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Florian D Zepf,1,2 Pradeep Rao,1,3 Kevin Runions,3,4 Richard M Stewart,1 Julia K Moore,1,5 Janice WY Wong,1,4 Maike Linden,1,2,6 Idil Sungurtekin,7 Franziska Glass,8 Linda Gut,8 Dirk Peetz,9,10 Gudrun Hintereder,11 Michael Schaab,12 Fritz Poustka,8 Lars Wöckel8,13 1Centre and Discipline of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, University of Western Australia, 2Specialised Child and Adolescent Mental Health Services (CAMHS), Department of Health in Western Australia, 3Community Child and Adolescent Mental Health Services, Department of Health in Western Australia, 4Telethon Kids Institute, University of Western Australia, 5Paediatric Consultation-Liaison Program, Child and Adolescent Mental Health Services, Department of Health in Western Australia, Perth, WA, Australia; 6Clinic for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, RWTH Aachen University, Aachen, 7Department of Child and Adolescent Psychiatry and Psychotherapy, Central Institute of Mental Health, Mannheim, 8Department of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, Goethe University, Frankfurt am Main, 9Institute of Laboratory Medicine, HELIOS Klinikum Berlin-Buch, Berlin, 10Department of Clinical Chemistry and Laboratory Medicine, University Center of the Johannes Gutenberg University Mainz, Mainz, 11Department of Laboratory Medicine, Goethe University, Frankfurt am Main, 12Institute of Laboratory Medicine, Clinical Chemistry and Molecular Diagnostics, University of Leipzig, Leipzig, Germany; 13Center of Child and Adolescent Psychiatry and Psychotherapy, Clienia Littenheid AG, Littenheid, Switzerland Background: Research has implicated that changes in zinc (Zn) metabolism may be associated with the biological underpinnings of eating disorders, in particular anorexia nervosa. However, to date research on the role of Zn in patients with bulimia nervosa (BN) is scarce.Objective: We aimed to explore serum Zn concentrations in young patients with BN, with a focus on the stage of the disorder, comparing acutely ill and recovered patients with BN with healthy controls.Methods: Serum Zn concentrations were obtained from healthy controls and from acutely ill and remitted young patients with BN. Mean duration of remission was 4.0±3.5 years.Results: Remitted patients showed elevated serum Zn concentrations when compared to controls (Cohen’s d=2.022), but concentrations were still in the normal range. Acutely ill patients also had higher serum Zn levels when compared to controls (all values still being within the reference range, Cohen’s d=0.882). There was no difference between acutely ill and remitted patients with BN in serum Zn concentrations. Of note, remitted patients had a significantly higher body weight when compared to the other two groups. Overall, there were no significant differences in dietary preferences with regard to Zn containing foods between the groups.Conclusion: The present study provides preliminary evidence that the underlying factors for changes in Zn serum concentrations in young patients with BN do not vary with regard to the stage of illness (acute versus remitted BN). Further prospective research is needed in order to disentangle the possible interplay between serum Zn status and bulimic eating behaviors. Keywords: bulimia nervosa, zinc, serum concentrations, remission, eating disorders

Changing climate conditions affect dust emissions and the global dust cycle, which in turn affects climate and biogeochemistry. In this study we use observationally constrained model reconstructions of the global dust cycle since the Last Glacial Maximum, combined with different simplified assumptions of atmospheric and sea ice processing of dust-borne iron, to provide estimates of soluble iron deposition to the oceans. For different climate conditions, we discuss uncertainties in model-based estimates of atmospheric processing and dust deposition to key oceanic regions, highlighting the large degree of uncertainty of this important variable for ocean biogeochemistry and the global carbon cycle. We also show the role of sea ice acting as a time buffer and processing agent, which results in a delayed and pulse-like soluble iron release into the ocean during the melting season, with monthly peaks up to ~17 Gg/month released into the Southern Oceans during the Last Glacial Maximum (LGM).

A large database of field estimates of phytoplankton community growth rates in natural populations was compiled and analyzed to determine the apparent temperature effect on phytoplankton community growth rate. We conducted an ordinary least squares regression to optimize the parameters in two commonly used growth-temperature relations (Arrhenius and Q10 models). Both equations fit the observational data equally with the optimized parameter values. The optimum apparent Q10 value was 1.47 ± 0.08 (95% confidence interval, CI). Microzooplankton grazing rates closely matched the temperature trends for phytoplankton growth. This likely reflects a dynamic adjustment of biomass and grazing rates by the microzooplankton to match their available food source, illustrating tight coupling of phytoplankton growth and microzooplankton grazing rates. The field-measured temperature effect and growth rates were compared with estimates from the satellite Carbon-based Productivity Model (CbPM) and three Earth System Models (ESMs), with model output extracted at the same month and sampling locations as the observations. The optimized, apparent Q10 value calculated for the CbPM was 1.51, with overestimation of growth rates. The apparent Q10 value in the Community Earth System Model (V1.0) was 1.65, with modest underestimation of growth rates. The GFDL-ESM2M and GFDL-ESM2G models produced apparent Q10 values of 1.52 and 1.39, respectively. Models with an apparent Q10 that is significantly greater than ~1.5 will overestimate the phytoplankton community growth response to the ongoing climate warming and will have spatial biases in estimated growth rates for the current era.

Numerical models of ocean biogeochemistry are relied upon to make projections about the impact of climate change on marine resources and test hypotheses regarding the drivers of past changes in climate and ecosystems. In large areas of the ocean, iron availability regulates the functioning of marine ecosystems and hence the ocean carbon cycle. Accordingly, our ability to quantify the drivers and impacts of fluctuations in ocean ecosystems and carbon cycling in space and time relies on first achieving an appropriate representation of the modern marine iron cycle in models. When the iron distributions from 13 global ocean biogeochemistry models are compared against the latest oceanic sections from the GEOTRACES program, we find that all models struggle to reproduce many aspects of the observed spatial patterns. Models that reflect the emerging evidence for multiple iron sources or subtleties of its internal cycling perform much better in capturing observed features than their simpler contemporaries, particularly in the ocean interior. We show that the substantial uncertainty in the input fluxes of iron results in a very wide range of residence times across models, which has implications for the response of ecosystems and global carbon cycling to perturbations. Given this large uncertainty, iron fertilization experiments based on any single current generation model should be interpreted with caution. Improvements to how such models represent iron scavenging and also biological cycling are needed to raise confidence in their projections of global biogeochemical change in the ocean.

Organic macromolecules constitute a high percentage of remote sea spray. They enter the atmosphere through adsorption onto bubbles followed by bursting at the ocean surface, and go on to influence the chemistry of the fine mode aerosol. We present a global estimate of mixed-layer macromolecular distributions, driven by offline marine systems model output. The approach permits estimation of oceanic concentrations and bubble film surface coverages for several classes of organic compound. Mixed layer levels are computed from the output of a global ocean ecodynamics model by relating the macromolecules to standard biogeochemical tracers. Steady state is assumed for labile forms, and for longer-lived components we rely on ratios to existing transported variables. Adsorption is then represented through conventional Langmuir isotherms, with equilibria deduced from laboratory analogs. Open water concentrations locally exceed one micromolar carbon for the total of proteins, polysaccharides and refractory heteropolycondensates. The shorter-lived lipids remain confined to regions of strong biological activity. Results are evaluated against available measurements for all compound types, and agreement is generally well within an order of magnitude. Global distributions are further estimated for both fractional coverage of bubble films at the air–water interface and the two-dimensional concentration excess. Overall, we show that macromolecular mapping provides a novel tool for the comprehension of oceanic surfactant patterns. These results may prove useful in planning field experiments and assessing the potential response of surface chemical behaviors to global change.

©2015. American Geophysical Union. Improved constraints on carbon cycle responses to climate change are needed to inform mitigation policy, yet our understanding of how these responses may evolve after 2100 remains highly uncertain. Using the Community Earth System Model (v1.0), we quantified climate-carbon feedbacks from 1850 to 2300 for the Representative Concentration Pathway 8.5 and its extension. In three simulations, land and ocean biogeochemical processes experienced the same trajectory of increasing atmospheric CO2. Each simulation had a different degree of radiative coupling for CO2 and other greenhouse gases and aerosols, enabling diagnosis of feedbacks. In a fully coupled simulation, global mean surface air temperature increased by 9.3K from 1850 to 2300, with 4.4K of this warming occurring after 2100. Excluding CO2, warming from other greenhouse gases and aerosols was 1.6K by 2300, near a 2K target needed to avoid dangerous anthropogenic interference with the climate system. Ocean contributions to the climate-carbon feedback increased considerably over time and exceeded contributions from land after 2100. The sensitivity of ocean carbon to climate change was found to be proportional to changes in ocean heat content, as a consequence of this heat modifying transport pathways for anthropogenic CO2 inflow and solubility of dissolved inorganic carbon. By 2300, climate change reduced cumulative ocean uptake by 330PgC, from 1410PgC to 1080PgC. Land fluxes similarly diverged over time, with climate change reducing stocks by 232PgC. Regional influence of climate change on carbon stocks was largest in the North Atlantic Ocean and tropical forests of South America. Our analysis suggests that after 2100, oceans may become as important as terrestrial ecosystems in regulating the magnitude of the climate-carbon feedback.

Selective removal of nitrogen (N) and phosphorus (P) from the marine dissolved organic matter (DOM) pool has been reported in several regional studies. Because DOM is an important advective/mixing pathway of carbon (C) export from the ocean surface layer and its non-Redfieldian stoichiometry would affect estimates of marine export production per unit N and P, we investigated the stoichiometry of marine DOM and its remineralization globally using a compiled DOM data set. Marine DOM is enriched in C and N compared to Redfield stoichiometry, averaging 317:39:1 and 810:48:1 for C:N:P within the degradable and total bulk pools, respectively. Dissolved organic phosphorus (DOP) is found to be preferentially remineralized about twice as rapidly with respect to the enriched C:N stoichiometry of marine DOM. Biogeochemical simulations with the Biogeochemical Elemental Cycling model using Redfield and variable DOM stoichiometry corroborate the need for non-Redfield dynamics to match the observed DOM stoichiometry. From our model simulations, preferential DOP remineralization is found to increase the strength of the biological pump by ∼9% versus the case of Redfield DOM cycling. Global net primary productivity increases ∼10% including an increase in marine nitrogen fixation of ∼26% when preferential DOP remineralization and direct utilization of DOP by phytoplankton are included. The largest increases in marine nitrogen fixation, net primary productivity, and carbon export are observed within the western subtropical gyres, suggesting the lateral transfer of P in the form of DOP from the productive eastern and poleward gyre margins may be important for sustaining these processes downstream in the subtropical gyres.

Dissolved organic matter (DOM) plays an important role in the ocean's biological carbon pump by providing an advective/mixing pathway for ∼ 20% of export production. DOM is known to have a stoichiometry depleted in nitrogen (N) and phosphorus (P) compared to the particulate organic matter pool, a fact that is often omitted from biogeochemical ocean general circulation models. However the variable C : N : P stoichiometry of DOM becomes important when quantifying carbon export from the upper ocean and linking the nutrient cycles of N and P with that of carbon. Here we utilize recent advances in DOM observational data coverage and offline tracer-modeling techniques to objectively constrain the variable production and remineralization rates of the DOM C : N : P pools in a simple biogeochemical-ocean model of DOM cycling. The optimized DOM cycling parameters are then incorporated within the Biogeochemical Elemental Cycling (BEC) component of the Community Earth System Model (CESM) and validated against the compilation of marine DOM observations. The optimized BEC simulation including variable DOM C : N : P cycling was found to better reproduce the observed DOM spatial gradients than simulations that used the canonical Redfield ratio. Global annual average export of dissolved organic C, N, and P below 100 m was found to be 2.28 Pg C yr-1 (143 Tmol C yr-1, 16.4 Tmol N yrg1, and 1 Tmol P yr-1, respectively, with an average export C : N : P stoichiometry of 225 : 19 : 1 for the semilabile (degradable) DOM pool. Dissolved organic carbon (DOC) export contributed ∼ 25% of the combined organic C export to depths greater than 100 m.

The ratio of carbon (C) to phosphorus (P) in marine phytoplankton is thought to be constant throughout the worlds'oceans. Known as the Redfield ratio, this relationship describes the links between carbon and phosphorus cycling and marine ecosystems. However, variations in the stoichiometry of phytoplankton have recently been identified, in particular strong latitudinal variability. Here we assess the impact of this variability in the C:P ratio of biomass on the C:P ratio of organic matter that is exported to the deep ocean using a biogeochemical inverse-model based on a data-constrained ocean circulation model and a global database of dissolved inorganic carbon and phosphate measurements. We identify global patterns of variability in the C:P ratios of exported organic matter, with higher values in the nutrient-depleted subtropical gyres, where organic matter export is relatively low, and lower ratios in nutrient-rich upwelling zones and high-latitude regions, where organic matter export is high. This suggests that total carbon export is relatively constant throughout the oceans, in agreement with recent estimates of carbon fluxes. We conclude that the latitudinal patterns of C:P in exported organic matter are consistent with the large-scale stoichiometric variations in phytoplankton C:P. We suggest that a future expansion of nutrient-depleted waters could result in a shift to more efficient C export that compensates for the expected decline in productivity.

Iron is a key nutrient for phytoplankton growth in the surface ocean. At high latitudes, the iron cycle is closely related to the dynamics of sea ice. In recent decades, Arctic sea ice cover has been declining rapidly and Antarctic sea ice has exhibited large regional trends. A significant reduction of sea ice in both hemispheres is projected in future climate scenarios. In order to adequately study the effect of sea ice on the polar iron cycle, sea ice bearing iron was incorporated in the Community Earth System Model (CESM). Sea ice acts as a reservoir for iron during winter and releases the trace metal to the surface ocean in spring and summer. Simulated iron concentrations in sea ice generally agree with observations in regions where iron concentrations are relatively low. The maximum iron concentrations simulated in Arctic and Antarctic sea ice are much lower than observed, which is likely due to underestimation of iron inputs to sea ice or missing mechanisms. The largest iron source to sea ice is suspended sediments, contributing fluxes of iron of 2.2 × 108mol Fe month-1in the Arctic and 4.1 × 106mol Fe month-1in the Southern Ocean during summer. As a result of the iron flux from ice, iron concentrations increase significantly in the Arctic. Iron released from melting ice increases phytoplankton production in spring and summer and shifts phytoplankton community composition in the Southern Ocean. Results for the period of 1998 to 2007 indicate that a reduction of sea ice in the Southern Ocean will have a negative influence on phytoplankton production. Iron transport by sea ice appears to be an important process bringing iron to the central Arctic. The impact of ice to ocean iron fluxes on marine ecosystems is negligible in the current Arctic Ocean, as iron is not typically the growth-limiting nutrient. However, it may become a more important factor in the future, particularly in the central Arctic, as iron concentrations will decrease with declining sea ice cover and transport.

Version 1 of the Community Earth SystemModel, in the configurationwhere its full carbon cycle is enabled, is introduced and documented. In this configuration, the terrestrial biogeochemical model, which includes carbon-nitrogen dynamics and is present in earlier model versions, is coupled to an ocean biogeochemical model and atmospheric CO2 tracers. The authors provide a description of the model, detail how preindustrial-control and twentieth-century experiments were initialized and forced, and examine the behavior of the carbon cycle in those experiments. They examine how sea- and land-to-air CO2 fluxes contribute to the increase of atmospheric CO2 in the twentieth century, analyze how atmospheric CO2 and its surface fluxes vary on interannual time scales, including how they respond to ENSO, and describe the seasonal cycle of atmospheric CO2 and its surface fluxes. While the model broadly reproduces observed aspects of the carbon cycle, there are several notable biases, including having too large of an increase in atmospheric CO2 over the twentieth century and too small of a seasonal cycle of atmospheric CO2 in the Northern Hemisphere. The biases are related to a weak response of the carbon cycle to climatic variations on interannual and seasonal time scales and to twentieth-century anthropogenic forcings, including rising CO2, land-use change, and atmospheric deposition of nitrogen.

Microbial activity is a fundamental component of oceanic nutrient cycles. Photosynthetic microbes, collectively termed phytoplankton, are responsible for the vast majority of primary production in marine waters. The availability of nutrients in the upper ocean frequently limits the activity and abundance of these organisms. Experimental data have revealed two broad regimes of phytoplankton nutrient limitation in the modern upper ocean. Nitrogen availability tends to limit productivity throughout much of the surface low-latitude ocean, where the supply of nutrients from the subsurface is relatively slow. In contrast, iron often limits productivity where subsurface nutrient supply is enhanced, including within the main oceanic upwelling regions of the Southern Ocean and the eastern equatorial Pacific. Phosphorus, vitamins and micronutrients other than iron may also (co-)limit marine phytoplankton. The spatial patterns and importance of co-limitation, however, remain unclear. Variability in the stoichiometries of nutrient supply and biological demand are key determinants of oceanic nutrient limitation. Deciphering the mechanisms that underpin this variability, and the consequences for marine microbes, will be a challenge. But such knowledge will be crucial for accurately predicting the consequences of ongoing anthropogenic perturbations to oceanic nutrient biogeochemistry. © 2013 Macmillan Publishers Limited. All rights reserved.

Nearly 75 years ago, Alfred C. Redfield observed a similarity between the elemental composition of marine plankton in the surface ocean and dissolved nutrients in the ocean interior. This stoichiometry, referred to as the Redfield ratio, continues to be a central tenet in ocean biogeochemistry, and is used to infer a variety of ecosystem processes, such as phytoplankton productivity and rates of nitrogen fixation and loss2-4. Model, field and laboratory studies have shown that different mechanisms can explain both constant and variable ratios of carbon to nitrogen and phosphorus among ocean plankton communities. The range of C/N/P ratios in the ocean, and their predictability, are the subject of much active research. Here we assess global patterns in the elemental composition of phytoplankton and particulate organic matter in the upper ocean, using published and unpublished observations of particulate phosphorus, nitrogen and carbon from a broad latitudinal range, supplemented with elemental data for surface plankton populations. We show that the elemental ratios of marine organic matter exhibit large spatial variations, with a global average that differs substantially from the canonical Redfield ratio. However, elemental ratios exhibit a clear latitudinal trend. Specifically, we observed a ratio of 195:28:1 in the warm nutrient-depleted low-latitude gyres, 137:18:1 in warm, nutrient-rich upwelling zones, and 78:13:1 in cold, nutrient-rich high-latitude regions. We suggest that the coupling between oceanic carbon, nitrogen and phosphorus cycles may vary systematically by ecosystem. © 2013 Macmillan Publishers Limited. All rights reserved.

Ocean carbon uptake and storage simulated by the Community Earth System Model, version 1-Biogeochemistry [CESM1(BGC)], is described and compared to observations. Fully coupled and ocean-ice configurations are examined; both capture many aspects of the spatial structure and seasonality of surface carbon fields. Nearly ubiquitous negative biases in surface alkalinity result from the prescribed carbonate dissolution profile. The modeled sea-air CO2 fluxes match observationally based estimates over much of the ocean; significant deviations appear in the Southern Ocean. Surface ocean pCO2 is biased high in the subantarctic and low in the sea ice zone. Formation of the water masses dominating anthropogenic CO2 (Cant) uptake in the Southern Hemisphere is weak in the model, leading to significant negative biases in Cant and chlorofluorocarbon (CFC) storage at intermediate depths. Column inventories of Cant appear too high, by contrast, in the North Atlantic. In spite of the positive bias, this marks an improvement over prior versions of the model, which underestimated North Atlantic uptake. The change in behavior is attributable to a new parameterization of density-driven overflows. CESM1(BGC) provides a relatively robust representation of the ocean-carbon cycle response to climate variability. Statistical metrics of modeled interannual variability in sea-air CO2 fluxes compare reasonably well to observationally based estimates. The carbon cycle response to key modes of climate variability is basically similar in the coupled and forced ocean-ice models; however, the two differ in regional detail and in the strength of teleconnections. © 2013 American Meteorological Society.

We quantify the mechanisms governing interannual variability in the global, upper-ocean inorganic carbon system using a hindcast simulation (1979-2004) of an ecosystem-biogeochemistry model forced with time-evolving atmospheric physics and dust deposition. We analyze the variability of three key, interrelated metrics-air-sea CO2 flux, surface-water carbon dioxide partial pressure pCO2, and upper-ocean dissolved inorganic carbon (DIC) inventory-presenting for each metric global spatial maps of the root mean square (rms) of anomalies from a model monthly climatology. The contribution of specific driving factors is diagnosed using Taylor expansions and linear regression analysis. The major regions of variability occur in the Southern Ocean, tropical Indo-Pacific, and Northern Hemisphere temperate and subpolar latitudes. Ocean circulation is the dominant factor driving variability over most of the ocean, modulating surface dissolved inorganic carbon that in turn alters surface-water pCO2 and air-sea CO2 flux variability (global integrated anomaly rms of 0.34 Pg C yr-1). Biological export and thermal solubility effects partially damp circulation-driven pCO2 variability in the tropics, while in the subtropics, thermal solubility contributes positively to surface-water pCO2 and air-sea CO2 flux variability. Gas transfer and net freshwater inputs induce variability in the air-sea CO2 flux in some specific regions. A component of air-sea CO2 flux variability (global integrated anomaly rms of 0.14 Pg C yr-1) arises from variations in biological export production induced by variations in atmospheric iron deposition downwind of dust source regions. Beginning in the mid-1990s, reduced global dust deposition generates increased air-sea CO2 outgassing in the Southern Ocean, consistent with trends derived from atmospheric CO2 inversions. © 2008 Elsevier Ltd.

Depth-integrated primary productivity (PP) estimates obtained from satellite ocean color-based models (SatPPMs) and those generated from biogeochemical ocean general circulation models (BOGCMs) represent a key resource for biogeochemical and ecological studies at global as well as regional scales. Calibration and validation of these PP models are not straightforward, however, and comparative studies show large differences between model estimates. The goal of this paper is to compare PP estimates obtained from 30 different models (21 SatPPMs and 9 BOGCMs) to a tropical Pacific PP database consisting of ∼ 1000 14C measurements spanning more than a decade (1983-1996). Primary findings include: skill varied significantly between models, but performance was not a function of model complexity or type (i.e. SatPPM vs. BOGCM); nearly all models underestimated the observed variance of PP, specifically yielding too few low PP (< 0.2 g C m- 2 d- 1) values; more than half of the total root-mean-squared model-data differences associated with the satellite-based PP models might be accounted for by uncertainties in the input variables and/or the PP data; and the tropical Pacific database captures a broad scale shift from low biomass-normalized productivity in the 1980s to higher biomass-normalized productivity in the 1990s, which was not successfully captured by any of the models. This latter result suggests that interdecadal and global changes will be a significant challenge for both SatPPMs and BOGCMs. Finally, average root-mean-squared differences between in situ PP data on the equator at 140°W and PP estimates from the satellite-based productivity models were 58% lower than analogous values computed in a previous PP model comparison 6 years ago. The success of these types of comparison exercises is illustrated by the continual modification and improvement of the participating models and the resulting increase in model skill. © 2008 Elsevier B.V.

We present a generalized framework for assessing the skill of global upper ocean ecosystem-biogeochemical models against in-situ field data and satellite observations. We illustrate the approach utilizing a multi-decade (1979-2004) hindcast experiment conducted with the Community Climate System Model (CCSM-3) ocean carbon model. The CCSM-3 ocean carbon model incorporates a multi-nutrient, multi-phytoplankton functional group ecosystem module coupled with a carbon, oxygen, nitrogen, phosphorus, silicon, and iron biogeochemistry module embedded in a global, three-dimensional ocean general circulation model. The model is forced with physical climate forcing from atmospheric reanalysis and satellite data products and time-varying atmospheric dust deposition. Data-based skill metrics are used to evaluate the simulated time-mean spatial patterns, seasonal cycle amplitude and phase, and subannual to interannual variability. Evaluation data include: sea surface temperature and mixed layer depth; satellite-derived surface ocean chlorophyll, primary productivity, phytoplankton growth rate and carbon biomass; large-scale climatologies of surface nutrients, pCO2, and air-sea CO2 and O2 flux; and time-series data from the Joint Global Ocean Flux Study (JGOFS). Where the data is sufficient, we construct quantitative skill metrics using: model-data residuals, time-space correlation, root mean square error, and Taylor diagrams. © 2008 Elsevier B.V. All rights reserved.

To better understand the role of iron in driving marine ecosystems, the Southern Ocean Iron Experiment (SOFeX) fertilized two surface water patches with iron north and south of the Antarctic Polar Front Zone (APFZ). Using 1-D coupled biological-physical simulations, we examine the biogeochemical dynamics that occurred both inside and outside of the fertilized patches during and shortly after the SOFeX field campaign. We focus, in particular, on three main issues governing the biological response to deliberate iron fertilization: the interaction among phytoplankton, light, macronutrient and iron limitation; dilution and lateral mixing between the fertilized patch and external, unfertilized waters; and the effect of varying mixed layer depth on the light field. At the patch south of the APFZ, sensitivity simulations with no dilution results in the maximum bloom magnitude, whereas dilution with external water extends the development of the north patch bloom by relieving silicon limitation. In model sensitivity studies for both sites, maximum chlorophyll concentration and dissolved inorganic carbon depletion inside the fertilized patches are inversely related to mixed layer depth, similar to the patterns observed across a number of iron fertilization field experiments. Our results suggest that Southern Ocean phytoplankton blooms resulting from natural or deliberate iron fertilization will tend to become iron-light co-limited unless the mixed layer depth is quite shallow. © 2007 Elsevier B.V. All rights reserved.

We present a synthesis of the rates of gross, new, net and primary production along with particulate organic carbon (POC) flux at 100 m from four cruises along 170°W in the Southern Ocean. Concurrent satellite pigment data, a primary productivity model, and a nitrate mass balance are used to extrapolate daily production estimates in space and time to seasonal and annual rates. From this analysis, we gain a better understanding of the timing, magnitude and impact of the phytoplankton blooms in this region. One of the dominant features with respect to plankton biomass is the association of high chlorophyll levels with the retreat of the sea ice which begins in October just south of the Polar Front. Our primary production model and satellite pigment data suggest higher production and flux levels characterize the marginal ice zone than previous estimates. Elevated rates of new production in ice impacted regions are restricted to relatively short periods following retreat of the ice edge. Export is found to lag the onset of production by up to 1 month. The ratio of POC flux at 100 m to primary production when averaged over the entire season is quite high, increasing from 15% to 25% in the Subantarctic zones to 35-40% near the Polar Front and as high as 50-65% in the southernmost stations, just north of the Ross Sea gyre. Comparisons of phytoplankton community structure and Fe stress indicators suggest that blooms at the Polar Front are initially dominated by large centric diatoms, but are replaced by smaller pennate diatom and non-diatom species as Fe levels decrease. Further south, where Fe levels are never as high and large diatoms are not found, we still observe relatively high biomass and elevated production rates and POC fluxes during the short growing season. © 2003 Elsevier Science Ltd. All rights reserved.

Satellite ocean color data from the Sea Viewing Wide Field of View Sensor (SeaWiFS) are used to investigate phytoplankton bloom dynamics at the Antarctic Polar Front (PF). Satellite sea surface temperature (SST) data are used to map the location of the PF at weekly timescales. Elevated chlorophyll within the PF often appears as a narrow band that occupies only a portion of the SST gradient across the PF. Phytoplankton blooms within the PF occur most frequently during the month of December and are unevenly distributed within the Southern Ocean. Elevated chlorophyll concentrations at the PF are most frequently observed where the current is interacting with large topographic features. Mesoscale physical processes, including meander-induced upwelling and increased eddy mixing, where the PF encounters large topographic features likely leads to increased nutrient flux to surface waters in these regions. The highest mean chlorophyll values associated with the PF occur where the front comes into contact with relatively shallow waters along the North Scotia Ridge and at Kerguelen Plateau. Iron input from sedimentary sources likely plays an important role in these regions. Over seasonal timescales it appears likely that light-limitation prevents phytoplankton blooms at the PF during winter and spring months. PF blooms are observed most commonly during December when surface radiation peaks and mixed layer depths are rapidly shoaling. Even during December, when the light regime would seem to be favorable, PF blooms are largely restricted to regions where enhanced nutrient fluxes to surface waters due to frontal dynamics are likely. During late summer, nutrient limitation due to depletion of iron and possibly silicate largely prevent blooms at the PF. In the fall, deepening mixed layers would provide some relief from nutrient limitation but likely lead again to light-limitation of growth rates and the prevention of blooms. © 2002 Elsevier Science B.V. All rights reserved.

A global marine ecosystem mixed-layer model is used to study iron cycling and nutrient-limitation patterns in surface waters of the world ocean. The ecosystem model has a small phytoplankton size class whose growth can be limited by N, P, Fe, and/or light, a diatom class which can also be Si-limited, and a diazotroph phytoplankton class whose growth rates can be limited by P, Fe, and/or light levels. The model also includes a parameterization of calcification by phytoplankton and is described in detail by Moore et al. (Deep-Sea Res. II, 2002). The model reproduces the observed high nitrate, low chlorophyll (HNLC) conditions in the Southern Ocean, subarctic Northeast Pacific, and equatorial Pacific, and realistic global patterns of primary production, biogenic silica production, nitrogen fixation, particulate organic carbon export, calcium carbonate export, and surface chlorophyll concentrations. Phytoplankton cellular Fe/C ratios and surface layer dissolved iron concentrations are also in general agreement with the limited field data. Primary production, community structure, and the sinking carbon flux are quite sensitive to large variations in the atmospheric iron source, particularly in the HNLC regions, supporting the Iron Hypothesis of Martin (Paleoceanography 5 (1990) 1-13). Nitrogen fixation is also strongly influenced by atmospheric iron deposition. Nitrogen limits phyuoplankton growth rates over less than half of the world ocean during summer months. Export of biogenic carbon is dominated by the sinking particulate flux, but detrainment and turbulent mixing account for 30% of global carbon export. Our results, in conjunction with other recent studies, suggest the familiar paradigm that nitrate inputs to the surface layer can be equated with particulate carbon export needs to be expanded to include multiple limiting nutrients and modes of export. © 2001 Elsevier Science Ltd. All rights reserved.

A new marine ecosystem model designed for the global domain is presented, and model output is compared with field data from nine different locations. Field data were collected as part of the international Joint Global Ocean Flux Study (JGOFS) program, and from historical time series stations. The field data include a wide variety of marine ecosystem types, including nitrogen- and iron-limited systems, and different physical environments from high latitudes to the mid-ocean gyres. Model output is generally in good agreement with field data from these diverse ecosystems. These results imply that the ecosystem model presented here can be reliably applied over the global domain. The model includes multiple potentially limiting nutrients that regulate phytoplankton growth rates. There are three phytoplankton classes, diatoms, diazotrophs, and a generic small phytoplankton class. Growth rates can be limited by available nitrogen, phosphorus, iron, and/or light levels. The diatoms can also be limited by silicon. The diazotrophs are capable of nitrogen fixation of N2 gas and cannot be nitrogen-limited. Calcification by phytoplankton is parameterized as a variable fraction of primary production by the small phytoplankton group. There is one zooplankton class that grazes the three phytoplankton groups and a large detrital pool. The large detrital pool sinks out of the mixed layer, while a smaller detrital pool, representing dissolved organic matter and very small particulates, does not sink. Remineralization of the detrital pools is parameterized with a temperature-dependent function. We explicitly model the dissolved iron cycle in marine surface waters including inputs of iron from subsurface sources and from atmospheric dust deposition. © 2001 Elsevier Science Ltd. All rights reserved.

The United States Southern Ocean Joint Global Ocean Flux Study (JGOFS), also known as AESOPS (Antarctic Environment and Southern Ocean Process Study), focused on two distinct regions. The first was the Ross-Sea continental shelf, where a series of six cruises collected a variety of data from October 1996 through February 1998. The second area was the southwest Pacific sector of the Southern Ocean, spanning the Antarctic Circumpolar Current (ACC) at ∼ 170°W. Data were collected within this region during five cruises from September 1996 through March 1998, as well as during selected transits between New Zealand and the Ross Sea. The first results of these cruises are described in this issue. The Ross-Sea investigation extensively sampled the area along 76°30′S to elucidate the temporal patterns and processes that contribute to making this one of the Antarctic's most productive seas. Hydrographic distributions confirm that stratification is initiated early in October within the polynya, generating an environment that is favorable for phytoplankton growth. Significant spatial variations in mixed-layer depths, the timing of the onset of stratification, and the strength of the stratification existed throughout the growing season. Nutrient concentrations reflected phytoplankton uptake, and reached their seasonal minimal in early February. Chlorophyll concentrations were maximal in early January, whereas productivity was maximal in late November, which reflects the temporal uncoupling between growth and biomass accumulation in the region. Independent estimates of biogenic export suggest that majority of the flux occurred in late summer and was strongly uncoupled from phytoplankton growth. The ACC region exhibited seasonal changes that in some cases were greater than those observed in the Ross Sea.

The growth rates and buoyancy properties of 3 oceanic diatoms in the genus Rhizosolenia were examined at light levels from 8 to 211 umol quanta m-2 s-1. Maximum growth rates ranged from 0.37 to 0.78 divisions d-1 with saturation occurring between 29 and 164 umol quanta m-2 s-1. Severe growth rate depressions were noted in R. acuminata and R. formosa at irradiance levels above 50 to 155 umol quanta m-2 s-1. In all 3 species the percentage of positively buoyant cells was inversely related to light intensity. In R. formosa both growth rate and tolerance to high light levels decreased substantially as cell size decreased. Batch culture C:chlorophyll ratios (130 to 261) replicated values found in fieldEthmodiscus and Rhizosolenia mats, and suggest that the elevated C:chlorophyll ratios found in buoyant, oceanic phytoplankton are typical of healthy cells. Calculations suggest that carbohydrate ballasting can account for buoyancy changes and that these reserves are adequate to support dark NO3- uptake. Under steady-state conditions in situ, the observed growth and buoyancy properties would lead to subsurface population maxima in all 3 species. However, the dynamic light-related buoyancy changes probably occur on a shorter time scale than these batch culture experiments. These results indicate that vertical migration is a property basic to these diatoms life history strategy, and, like multispecies Rhizosolenia mats, solitary Rhizosolenia chains transport new nitrogen to the euphotic zone in oligotrophic seas.

Rhizosolenia real abundance, distribution and chemical composition were studied on two cruises in the central North Pacific eyre in order to determine large-scale distribution patterns and contribution to upward nitrogen (N) flux. These macroscopic diatom mats are composed of multiple species of Rhizosolenia that exploit subsurface nitrate pools by vertically migrating below the euphotic zone. Although numerically dominated by the small-diameter species. R.fallax (73-95% of total numbers), mat biovolume was dominated by large-diameter (>50 μm diameter) Rhizostdenia spp. (85- 99% of total volume). Integrated mat abundance was substantially higher when mats accumulated at the surface during calm weather (

The objective of this study was to identify patients' and parents' preferences for anaesthesia in a large sample of adult and paediatric day-surgery patients from two hospitals in the North West of England who had participated in a randomised controlled trial (RCT) of different anaesthetic techniques.The study consisted of telephone interviews up to one week postoperatively. Of the recruited sample, 907 (85%) adults and 260 parents/guardians (81%) were contacted by telephone. Of these, 694 (77%) adult patients and 132 (51%) children received an intravenous induction, and 213 (24%) adult patients and 128 (49%) children received an inhalational induction.Fifty-nine parents and 226 adults refused to be in the RCT because there was a 50% chance of the child and 25% chance of the adult being randomised to the inhalational induction arm. Patients who had an intravenous induction were more likely to rate the experience as 'pleasant' compared to an inhalational induction (P<0.0005). Twenty-four percent of adults and 37% of parents reported discomfort from the injection. Seventeen percent of adults and 37% of parents who had a inhalation induction reported some discomfort with the mask. Forty-four percent of adults and 66% of parents/guardians who had an inhalational induction this time said they would prefer it if they required a surgical procedure in future. Only 6% of adults and 13% of parents/guardians who had an intravenous induction this time would prefer an inhalational induction next time.Patients and parents had strong preferences for modes of anaesthesia. Inhalational induction was unpopular with adult patients and parents of paediatric patients. Experience of this technique improved acceptability considerably. [ABSTRACT FROM AUTHOR]

Purpose: Children far in advance of pubertal development may be deferred from further assessment for gender-affirming medical treatment until nearer puberty. It is vital that returning peripubertal patients are seen promptly to ensure time-sensitive assessment and provision of puberty suppression treatment where appropriate. This study investigates (1) how many referrals to the Child and Adolescent Health Service Gender Diversity Service at Perth Children's Hospital are deferred due to prepubertal status; and (2) how many deferred patients return peripubertally. Methods: A retrospective review of all closed referrals to the service was conducted to determine the frequency of prepubertal deferral and peripubertal re-referral. Results: Of 995 referrals received (2014 to 2020), 552 were closed. The reason for closure was determined for 548 referrals (99.3%). Prepubertal status was the second-most frequent reason for closure, and the most frequent for birth-registered males. Twenty-five percent of all deferred prepubertal patients returned peripubertally, before audit closure. A greater return frequency (55.6%) was estimated for those older than 13 years at audit closure. Conclusion: High rates of prepubertal referral indicate the importance of pediatric gender services in providing information, advice, and reassurance to concerned families. With increasing service demand, high rates of return peripubertally have implications for service planning to ensure that returning peripubertal patients are seen promptly for time-sensitive care. Frequency of peripubertal re-referral cannot, however, speak to the stability of trans identity or gender incongruence from childhood to adolescence. Clinics advising prepubertal deferral must proactively plan to ensure that sufficient clinical resources are reserved for this purpose.

The exon junction complex (EJC), nucleated by EIF4A3, is indispensable for mRNA fate and function throughout eukaryotes. We discover that EIF4A3 directly controls microtubules, independent of RNA, which is critical for neural wiring. While neuronal survival in the developing mouse cerebral cortex depends upon an intact EJC, axonal tract development requires only Eif4a3. Using human cortical organoids, we show that EIF4A3 disease mutations also impair neuronal growth, highlighting conserved functions relevant for neurodevelopmental pathology. Live imaging of growing neurons shows that EIF4A3 is essential for microtubule dynamics. Employing biochemistry and competition experiments, we demonstrate that EIF4A3 directly binds to microtubules, mutually exclusive of the EJC. Finally, in vitro reconstitution assays and rescue experiments demonstrate that EIF4A3 is sufficient to promote microtubule polymerization and that EIF4A3-microtubule association is a major contributor to axon growth. This reveals a fundamental mechanism by which neurons re-utilize core gene expression machinery to directly control the cytoskeleton., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

RNA molecules are localized to subcellular regions through interactions between localization-regulatory cis-elements and trans-acting RNA binding proteins (RBPs). However, the identities of RNAs whose localization is regulated by a specific RBP as well as the impacts of that RNA localization on cell function have generally remained unknown. Here, we demonstrate that the RBP HNRNPA2B1 acts to keep specific RNAs out of neuronal projections. Using subcellular fractionation, high-throughput sequencing, and single molecule RNA FISH, we find that hundreds of RNAs demonstrate markedly increased abundance in neurites in HNRNPA2B1 knockout cells. These RNAs often encode motor proteins and are enriched for known HNRNPA2B1 binding sites and motifs in their 3' UTRs. The speed and processivity of microtubule-based transport is impaired in these cells, specifically in their neurites. HNRNPA2B1 point mutations that increase its cytoplasmic abundance relative to wildtype lead to stronger suppression of RNA mislocalization defects than seen with wildtype HNRNPA2B1. We further find that the subcellular localizations of HNRNPA2B1 target RNAs are sensitive to perturbations of RNA decay machinery, suggesting that it is HNRNPA2B1's known role in regulating RNA stability that may explain these observations. These findings establish HNRNPA2B1 as a negative regulator of neurite RNA abundance and link the subcellular activities of motor proteins with the subcellular abundance of the RNAs that encode them.

β-tubulin isotypes exhibit similar sequences but different activities, suggesting that limited sequence divergence is functionally important. We investigated this hypothesis for TUBB3/β3, a β-tubulin linked to aggressive cancers and chemoresistance in humans. We created mutant yeast strains with β-tubulin alleles that mimic variant residues in β3 and find that residues at the lateral interface are sufficient to alter microtubule dynamics and response to microtubule targeting agents. In HeLa cells, β3 overexpression decreases the lifetime of microtubule growth, and this requires residues at the lateral interface. These microtubules exhibit a shorter region of EB binding at the plus end, suggesting faster lattice maturation, and resist stabilization by paclitaxel. Resistance requires the H1-S2 and H2-S3 regions at the lateral interface of β3. Our results identify the mechanistic origins of the unique activity of β3 tubulin and suggest that tubulin isotype expression may tune the rate of lattice maturation at growing microtubule plus ends in cells.

Objective: The aim of this study was to develop best practice guidelines for preventing suicide and reducing suicidal thoughts and behaviours in LGBTQA+ young people (lesbian, gay, bisexual, trans, queer/questioning, asexual, and those of other diverse sexualities and genders) within clinical and community service settings in Australia., Methods: We conducted a Delphi expert consensus study. A systematic literature search and interviews with key informants informed an initial 270-item questionnaire. Two expert panels completed the questionnaire, delivered over two rounds: (1) Australian professionals with expertise in LGBTQA+ mental health/suicide prevention and (2) Australian LGBTQA+ young people aged 14-25 with lived experience of suicidal thoughts and/or behaviours. Items endorsed as 'essential' or 'important' by >80% of both expert panels were included in the guidelines., Results: A total of 115 people participated in the Delphi process; n  = 52 professionals completed Round 1, and n  = 42 completed Round 2; n  = 63 LGBTQA+ young people completed Round 1, and n  = 50 completed Round 2. A total of 290 items were included in the guidelines and grouped into: (1) general principles for creating an affirming and inclusive environment for LGBTQA+ young people; (2) assessing suicide risk and working with suicidal LGBTQA+ young people; (3) considerations for specific LGBTQA+ populations; and (4) advocating for LGBTQA+ young people., Conclusion: These guidelines are the first of their kind in Australia. They provide practical support to service providers regardless of prior training in LGBTQ+ identities or mental health, with the aim of reducing suicidal thoughts and behaviours, and preventing suicide, in LGBTQA+ young people., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Importance: Some young people who identify as transgender and seek gender-affirming medical care subsequently reidentify with their sex registered at birth. Evidence regarding the frequency and characteristics of this experience is lacking., Objective: To determine the frequency of reidentification and explore associated characteristics in a pediatric gender clinic setting., Design, Setting, and Participants: This retrospective cohort study examined all referrals to the Child and Adolescent Health Service Gender Diversity Service at Perth Children's Hospital between January 1, 2014, and December 31, 2020. The Gender Diversity Service is the sole statewide specialist service in Western Australia that provides children and adolescents up to age 18 years with multidisciplinary assessment, information, support, and gender-affirming medical care. All closed referrals for this study were audited between May 1, 2021, and August 8, 2022., Exposure: Reidentification with birth-registered sex., Main Outcomes and Measures: The number of referrals closed due to reported reidentification with birth-registered sex was determined, as well as descriptives and frequencies of patient demographics (age, birth-registered sex), informant source, International Statistical Classification of Diseases, Tenth Revision gender-related diagnoses, pubertal status, any gender-affirming medical treatment received, and whether subsequent re-referrals were received., Results: Of 552 closed referrals during the study period, a reason for closure could be determined for 548 patients, including 211 birth-registered males (mean [SD] age, 13.88 [2.00] years) and 337 birth-registered females (mean [SD] age, 15.81 [2.22] years). Patients who reidentified with their birth-registered sex comprised 5.3% (29 of 548; 95% CI, 3.6%-7.5%) of all referral closures. Except for 2 patients, reidentification occurred before or during early stages of assessment (93.1%; 95% CI, 77.2%-99.2%). Two patients who reidentified with their birth-registered sex did so following initiation of puberty suppression or gender-affirming hormone treatment (1.0% of 196 patients who initiated any gender-affirming medical treatment; 95% CI, 0.1%-3.6%)., Conclusions and Relevance: These findings from a pediatric gender clinic audit indicate that a small proportion of patients, and a very small proportion of those who initiated medical gender-affirming treatment, reidentified with their birth-registered sex during the study period. Longitudinal follow-up studies, including qualitative self-report, are required to understand different pathways of gender identity experience.

We assess which waters the Clean Water Act protects and how Supreme Court and White House rules change this regulation. We train a deep learning model using aerial imagery and geophysical data to predict 150,000 jurisdictional determinations from the Army Corps of Engineers, each deciding regulation for one water resource. Under a 2006 Supreme Court ruling, the Clean Water Act protects two-thirds of US streams and more than half of wetlands; under a 2020 White House rule, it protects less than half of streams and a fourth of wetlands, implying deregulation of 690,000 stream miles, 35 million wetland acres, and 30% of waters around drinking-water sources. Our framework can support permitting, policy design, and use of machine learning in regulatory implementation problems.

The primary cilium is a critical sensory organelle that is built of axonemal microtubules ensheathed by a ciliary membrane. In polarized epithelial cells, primary cilia reside on the apical surface and must extend these microtubules directly into the extracellular space and remain a stable structure. However, the factors regulating cross-talk between ciliation and cell polarization, as well as axonemal microtubule growth and stabilization in polarized epithelia, are not fully understood. In this study, we find TTLL12, a previously uncharacterized member of the Tubulin Tyrosine Ligase-Like (TTLL) family, localizes to the base of primary cilia and is required for cilia formation in polarized renal epithelial cells. We also show that TTLL12 directly binds to the α/β-tubulin heterodimer in vitro and regulates microtubule dynamics, stability, and post-translational modifications (PTMs). While all other TTLLs catalyze the addition of glutamate or glycine to microtubule C-terminal tails, TTLL12 uniquely affects tubulin PTMs by promoting both microtubule lysine acetylation and arginine methylation. Together, this work identifies a novel microtubule regulator and provides insight into the requirements for apical extracellular axoneme formation., (© 2023. The Author(s).)

Across eukaryotic genomes, multiple α- and β-tubulin genes require regulation to ensure sufficient production of tubulin heterodimers. Features within these gene families that regulate expression remain underexplored. Here, we investigate the role of the 5' intron in regulating α-tubulin expression in Saccharomyces cerevisiae. We find that the intron in the α-tubulin, TUB1, promotes α-tubulin expression and cell fitness during microtubule stress. The role of the TUB1 intron depends on proximity to the TUB1 promoter and sequence features that are distinct from the intron in the alternative α-tubulin isotype, TUB3. These results lead us to perform a screen to identify genes that act with the TUB1 intron. We identified several genes involved in chromatin remodeling, α/β-tubulin heterodimer assembly, and the spindle assembly checkpoint. We propose a model where the TUB1 intron promotes expression from the chromosomal locus and that this may represent a conserved mechanism for tubulin regulation under conditions that require high levels of tubulin production., Competing Interests: Conflicts of interest The authors declare no conflict of interest., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Genetics Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)