Minimising the limitations of using dietary analysis to assess foodweb changes by combining multiple techniques

Dietary studies of marine predators offer an immediate signal of foodweb changes occurring at lower trophic levels, and therefore are often used to assess the ecosystem status of marine systems. Conventionally, these studies are based on morphological analysis of prey remains in stomach contents, involving invasive and destructive techniques to collect samples. More recently, the number of dietary studies based on less invasive biochemical and molecular approaches has dramatically increased. However, all three methods, morphological, biochemical and molecular, have well-documented limitations for resolving taxonomy, temporal variation or biomass composition. In this study, we minimise these limitations by considering multiple techniques in combination. As a case study, we report the target prey species and diet composition of a marine predator that has been used to assess annual change in managed fishing areas for several decades, the macaroni penguin Eudyptes chrysolophus. We use biochemical (stable isotope) and molecular (DNA) analysis of faecal samples collected across the different phases of a single breeding season, and compare the resolved diet to a 26-year dataset of stomach contents collected from a closely located colony (0.25 km apart) that exploits identical foraging grounds. Molecular analysis increased the known target prey species for this highly monitored population by 31%, including a fish species of commercial importance. Biochemical analysis detected subtle changes in the proportion of fish and krill in the diet, demonstrating promising opportunities for using a combined molecular and biochemical method to assess inter-annual foodweb changes at lower trophic levels. The combined approach offers a less invasive sampling methodology, compared to morphological analysis, and provides more information regarding prey species diversity and the overall trophic signature of the diet. Further studies are required to examine the feasibility of using this approach for long-term dietary studies of different marine predator species

SPECTRA OF YOUNG GALAXIES

Invited review, Ringberg conference on "Galaxies in the Young Universe" (Sept94)Comment: 12 pages, uuencoded compressed Postscript fil

Measurement of the Nucleon Structure Function F2 in the Nuclear Medium and Evaluation of its Moments

We report on the measurement of inclusive electron scattering off a carbon target performed with CLAS at Jefferson Laboratory. A combination of three different beam energies 1.161, 2.261 and 4.461 GeV allowed us to reach an invariant mass of the final-state hadronic system W~2.4 GeV with four-momentum transfers Q2 ranging from 0.2 to 5 GeV2. These data, together with previous measurements of the inclusive electron scattering off proton and deuteron, which cover a similar continuous two-dimensional region of Q2 and Bjorken variable x, permit the study of nuclear modifications of the nucleon structure. By using these, as well as other world data, we evaluated the F2 structure function and its moments. Using an OPE-based twist expansion, we studied the Q2-evolution of the moments, obtaining a separation of the leading-twist and the total higher-twist terms. The carbon-to-deuteron ratio of the leading-twist contributions to the F2 moments exhibits the well known EMC effect, compatible with that discovered previously in x-space. The total higher-twist term in the carbon nucleus appears, although with large systematic uncertainites, to be smaller with respect to the deuteron case for n<7, suggesting partial parton deconfinement in nuclear matter. We speculate that the spatial extension of the nucleon is changed when it is immersed in the nuclear medium.Comment: 37 pages, 15 figure

Beam-target helicity asymmetry e in K0 Λ and K0 Σ0 photoproduction on the neutron

We report the first measurements of the E beam-target helicity asymmetry for the γ - n - →K0Λ and K0Σ0 channels in the energy range 1.70≤W≤2.34 GeV. The CLAS system at Jefferson Lab uses a circularly polarized photon beam and a target consisting of longitudinally polarized solid molecular hydrogen deuteride with low background contamination for the measurements. The multivariate analysis method boosted decision trees is used to isolate the reactions of interest. Comparisons with predictions from the KaonMAID, SAID, and Bonn-Gatchina models are presented. These results will help separate the isospin I=0 and I=1 photocoupling transition amplitudes in pseudoscalar meson photoproduction

The Influence of Age and Sex on Genetic Associations with Adult Body Size and Shape : A Large-Scale Genome-Wide Interaction Study

Genome-wide association studies (GWAS) have identified more than 100 genetic variants contributing to BMI, a measure of body size, or waist-to-hip ratio (adjusted for BMI, WHRadjBMI), a measure of body shape. Body size and shape change as people grow older and these changes differ substantially between men and women. To systematically screen for age-and/or sex-specific effects of genetic variants on BMI and WHRadjBMI, we performed meta-analyses of 114 studies (up to 320,485 individuals of European descent) with genome-wide chip and/or Metabochip data by the Genetic Investigation of Anthropometric Traits (GIANT) Consortium. Each study tested the association of up to similar to 2.8M SNPs with BMI and WHRadjBMI in four strata (men 50y, women 50y) and summary statistics were combined in stratum-specific meta-analyses. We then screened for variants that showed age-specific effects (G x AGE), sex-specific effects (G x SEX) or age-specific effects that differed between men and women (G x AGE x SEX). For BMI, we identified 15 loci (11 previously established for main effects, four novel) that showed significant (FDR= 50y). No sex-dependent effects were identified for BMI. For WHRadjBMI, we identified 44 loci (27 previously established for main effects, 17 novel) with sex-specific effects, of which 28 showed larger effects in women than in men, five showed larger effects in men than in women, and 11 showed opposite effects between sexes. No age-dependent effects were identified for WHRadjBMI. This is the first genome-wide interaction meta-analysis to report convincing evidence of age-dependent genetic effects on BMI. In addition, we confirm the sex-specificity of genetic effects on WHRadjBMI. These results may providefurther insights into the biology that underlies weight change with age or the sexually dimorphism of body shape.Peer reviewe

Diving patterns in relation to diet of Gentoo and Macaroni penguins at South Georgia

The depthsa ttainedo n 1,444d ivesb y 14 GentooP enguins(P ygosceliPs apua) and 6,352d ivesb y eightM acaroniP enguins(E udyptesc hrysolophusw)e re recordedt,o gether with the timing and durationo f the foragingt rip and the amounta nd type of prey caught. MacaroniP enguinsa te only Antarctick rill Euphausias uperba.W hen feedingo nly at night they maden o divesd eepert han 20 m; on all-day trips 36% of divesw ereb etween2 0 to 80 m. GentooP enguinsfe dd uringt he day.W hen theyc aughkt rill, 77%o f divesw eres hallower than 54 m; when fish were taken, 59% of dives were 54 to 136 m, which is consistent with the benthic-demersahla bit of thej uvenile Nototheniaa nd Champsocephalufsis ht hey eat. The patterno f predationo n krill by both penguins peciesis consistenwt ith its vertical migrationt o the surfacea t night and dispersatlh rought he water column during the day. The food requirements of chick-rearing Macaroni Penguins would be met by catching at least six adult krill per dive (or 150 juvenile krill or amphipods). For similar Gentoo Penguins, a minimum of 15 adult krill per dive (one every 8 set), or one fish every third dive, is needed. Recorded interannual variations in krill size can treble these rates, which would also be doubled if half the dives were for travelling, not feeding

The reproductive energetics of gentoo (Pygoscelis papua) and macaroni (Eudyptes chrysolophus) penguins at South Georgia

(1) The doubly-labelled water method was used in the first comprehensive study of penguin energetics throughout the reproduction and moult season, comparing gentoo penguins (inshore feeding, sexually monomorphic, share breeding duties equally) with macaroni penguins (offshore feeding, dimorphic, duties unequally shared). (2) While fasting during courtship and incubation, macaronis (both sexes) and female gentoos had field metabolic rates (FMR) of 4.1 and 3.8 W kg-1, respectively. Male gentoos also spending time at sea had an FMR of 7.5 W kg-1. Male macaroni FMR for fasting while brooding was 3.8 W kg-1. During chick-rearing, gentoo FMR was 6.8 W kg-1 early on, rising to 7.4 W kg-1 later; for macaronis FMR was 13 W kg-1. Estimated energy cost of foraging at sea was 16 and 22 W kg-1 for gentoos and macaronis, respectively. Gentoo and macaroni FMR during moult was 5.3 and 6.7 W kg-1. (3) Over the breeding and moult season, male and female gentoos have total and average daily energy expenditure (DEE) only 1% different, agreeing with expectation for monomorphic species sharing duties equally. Female macaronis (10% smaller than males) have average DEE 9% (17% on a mass-specific basis) greater than males, mainly because they spend more time rearing chicks, involving intensive foraging at sea. However, males spent more days at the colony so over the whole season female energy expenditure is only 3.5% above males. (4) Scaled mass-specific average DEE is 18% greater for macaronis than gentoos, chiefly because of the energy costs of offshore foraging trips. As their breeding and moult season is 20% shorter than gentoos, average absolute DEE is 13% less for macaronis; however, macaroni chick production is only half that of gentoos