Areas of greatest concordance were in the fields of surveillance endoscopy and medical management of GERD. Areas for potential educational opportunities include: the differential diagnosis and appropriate investigation of dysphagia and the diagnostic evaluation of extraesophageal symptoms. CONCLUSIONS: This survey highlights the importance of improving the understanding and adherence to the EA guidelines amongst clinicians involved in the care of these patients.

What General and Pain-associated Psychological Distress Phenotypes Exist Among Patients with Hip and Knee Osteoarthritis?

BACKGROUND: Psychological distress can negatively influence disability, quality of life, and treatment outcomes for individuals with hip and knee osteoarthritis (OA). Clinical practice guidelines recommend a comprehensive disease management approach to OA that includes the identification, evaluation, and management of psychological distress. However, uncertainty around the best psychological screening and assessment methods, a poor understanding of the heterogeneity of psychological distress in those with OA, and lack of guidance on how to scale treatment have limited the growth of OA care models that effectively address individual psychological needs. QUESTIONS/PURPOSES: (1) Across which general and pain-related psychological distress constructs do individuals seeking conservative care for hip or knee OA report higher scores than the general population of individuals seeking conservative care for musculoskeletal pain conditions? (2) What common psychological phenotypes exist among nonsurgical care-seeking individuals with hip or knee OA? METHODS: The sample included participants from the Duke Joint Health Program (n = 1239), a comprehensive hip and knee OA care program, and the Optimal Screening for Prediction of Referral and Outcome (OSPRO) cohort studies (n = 871) comprising individuals seeking conservative care for knee, shoulder, low back, or neck pain. At the initial evaluation, patients completed the OSPRO Yellow Flag (OSPRO-YF) Assessment Tool, which assesses 11 general and pain-related psychological distress constructs (depression, anxiety, fear of movement, self-efficacy for managing one's own pain). We used OSPRO-YF scores to compare levels of psychological distress between the cohorts. Cohen's d effect sizes were calculated to determine the magnitude of differences between the groups, with d = 0.20, d = 0.50, and d = 0.80 indicating small, medium, and large effect sizes, respectively. We used a latent class analysis to derive psychological distress phenotypes in people with OA based on the 11 OSPRO-YF psychological distress indicators. Psychological distress phenotypes are characterized by specific mood, belief, and behavioral factors that differentiate subgroups within a population. Phenotyping can help providers develop scalable treatment pathways that are better tailored to the common needs of patients. RESULTS: Patients with OA demonstrated higher levels of general and pain-related psychological distress across all psychological constructs except for trait anxiety (that is, anxiety level as a personal characteristic rather than as a response to a stressful situation, like surgery) with small-to-moderate effect sizes. Characteristics with the largest effect sizes in the OA and overall OSPRO cohort were (Cohen's d) general anxiety (-0.66, lower in the OA cohort), pain catastrophizing (the tendency to ruminate over, maginfiy, or feel helpless about a pain experience, 0.47), kinesiophobia (pain-related fear of movement, 0.46), pain self-efficacy (confidence in one's own ability to manage his or her pain, -0.46, lower in the OA cohort), and self-efficacy for rehabilitation (confidence in one's own ability to perform their rehabilitation treatments, -0.44, lower in the OA cohort). The latent class analysis yielded four phenotypes (% sample): high distress (52%, 647 of 1239), low distress (26%, 322 of 1239), low self-efficacy and acceptance (low confidence in managing and willingness to accept pain) (15%, 186 of 1239), and negative pain coping (exhibiting poor pain coping skills) (7%, 84 of 1239). The classification error rate was near zero (2%), and the median of posterior probabilities used to assign subgroup membership was 0.99 (interquartile range 0.98 to 1.00), both indicating excellent model performance. The high-distress group had the lowest mean age (61 ± 11 years) and highest levels of pain intensity (6 ± 2) and disability (HOOS JR: 50 ± 15; KOOS JR: 47 ± 15), whereas the low-distress group had the highest mean age (63 ± 10 years) and lowest levels of pain (4 ± 2) and disability (HOOS JR: 63 ± 15; KOOS JR: 60 ± 12). However, none of these differences met or exceeded anchor-based minimal clinically important difference thresholds. CONCLUSIONS: General and pain-related psychological distress are common among individuals seeking comprehensive care for hip or knee OA. Predominant existing OA care models that focus on biomedical interventions, such as corticosteroid injection or joint replacement that are designed to directly address underlying joint pathology and inflammation, may be inadequate to fully meet the care-related needs of many patients with OA due to their underlying psychological distress. We believe this because biomedical interventions do not often address psychological characteristics, which are known to influence OA-related pain and disability independent of joint pathology. Healthcare providers can develop new comprehensive hip and knee OA treatment pathways tailored to these phenotypes where services such as pain coping skills training, relaxation training, and psychological therapies are delivered to patients who exhibit phenotypes characterized by high distress or negative pain coping. Future studies should evaluate whether tailoring treatment to specific psychological phenotypes yields better clinical outcomes than nontailored treatments, or treatments that have a more biomedical focus. LEVEL OF EVIDENCE: Level III, diagnostic study.

Disparity of health services in patients with knee osteoarthritis before total knee arthroplasty.

BACKGROUND: Recent evidence describes which interventions are driving insurance payments in the management of osteoarthritis (OA) before total knee arthroplasty (TKA); however, relatively little is known about how these costs are distributed among patients. METHODS: We reviewed the Humana claims database for patients who underwent primary TKA from 2009 to 2016. Insurance payments for treatment, imaging, and evaluation and management were calculated from OA diagnosis to TKA, the distribution of payments was determined, and a high-payment group was identified by determining the point at which patients began to account for a disproportionate percentage of payments. This group of high-payment patients was compared with remaining patients (low-payment patients) based on demographic factors and nonarthroplasty payments and utilization. RESULTS: The top 30% of patients accounted for more than 70% of nonarthroplasty payments. High-payment patients were more likely to be younger, female, and more comorbid. Median time from diagnosis to TKA for high-payment patients was 3 times longer than that for low-payment patients (654 days [320-1191] vs 204 days [68-582], P < .001), and median payment per patient was more than 5 times higher ($1891 [1405-2782] vs $362 [198-613], P < .001). CONCLUSIONS: Identification of high-payment patients in the management of knee OA may allow for targeted care pathways and cost-reduction strategies in the nonarthroplasty period, although additional studies are necessary to further characterize this population and efficiently recognize appropriate TKA candidates and timing.

Development of a Comprehensive, Nonsurgical Joint Health Program for People With Osteoarthritis: A Case Report.

BACKGROUND AND PURPOSE: Existing osteoarthritis (OA) care models often fall short in addressing the many biological, psychological, social, and behavioral characteristics that contribute to disability. As US health care shifts towards value-based payment, there is an increasing need to develop and test scalable, cost-effective, and multi-modal OA care models. This administrative case report will describe the development and pilot of a new, value-based comprehensive care model for OA. CASE DESCRIPTION: The Joint Health Program (JHP) is a physical therapist-led conservative care model for individuals with hip and knee OA. In the JHP, physical therapists with specialized training in cognitive behavioral-theory based strategy function as the central care provider (ie, the primary osteoarthritis provider) who delivers evidence-based, psychologically informed interventions and coordinates care within a multi-disciplinary network of dietitians, behavioral health specialists, and orthopedic providers. The JHP is focused on enhancing patient engagement, shared decision making, self-management and multi-modal patient interaction, and long-term follow-up. OUTCOMES: A value-based, comprehensive care program for OA led by physical therapists demonstrated feasibility and acceptability within a large, academic health care system, which has led to its early growth. Barriers to development and integration of the program were addressed through effective collaboration among health care providers, program and health system administrators, and executive leadership. DISCUSSION: The JHP serves as a model for future physical therapist-led, value-based care models that could be developed in other health care systems for OA and other chronic conditions. Future work will identify characteristics that predict program response and compare the effectiveness of this program to existing models of care.

Rapid carbon loss and slow recovery following permafrost thaw in boreal peatlands.

Permafrost peatlands store one-third of the total carbon (C) in the atmosphere and are increasingly vulnerable to thaw as high-latitude temperatures warm. Large uncertainties remain about C dynamics following permafrost thaw in boreal peatlands. We used a chronosequence approach to measure C stocks in forested permafrost plateaus (forest) and thawed permafrost bogs, ranging in thaw age from young (<10 years) to old (>100 years) from two interior Alaska chronosequences. Permafrost originally aggraded simultaneously with peat accumulation (syngenetic permafrost) at both sites. We found that upon thaw, C loss of the forest peat C is equivalent to ~30% of the initial forest C stock and is directly proportional to the prethaw C stocks. Our model results indicate that permafrost thaw turned these peatlands into net C sources to the atmosphere for a decade following thaw, after which post-thaw bog peat accumulation returned sites to net C sinks. It can take multiple centuries to millennia for a site to recover its prethaw C stocks; the amount of time needed for them to regain their prethaw C stocks is governed by the amount of C that accumulated prior to thaw. Consequently, these findings show that older peatlands will take longer to recover prethaw C stocks, whereas younger peatlands will exceed prethaw stocks in a matter of centuries. We conclude that the loss of sporadic and discontinuous permafrost by 2100 could result in a loss of up to 24 Pg of deep C from permafrost peatlands.

Novel wildlife in the Arctic: the influence of changing riparian ecosystems and shrub habitat expansion on snowshoe hares.

Warming during the 20th century has changed the arctic landscape, including aspects of the hydrology, vegetation, permafrost, and glaciers, but effects on wildlife have been difficult to detect. The primary aim of this study is to examine the physical and biological processes contributing to the expanded riparian habitat and range of snowshoe hares (Lepus americanus) in northern Alaska. We explore linkages between components of the riparian ecosystem in Arctic Alaska since the 1960s, including seasonality of stream flow, air temperature, floodplain shrub habitat, and snowshoe hare distributions. Our analyses show that the peak discharge during spring snowmelt has occurred on average 3.4 days per decade earlier over the last 30 years and has contributed to a longer growing season in floodplain ecosystems. We use empirical correlations between cumulative summer warmth and riparian shrub height to reconstruct annual changes in shrub height from the 1960s to the present. The effects of longer and warmer growing seasons are estimated to have stimulated a 78% increase in the height of riparian shrubs. Earlier spring discharge and the estimated increase in riparian shrub height are consistent with observed riparian shrub expansion in the region. Our browsing measurements show that snowshoe hares require a mean riparian shrub height of at least 1.24-1.36 m, a threshold which our hindcasting indicates was met between 1964 and 1989. This generally coincides with observational evidence we present suggesting that snowshoe hares became established in 1977 or 1978. Warming and expanded shrub habitat is the most plausible reason for recent snowshoe hare establishment in Arctic Alaska. The establishment of snowshoe hares and other shrub herbivores in the Arctic in response to increasing shrub habitat is a contrasting terrestrial counterpart to the decline in marine mammals reliant on decreasing sea ice.

Perceptions of palliative care among hematologic malignancy specialists: a mixed-methods study.

PURPOSE: Patients with hematologic malignancies are less likely to receive specialist palliative care services than patients with solid tumors. Reasons for this difference are poorly understood. METHODS: This was a multisite, mixed-methods study to understand and contrast perceptions of palliative care among hematologic and solid tumor oncologists using surveys assessing referral practices and in-depth semistructured interviews exploring views of palliative care. We compared referral patterns using standard statistical methods. We analyzed qualitative interview data using constant comparative methods to explore reasons for observed differences. RESULTS: Among 66 interviewees, 23 oncologists cared exclusively for patients with hematologic malignancies; 43 treated only patients with solid tumors. Seven (30%) of 23 hematologic oncologists reported never referring to palliative care; all solid tumor oncologists had previously referred. In qualitative analyses, most hematologic oncologists viewed palliative care as end-of-life care, whereas most solid tumor oncologists viewed palliative care as a subspecialty that could assist with complex patient cases. Solid tumor oncologists emphasized practical barriers to palliative care referral, such as appointment availability and reimbursement issues. Hematologic oncologists emphasized philosophic concerns about palliative care referrals, including different treatment goals, responsiveness to chemotherapy, and preference for controlling even palliative aspects of patient care. CONCLUSION: Most hematologic oncologists view palliative care as end-of-life care, whereas solid tumor oncologists more often view palliative care as a subspecialty for comanaging patients with complex cases. Efforts to integrate palliative care into hematologic malignancy practices will require solutions that address unique barriers to palliative care referral experienced by hematologic malignancy specialists.

Evaluation of Pillars4life: a virtual coping skills program for cancer survivors.

OBJECTIVE: Pillars4Life is an educational program that teaches coping skills to cancer patients in a virtual group setting; it was recently implemented at 17 hospitals across the USA. The cost-effective, scalable, and assessable Pillars4Life curriculum targets psychosocial resources (e.g., self-efficacy and coping skills) as a means to reduce symptoms (e.g., depression, anxiety, and posttraumatic stress) and enhance quality of life. METHODS: Cancer patients were recruited from hospitals that received the LIVESTRONG Community Impact Project Award to enroll in a pilot study of Pillars4Life. Consenting participants met with a certified instructor weekly for 10 weeks in a virtual environment; the manualized intervention trained participants in personal coping skills. Longitudinal assessments over 6 months were assessed using validated instruments to determine changes in Pillars4Life targeted resources and outcomes. Multiple linear regression models examined the relationship between changes in targeted resources and changes in outcome from baseline to 3 months post-intervention. RESULTS: Participants (n = 130) had the following characteristics: mean age of 56 ± 11 years, 87% women, 11% non-Caucasian, and 77% with college degree. At 3- and 6-month follow-up, mean scores improved on all key outcome measures such as depression (Patient Health Questionnaire), anxiety (Generalized Anxiety Disorder), posttraumatic stress (Posttraumatic Stress Disorder Checklist), fatigue (Functional Assessment of Chronic Illness Therapy-Fatigue), and well-being (Functional Assessment of Cancer Therapy-General) from baseline (all p < 0.01); results were most pronounced among participants who reported ≥4/10 on the Distress Thermometer at baseline (all p < 0.001). Changes in each targeted resource were associated with 3-month improvements in at least one outcome. CONCLUSIONS: Participation in the Pillars4Life program was associated with statistically and clinically significant improvements in scores on pre-specified outcomes and targeted resources.

Water and heat transport in boreal soils: implications for soil response to climate change.

Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with different stand ages and drainage classes. Overall, soil temperatures during the growing season tended to be over-estimated by 2-4°C when movement of liquid water and water vapor was not represented in the model. The role of heat transport in water has broad implications for site responses to warming and suggests reduced vulnerability of permafrost to thaw at drier sites. This result is consistent with field observations of faster thaw in response to warming in wet sites compared to drier sites over the past 30 years in Canadian boreal forests. These results highlight that representation of water flow in heat transport models is important to simulate future soil thermal or permafrost dynamics under a changing climate.

Effects of ammonia on juvenile unionid mussels (Lampsilis cardium) in laboratory sediment toxicity tests.

Ammonia is a relatively toxic compound generated in water and sediments by heterotrophic bacteria and accumulates in sediments and pore water. Recent data suggest that unionid mussels are sensitive to un-ionized ammonia (NH3) relative to other organisms. Existing sediment exposure systems are not suitable for ammonia toxicity studies with juvenile unionids; thus, we modified a system to expose juveniles to ammonia that was continuously infused into sediments. This system maintained consistent concentrations of ammonia in pore water up to 10 d. Juvenile Lampsilis cardium mussels were exposed to NH3 in pore water in replicate 96-h and 10-d sediment toxicity tests. The 96-h median lethal concentrations (LC50s) were 127 and 165 microg NH3-N/L, and the 10-d LC50s were 93 and 140 microg NH3-N/L. The median effective concentrations (EC50s) (based on the proportion affected, including dead and inactive mussels) were 73 and 119 microg NH3-N/L in the 96-h tests and 71 and 99 microg NH3-N/L in the 10-d tests. Growth rate was substantially reduced at concentrations between 31 and 76 microg NH3-N/L. The lethality results (when expressed as total ammonia) are about one-half the acute national water quality criteria for total ammonia, suggesting that existing criteria may not protect juvenile unionids.

Effects of pore-water ammonia on in situ survival and growth of juvenile mussels (Lampsilis cardium) in the St. Croix Riverway, Wisconsin, USA.

We conducted a series of in situ tests to evaluate the effects of pore-water ammonia on juvenile Lampsilis cardium in the St. Croix River (WI, USA). Threats to this river and its associated unionid fauna have accelerated in recent years because of its proximity to Minneapolis-St. Paul, Minnesota, USA. In 2000, caged juveniles were exposed to sediments and overlying water at 12 sites for 10 d. Survival and growth of juveniles was significantly different between sediment (mean, 47%) and water column (mean, 86%) exposures; however, these effects were unrelated to pore-water ammonia. During 2001, juveniles were exposed to sediments for 4, 10, and 28 d. Pore-water ammonia concentrations ranged from 0.3 to 62.0 microg NH3-N/L in sediments and from 0.5 to 140.8 microg NH3-N/L within exposure chambers. Survival (mean, 45, 28, and 41% at 4, 10, and 28 d, respectively) and growth (range, 3-45 microm/d) of juveniles were highly variable and generally unrelated to ammonia concentrations. Although laboratory studies have shown unionids to be quite sensitive to ammonia, further research is needed to identify the route(s) of ammonia exposure in unionids and to understand the factors that contribute to the spatial variability of ammonia in rivers.