Neuropsychological profiles of children and adolescents with selective eating in the presence or absence of elevated autistic traits

Selective eating (SE) refers to an individual narrowing their range of preferred foods, resulting in a restricted food intake, high levels of rigidity and food refusal (Bryant-Waugh, 2000). SE is encompassed in the new Diagnostic and Statistical Manual of Mental Disorders 5th Edition (DSM-V) (American Psychiatric Association, 2013) category avoidant restrictive food intake disorder (ARFID). Such difficulties are common in children with an autism spectrum disorder (ASD) (Raiten & Massaro, 1986) and neuropsychological differences have been found in children with ASD (Hill, 2004). This research aimed to be the first to investigate whether a distinct neuropsychological profile exists in children and adolescents with SE and furthermore, whether aspects of the profile vary depending on whether the child or adolescent displays elevated autistic traits. A case series of 10 children between the ages of 8 to 13 years old were recruited. A well-established neuropsychological test battery, the Ravello Profile (Rose, Frampton & Lask, 2012), was modified and administered to assess visuospatial processing, central coherence, executive functions (including cognitive flexibility, inhibition and planning) and theory of mind abilities. The results demonstrated a high degree of variability across the group in terms of visuospatial processing and theory of mind, weak central coherence across all participants and otherwise relatively intact abilities in executive function domains. There were no substantive findings in relation to those children with elevated autistic traits although a trend toward visuospatial processing differences did emerge. This exploratory case series was the first attempt to describe a neuropsychological profile in SE, however the small sample size and high variability in the data meant that a distinct neuropsychological profile did not emerge. The results did however provide an initial indication of possible trends in strengths and weaknesses across neuropsychological domains in SE. These findings have implications for the assessment and treatment of SE difficulties

Cenozoic records of seawater chemistry : chemical proxies as indicators of past climate

The ratios of trace metals to calcium in the calcium carbonate tests of benthic foraminifera have been used as palaeoceanographic proxies for several decades and are now routinely used to reconstruct past climate change on a variety of Cenozoic timescales. Recent research, however, reveals gaps in our understanding of the effects of oceanic variables such as temperature and carbonate saturation state on these trace metal ratios, which limits their application as proxies. Additional uncertainties arise because of physiological effects (“vital effects”) and microhabitat of the living foraminifera. Moreover, much of what is known about trace metal uptake into benthic foraminiferal calcite is derived from modern core-top calibrations and laboratory experiments and it is unknown as to what extent our understanding from these models can be applied to the early and mid Cenozoic. This thesis attempts to address some of these questions using a novel depth transect approach and presenting benthic foraminiferal trace metal records across three major Cenozoic climate change events from Ocean Drilling Program (ODP) deep sea core material. The events are: (i) The Eocene-Oligocene transition (EOT), (ii) The Oligocene- Miocene boundary event (Mi-1) and (iii) The Middle Miocene Climatic Transition (MMCT). These records have allowed examination of the validity of the application of current knowledge of benthic foraminiferal trace metal proxies to Cenozoic records, and also the comparison of the records of two different benthic foraminiferal species, which has shed new light on the importance of foraminiferal habitat in the interpretation of the proxy data. The identification of a dissolution effect operating on benthic foraminiferal Mg/Ca in undersaturated waters has allowed a reasonable estimate of cooling (~2-3˚C) to be obtained from deep-sea records across the Eocene-Oligocene Transition. The transient glaciation at the Oligocene-Miocene boundary is estimated to comprise of a deep-sea cooling of ~2°C and a sea level decrease of ~80 metres based on Oridorsalis umbonatus Mg/Ca. Comparison of new Middle Miocene trace metal records across a water depth transect has shed light on the relative interplay of temperature and saturation state on published Mg/Ca records, enabling more accurate estimates of temperature and ice volume change. The new interpretations suggest that deep sea temperatures cooled by ~4.5C, and sea level fell by 70-100 metres between 16.2 and 11.6 Ma. The recently developed paired Mg/Ca-Li/Ca approach to calculating simultaneous variations in bottom water temperature and saturation state has been used to assess inter-basinal differences in water mass composition for the first time. Down-core benthic foraminiferal Li/Ca records from Ceara Rise Sites do not behave as expected, indicating that there may be times when this proxy is affected by an additional environmental parameter. This is tentatively suggested to be a growth-rate related oxygenation signal. U/Ca in benthic foraminifera does not appear to work as a saturation state proxy in these records, again indicating either different behaviour to the observed modern behaviour, or additional factors absent from the modern calibration, such as bottom water oxygenation. Benthic foraminiferal Sr/Ca follows the linear negative water-depth relationship of Lear et al., (2003) suggesting a pressure-related effect. This study demonstrates that benthic foraminiferal trace metal chemistry can be used to provide information about climate events in the Cenozoic, however additional empirical work is required to fully understand the systematics of trace metal incorporation into benthic foraminiferal tests.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Cenozoic records of seawater chemistry: chemical proxies as indicators of past climate.

The ratios of trace metals to calcium in the calcium carbonate tests of benthic foraminifera have been used as palaeoceanographic proxies for several decades and are now routinely used to reconstruct past climate change on a variety of Cenozoic timescales. Recent research, however, reveals gaps in our understanding of the effects of oceanic variables such as temperature and carbonate saturation state on these trace metal ratios, which limits their application as proxies. Additional uncertainties arise because of physiological effects (“vital effects”) and microhabitat of the living foraminifera. Moreover, much of what is known about trace metal uptake into benthic foraminiferal calcite is derived from modern core-top calibrations and laboratory experiments and it is unknown as to what extent our understanding from these models can be applied to the early and mid Cenozoic. This thesis attempts to address some of these questions using a novel depth transect approach and presenting benthic foraminiferal trace metal records across three major Cenozoic climate change events from Ocean Drilling Program (ODP) deep sea core material. The events are: (i) The Eocene-Oligocene transition (EOT), (ii) The Oligocene- Miocene boundary event (Mi-1) and (iii) The Middle Miocene Climatic Transition (MMCT). These records have allowed examination of the validity of the application of current knowledge of benthic foraminiferal trace metal proxies to Cenozoic records, and also the comparison of the records of two different benthic foraminiferal species, which has shed new light on the importance of foraminiferal habitat in the interpretation of the proxy data. The identification of a dissolution effect operating on benthic foraminiferal Mg/Ca in undersaturated waters has allowed a reasonable estimate of cooling (~2-3˚C) to be obtained from deep-sea records across the Eocene-Oligocene Transition. The transient glaciation at the Oligocene-Miocene boundary is estimated to comprise of a deep-sea cooling of ~2°C and a sea level decrease of ~80 metres based on Oridorsalis umbonatus Mg/Ca. Comparison of new Middle Miocene trace metal records across a water depth transect has shed light on the relative interplay of temperature and saturation state on published Mg/Ca records, enabling more accurate estimates of temperature and ice volume change. The new interpretations suggest that deep sea temperatures cooled by ~4.5C, and sea level fell by 70-100 metres between 16.2 and 11.6 Ma. The recently developed paired Mg/Ca-Li/Ca approach to calculating simultaneous variations in bottom water temperature and saturation state has been used to assess inter-basinal differences in water mass composition for the first time. Down-core benthic foraminiferal Li/Ca records from Ceara Rise Sites do not behave as expected, indicating that there may be times when this proxy is affected by an additional environmental parameter. This is tentatively suggested to be a growth-rate related oxygenation signal. U/Ca in benthic foraminifera does not appear to work as a saturation state proxy in these records, again indicating either different behaviour to the observed modern behaviour, or additional factors absent from the modern calibration, such as bottom water oxygenation. Benthic foraminiferal Sr/Ca follows the linear negative water-depth relationship of Lear et al., (2003) suggesting a pressure-related effect. This study demonstrates that benthic foraminiferal trace metal chemistry can be used to provide information about climate events in the Cenozoic, however additional empirical work is required to fully understand the systematics of trace metal incorporation into benthic foraminiferal tests

Carbon cycle feedbacks during the Oligocene-Miocene transient glaciation

Ice sheet models suggest that once formed, the large, high- altitude East Antarctic Ice Sheet was relatively self-stabilizing, due to its cold upper surface. The ice sheet hysteresis problem results from an inability to reconcile this expectation with geological evidence for episodes of ice sheet retreat. A classic example of this problem is manifested in benthic foraminiferal oxygen isotope records across the Oligocene-Miocene boundary (ca. 23 Ma), which display a transient ~1‰ excursion to higher values. The inferred increase and subsequent decrease in ice volume has been linked to advance and retreat of the Antarctic ice sheet across the continental shelf. However, oxygen isotope records alone do not provide unambiguous records of temperature and ice volume, hindering assessment of the driving mechanism for these variations. Here we present new benthic foraminiferal Mg/Ca, Li/Ca, and U/Ca records across the Oligocene- Miocene boundary from Ocean Drilling Program Sites 926 and 929. Our records demonstrate that Atlantic bottom-water temperatures varied cyclically, with the main cooling and warming steps followed by ice growth and decay respectively. We suggest that enhanced organic carbon burial acted as a positive feedback as climate cooled. Several lines of evidence suggest that the deglaciation was associated with an input of carbon to the ocean-atmosphere system, culminating in a previously unidentified seafloor dissolution event. We suggest that one of the initial sources of carbon was organic matter oxidation in ocean sediments. This study demonstrates that carbon cycle feedbacks should be considered when evaluating the stability of ancient ice sheets

Cenozoic benthic foraminiferal Mg/Ca and Li/Ca records: toward unlocking temperatures and saturation states

The sensitivities of benthic foraminiferal Mg/Ca and Li/Ca to bottom water temperature and carbonate saturation state have recently been assessed. Here we present a new approach that uses paired Mg/Ca and Li/Ca records to calculate simultaneous changes in temperature and saturation state. Using previously published records, we first use this approach to document a cooling of deep ocean waters associated with the establishment of the Antarctic ice sheet at the Eocene-Oligocene climate transition. We then apply this approach to new records of the Middle Miocene Climate Transition from ODP Site 761 to estimate variations in bottom water temperature and the oxygen isotopic composition of seawater. We estimate that the oxygen isotopic composition of seawater varied by ∼1‰ between the deglacial extreme of the Miocene Climatic Optimum and the glacial maximum following the Middle Miocene Climate Transition, indicating large amplitude variations in ice volume. However, the longer-term change between 15.3 and 12.5 Ma is marked by a ∼1°C cooling of deep waters, and an increase in the oxygen isotopic composition of seawater of ∼0.6‰. We find that bottom water saturation state increased in the lead up to the Middle Miocene Climate Transition and decreased shortly after. This supports decreasing pCO2 as a driver for global cooling and ice sheet expansion, in agreement with existing boron isotope and leaf stomatal index CO2 records but in contrast to the published alkenone CO2 records

Mg/Ca-Temperature Calibration of Polar Benthic foraminifera species for reconstruction of bottom water temperatures on the Antarctic shelf

Benthic foraminifera Mg/Ca is a well-established bottom water temperature (BWT) proxy used in paleoclimate studies. The relationship between Mg/Ca and BWT for numerous species has been determined using core-top and culturing studies. However, the scarcity of calcareous microfossils in Antarctic shelf sediments and poorly defined calibrations at low temperatures has limited the use of the foraminiferal Mg/Ca paleothermometer in ice proximal Antarctic sediments. Here we present paired ocean temperature and modern benthic foraminifera Mg/Ca data for three species, Trifarina angulosa, Bulimina aculeata, and Globocassidulina subglobosa, but with a particular focus on Trifarina angulosa. The core-top data from several Antarctic sectors span a BWT range of −1.7 to +1.2 °C and constrain the relationship between Mg/Ca and cold temperatures. We compare our results to published lower-latitude core-top data for species in the same or related genera, and in the case of Trifarina angulosa, produce a regional calibration. The resulting regional equation for Trifarina angulosa is Temperature (°C) = (Mg/Ca −1.14 ± 0.035)/0.069 ± 0.033). Addition of our Trifarina angulosa data to the previously published Uvigerina spp. dataset provides an alternative global calibration, although some data points appear to be offset from this relationship and are discussed. Mg-temperature relationships for Bulimina aculeata and Globocassidulina subglobosa are also combined with previously published data to produce calibration equations of Temperature (°C) = (Mg/Ca-1.04 ± 0.07)/0.099 ± 0.01 and Temperature (°C) = (Mg/Ca-0.99 ± 0.03)/0.087 ± 0.01, respectively. These refined calibrations highlight the potential utility of benthic foraminifera Mg/Ca-paleothermometry for reconstructing past BWT in Antarctic margin settings

Silicate weathering and carbon cycle controls on the Oligocene-Miocene transition glaciation

Changes in both silicate weathering rates and organic carbon burial have been proposed as drivers of the transient “Mi-1” glaciation event at the Oligocene-Miocene transition (OMT; ~23 Ma). However detailed geochemical proxy data are required to test these hypotheses. Here we present records of Li/Ca, Mg/Ca, Cd/Ca, U/Ca, δ18O, δ13C, and shell weight in planktonic foraminifera from marine sediments spanning the OMT in the equatorial Atlantic Ocean. Li/Ca values increase by 1 μmol/mol across this interval. We interpret this to indicate a ~20% increase in silicate weathering rates, which would have lowered atmospheric CO2, potentially forcing the Antarctic glaciation circa 23 Ma. δ13C of thermocline dwelling planktonic foraminifera track the global increase in seawater δ13C across the OMT and during the Mi-1 event, hence supporting a hypothesized global increase in organic carbon burial rates. High δ13C previously measured in epipelagic planktonic foraminifera and high Cd/Ca ratios during Mi-1 are interpreted to represent locally enhanced primary productivity, stimulated by increased nutrients supply to surface waters. The fingerprint of high export production and associated organic carbon burial at this site is found in reduced bottom water oxygenation (inferred from high foraminiferal U/Ca), and enhanced respiratory dissolution of carbonates, characterised by reduced foraminiferal shell weight. Replication of our results elsewhere would strengthen the case that weathering-induced CO2 sequestration preconditioned climate for Antarctic ice sheet growth across the OMT and increased burial of organic carbon acted as a feedback that intensified cooling at this time

Reconstructing Circumpolar Deep Water: A new Mg/Ca-Temperature calibration for the benthic foraminifer Trifarina angulosa around Antarctica

The West Antarctic Ice Sheet (WAIS) represents a large potential source of sea level rise. Observations of ice sheet instabilities in the region have increased in recent decades, with a 77% recorded increase in the net loss of glaciers the Amundsen Sea Embayment (ASE) sector of the WAIS since 1973. This has been attributed to increasing basal melting of floating ice shelves caused by warmer Circumpolar Deep Water (CDW) upwelling onto the shelf. Understanding the role of CDW in glacial retreat in the ASE over longer timescales is key to reducing the uncertainty of future sea level predictions. The aim of this research is to reconstruct CDW incursions onto the ASE continental shelf and correlate them to the glacial history of the area since the Last Glacial Maximum. To achieve this, it is crucial to develop a proxy for detecting the presence or absence of CDW. Whilst foraminiferal preservation is rare in this locality due to the corrosive nature of water masses around the Antarctic Peninsula, several cores from the ASE contain specimens including the benthic species Trifarina angulosa, which is a shallow infaunal species therefore ideal for Mg/Ca temperature reconstructions. Here we present a core-top calibration for T. angulosa for temperatures between -1.75°C and +1.5°C from sites situated in the Southern Ocean. We apply this Mg/Ca temperature calibration to down-core archives at several sites, which are well-dated using radiocarbon. The results are presented here along with benthic and planktonic foraminiferal stable isotope data and complementary trace metal data. Keywords: Circumpolar deep water, foraminifera, Mg/C