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Vaccination has been critical to the decline in infectious disease prevalence in recent centuries. Nonetheless, vaccine refusal has increased in recent years, with complacency associated with reductions in disease prevalence highlighted as an important contributor. We exploit a natural experiment in Glasgow at the beginning of the twentieth century to investigate whether prior local experience of an infectious disease matters for vaccination decisions. Our study is based on smallpox surveillance data and administrative records of parental refusal to vaccinate their infants. We analyse variation between administrative units of Glasgow in cases and deaths from smallpox during two epidemics over the period 1900–1904, and vaccine refusal following its legalization in Scotland in 1907 after a long period of compulsory vaccination. We find that lower local disease incidence and mortality during the epidemics were associated with higher rates of subsequent vaccine refusal. This finding indicates that complacency influenced vaccination decisions in periods of higher infectious disease risk, responding to local prior experience of the relevant disease, and has not emerged solely in the context of the generally low levels of infectious disease risk of recent decades. These results suggest that vaccine delivery strategies may benefit from information on local variation in incidence.

Cancer cachexia (CC) is highly prevalent and associated with significant morbidity and mortality, yet underrecognized. In 2011, an international cachexia consensus (ICC) proposed a definition, assessment framework, and stages for classification: cancer precachexia, cachexia, and refractory cachexia. The authors anticipated that a "more practical classification approach for clinical practice" would be required, which we interpreted as a bedside assessment based on clinical data. We investigated whether the ICC classification could be employed in routine dietetic practice without access to objective muscle mass measures.Data from 200 consecutive patients with solid tumors were collected as part of clinical practice by oncology dietitians in five tertiary referral hospitals. Dietitians used information gathered during their routine assessment and applied the ICC framework to assign a stage. When the dietitian was unable to assign a stage, the reason was noted.Based on available data, classification was possible in 177 (88%); 23 (12%) could not be staged. The reasons cited were as follows: unknown C-reactive protein (n = 14), complex clinical situation (n = 5), unknown weight loss (n = 2), and acute illness (n = 2). Thirty (17%) of the 177 participants were judged to be noncachectic. 112 (83%) met the criteria for one of the three ICC stages: 92 (52%) were cachectic; 35 (20%) precachectic, and 20 (11%) refractory.CC staging based on the ICC classification was feasible and practical in routine dietetic practice even without access to objective muscle mass measures. Once validated and operationalized, expert clinical assessment by a dietitian could be a cost-effective means to identify and stage CC, with more resource-intensive means used when there is clinical doubt.

This article explores how a Midwestern Christian university’s doctoral program aligns an authentic assessment process of evaluation, in lieu of comprehensive exams, with the university’s tag line t...

Comprehensive exams, or “comps,” are a staple of doctoral programs as a way for students to express their understanding of material, synthesize their learning, and apply that learning to their fiel...

PURPOSE: Credible evidence-based diet and nutrition advice is essential for patients with cancer. This study aimed to explore what advice patients with cancer obtained before a formal dietetic visit. METHODS: A multicenter, observational study was conducted in seven hospital-based oncology services. Consecutive patients were recruited at first dietetic assessment. In addition to routine dietetic assessment, participants completed a four-item questionnaire describing diet and nutrition advice obtained since diagnosis. RESULTS: Seventy-seven patients participated. More than 80% had multiple nutrition-impact symptoms. In total, 53 (69%) obtained advice from professional and nonprofessional sources before dietetic visit. Family and friends were the most common sources of advice. More than one third got advice from (nondietetic) healthcare professionals. Most advice related to “foods to include” (61%) and “foods to avoid” (54%) in the diet. Many of the “foods to avoid” were important sources of micro- and macronutrients. Advice about dietary supplements (31%) and specific diets (28%) was common, rarely evidence-based, and frequently contradictory. Participants found it difficult to discern what advice was trustworthy and reliable. Despite this, most followed the advice. CONCLUSION: The majority of patients received diet and nutrition advice before first dietetic visit. Most of this came from nonprofessional sources. Any advice from nondietetic healthcare professionals was inconsistent or vague. This was mainly related to the avoidance and/or inclusion of particular foods and was often contradictory. Nevertheless, patients usually followed such advice fully. To help manage their frequent nutrition-impact symptoms and resolve the contradictory advice they had received, many expressed the need for earlier professional dietetic consultation.

Cancer patients experience many diet and nutrition-related problems, which are often under-recognised and under-treated. Research suggests few healthcare professionals discuss dietary information with cancer patients. Consequently, patients may seek information from other sources. It is unknown what these information sources are or what types of advice patients obtain and follow. The aim of this study was to determine the source and type of diet information cancer patients obtain before their first dietetic assessment and the degree to which this is followed. This was a prospective, multi-center, cross-sectional observational study. Ethical approval was obtained for each centre. Consecutive cancer inpatients and outpatients were recruited for six months at seven tertiary centers. Patients were screened for eligibility. Inclusion criteria included solid tumour, over 18 years of age, new dietetic referral and ability to sign consent. Data collection was carried out by a dietitian during initial routine dietetic assessment. Participants were asked four questions about dietary advice since cancer diagnosis. To date, 74 participants (50% female) with a median age 60 (range 23–80) have been recruited. Forty percent reported weight loss of ≥ 5%. The median time from diagnosis to initial dietetic assessment was 3 months (range 0–242). Patients who obtained advice did so from several sources (median 2 sources per patient, range 0–6) prior to dietetic referral. In rank order these were; 1) family or friend (n = 31), 2) health professional (n = 24), 3) online forums or websites (n = 16) and 4) media (n = 14). Twenty-one (28%) had received no dietary advice. The most frequent advice obtained related to avoidance of certain foods; particularly dairy, meat and sugar. Fruit, vegetables, protein, juices and wholegrain were advised. Fifty-one percent followed the advice fully and 4% partially. Seven expressed disappointment at not having a dietetics referral earlier and identified the need for the hospital “to introduce good information early”. In conclusion, the majority of dietary and nutritional advice prior to dietetic referral came from friends, family, media and online forums and websites. Most advice related to the avoidance and/or promotion of particular foods. Cancer patients want dietary advice from dietitians at diagnosis to prevent unnecessary avoidance of certain foods and to reduce the risk of unintentional weight loss.

Vertical distributions of total and particulate polonium-210 (210Po) and lead-210 (210Pb) activities in the water column were measured at 11 stations in the North Atlantic during the GEOTRACES GA01 transect: GEOVIDE cruise in May–June 2014. Total 210Po activity was on average 24 % lower than 210Pb activity in the upper 100 m, and it was closer to unity in the mesopelagic (100–1000 m). The partitioning coefficients (Kd) along the transect suggest the preferential association of 210Po relative to 210Pb onto particles. The prominent role of small particles in sorption was confirmed by the observation that over 80 % of the particulate radionuclide activity was on small particles. To account for the observed surface water 210Po ∕ 210Pb disequilibria, particulate radionuclide activities and export of both small (1–53 µm) and large (>53 µm) particles must be considered. A comparison between the GEOVIDE total particulate 210Po ∕ 210Pb activity ratios (ARs) and the ratios in previous studies revealed a distinct geographic distribution, with lower particulate ARs in the high-latitude North Atlantic (including this study) and Arctic in relation to all other samples. For the samples where apparent oxygen utilization (AOU) was calculated at the same depth and time as the 210Po ∕ 210Pb AR (40 stations including this study), there was a two-phase correlation between the total particulate AR and AOU, likely reflecting the nature of the particles and demonstrating the forces of remineralization and radionuclide decay from particles as they age.

Through a mixed methodology study of college and university faculty and presidents’ perceptions as they experience presidential change in Christian higher education, researchers addressed t...

The disequilibrium between 210Po and 210Pb has been used as a proxy for the particle flux from the upper ocean. The particle concentration and composition effect on the partitioning behavior of 210Po and 210Pb is, however, still unclear. Here, we investigate this association by comparing dissolved ( 51 µm) 210Po and 210Pb activity with size-fractionated major particle concentration and composition data from the US GEOTRACES GA03 zonal transect cruises. We observed inverse relationships between partition coefficients (Kd) for the radionuclides and the concentration of suspended particulate matter (SPM) in the water column, known as the “particle concentration effect.” We examined the relationships between 210Po, 210Pb, and particle composition in the top 500 m by using Pearson pairwise correlations for individual phases and principal components analysis (PCA) for variations among multiple phases. In addition to these analyses, an end-member mixing model was developed to estimate Kd for 210Po and 210Pb in the small particulate size fraction from the compositional phases. The model predicted the range of observed Kd(Pb) well, but was unable to predict the observed Kd(Po) as consistently, possibly because of the bio-reactive nature of 210Po. Despite this, we found a strong relationship between 210Po and both CaCO3 and POM, as well as between 210Pb and both opal and lithogenic phases. All of our analyses demonstrated that the fractionation of 210Po and 210Pb differed between the margins and open ocean along the GA03 transect.

Deposition of atmospheric aerosols to the surface ocean is considered an important mechanism for the supply of iron (Fe) to remote ocean regions, but direct observations of the oceanic response to aerosol deposition are sparse. In the high nutrient, low chlorophyll (HNLC) subarctic Pacific Ocean we observed a dissolved Fe and Fe(II) anomaly at depth that is best explained as the result of aerosol deposition from Siberian forest fires in May 2012. Interestingly, there was no evidence of enhanced dFe concentrations in surface waters, nor was there a detectable phytoplankton bloom in response to the suspected aerosol deposition. Dissolved Fe (dFe) and Fe(II) showed the strongest enhancement in the subsurface oxygen deficient zone (ODZ), where oxygen concentrations

The disequilibrium between 210Po activity and 210Pb activity in seawater samples was determined along the GEOTRACES GA01 transect in the North Atlantic during the GEOVIDE cruise (May–June 2014). A steady-state model was used to quantify vertical export of particulate 210Po. The deficits of 210Po in the Iberian Basin and at the Greenland Shelf were strongly affected by vertical advection. Using the export flux of 210Po and the particulate organic carbon (POC) to 210Po ratio on total (> 1 µm) particles, we determined the POC export fluxes along the transect. Both the magnitude and efficiency of the estimated POC export flux from the surface ocean varied spatially within our study region. Export fluxes of POC ranged from negligible to 10 mmol C m−2 d−1, with enhanced POC export in the Labrador Sea. The cruise track was characterized by overall low POC export relative to net primary production (export efficiency

The GEOTRACES Intermediate Data Product 2017 (IDP2017) is the second publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2016. The IDP2017 includes data from the Atlantic, Pacific, Arctic, Southern and Indian oceans, with about twice the data volume of the previous IDP2014. For the first time, the IDP2017 contains data for a large suite of biogeochemical parameters as well as aerosol and rain data characterising atmospheric trace element and isotope (TEI) sources. The TEI data in the IDP2017 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at crossover stations. The IDP2017 consists of two parts: (1) a compilation of digital data for more than 450 TEIs as well as standard hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing an on-line atlas that includes more than 590 section plots and 130 animated 3D scenes. The digital data are provided in several formats, including ASCII, Excel spreadsheet, netCDF, and Ocean Data View collection. Users can download the full data packages or make their own custom selections with a new on-line data extraction service. In addition to the actual data values, the IDP2017 also contains data quality flags and 1-σ data error values where available. Quality flags and error values are useful for data filtering and for statistical analysis. Metadata about data originators, analytical methods and original publications related to the data are linked in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2017 as section plots and rotating 3D scenes. The basin-wide 3D scenes combine data from many cruises and provide quick overviews of large-scale tracer distributions. These 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of tracer plumes near ocean margins or along ridges. The IDP2017 is the result of a truly international effort involving 326 researchers from 25 countries. This publication provides the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP2017. This article is part of a special issue entitled: Conway GEOTRACES - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González., National Science Foundation (U.S.) (Grant OCE-0608600), National Science Foundation (U.S.) (Grant OCE0938349), National Science Foundation (U.S.) (Grant OCE-1243377), National Science Foundation (U.S.) (Grant OCE-1546580)

Vertical distributions of total and particulate 210Po and 210Pb activities in the water column were measured at eleven stations in the North Atlantic during the GEOTRACES GA01 GEOVIDE cruise in May–June 2014. Total 210Po activity was on average 24 % lower than 210Pb activity in the upper 100 m, and was closer to unity in the mesopelagic (100–1000 m). The partitioning coefficients (Kd) along the transect suggest the preferential association of 210Po relative to 210Pb onto particles. The prominent role of small particles in sorption was confirmed by the observation that over 80 % of the particulate radionuclide activity was on small particles. To account for the observed surface water 210Po / 210Pb disequilibria, particulate radionuclide activities and export of both small (1–53 μm) and large (> 53 μm) particles must be considered. A comparison between the GEOVIDE total particulate 210Po / 210Pb activity ratios (AR) and the ratios in previous studies revealed a distinct geographic distribution, with lower particulate AR in the high-latitude North Atlantic (including this study) and Arctic in relation to all other samples. For the samples where apparent oxygen utilization (AOU) was calculated at the same depth and time as the 210Po / 210Pb AR (40 stations including this study), there was a two-phase correlation between the total particulate AR and AOU demonstrating the competing forces of remineralization and radionuclide decay from particles as they age.

The GEOVIDE cruise, a collaborative project within the framework of the international GEOTRACES programme, was conducted along the French-led section in the North Atlantic Ocean (Section GA01), between 15 May and 30 June 2014. In this Special Issue, results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among seventeen articles. Here, the scientific context, project objectives and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue.

The contributions of micro-, nano-, and picoplankton to particle export were estimated from measurements of size-fractionated particulate 234Th, organic carbon, and phytoplankton indicator pigments obtained during five cruises between 2010 and 2012 along Line P in the subarctic northeast Pacific Ocean. Sinking fluxes of particulate organic carbon (POC) and indicator pigments were calculated from 234Th–238U disequilibria and, during two cruises, measured by a sediment trap at Ocean Station Papa. POC fluxes at 100 m ranged from 0.65 to 7.95 mmol m−2 d−1, similar in magnitude to previous results at Line P. Microplankton pigments dominate indicator pigment fluxes (averaging 69 ± 19% of total pigment flux), while nanoplankton pigments comprised the majority of pigment standing stocks (averaging 64 ± 23% of total pigment standing stocks). Indicator pigment loss rates (the ratio of pigment export flux to pigment standing stocks) point to preferential export of larger microplankton relative to smaller nano- and picoplankton. However, indicator pigments do not quantitatively trace particle export resulting from zooplankton grazing, which may be an important pathway for the export of small phytoplankton. These results have important implications for understanding the magnitude and mechanisms controlling the biological pump at Line P in particular, and more generally in oligotrophic gyres and high-nutrient, low-chlorophyll (HNLC) regions where small phytoplankton represent a major component of the autotrophic community.

Relapsed or refractory classical Hodgkin lymphoma (cHL) is associated with a poor outcome when standard chemotherapy fails. Brentuximab vedotin (BV) is an anti-CD30 monoclonal antibody-drug conjugate licensed for use at relapse after autologous stem cell transplant (ASCT) or following two prior therapies in those unsuitable for ASCT. There are limited data assessing the ability of BV to enable curative SCT. We performed a UK-wide retrospective study of 99 SCT-naïve relapsed/refractory cHL. All had received 2 prior lines and were deemed fit for transplant but had an insufficient remission to proceed. The median age was 32 years. Most had nodular sclerosis subtype, Eastern Cooperative Oncology Group performance status 0-1 and advanced stage disease. The median progression-free survival (PFS) was 5·6 months and median overall survival (OS) was 37·2 months. The overall response rate was 56% (29% complete response; 27% partial response). 61% reached SCT: 34% immediately post-BV and 27% following an inadequate BV response but were salvaged and underwent deferred SCT. Patients consolidated with SCT had a superior PFS and OS to those not receiving SCT (P < 0·001). BV is an effective, non-toxic bridge to immediate SCT in 34% and deferred SCT in 27%. 39% never reached SCT with a PFS of 3·0 months, demonstrating the unmet need to improve outcomes in those unsuitable for SCT post-BV.

Depth profiles of 210 Po and 210 Pb activity and phytoplankton and zooplankton abundance were collected during two cruises along the Canadian time-series Line P in the Northeast Subarctic Pacific (ranging from 48o39 N to 50o00 N and 126o40 W to 145o00 W) in August 2010 and February 2011 to evaluate connections between the planktonic community and distributions of these radionuclides in the upper 500 m of the water column. Statistical analysis indicates that 210 Po is more effectively removed from the surface ocean when large (>0.1 mg ind � 1 dry wt) zooplankton dominate, and is less effectively scavenged when the picoplankton Synechococcus is present at high concentrations (>1 � 10 5 cells ml � 1 ). While the zooplankton field data are consistent with previous lab studies and field observations, the phytoplankton results seem to conflict with recent evidence that small cells may contribute significantly to export in other oligotrophic regions. Differences in ecosystem mechanisms between the Subarctic Pacific and other oligotrophic systems that limit the contribution of small cells to sinking flux remain to be identified. 2014 Published by Elsevier Ltd.

In coastal ecosystems with decades of eutrophication and other anthropogenic stressors, the impact of climate change on planktonic communities can be difficult to detect. A time series of monthly water temperatures in the Central Basin of Long Island Sound (LIS) from the late 1940s until 2012 indicates a warming rate of 0.03 °C year−1. Relative to the early 1950s, there has been a concurrent decrease in the mean size of the dominant copepod species Acartia tonsa and Acartia hudsonica, an increase in the proportion of the small copepod Oithona sp., and the disappearance of the two largest-sized copepod genera from the 1950s. These changes are consistent with predictions of the impact of climate change on aquatic ectotherms. This suggests that even in eutrophic systems where food is not limiting, a continued increase in temperature could result in a smaller-sized copepod community. Since copepods dominate the zooplankton, which in turn link primary producers and upper trophic levels, a reduction in mean size could alter food web connectivity, decreasing the efficiency of trophic transfer between phytoplankton and endemic larval fish.

The deviation from secular equilibrium between the natural radionuclide 210Po (half-life: 138.4 d) and its radioactive grandparent 210Pb (half-life: 22.3 y) has been used to examine particle export from the surface ocean. Here we combine 210Po and 210Pb activity results from three GEOTRACES transects: two transects of the North Atlantic Ocean (GA03: 15–40°N, and GA01: 40–60°N) and one transect of the South Pacific Ocean (GP16: 10–15°S), and estimate 210Po export fluxes at the base of the primary production zone (PPZ) by assuming steady state (SS) without advection or diffusion of the isotopes. The SS 210Po flux was sometimes lower at basin margins than at the open-ocean stations along the transects. High SS 210Po flux estimations derived in the North Atlantic subtropical gyre may be associated with the atmospheric deposition of 210Pb to the surface ocean. In this paper we also question the validity of the SS assumption and discuss the influence of vertical advection and diffusion on the overall 210Po activity balance. The SS model may have underestimated the export flux of 210Po at margin stations in the GA03 and GP16 transects and along the GA01 cruise track. We found that upwelling in the Peruvian coastal region and near the Greenland shelf had a dramatic impact on the estimated 210Po flux balance. Vertical diffusion had limited influence on the 210Po export fluxes along GA03 and GA01 in the North Atlantic whereas it added 210Po export fluxes by as much as 190% in GP16 in the Pacific, especially at the shelf stations 1 and 4. Further, analysis of the partitioning coefficient suggested the importance of small particles in the scavenging of radionuclides. This suggests it is wise to sample small particles along with large particles to determine the ratio of the concentration of particulate organic carbon (POC) to 210Po activity (POC/210Po) for the lower limit of POC export flux estimations. Finally, the observation of the deficit of 210Po relative to 210Pb activity (210Po/210Pb

Few coastal systems have time series data that allow researchers to examine the impact of two important stressors on estuarine ecosystems: climate change and eutrophication. The Central Basin of Long Island Sound (LIS), between New York and Connecticut, is one such system. LIS has seen annual average surface temperatures increase at a rate of 0.03 °C/yr since 1976, with increases most pronounced during summer and early fall. Over the past 15 years, annual stratification (difference between mean annual surface and bottom temperatures) has also increased at the same rate. Despite expansion of waste-water treatment and declining point-source nutrient input, LIS remains eutrophic. An increase toward historic mean annual chlorophyll concentration has occurred since a minimum in the early 1990s, driven in part by higher fall chlorophyll values. There is also an apparent shift in the seasonality of phytoplankton blooms, with more frequent fall chlorophyll peaks and reduced early spring peaks relative to the 1950s. Non-metric Multidimensional Scaling (NMDS) analysis of phytoplankton communities from fall and summer 2002–8 indicated that cyanobacteria and flagellates are associated with higher amounts of chlorophyll at higher temperatures during these two seasons. These results suggest that as surface temperatures continue to increase, smaller cells and flagellates may maintain chlorophyll values at higher levels despite decreased or static surface nutrient concentrations in this system.

Between 1939 and 1982, several surveys indicated that zooplankton in Long Island Sound, NY (LIS) appeared to follow an annual cycle typical of the Mid-Atlantic coast of North America. Abundance peaked in both early spring and late summer and the peaks were similar in magnitude. In recent decades, this cycle appeared to have shifted. Only one large peak tended to occur, and summer copepod abundance was consistently reduced by ∼60% from 1939 to 1982 levels. In other Mid-Atlantic coastal systems such a dramatic shift has been attributed to the earlier appearance of ctenophores, particularly Mnemiopsis leidyi, during warmer spring months. However, over a decade of surveys in LIS have consistently found near-zero values in M. leidyi biomass during spring months. Our multiple linear regression model indicates that summer M. leidyi biomass during this decade explains25% of the variation in summer copepod abundance. During these recent, warmer years, summer copepod community shifts appear to explain the loss of copepod abundance. Although Acartia tonsa in 2010-2011 appeared to be present all year long, it was no longer the dominant summer zooplankton species. Warmer summers have been associated with an increase in cyanobacteria and flagellates, which are not consumed efficiently by A. tonsa. This suggests that in warming coastal systems multiple environmental and biological factors interact and likely underlie dramatic alterations to copepod phenology, not single causes.

Documented is an intercalibration (IC) exercise for both 210 Po and 210 Pb in seawater aliquots distributed between up to eight international laboratories that followed individual protocols. Dissolved and particulate sam ples were provided by GEOTRACES during two IC cruises at baseline stations in the North Atlantic and North Pacific oceans. Included were surface and/or deep dissolved and particulate samples at each site, plus complete profiles analyzed by the laboratory of the lead author. An unspecified solid phase standard was also distributed with 210 Po and 210 Pb in secular equilibrium to confirm spike calibrations. The 210 Po activities reported n = 8) for the standard were very similar with a relative standard deviation (RSD) of 3.6% and mean value indistinguish able from the certified value, confirming accurate calibration of Po spikes. For seawater samples, the agreement was strongly dependent for both nuclides on the activity of the samples. The agreement was relatively good for dissolved seawater samples (RSD = 9% to 29%, n = 4), moderate for the particulate samples (RSD = 12% to 80%, n = 8), and poor for particulate dip blanks (RSD = 50% to 200%, n = 8). Noted is the higher apparent affinity of 210 Po versus 210

Grass shrimp Palaemonetes pugio were fed mercury (Hg)-contaminated oligochaetes for 15 days and analyzed for Hg, cadmium (Cd), and carbon assimilation efficiencies (AE) as well as toxicological end points related to digestion. Disproportionate increases in stable Hg concentrations in shrimp did not appear to be related to partitioning to trophically available Hg in worms. Hg AE by pre-exposed shrimp reached a plateau (approximately 53 %), whereas Cd AE varied (approximately 40-60 %) in a manner that was not dose-dependent. Carbon AE did not differ among treatments (approximately 69 %). Gut residence time was not impacted significantly by Hg pre-exposure (grand median approximately 465 min), however, there was a trend between curves showing percentages of individuals with markers in feces over time versus treatment. Feces-elimination rate did not vary with dietary pre-exposure. Extracellular protease activity varied approximately 1.9-fold but did not exhibit dose-dependency. pH increased over the range of Hg pre-exposures within the anterior (pH approximately 5.33-6.51) and posterior (pH approximately 5.29-6.25) regions of the cardiac proventriculus and Hg assimilation exhibited a negative relationship to hydrogen ion concentrations. The results of this study indicate that previous Hg ingestion can elicit post-assimilatory impacts on grass shrimp digestive physiology, which may, in turn, influence Hg assimilation during subsequent digestive cycles.

Naïve grass shrimp Palaemonetes pugio were pulse-fed cadmium-contaminated meals containing carbon-14, fluorescent or near-infrared markers and analyzed for carbon assimilation efficiency, gut residence time, feces elimination rate, extracellular digestive protease activity or gut pH. Carbon assimilation efficiency (~83%), minimum gut residence time (~435 min) and proventriculus pH (~5.29 to ~6.01) were not impacted significantly by cadmium ingestion. A dose-dependent decrease in feces elimination rate (from ~14.4 to ~6.4 mm h(-1)) was observed for shrimp for 2 h following minimum gut residence time. Protease activities increased ~2.4-fold over the range of dietary cadmium exposures, however, this variation was not dose-dependent. Differential impacts of cadmium exposure on carbon and cadmium assimilation reported previously are consistent with work involving shrimp subjected to chronic field exposure. The influence of ingested cadmium on feces elimination rate may be related to pre-assimilatory impacts on packaging, intestinal transport or release of feces. Protease activities may have been influenced by pre-assimilatory interactions between available cadmium ions in gut fluid and enzyme-secreting cells of the hepatopancreatic epithelium or direct impacts on active enzymes.

The quantitative relationship between organic carbon and mineral contents of particles sinking below 1800 m in the ocean indicates that organisms with mineral shells such as coccolithophores are of special importance for transporting carbon into the deep sea. Several hypotheses about the mechanism behind this relationship between minerals and organic matter have been raised, such as mineral protection of organic matter or enhanced sinking rates through ballast addition. We examined organic matter decomposition of calcifying and non-calcifying Emiliania huxleyi cultures in an experiment that allowed aggregation and settling in rotating tanks. Biogenic components such as particulate carbon, particulate nitrogen, particulate volume, pigments, transparent exopolymer particles (TEP), and particulate amino acids in suspended particles and aggregates were followed over a period of 30 d. The overall pattern of decrease in organic matter, the amount of recalcitrant organic matter left after 30 d, and the compositional changes within particulate organic matter indicated that cells without a shell are more subject to loss than calcified cells. It is suggested that biogenic calcite helps in the preservation of particulate organic matter (POM) by offering structural support for organic molecules. Over the course of the experiment, half the particulate organic carbon in both calcifying and non-calcifying cultures was partitioned into aggregates and remained so until the end of the experiment. The partial protection of particulate organic matter from solubilization by biominerals and by aggregation that was observed in our experiment may help explain the robustness of the relationship between organic and mineral matter fluxes in the deep ocean.

Disequilibrium between 234Th and 238U in water column profiles has been used to estimate the settling flux of Th (and, by proxy, of particulate organic carbon); yet potentially major non-steady-state influences on 234Th profiles are often not able to be considered in estimations of flux. We have compared temporal series of 234Th distributions in the upper water column at both coastal and deep-water sites in the northwestern Mediterranean Sea to coeval sediment trap records at the same sites. We have used sediment trap records of 234Th fluxes to predict temporal changes in water column 234Th deficits and have compared the predicted deficits to those measured to determine whether the time-evolution of the two coincide. At the coastal site (327 m water depth), trends in the two estimates of water column 234Th deficits are in fairly close agreement over the 1-month deployment during the spring bloom in 1999. In contrast, the pattern of water column 234Th deficits is poorly predicted by sediment trap records at the deep-water site (DYFAMED, ∼2300 m water depth) in both 2003 and 2005. In particular, the transition from a mesotrophic to an oligotrophic system, clearly seen in trap fluxes, is not evident in water column 234Th profiles, which show high-frequency variability. Allowing trapping efficiencies to vary from 100% does not reconcile the differences between trap and water column deficit observations; we conclude that substantial lateral and vertical advective influences must be invoked to account for the differences. Advective influences are potentially greater on 234Th fluxes derived from water column deficits relative to those obtained from traps because the calculation of deficits in open-ocean settings is dominated by the magnitude of the “dissolved” 234Th fraction. For observed current velocities of 5–20 cm s−1, in one radioactive mean-life of 234Th, the water column at the DYFAMED site can reflect 234Th scavenging produced tens to hundreds of kilometers away. In contrast, most of the 234Th flux collected in shallow sediment traps at the DFYFAMED site was in the fraction settling >200 m d−1; in effect the sediment trap can integrate the 234Th flux over distances ∼40-fold less than water column 234Th distributions. In some sense, sediment trap and water column sampling for 234Th provide complementary pictures of 234Th export. However, because the two methods can be dominated by different processes and are subject to different biases, their comparison must be treated with caution.

234 Th ( T 1/2 =24.1 d) and 210 Po ( T 1/2 =138.4 d) are particle reactive radioisotopes that are used as tracers for particle cycling in the upper ocean. Particulate organic carbon (POC) export has frequently been estimated using 234 Th/ 238 U disequilibrium. Recent evidence suggests that 210 Po/ 210 Pb disequilibrium may be used as an additional tool to examine particle export, given the direct biological uptake of 210 Po into cellular material. Differences in these two radioisotope pairs with regard to their half-lives, particle reactivity and scavenging affinity in seawater should provide complementary information to be obtained on the processes occurring in the water column. Here, we review eight different studies that have simultaneously used both approaches to estimate POC export fluxes from the surface ocean. Our aim is to provide a complete “dataset” of all the existing POC flux data derived from the coupled use of both 234 Th and 210 Po and to evaluate the advantages and limitations of each tracer pair. Our analysis suggests that the simultaneous use of both radiotracers provides more useful comparative data than can be derived from the use of a single tracer alone. The difference in half-lives of 234 Th and 210 Po enables the study of export production rates over different time scales. In addition, their different biogeochemical behaviour and preferred affinity for specific types of particles leads to the conclusion that 234 Th is a better tracer of total mass flux, whereas 210 Po tracks POC export more specifically. The synthesis presented here is also intended to provide a basis for planning future sampling strategies and promoting further work in this field to help reveal the more specific application of each tracer under specific water column biogeochemistries.

We compare POC fluxes estimated using 234Th/238U and 210Po/210Pb disequilibria at the DYFAMED site, northwestern Mediterranean Sea. We also compare the POC fluxes estimated from these two isotope pairs with fluxes below the euphotic zone measured in moored sediment traps. The POC flux at 200 m estimated from 234Th and 210Po deficits and the POC/210Po or POC/234Th on >70 μm filterable particles measured through three seasons (early spring, late spring, summer) ranged from 3.8 to 17.5 mmol C/m2/d based on 234Th/238U and from 4.4 to 7.0 mmol C/m2/d based on 210Po/210Pb disequilibrium. In comparison, sediment trap fluxes of POC at approximately 200 m ranged from 0.2 to 6.0 mmol C/m2/d over the same interval. Values of POC/210Po and POC/234Th ratios in sediment trap material collected in time series or separated according to settling velocity (SV) were generally lower than values in the >70 μm filterable particles at the same depth. The variation in POC/210Po and POC/234Th in material separated according to SV showed no clear relationship with SV and was controlled more by particle composition and degree of degradation. Both 234Th and 210Po showed sustained deficits in late spring and summer, despite low fluxes recorded in the trap. Lateral processes (transport of particles along isopycnals or intrusion of shelf waters to the site) and violations of temporal assumptions (steady-state vs. non-steady-state) may be responsible for this disparity. Based on the results of this study, we conclude that 210Po/210Pb disequilibrium is as valid as 234Th/238U as a proxy for estimating POC flux in the ocean.

The disequilibrium between 210 Po and its grandparent 210 Pb has been proposed as a tracer of the vertical flux of sinking particulate organic matter in the ocean. The mechanism of association between 210 Po and organic matter is, however, still unclear. To investigate this association we measured trace metals, minerals, organic carbon, nitrogen, and the natural radioisotopes 234 Th, 228 Th, 210 Po, and 210 Pb in sinking particles collected in sediment traps at 200 m in the northwestern Mediterranean. Pigments, fatty acids, and amino acids were used to identify the types and sources of particulate organic matter. Multivariate analyses were used to determine which components of sinking particulate matter are traced by 210 Po and/or by the 210 Po/ 210 Pb ratio. Statistical analysis of the results indicates that the distribution of polonium in sinking marine particles is influenced by fresh phytoplankton-derived, nitrogen-rich organic matter as well as sulfur-containing amino acids. These findings are consistent with previous laboratory observations that the distribution of 210 Po in biota parallels the distributions of both sulfur and protein, and indicate that these associations persist as material sinks through the water column. While this research generally supports the use of 210 Po as a specific tracer of the flux of organic matter, the signals traced by 210 Po/ 210 Pb and 234 Th/ 238 U are not as distinct in the field as in laboratory experiments. Further work is needed to determine more precisely what 210 Po/ 210 Pb traces in order to increase the correspondence of 210 Po/ 210 Pb measurements to biogeochemically important rates and quantities.

International audience; North Atlantic Ocean Hydrothermal plume Benthic nepheloid layer GEOTRACES a b s t r a c t Vertical profiles of 210 Po and 210 Pb in the water column were measured in the dissolved phase (o0.45 mm), and small (0.8–51 mm) and large (4 51 mm) particles at seven stations along the US GEOTRACES North Atlantic Zonal Transect (GA03). Mass balance calculations were employed to assess nuclide exchange rates at the dissolved-small particle interface and between small and large particles, and to quantify export with settling large particles. In the surface ocean, 210 Po scavenging is linearly correlated with the concentration of particulate organic carbon (POC) in large particles, supporting the role of biogenic particle in 210 Po bioaccumulation and export. In stations near the coast, this link is more complex due to the variable source of biogenic material and temporal changes in the surface biogeochemical and physical conditions. At depth, 210 Po exhibits significant widespread deficit with respect to 210 Pb that could in part be attributed to in situ 210 Po scavenging and may be related to surface biological productivity. As previously reported the 210 Pb scavenging rates in the surface ocean were higher at ocean margins. At depth, 210 Pb scavenging increases with depth and eastward due to the increase of adsorption sites available in the benthic layers and to a regional contribution of benthic 210 Pb scavenging and/or particle flux, respectively. The benthic nepheloid layer (BNL) and the Hydrothermal TAG plume distinctly enhance 210 Pb scavenging due to increased surface adsorption in association with resuspended or freshly formed particles. In contrast, 210 Po is not seen to be significantly scavenged in these environments due to its relatively short half-life and the long residence time of particles.

Thorium-234 is increasingly used as a tracer of ocean particle flux, primarily as a means to estimate particulate organic carbon export from the surface ocean. This requires determination of both the 234 Th activity distribution (in order to calculate 234 Th fluxes) and an estimate of the C / 234 Th ratio on sinking particles, to empirically derive C fluxes. In reviewing C / 234 Th variability, results obtained using a single sampling method show the most predictable behavior. For example, in most studies that employ in situ pumps to collect size fractionated particles, C / 234 Th either increases or is relatively invariant with increasing particle size (size classes > 1 to 100s μm). Observations also suggest that C / 234 Th decreases with depth and can vary significantly between regions (highest in blooms of large diatoms and highly productive coastal settings). Comparisons of C fluxes derived from 234 Th show good agreement with independent estimates of C flux, including mass balances of C and nutrients over appropriate space and time scales (within factors of 2–3). We recommend sampling for C / 234 Th from a standard depth of 100 m, or at least one depth below the mixed layer using either large volume size fractionated filtration to capture the rarer large particles, or a sediment trap or other device to collect sinking particles. We also recommend collection of multiple 234 Th profiles and C / 234 Th samples during the course of longer observation periods to better sample temporal variations in both 234 Th flux and the characteristic of sinking particles. We are encouraged by new technologies which are optimized to more reliably sample truly settling particles, and expect the utility of this tracer to increase, not just for upper ocean C fluxes but for other elements and processes deeper in the water column.

Systematic discrepancies between concentrations of particulate organic carbon (POC) measured using bottles (small volume) versus in-situ pumps (large volume) have long been of concern to oceanographers. Usually bottle samples yield higher values of POC than pump samples taken concurrently. Several factors, including pressure effects during filtration, particle formation during handling, contamination, and adsorption of dissolved organic carbon (DOC) onto filters, have been suggested as responsible for these differences. As part of a larger study of particles and particle fluxes in the Mediterranean Sea (MedFlux), we systematically and contemporaneously measured various factors that could allow comparison of particle types. The comparison of chlorophyll (Chl-a) and POC immediately suggested a disconnection between concentrations of carbon and Chl-a: bottle and pump estimates of Chl-a concentrations agreed at all depths, while POC and particulate organic nitrogen (PON) measurements did not, especially in the upper 50 m of the water column. These observations suggest that pumps and bottles are equally adept at capturing Chl-a, but that Chl-a:C and Chl-a:N are collected in different proportions by the two methods. Additional experiments using samples collected from the coastal waters of Long Island Sound and in the open Mediterranean, and using algal cultures of both non-fragile Thalassiosira pseudonana 3H and fragile Isocrysis galbana cells, showed no effects of filtration pressure on POC, PN, or Chl-a concentrations over the pressure range of 0.2–0.9 atm. In addition, shaking experiments using bottle samples from the Mediterranean did not show particle formation during handling. Corrections for DOC adsorption on the filters were made and cannot account for the discrepancy between pump and bottle POC. One possible explanation for the pump–bottle POC discrepancy is that bottle samples capture zooplankton that can evade pumps but not bottles. In support of this hypothesis, comparisons of zooplankton caught in Niskin bottles with those retained on >70 μm in-situ pump filters, showed greater abundances in bottle relative to pump samples. In addition, non-swimming zooplankton (radiolaria) were under-collected by pumps, suggesting that washout of particles off the 70 μm mesh of in-situ pumps during use or recovery may also cause lower POC values. This possibility needs to be further investigated. This study does not address whether zooplankton should or should not be included as POC, but only suggests constraints on the difference between the two methods.

Po, a naturally occurring radioisotope that is ubiquitous in seawater, is especially enriched in proteinaceous tissues of marine organisms and may therefore be useful as a tracer of organic carbon flux in marine systems. Due in part to its biomagnification in marine food chains, 210 Po provides the largest radiation dose to any organism under natural conditions. To better understand the extent to which zooplankton can influence the fluxes of 210 Po and serve as a conduit between phytoplankton, which concentrate it greatly from ambient water and higher trophic levels, we conducted a series of laboratory experiments with the calanoid copepod Acartia tonsa. A. tonsa was presented with either dissolved 210 Po or with one of eight different phytoplankton species and sterile glass beads, all labeled with 210 Po. Assimilation efficiencies (AEs) of ingested 210 Po in copepods ranged from 19% to 55% among the phytoplankton diets, and correlated directly with 210 Po’s cytoplasmic distributions in the algal cells. The AE of 210 Po from ingested glass beads was 0%. The high AE and low efflux rates (mean of 3% d 21 )o f 210 Po in copepods can explain its biomagnification in marine food chains. Uptake and loss parameters of 210 Po in copepods measured in these experiments were used in a model to quantify the relative sources of 210 Po for copepods. Under all realistic scenarios, .90% of 210 Po in copepods appears to be taken up through diet. Model-predicted 210 Po concentrations in copepods in different ocean regions closely matched independent measurements, suggesting that we understand the processes governing this element’s enrichment in zooplankton and thus can make quantitative predictions of its bioconcentration on a site-specific basis.

Bioaccumulation of polonium-210 (t1/2 5 138 d) in marine phytoplankton can introduce this naturally occurring radioisotope into food chains, where it accounts for most of the radiation dose to marine organisms and to human consumers of seafood. Moreover, this isotope could be useful as a tracer of the flux of organic matter in ocean surface waters. We performed laboratory experiments with eight algal species representing six algal divisions to quantify the uptake, cellular partitioning, and retention of 210 Po by algae. Biological uptake was unaffected by temperature or light, and volume concentration factors (VCFs) for these algal species ranged between 0.5 and 3.0 3 10 4 . Interspecific differences in VCFs could be explained by considering the surface area to volume ratios of the cells and cellular protein content. Once associated with the cells, between 30 and 60% of the total cellular 210 Po was in the cytoplasm of the different species. 210 Po was not irreversibly bound to the cells but displayed a biological half-life of ;23 d. Because

Spectres d'absorption dus a des especes Cr(CO) 5 et Cr(CO 5 )Q (avec Q=Cr(CO) 6 ; N 2 ; NH 3 ; methanol; acetone; ethylene et silane). Formation d'un produit inconnu par reaction de deux molecules Cr(CO) 5

Particle-reactive, naturally occurring radionuclides are useful tracers of the sinking flux of organic matter from the surface to the deep ocean. Since the Joint Global Ocean Flux Study (JGOFS) began in 1987, the disequilibrium between (234)Th and its parent (238)U has become widely used as a technique to measure particle export fluxes from surface ocean waters. Another radionuclide pair, (210)Po and (210)Pb, can be used for the same purpose but has not been as widely adopted due to difficulty with accurately constraining the (210)Po/(210)Pb radiochemical balance in the ocean and because of the more time-consuming radiochemical procedures. Direct comparison of particle flux estimated in different ocean regions using these short-lived radionuclides is important in evaluating their utility and accuracy as tracers of particle flux. In this paper, we present paired (234)Th/(238)U and (210)Po/(210)Pb data from oligotrophic surface waters of the subtropical Northwest Atlantic and discuss their advantages and limitations. Vertical profiles of total and particle size-fractionated (210)Po and (234)Th activities, together with particulate organic carbon (POC) concentrations, were measured during three seasons at the Bermuda Atlantic Time-series Study (BATS) site. Both (210)Po and (234)Th reasonably predict sinking POC flux caught in sediment traps, and each tracer provides unique information about the magnitude and efficiency of the ocean's biological pump.