Predicting mercury levels in freshwater fish through biotic and abiotic factors: a case study of Nantucket Island

https://digitalcommons.dartmouth.edu/wetterhahnsymposium-2018/1003/thumbnail.jp

Experimental and Natural Warming Elevates Mercury Concentrations in Estuarine Fish

Marine food webs are the most important link between the global contaminant, methylmercury (MeHg), and human exposure through consumption of seafood. Warming temperatures may increase human exposure to MeHg, a potent neurotoxin, by increasing MeHg production as well as bioaccumulation and trophic transfer through marine food webs. Studies of the effects of temperature on MeHg bioaccumulation are rare and no study has specifically related temperature to MeHg fate by linking laboratory experiments with natural field manipulations in coastal ecosystems. We performed laboratory and field experiments on MeHg accumulation under varying temperature regimes using the killifish, Fundulus heteroclitus. Temperature treatments were established in salt pools on a coastal salt marsh using a natural temperature gradient where killifish fed on natural food sources. Temperatures were manipulated across a wider range in laboratory experiments with killifish exposed to MeHg enriched food. In both laboratory microcosms and field mesocosms, MeHg concentrations in killifish significantly increased at elevated temperatures. Moreover, in field experiments, other ancillary variables (salinity, MeHg in sediment, etc.) did not relate to MeHg bioaccumulation. Modeling of laboratory experimental results suggested increases in metabolic rate as a driving factor. The elevated temperatures we tested are consistent with predicted trends in climate warming, and indicate that in the absence of confounding factors, warmer sea surface temperatures could result in greater in bioaccumulation of MeHg in fish, and consequently, increased human exposure

Assessment of Selected Reef Sites in Northern and South-Central Belize, Including Recovery from Bleaching and Hurricane Disturbances (Stony Corals, Algae and Fish)

The condition of coral. algal. and fish populations in fore reefs. patch reefs, and coral reef ridges was investigated at 13 sites along the northern and south-central Belize barrier reef during May 1999, documenting effects of the 1998 warming episode and Hurricane Mitch. We found high percentages of partial, or even complete, colony mortality of major reef-builders (Acropora palmata, the Montastraea annuluris species complex and Agaricia tenuifolia) that were rarely censused as recruits. A. tenuifolia, formerly a space-dominant coral in reef ridges, had incurred nearly 100% mortality after bleaching. Nearly 45% of the M. annurluris complex was still discolored (50% had been bleached in January 1999) on some south-central patch reefs where the total (recent + old) partial mortality exceeded 60% of colony surfaces. Although turf algae dominated patch reefs and coral reef ridges, macroalgae were quite prevalent representing \u3e30% cover at six sites. Parrotfish densities exceeded surgeontishes at most sites (11/13). Consistent patterns of lower partial-colony mortality of stony corals and greater fish densities and sizes near and within the Hol Chan Marine Reserve highlight the ecological benefits of protected areas for the maintenance of reef corals and attendant fish populations

Is there scope for community health nurses to address lifestyle risk factors? : the community nursing SNAP trial

Background: This paper examines the opportunity and need for lifestyle interventions for patients attending generalist community nursing services in Australia. This will help determine the scope for risk factor management within community health care by generalist community nurses (GCNs).Methods: This was a quasi-experimental study conducted in four generalist community nursing services in NSW, Australia. Prior to service contacts, clients were offered a computer-assisted telephone interview to collect baseline data on socio-demographics, health conditions, smoking status, physical activity levels, alcohol consumption, height and weight, fruit and vegetable intake and 'readiness-to-change' for lifestyle risk factors.Results: 804 clients participated (a response rate of 34.1%). Participants had higher rates of obesity (40.5% vs 32.1%) and higher prevalence of multiple risk factors (40.4% vs 29.5%) than in the general population. Few with a SNAPW (Smoking-Nutrition-Alcohol-Physical-Activity-Weight) risk factor had received advice or referral in the previous 3 months. The proportion of clients identified as at risk and who were open to change (i.e. contemplative, in preparation or in action phase) were 65.0% for obese/overweight; 73.8% for smokers; 48.2% for individuals with high alcohol intake; 83.5% for the physically inactive and 59.0% for those with poor nutrition.Conclusions: There was high prevalence of lifestyle risk factors. Although most were ready to change, few clients recalled having received any recent lifestyle advice. This suggests that there is considerable scope for intervention by GCNs. The results of this trial will shed light on how best to implement the lifestyle risk factor management in routine practice

Nutrient Supply and Mercury Dynamics in Marine Ecosystems: A Conceptual Model

There is increasing interest and concern over the impacts of mercury (Hg) inputs to marine ecosystems. One of the challenges in assessing these effects is that the cycling and trophic transfer of Hg are strongly linked to other contaminants and disturbances. In addition to Hg, a major problem facing coastal waters is the impacts of elevated nutrient, particularly nitrogen (N), inputs. Increases in nutrient loading alter coastal ecosystems in ways that should change the transport, transformations and fate of Hg, including increases in fixation of organic carbon and deposition to sediments, decreases in the redox status of sediments and changes in fish habitat. In this paper we present a conceptual model which suggests that increases in loading of reactive N to marine ecosystems might alter Hg dynamics, decreasing bioavailabilty and trophic transfer. This conceptual model is most applicable to coastal waters, but may also be relevant to the pelagic ocean. We present information from case studies that both support and challenge this conceptual model, including marine observations across a nutrient gradient; results of a nutrient‐trophic transfer Hg model for pelagic and coastal ecosystems; observations of Hg species, and nutrients from coastal sediments in the northeastern U.S.; and an analysis of fish Hg concentrations in estuaries under different nutrient loadings. These case studies suggest that changes in nutrient loading can impact Hg dynamics in coastal and open ocean ecosystems. Unfortunately none of the case studies is comprehensive; each only addresses a portion of the conceptual model and has limitations. Nevertheless, our conceptual model has important management implications. Many estuaries near developed areas are impaired due to elevated nutrient inputs. Widespread efforts are underway to control N loading and restore coastal ecosystem function. An unintended consequence of nutrient control measures could be to exacerbate problems associated with Hg contamination. Additional focused research and monitoring are needed to critically examine the link between nutrient supply and Hg contamination of marine waters

Basal fatty acid oxidation increases after recurrent low glucose in human primary astrocytes

YesAims/hypothesis Hypoglycaemia is a major barrier to good glucose control in type 1 diabetes. Frequent hypoglycaemic episodes impair awareness of subsequent hypoglycaemic bouts. Neural changes underpinning awareness of hypoglycaemia are poorly defined and molecular mechanisms by which glial cells contribute to hypoglycaemia sensing and glucose counterregulation require further investigation. The aim of the current study was to examine whether, and by what mechanism, human primary astrocyte (HPA) function was altered by acute and recurrent low glucose (RLG). Methods To test whether glia, specifically astrocytes, could detect changes in glucose, we utilised HPA and U373 astrocytoma cells and exposed them to RLG in vitro. This allowed measurement, with high specificity and sensitivity, of RLG-associated changes in cellular metabolism. We examined changes in protein phosphorylation/expression using western blotting. Metabolic function was assessed using a Seahorse extracellular flux analyser. Immunofluorescent imaging was used to examine cell morphology and enzymatic assays were used to measure lactate release, glycogen content, intracellular ATP and nucleotide ratios. Results AMP-activated protein kinase (AMPK) was activated over a pathophysiologically relevant glucose concentration range. RLG produced an increased dependency on fatty acid oxidation for basal mitochondrial metabolism and exhibited hallmarks of mitochondrial stress, including increased proton leak and reduced coupling efficiency. Relative to glucose availability, lactate release increased during low glucose but this was not modified by RLG. Basal glucose uptake was not modified by RLG and glycogen levels were similar in control and RLG-treated cells. Mitochondrial adaptations to RLG were partially recovered by maintaining euglycaemic levels of glucose following RLG exposure. Conclusions/interpretation Taken together, these data indicate that HPA mitochondria are altered following RLG, with a metabolic switch towards increased fatty acid oxidation, suggesting glial adaptations to RLG involve altered mitochondrial metabolism that could contribute to defective glucose counterregulation to hypoglycaemia in diabetes.Diabetes UK (RD Lawrence Fellowship to CB; 13/0004647); the Medical Research Council (MR/N012763/1) to KLJE, ADR and CB; and a Mary Kinross Charitable Trust PhD studentship to CB, ADR and RW to support PGWP. Additional support for this work came from awards from the British Society for Neuroendocrinology (to CB and KLJE), the Society for Endocrinology (CB), Tenovus Scotland (CB) and the University of Exeter Medical School (CB and KLJE). AR was also supported by a Royal Society Industry Fellowship

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

SummaryBackground Azithromycin has been proposed as a treatment for COVID-19 on the basis of its immunomodulatoryactions. We aimed to evaluate the safety and efficacy of azithromycin in patients admitted to hospital with COVID-19.Methods In this randomised, controlled, open-label, adaptive platform trial (Randomised Evaluation of COVID-19Therapy [RECOVERY]), several possible treatments were compared with usual care in patients admitted to hospitalwith COVID-19 in the UK. The trial is underway at 176 hospitals in the UK. Eligible and consenting patients wererandomly allocated to either usual standard of care alone or usual standard of care plus azithromycin 500 mg once perday by mouth or intravenously for 10 days or until discharge (or allocation to one of the other RECOVERY treatmentgroups). Patients were assigned via web-based simple (unstratified) randomisation with allocation concealment andwere twice as likely to be randomly assigned to usual care than to any of the active treatment groups. Participants andlocal study staff were not masked to the allocated treatment, but all others involved in the trial were masked to theoutcome data during the trial. The primary outcome was 28-day all-cause mortality, assessed in the intention-to-treatpopulation. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936.Findings Between April 7 and Nov 27, 2020, of 16 442 patients enrolled in the RECOVERY trial, 9433 (57%) wereeligible and 7763 were included in the assessment of azithromycin. The mean age of these study participants was65·3 years (SD 15·7) and approximately a third were women (2944 [38%] of 7763). 2582 patients were randomlyallocated to receive azithromycin and 5181 patients were randomly allocated to usual care alone. Overall,561 (22%) patients allocated to azithromycin and 1162 (22%) patients allocated to usual care died within 28 days(rate ratio 0·97, 95% CI 0·87–1·07; p=0·50). No significant difference was seen in duration of hospital stay (median10 days [IQR 5 to >28] vs 11 days [5 to >28]) or the proportion of patients discharged from hospital alive within 28 days(rate ratio 1·04, 95% CI 0·98–1·10; p=0·19). Among those not on invasive mechanical ventilation at baseline, nosignificant difference was seen in the proportion meeting the composite endpoint of invasive mechanical ventilationor death (risk ratio 0·95, 95% CI 0·87–1·03; p=0·24).Interpretation In patients admitted to hospital with COVID-19, azithromycin did not improve survival or otherprespecified clinical outcomes. Azithromycin use in patients admitted to hospital with COVID-19 should be restrictedto patients in whom there is a clear antimicrobial indication

Biotic and abiotic interactions of deep-sea hydrothermal vent-endemic fish on the East Pacific Rise

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2009A study of the ecology of fish endemic to hydrothermal vents on the East Pacific Rise was undertaken utilizing a variety of techniques, focusing on the bythitid Thermichthys hollisi. Stable isotope and gut content analyses were used to elucidate prey choice and trophic relationships. Otolith chemical signatures were investigated to determine whether this technique could be utilized to examine life history strategy and habitat use. Chemical characteristics of preferred fish habitat and gene expression responses habitat chemistry were explored. Gut contents indicated that T. hollisi specimens were actively feeding upon a combination of brachyuran crabs, Alvinocaris shrimp, polychaetes, and zoarcid fish with the majority of fish containing evidence of crustacean prey. Carbon, nitrogen, and sulfur stable isotopic measurements support a chemosynthetically based prey source and place T. hollisi in the uppermost trophic levels of vent communities. The influence of exposure to hydrothermal fluids was apparent in otoliths from both species of vent fish, most noticeably within the relatively elevated Sr:Ca and depleted Mg:Ca ratios. Otolith chemistry suggested that the zoarcid Thermarces cerberus experiences greater direct exposure to diffuse fluids than does T. hollisi, which is concurrent with apparent habitat preferences. Isotopic patterns across the span of the otolith suggested that T. cerberus spends its entire life within the vent system. In contrast, it appeared that T. hollisi exists outside of the influence of hydrothermal activity for some early portion of its life-cycle. Time-lapse photography and in situ electrochemistry indicated that T. hollisi are preferentially utilizing fish holes where there are elevated temperatures and sulfide levels, and variable oxygen levels in comparison to ambient bottom water. A fragment of Cu, Zn superoxide dismutase was successfully amplified from T. hollisi mRNA, but there were no differences in expression levels between tissue types or among individuals within the small sample examined. In general, it appears that T. hollisi is both influenced by and may exert a greater influence on hydrothermal vent communities to a greater degree than initially hypothesized.I was the recipient of a 2003 MIT Presidential Fellowship, a 2004-2007 National Defense Science and Engineering Graduate Fellowship, and received support from the Woods Hole Oceanographic Institution Academic Programs Office as well as National Science Foundation’s Office of Polar Programs (ANT-073965) support to TMS. Funding for my research was provided in part by the National Science Foundation (OCE-032726 and OCE-0324232), the National Oceanic and Atmospheric Administration’s Office of Ocean Exploration and Research (Award Nos. NA03OAR4600110, NA16RP2390, and NA 04OAR4600049) support to TMS and a 2008 Lerner-Gray Grant for Marine Research from the Lerner Gray Memorial Fund of the American Museum of Natural History support to KLB

Building quality mHealth for low resource settings

ISSN:0309-1902ISSN:1464-522