Sampling Occasions Research Articles

Do constructed wetlands remove metals or increase metal bioavailability?

The H-02 wetland was constructed to treat building process water and storm runoff water from the Tritium Processing Facility on the Department of Energy's Savannah River Site (Aiken, SC). Monthly monitoring of copper (Cu) and zinc (Zn) concentrations and water quality parameters in surface waters continued from 2014 to 2016. Metal speciation was modeled at each sampling occasion. Total Cu and Zn concentrations released to the effluent stream were below the NPDES limit, and the average removal efficiency was 65.9% for Cu and 71.1% for Zn. The metal-removal processes were found out to be seasonally regulated by sulfur cycling indicated by laboratory and model results. High temperature, adequate labile organic matter, and anaerobic conditions during the warm months (February to August) favored sulfate reduction that produced sulfide minerals to significantly remove metals. However, the dominant reaction in sulfur cycling shifted to sulfide oxidation during the cool months (September to next March). High concentrations of metal-organic complexes were observed, especially colloidal complexes of metal and fulvic acid (FA), demonstrating adsorption to organic matter became the primary process for metal removal. Meanwhile, the accumulation of metal-FA complexes in the wetland system will cause negative effects to the surrounding environment as they are biologically reactive, highly bioavailable, and can be easily taken up and transferred to ecosystems by trophic exchange.

Survival rate and population size of Indo‐Pacific humpback dolphins (Sousa chinensis) in Xiamen Bay, China

AbstractThe survival rate and population size of Indo‐Pacific humpback dolphins (Sousa chinensis) in Xiamen, China, were estimated from vessel‐based surveys during 2007–2010. Over the course of 202 d (881.1 observation hours), 76 groups were observed, and 52 dolphins were successfully identified. The Cormack‐Jolly‐Seber model estimated a constant apparent survival of 0.948 (95% CI: 0.922–0.966). Based on the open/POPAN model, the population size was estimated at 70 individuals (95% CI: 63–88). To explore the effect of uneven yearly survey effort, we pooled the data with seven sampling occasions with similar effort. This data set generated similar results of a constant survival of 0.957 (95% CI: 0.918–0.978) and population size of 72 (95% CI: 65–88). The small population size of the Xiamen humpback dolphins satisfies the Critically Endangered criterion of IUCN (D), and emphasizes urgency of the need for protection of the population. Improved monitoring efforts should be focused on enhancing our understanding of current status and evaluating impacts of all anthropogenic activities. A conservation plan for the population should also be drawn up.

Trophic overlap between non‐native brown bullhead (Ameiurus nebulosus) and native shortfin eel (Anguilla australis) in shallow lakes

AbstractWe quantified trophic overlap between the invasive, non‐native catfish brown bullhead (Ameiurus nebulosus) and the New Zealand native shortfin eel (Anguilla australis) in four peat and riverine lakes using stable isotope (δ13C and δ15N) and gut content analyses. Across all lakes and fish sizes over the austral spring–summer period, shortfin eel guts were dominated numerically by fish prey (57% occurrence cf 42% in brown bullhead), while Diptera larvae were most commonly encountered in guts of brown bullhead (45% cf 14% in eels). Significant differences in % composition of animal contents in guts were detected between fish species and sampling occasions (n = 4) but not between lakes. In contrast, stable isotope signatures of brown bullhead and shortfin eel did differ significantly between lakes but not between sampling occasions, indicating enduring sources of nutrition despite apparently differing ingestion patterns over time. The R mixing model MixSIAR indicated that shortfins likely assimilated higher proportions of fish prey carbon compared to brown bullheads, which appeared to show greater assimilation of invertebrates, consistent with the results of gut content analyses. Isotopic niche regions, calculated in nicheROVER using probabilistic ellipses, indicated that shortfin eels occupied at least c.60% of brown bullhead trophic niche, which occupied less than 30% of eel trophic niche in all but one lake. These estimates suggest that brown bullhead has higher potential to influence shortfin eel nutrition than vice versa, or that a broad trophic niche occupied by eels provides resilience to the effects of overlapping consumption patterns with invasive omnivores.

Seasonal variability of the vitamin C content of fresh fruits and vegetables in a local retail market.

Seasonal variation of vitamin C in fresh fruits and vegetables is not reflected in food composition database average values, yet many factors influence content and retention. Fresh fruits and vegetables were sampled on three occasions in each season, from the same local retail outlets, for 1 or 2 years. Vitamin C was significantly higher in winter-sampled spinach (436 mg kg-1 ) compared with spring (298 mg kg-1 ) and summer/fall (180 mg kg-1 ); in potatoes in summer/fall (156 mg kg-1 ) versus winter/spring (106 mg kg-1 ); and in oranges in winter (616 mg kg-1 ), spring (592 mg kg-1 ), and summer (506 mg kg-1 ). Ranges were dramatic among sampling occasions for broccoli, oranges, potatoes, and spinach (700-1210 mg kg-1 , 420-780 mg kg-1 , 70-280 mg kg-1 , and 90-660 mg kg-1 respectively). Mean values for apples, bananas, tomatoes, and potatoes differed from the USDA National Nutrient Database for Standard Reference (SR) average by ≥10% of the daily recommended intake (90 mg). For broccoli, oranges, and spinach, vitamin C was substantially above or below the SR range in 50-100% of the samples. For spinach, the average content did not differ from SR, but vitamin C in winter was 55% higher than SR. Database average values for vitamin C in fresh produce can significantly over- or underestimate the content in a specific food supply. © 2018 Society of Chemical Industry.

Evaluation of Multiple Linear Regression–Based Limited Sampling Strategies for Enteric-Coated Mycophenolate Sodium in Adult Kidney Transplant Recipients

Although multiple linear regression-based limited sampling strategies (LSSs) have been published for enteric-coated mycophenolate sodium, none have been evaluated for the prediction of subsequent mycophenolic acid (MPA) exposure. This study aimed to examine the predictive performance of the published LSS for the estimation of future MPA area under the concentration-time curve from 0 to 12 hours (AUC0-12) in renal transplant recipients. Total MPA plasma concentrations were measured in 20 adult renal transplant patients on 2 occasions a week apart. All subjects received concomitant tacrolimus and were approximately 1 month after transplant. Samples were taken at 0, 0.33, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 6, and 8 hours and 0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2, 3, 4, 6, 9, and 12 hours after dose on the first and second sampling occasion, respectively. Predicted MPA AUC0-12 was calculated using 19 published LSSs and data from the first or second sampling occasion for each patient and compared with the second occasion full MPA AUC0-12 calculated using the linear trapezoidal rule. Bias (median percentage prediction error) and imprecision (median absolute prediction error) were determined. Median percentage prediction error and median absolute prediction error for the prediction of full MPA AUC0-12 were <15% for 4 LSSs, using the data from the same (second) occasion. One equation (1.583C1 + 0.765C2 + 0.369C2.5 + 0.748C3 + 1.518C4 + 2.158C6 + 3.292C8 + 3.6690) showed bias and imprecision <15% for the prediction of future MPA AUC0-12, where the predicted AUC0-12 from the first occasion was compared with the full AUC0-12 from the second. All LSSs with an acceptable predictive performance included concentrations taken at least 6 hours after the dose. Only one LSS had an acceptable bias and precision for future estimation. Accurate dosage prediction using a multiple linear regression-based LSS was not possible without concentrations up to at least 8 hours after the dose.

The relative importance of autochthony along the longitudinal gradient of a small South African river influenced by agricultural activities

Generalisations about the sources of organic matter that support aquatic consumers are usually focussed on certain parts of the world (particularly the northern hemisphere) and large rivers, and therefore may not include the full spectrum of food webs that occur in the southern hemisphere (particularly those with high nitrogen inputs). We studied the relative importance of organic matter sources to macroinvertebrate consumers in a small South African river. Based on previous observations of our system of interest and other agricultural streams, we hypothesised that (a) the carbon fuelling consumers is primarily derived from autochthonous (in situ) food sources regardless of sampling time and, (b) the contribution of autochthonous basal resources to consumers increases in importance as the river widens (from upper to downstream reaches). To test these predictions, stable carbon (δ13C) and nitrogen (δ15N) isotopes were used to estimate the contributions of local algal and land-based production to aquatic macroinvertebrates over space (six sites) and time (four sampling occasions between November 2012 and September 2013) along the Kowie River, South Africa. Mixing models revealed that consumers in the upper reaches assimilated terrestrially-derived allochthonous organic matter, and consumers in the middle and lower reaches assimilated primarily autochthonous basal resources (macrophytes and algae). The isotopic values of consumers and their food sources changed over time, indicating that food sources and consumers should be analysed many times throughout the year to capture that variability and ensure that ephemeral components of the food web are not missed. Our results enhance the growing body of literature on the dynamics of riverine systems and indicate the importance of autochthony in a small temperate river with high nitrogen inputs.

Abstract P098: Plasma Levels of Persistent Organochlorine Pollutants, Blood Pressure and Hypertension: A Longitudinal Study

Background: Persistent organochlorine pollutants (POPs) include several groups of synthetic compounds with high lipophilic and bioaccumulative potential that accumulate in the food chain. Despite their long-term ban, they are still of concern and the general population is constantly exposed to these pollutants at low doses through diet. POPs are proposed to be involved in the atherosclerotic process and to cause endothelial cell dysfunction. We assess longitudinally whether plasma concentrations of different POPs were associated with blood pressure (BP) and risk of hypertension in middle-aged women and men. Methods: Study subjects were 850 participants in the Västerbotten Intervention Programme with two blood samples and BP measurements, 10 years apart, during 1990 to 2003 (baseline) and during 2001 to 2013 (follow-up). The POP measured were the fungicide hexachlorobenzene (HCB), the insecticide dichlorodiphenyl-trichloroethane (DDT) –and its persistent metabolite p,p′-dichlorodiphenyl-dichloroethylene (DDE)– and the dioxin-like and non-dioxin-like polychlorinated biphenyls (DL-PCBs, NDL-PCBs). We used generalized estimated equations to assess the associations. Results: At both sampling occasions, about 50% had hypertension. DL-PCBs and DDE, but not NDL-PCBs or HCB, were associated with hypertension, while only the association for DL-PCB remained statistically significant after lipid-standardization and adjustment for BMI and total plasma lipids. The multivariable-adjusted OR of hypertension based on repeated measurements were 1.50 (95% CI: 1.07-2.11) for DL-PCBs (3 rd vs. 1 st tertile of lipid-standardized POPs). In stratified adjusted analyses, ORs for those born after 1950 increased : 3.99 (95% CI: 2.15-7.43), while no association was observed among those born earlier. For DEE, when non-adjustment for BMI, the OR of hypertension were 1.43 (95% CI: 1.04, 1.97). Conclusions: Based on repeated measurements, the accumulated exposure to the pollutants DL-PCBs and DDE, although less clear for the latter, may disrupt the normal BP levels. Individuals born after 1950 –when early-life exposure to these substances became common– may be pre-disposed for these effects.

A framework for estimating the determinants of spatial and temporal variation in vital rates and inferring the occurrence of unobserved extreme events.

We develop a general framework that combines long-term tag–recapture data and powerful statistical and modelling techniques to investigate how population, environmental and climate factors determine variation in vital rates and population dynamics in an animal species, using as a case study the population of brown trout living in Upper Volaja (Western Slovenia). This population has been monitored since 2004. Upper Volaja is a sink, receiving individuals from a source population living above a waterfall. We estimate the numerical contribution of the source population on the sink population and test the effects of temperature, population density and extreme events on variation in vital rates among 2647 individually tagged brown trout. We found that individuals dispersing downstream from the source population help maintain high population densities in the sink population despite poor recruitment. The best model of survival for individuals older than juveniles includes additive effects of birth cohort and sampling occasion. Fast growth of older cohorts and higher population densities in 2004–2005 suggest very low population densities in the late 1990s, which we hypothesize were caused by a flash flood that strongly reduced population size and created the habitat conditions for faster individual growth and transient higher population densities after the extreme event.

IMPROVED ROTATION PATTERNS USING TWO AUXILIARY VARIABLES IN SUCCESSIVE SAMPLING

Abstract The present paper emphasizes the role of two auxiliary variables on both the occasions to improve the precision of estimates at the current (second) occasion in two-occasion successive sampling. Information on two auxiliary variables, which are positively correlated with the study variable, has been used with the aid of exponential type structures and an efficient estimation procedure of population mean on the current (second) occasion has been suggested. The behaviour of the proposed estimator has been studied and compared with the sample mean estimator, when there is no matching from the previous occasion and natural successive sampling estimator, which is a linear combination of the means of the matched and unmatched portions of the sample at the current (second) occasion. Optimal replacement strategy is also discussed. The concluding remarks are discussed justifying utility of the proposed sampling scheme. The results have been well supported analytically as well as empirically by using real life data.

Unwinding a Tangled Web: a Fine-Scale Approach towards Understanding the Drivers of Harmful Algal Bloom Species in a Eutrophic South African Estuary

A permanently eutrophic South African estuary provided an ideal model ecosystem from which to unravel the drivers of recurrent accumulations of harmful algal bloom (HAB) species. Designed to encapsulate broad- to fine-scale variations, seasonal in situ bihourly monitoring of abiotic and phytoplankton components took place at a fixed location over a 24-h period on four sampling occasions. Four known HAB species were recorded at bloom concentrations (> 20 μg Chl-a L−1) during the study, including Heterosigma akashiwo, Heterocapsa rotundata, Mesodinium rubrum, and Karenia cf. mikimotoi. Model results identified temperature as a key driver, with distinct community shifts between winter (~H. rotundata and M. rubrum) and spring/summer (~H. akashiwo and K. cf. mikimotoi) conditions. Evidence of niche overlap between all four HAB taxa was highlighted by their predilection for elevated nitrate levels, a vertically stratified water column and mesohaline (ca. 10) surface waters. As such, internal biotic processes such as plasticity of diel vertical migration patterns, reliance of M. rubrum on suitable ‘prey’ resources, and the suppressive pressure of H. akashiwo on co-occurring taxa-explained phytoplankton community dynamics beyond the influence of physico-chemical variability. These findings provide novel insight regarding the ecology of HAB taxa and how they have adapted to thrive in anthropogenically manipulated environments.

Estimating groundwater contribution to transpiration using satellite-derived evapotranspiration estimates coupled with stable isotope analysis

The relative importance of groundwater (GW) to sustain terrestrial vegetation has been well documented. However, quantifying GW use by riparian vegetation in data scarce regions may prove to be challenging. For this purpose, we coupled evapotranspiration (ET) estimates from the satellite-based surface energy balance system (SEBS) model with stable isotope analysis, to map and quantify the contribution of GW to transpiration (ETg), along the lower reaches of a perennial river system, in the semi-arid north-eastern region of South Africa. Plant stem, soil, stream and GW samples were collected on 3 sampling occasions during the 2016 dry season. δ2H and δ18O values of the respective samples were measured and analysed. We found that while GW use was prevalent and increased with aridity, overall ETg was fairly minimal. During the initial stages of the dry season ETg for the study area was extremely low, approximately 0.10% of daily ET or 0.01 mm d−1. However, as aridity increased, ETg increased to approximately 10% of daily ET or 0.30 mm d−1. The results of these various investigations undertaken demonstrates the potential of coupling satellite-based ET approaches with stable isotope analysis, to quantify spatial and seasonal dynamics in ETg.

Faecal shedding of pathogenic Yersinia enterocolitica determined by qPCR for yst virulence gene is associated with reduced live weight but not diarrhoea in prime lambs

Associations between faecal shedding of pathogenic Yersinia enterocolitica (based on the yst virulence gene) with growth, carcass weight and diarrhoea were investigated using an observational longitudinal study of 1200 crossbred prime (meat) lambs on eight Australian farms. Live weight, breech faecal soiling score (scale 1–5) and faecal consistency score (FCS; scale 1–5) were recorded, and faecal samples collected from each lamb on three sampling occasions; weaning (≈12 weeks of age), post-weaning (≈19 weeks) and pre-slaughter (≈29 weeks). Hot standard carcass weight was measured at slaughter. Faecal samples were screened for presence and concentration of pathogenic Y. enterocolitica using quantitative PCR. Associations of pathogenic Y. enterocolitica detection and shedding intensity with lamb health and production were assessed using general linear models (carcass weight), linear mixed effects models (live weight, FCS and breech soiling score) and non-parametric tests (FCS and breech soiling score). Prevalence for non-pelleted faeces (FCS ≥ 3.0) and diarrhoea (FCS ≥ 4.0) were compared with the two-tailed z-test, odds ratios and relative risk. Lambs shedding pathogenic Y. enterocolitica were 3.78 kg lighter post-weaning (P < 0.001) and 2.61 kg lighter pre-slaughter (P = 0.035) compared to lambs in which pathogenic Y. enterocolitica was not detected. Higher faecal concentration of pathogenic Y. enterocolitica was associated with lower live weight (P < 0.001). There was no association between pathogenic Y. enterocolitica detection and carcass weight. Overall, there was no evidence of association between pathogenic Y. enterocolitica detection and diarrhoea (higher FCS, higher risk for non-pelleted faeces or diarrhoea, or higher breech soiling score). Only one flock had increased relative risk for non-pelleted faeces associated with pathogenic Y. enterocolitica detection, and one other flock had increased relative risk for diarrhoea associated with pathogenic Y. enterocolitica detection. This is the first report of an association between reduced sheep live weight and pathogenic Y. enterocolitica based on the presence of the yst gene for heat stable enterotoxin determined by qPCR in sheep. Notably, impacts on live weight were observed in the absence of diarrhoea.

Colour change in a structural ornament is related to individual quality, parasites and mating patterns in the blue tit.

Carry-over effects refer to processes that occur in one season and influence fitness in the following. In birds, two costly activities, namely reproduction and moult, are restricted to a small time window, and sometimes overlap. Thus, colour in newly moulted feathers is likely to be affected by the costs of reproduction. Using models of bird vision we investigated male colour change in a free-living population of blue tits (Cyanistes caeruleus) in three sampling occasions: spring 1, winter and spring 2. We related crown, tail, breast and cheek feather colouration after the moult (winter) to the intensity of infections by blood parasites during reproduction (spring 1). In the following spring (spring 2), we explored mating patterns with respect to changes in feather colour (springs 1 vs. 2). Males that were less intensely infected by the malaria parasite Plasmodium while breeding showed purer white cheek feathers in winter, which may indicate higher feather quality. Increased brightness in the white cheek was associated with better body condition during reproduction. In the following season, males with brighter cheeks paired with females that had noticeably brighter cheek patches compared to the male's previous mate. These results suggest that the conditions experienced during reproduction are likely to affect moult and thus feather colouration, at least in the white patch. High quality individuals may allocate resources efficiently during reproduction increasing future reproductive success through variation in mating patterns. Carry-over effects from reproduction might extend not only to the non-breeding phase, but also to the following breeding season.

Spatiotemporal characteristics and temporal stability of soil water in an alpine meadow on the northern Tibetan Plateau

The spatiotemporal characteristics of soil water content (SWC) have a significant influence on vegetation degradation and growth in alpine meadow ecosystems. The spatiotemporal variability and temporal stability (TS) of SWC, however, have rarely been studied on the northern Tibetan Plateau owing to the rugged and hostile sampling environment. The objective of this study was to analyze the spatiotemporal variability and the TS of SWC in various layers of the soil, to a depth of 50 cm in a 33.5 hm2 plot, with the data obtained from 113 measuring locations collected on 22 sampling occasions during the growing seasons of 2015 and 2016. The SWC was moderately variable both in time (two consecutive growing seasons) and horizontal space (plot). The variabilities, however, did not vary consistently with increasing depth for the various dominant influencing factors. The SWC in the undeveloped, shallow, and stony alpine meadow soil was temporally stable; TS did not depend on depth due to disturbances by grass roots...

Improving mesocarnivore detectability with lures in camera-trapping studies

Context Camera trapping is commonly employed for studying carnivores because it provides better data than do other methods, and with lower costs. Increasing the probability of detecting the target species can reduce parameter uncertainty and survey effort required to estimate density and occurrence. Different methods, including attractants and baits, can be used to increase detectability. However, their efficacy has rarely been quantitatively assessed. Aims To quantify the efficacy of scent and bait attractants to increase the detection probability of mesocarnivores by camera trapping. Methods We tested two scent lures, valerian extract (Val) and lynx urine (LU), their combination (Val–LU), and a non-reward bait (i.e. not accessible to the animal), raw chicken, as carnivore attractants in two protected areas of central Spain. We used camera-trapping records under an occupancy-modelling framework to estimate attractant-specific detection probabilities for six mesocarnivore species, and quantified their effects by comparing these estimates with the baseline (i.e. no attractant) detectability. Key results The weekly detection probability of four mesocarnivore species (red fox, Vulpes vulpes, stone marten, Martes foina, common genet, Genetta genetta, and Eurasian badger, Meles meles) significantly increased when Val–LU (between 0.11 ± 0.07 and 0.67 ± 0.05) or chicken (between 0.31 ± 0.02 and 0.77 ± 0.22) were used as attractant, when compared with baseline detectability (between 0.01 ± 0.02 and 0.29 ± 0.05). Although rarely, wildcats (Felis silvestris) were mostly detected with Val–LU. The probability of detecting a species after k sampling occasions (7 days each) where it was present was highly improved with both Val–LU and chicken for all species (e.g. from 0.20 to 0.98 after four sampling occasions with chicken for the stone marten). Both attractants reduced the sampling time required to ascertain that a species was absent to between 42% and 15% of baseline values. Conclusions The tested attractants greatly improved the detectability of most Iberian mesocarnivores. Although chicken was preferable for some species such as stone marten, Val–LU is most efficient for detecting the whole mesocarnivore community, including rare species such as wildcats. Implications Attractant selection in studies using non-invasive detection methods must be supported by quantitative assessment of the detection probability associated to each attractant. Researchers must choose those attractants best fitting target species and study aims.

The fish assemblages of the mangroves of São Tomé island (Gulf of Guinea), patterns of functional diversity

The fish assemblages of the mangroves of São Tomé island (Gulf of Guinea), patterns of functional diversity

DISTINCTIVENESS AND POTENTIALS OF TWO FLOWERING ROADSIDE HEDGEROWS, TURNERA ULMIFOLIA AND MELASTOMA MALABATHRICUM AS BENEFICIAL PLANTS FOR INSECTS

Beneficial flowering plants play a vital role in attracting beneficial insects such as parasitoid that controls insect pests. In order to evaluate the effectiveness of two species of flowering plants as beneficial hedgerow plants, we identify insects communities of T. ulmifolia and M. malabathricum, which generally grown on roadside. We also compared the insects community of both plants based on time of the day. A total of 5,029 insect individuals were collected through three sampling occasions from five sampling stations of T. ulmifolia and five sampling stations of M. malabathricum. Chi-square test showed that there was a significant difference (χ2=37.3848, df=1, P<0.05) between the composition of insect communities on M. malabathricum and T. ulmifolia. The insect visiting M. malabathricum were similar at both night and day while T. ulmifolia attracted different insect community depending on the time of the day. The results suggested that different plant species would attract a different community of insects. T. ulmifolia success in attracting the visitation of beneficial insect but its effectiveness is limited to a short period of time. Meanwhile, the effectiveness of M. malabathricum as beneficial plant is yet illuminated.

Fungal community structure at pelagic and littoral sites in Lake Biwa determined with high-throughput sequencing

Fungi may play an important role in material cycling in lakes and oceans; however, only limited information is available on fungal community structure, especially in large lakes such as Lake Biwa. In this study, whole fungal communities were determined seasonally and spatially using a high-throughput sequencing technique. Water samples were collected from the epilimnion, 0–20 m depth, with a Van Dorn sampler at a pelagic site and from the surface at a littoral site in the north basin of Lake Biwa. All pelagic depth samples were combined into one sample. Sampling occurred on 24 April, 22 May, 10 July, and 16 September 2015. DNA was extracted from filtered samples. Metabarcoding analysis targeting fungi-specific internal transcribed spacer 2 regions was performed using an Illumina MiSeq platform. Epilimnetic fungal communities showed high diversity, with 479 operational taxonomic units (OTUs). The OTUs included 122 belonging to the phylum Ascomycota, 127 to Basidiomycota, 38 to Zygomycota, 45 to Chytridiomycota, 2 to Glomeromycota, and 145 were unclassified fungi. Fungal community structures varied seasonally and spatially. Few of the fungal OTUs overlapped between seasons and sites, and specific communities of fungi were detected on each sampling occasion. Results indicated that spatio-temporal variations in fungal communities were high and may be influenced by both internal factors and external factors, such as terrestrial inputs.

Efficient Class of Estimators of Population Variance Under Random Non-response in Two-Phase Successive Sampling

In this paper, an investigation has been carried out to deal with the problems of non-response in estimation of population variance on current occasion in two-occasion successive sampling under two-phase setup. Using readily available information on an auxiliary variable on both occasions, class of estimators of population variance on current occasion have been proposed in presence of random non-response on either of the occasions. Performances of the proposed class of estimators are compared with sample variance estimator under the similar realistic situations to study the properties of the suggested estimation procedures under missing at random response mechanism. Results are validated through empirical studies which justify the proposition of the class of estimators. Suitable recommendations have been made to the survey practitioners.

Drug use in pregnant women\u2014a pilot study of the coherence between reported use of drugs and presence of drugs in plasma

PurposeIn Sweden, information on drug use during pregnancy is obtained through an interview and recorded in a standardized medical record at every visit to the antenatal care clinic throughout the pregnancy. Antenatal, delivery, and neonatal records constitute the basis for the Swedish Medical Birth Register (MBR). The purpose of this exploratory study was to investigate the reliability of reported drug use by simultaneous screening for drug substances in the blood stream of the pregnant woman and thereby validate self-reported data in the MBR.MethodsPlasma samples from 200 women were obtained at gestational weeks 10–12 and 25 and screened for drugs by using ultra-high performance liquid chromatography with time of flight mass spectrometry (UHPLC-TOF-MS). The results from the analysis were then compared to medical records.ResultsAt the first sampling occasion, the drugs found by screening had been reported by 86% of the women and on the second sampling, 85.5%. Missed reported information was clearly associated with drugs for occasional use. The most common drugs in plasma taken in early and mid-pregnancy were meclizine and paracetamol. Two types of continuously used drugs, selective serotonin reuptake inhibitors and propranolol, were used. All women using them reported it and the drug screening revealed a 100% coherence.ConclusionsThis study shows good coherence between reported drug intake and the drugs found in plasma samples, which in turn positively validates the MBR.