Fishing has significant trophodynamic impacts on marine communities, including reductions in the mean trophic position (TP) of the ecosystem resulting from a decrease in the abundance and size of ...species and individuals with high TPs. This study demonstrates the erosion of fish TP, an additional process that results in lower TP of individuals of a given size, which may exacerbate the effects of fishing on the food web. A stable isotope approach based on the tRophicPosition Bayesian method was used to quantify the TP of 12 target marine species at a given length, and compare their TP between fishery-restricted areas and trawled areas. The results show a difference in the TP of six benthic and apical nekto-benthic predators, which feed in the median at about 0.5 TP lower in trawled areas. It appears that current ‘fishing down marine food webs’ analyses may underestimate the trophic effects of fishing. Accounting for changes in trophodynamics of individuals at a given size is important to detect indirect effects through food web interactions. The application of a trawling ban may lead to the restoration of lost trophic structure; however, trophic changes may occur more slowly than changes in biomass. This article is part of the theme issue ‘Connected interactions: enriching food web research by spatial and social interactions’.
Chemosynthetic primary production by microbes supports abundant faunal assemblages at deep-sea hydrothermal vents, with zonation of invertebrate species typically occurring along physico-chemical ...gradients. Recently discovered vent fields on the East Scotia Ridge (ESR) in the Southern Ocean represent a new province of vent biogeography, but the spatial dynamics of their distinct fauna have yet to be elucidated. This study determines patterns of faunal zonation, species associations, and relationships between faunal microdistribution and hydrothermal activity in a vent field at a depth of 2,400 m on the ESR. Remotely operated vehicle (ROV) dives obtained high-definition imagery of three chimney structures with varying levels of hydrothermal activity, and a mosaic image of >250 m(2) of seafloor co-registered with temperature measurements. Analysis of faunal microdistribution within the mosaiced seafloor reveals a consistent pattern of faunal zonation with increasing distance from vent sources and peak temperatures. Assemblages closest to vent sources are visibly dominated by a new species of anomuran crab, Kiwa n. sp. (abundance >700 individuals m(-2)), followed by a peltospiroid gastropod (>1,500 individuals m(-2)), eolepadid barnacle (>1,500 individuals m(-2)), and carnivorous actinostolid anemone (>30 individuals m(-2)). Peripheral fauna are not dominated by a single taxon, but include predatory and scavenger taxa such as stichasterid seastars, pycnogonids and octopus. Variation in faunal microdistribution on chimneys with differing levels of activity suggests a possible successional sequence for vent fauna in this new biogeographic province. An increase in δ(34)S values of primary consumers with distance from vent sources, and variation in their δ(13)C values also indicate possible zonation of nutritional modes of the vent fauna. By using ROV videography to obtain a high-resolution representation of a vent environment over a greater extent than previous studies, these results provide a baseline for determining temporal change and investigations of processes structuring faunal assemblages at Southern Ocean vents.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Treatment of gestational diabetes before 20 weeks’ gestation led to a modestly lower incidence of a composite of adverse neonatal outcomes but no material differences in pregnancy-related ...hypertension or neonatal lean body mass.
Since the first discovery of deep-sea hydrothermal vents along the Galápagos Rift in 1977, numerous vent sites and endemic faunal assemblages have been found along mid-ocean ridges and back-arc ...basins at low to mid latitudes. These discoveries have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in different oceans but is little explored because of extreme conditions. Since 2009 we have explored two segments of the East Scotia Ridge (ESR) in the Southern Ocean using a remotely operated vehicle. In each segment we located deep-sea hydrothermal vents hosting high-temperature black smokers up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new yeti crab (Kiwa n. sp.), stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star. Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae), bathymodiolid mussels, and alvinocaridid shrimps, are absent from the ESR vents. These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates, suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa. Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic vent ecosystems represent a new vent biogeographic province. However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate that vent biogeography is more complex than previously recognised.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Gestational diabetes is the most common medical complication in pregnancy. Historically, gestational diabetes was considered a pregnancy complication involving treatment of rising glycaemia late in ...the second trimester. However, recent evidence challenges this view. Pre-pregnancy and pregnancy-specific factors influence gestational glycaemia, with open questions regarding roles of non-glycaemic factors in the aetiology and consequences of gestational diabetes. Varying patterns of insulin secretion and resistance in early and late pregnancy underlie a heterogeneity of gestational diabetes in the timing and pathophysiological subtypes with clinical implications: early gestational diabetes and insulin resistant gestational diabetes subtypes are associated with a higher risk of pregnancy complications. Metabolic perturbations of early gestational diabetes can affect early placental development, affecting maternal metabolism and fetal development. Fetal hyperinsulinaemia can affect the development of multiple fetal tissues, with short-term and long-term consequences. Pregnancy complications are prevented by managing glycaemia in early and late pregnancy in some, but not all women with gestational diabetes. A better understanding of the pathophysiology and heterogeneity of gestational diabetes will help to develop novel management approaches with focus on improved prevention of maternal and offspring short-term and long-term complications, from pre-conception, throughout pregnancy, and beyond.
The hydrothermal vents on the East Scotia Ridge are the first to be explored in the Antarctic and are dominated by large peltospiroid gastropods, stalked barnacles (Vulcanolepas sp.) and anomuran ...crabs (Kiwa sp.) but their food webs are unknown. Vent fluid and macroconsumer samples were collected at three vent sites (E2, E9N and E9S) at distances of tens of metres to hundreds of kilometres apart with contrasting vent fluid chemistries to describe trophic interactions and identify potential carbon fixation pathways using stable isotopes. δ(13)C of dissolved inorganic carbon from vent fluids ranged from -4.6‰ to 0.8‰ at E2 and from -4.4‰ to 1.5‰ at E9. The lowest macroconsumer δ(13)C was observed in peltospiroid gastropods (-30.0‰ to -31.1‰) and indicated carbon fixation via the Calvin-Benson-Bassham (CBB) cycle by endosymbiotic gamma-Proteobacteria. Highest δ(13)C occurred in Kiwa sp. (-19.0‰ to -10.5‰), similar to that of the epibionts sampled from their ventral setae. Kiwa sp. δ(13)C differed among sites, which were attributed to spatial differences in the epibiont community and the relative contribution of carbon fixed via the reductive tricarboxylic acid (rTCA) and CBB cycles assimilated by Kiwa sp. Site differences in carbon fixation pathways were traced into higher trophic levels e.g. a stichasterid asteroid that predates on Kiwa sp. Sponges and anemones at the periphery of E2 assimilated a proportion of epipelagic photosynthetic primary production but this was not observed at E9N. Differences in the δ(13)C and δ(34)S values of vent macroconsumers between E2 and E9 sites suggest the relative contributions of photosynthetic and chemoautotrophic carbon fixation (rTCA v CBB) entering the hydrothermal vent food webs vary between the sites.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
1. Stable isotope data are widely used to track the origins and transformations of materials in food webs. Reliable interpretation of these data requires knowledge of the factors influencing isotopic ...fractionation between diet and consumer. For practical reasons, isotopic fractionation is often assumed to be constant but, in reality, a range of factors may affect fractionation. 2. To investigate effects of temperature and feeding rate on fractionation of carbon and nitrogen stable isotopes in a marine predator, we reared European sea bass Dicentrarchus labrax on identical diets at 11 and 16 °C on three ration levels for 600 days. 3. Nitrogen trophic fractionation (Δδ¹⁵N) was affected by temperature. Bass Δδ¹⁵N was 4·41per thousand at 11 °C and 3·78per thousand at 16 °C. 4. Carbon fractionation (Δδ¹³C) was also affected by temperature. Bass Δδ¹³C was 1·18per thousand at 11 °C and 1·64per thousand at 16 °C. The higher lipid content in the tissues of bass reared at cooler temperatures accounted for the temperature effect on Δδ¹³C. When Δδ¹³C was determined using mathematically defatted values, there was a direct effect of ration size and Δδ¹³C was 2·51, 2·39 and 2·31per thousand for high, medium and low rations, respectively. 5. Reported Δδ¹⁵N for all treatments exceeded the mean of 3·4per thousand widely used in ecological studies of fish populations and communities. This would confound the interpretation of δ¹⁵N as an indicator of trophic level when comparing populations that are exposed to different temperatures. 6. The Δδ¹³C of 0-1per thousand commonly applied in food web studies did not hold under any of the temperature or feeding regimes considered and a value of 2per thousand would be more appropriate.
Deep-sea chondrichthyans are cryptic species subject to increasing anthropogenic exploitation. Defining their role in deep-water ecosystems is therefore crucial for predicting the ecosystem-wide ...effects of their removal. Stable isotope analyses (SIA) of carbon and nitrogen have been increasingly used in chondrichthyan studies as a non-lethal method to investigate aspects of their ecology. In recent years these methods have been applied to deep-sea chondricthyans to investigate their trophic structure, niche width, and describe energy flow in the deep sea. Despite the increasing popularity of SIA in deep-sea chondrichthyan studies, methods rely on a multitude of assumptions, such as the need to determine accurate trophic discrimination and tissue turnover rates, which are currently lacking for most species. These uncertainties may preclude the reliability of isotope-based approaches, and as a result inferences from isotopic data must be viewed with relative caution. Due to the growing use of isotopic-based approaches in deep-sea chondrichthyans, we review the literature in the context of current methodological challenges and ecological inferences. We provide recommendations and novel approaches that may help develop and refine a rapidly growing field of study.
OBJECTIVE We evaluated associations between early-pregnancy oral glucose tolerance test (OGTT) glucose and complications in the Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) cohort to ...inform prognostic OGTT thresholds. RESEARCH DESIGN AND METHODS Individuals with risk factors for hyperglycemia were recruited for an international, multicenter, randomized controlled gestational diabetes mellitus (GDM) (World Health Organization 2013 criteria) treatment trial. A 2-h 75-g OGTT was performed at <20 weeks’ gestation. Individuals with early treated hyperglycemia in pregnancy were excluded from the primary analysis. Early OGTT glucose concentrations were analyzed continuously and in glycemic categories (normal, low band, and high band). RESULTS Overall, 3,645 individuals had an OGTT at (mean ± SD) 15.6 ± 2.5 weeks. For each 1-SD increase in fasting, 1-h, and 2-h glucose values, there were continuous positive associations with late GDM: adjusted odds ratio (aOR) 2.04 (95% CI 1.82–2.27), 3.05 (2.72–3.43), and 2.21 (1.99–2.45), respectively. There were continuous positive associations between 1-h and 2-h glucose and the perinatal composite (birth <37 + 0 weeks, birth trauma, birth weight ≥4,500 g, respiratory distress, phototherapy requirement, stillbirth/neonatal death, and shoulder dystocia), with aOR 1.15 (95% CI 1.04–1.26) and 1.14 (1.04–1.25), respectively, and with large-for-gestational-age offspring, with aOR 1.18 (1.06–1.31) and 1.26 (1.01–1.25), respectively. Significant associations were also observed between 1-h glucose and cesarean section and between fasting and 2-h glucose and neonatal hypoglycemia. In categorical analysis, only the high-band 1-h glucose (≥10.6 mmol/L 191 mg/dL) predicted the perinatal composite. CONCLUSIONS There is a continuous positive association between early-pregnancy OGTT glucose and complications. In individuals with hyperglycemia risk factors, only the high-glycemic-band 1-h glucose corresponded to increased risk of major perinatal complications.
Gestational diabetes is defined as hyperglycaemia first detected during pregnancy at glucose concentrations that are less than those of overt diabetes. Around 14% of pregnancies globally are affected ...by gestational diabetes; its prevalence varies with differences in risk factors and approaches to screening and diagnosis; and it is increasing in parallel with obesity and type 2 diabetes. Gestational diabetes direct costs are US$1·6 billion in the USA alone, largely due to complications including hypertensive disorders, preterm delivery, and neonatal metabolic and respiratory consequences. Between 30% and 70% of gestational diabetes is diagnosed in early pregnancy (ie, early gestational diabetes defined by hyperglycaemia before 20 weeks of gestation). Early gestational diabetes is associated with worse pregnancy outcomes compared with women diagnosed with late gestational diabetes (hyperglycaemia from 24 weeks to 28 weeks of gestation). Randomised controlled trials show benefits of treating gestational diabetes from 24 weeks to 28 weeks of gestation. The WHO 2013 recommendations for diagnosing gestational diabetes (one-step 75 gm 2-h oral glucose tolerance test at 24–28 weeks of gestation) are largely based on the Hyperglycemia and Adverse Pregnancy Outcomes Study, which confirmed the linear association between pregnancy complications and late-pregnancy maternal glycaemia: a phenomenon that has now also been shown in early pregnancy. Recently, the Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) trial showed benefit in diagnosis and treatment of early gestational diabetes for women with risk factors. Given the diabesity epidemic, evidence for gestational diabetes heterogeneity by timing and subtype, and advances in technology, a life course precision medicine approach is urgently needed, using evidence-based prevention, diagnostic, and treatment strategies.
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