Endolithic algae photoacclimate to increased irradiance during coral bleaching

The photoacclimation of endolithic algae ( of the genus Ostreobium) inhabiting the skeleton of the Mediterranean coral Oculina patagonica during a bleaching event was examined. Pulse amplitude modulated (PAM) chlorophyll fluorescence techniques in situ were used to assess the photosynthetic efficiency of endolithic algae in the coral skeleton and the symbiotic dinoflagellates (zooxanthellae) in the coral tissue. Relative photosynthetic electron transport rates (ETRs) of the endolithic algae under bleached areas of the colony were significantly higher than those of endolithic algae from a healthy section of the colony and those of zooxanthellae isolated from the same section. Endolithic algae under healthy parts of the colony demonstrated an ETRmax of 16.5% that of zooxanthellae from tissue in the same section whereas endolithic algae under bleached sections showed ETRmax values that were 39% of those found for healthy zooxanthellae. The study demonstrates that endolithic algae undergo photoacclimation with increased irradiance reaching the skeleton. As PAM fluorometry has become a major tool for assessing levels of stress and bleaching in corals, the importance of considering the contribution of the endolithic algae to the overall chlorophyll fluorescence measured is highlighted.

Tolerance of endolithic algae to elevated temperature and light in the coral Montipora monasteriata from the southern Great Barrier Reef

Photosynthetic endolithic algae and cyanobacteria live within the skeletons of many scleractinians. Under normal conditions, less than 5% of the photosynthetically active radiation (PAR) reaches the green endolithic algae because of the absorbance of light by the endosymbiotic dinoflagellates and the carbonate skeleton. When corals bleach (loose dinoflagellate symbionts), however, the tissue of the corals become highly transparent and photosynthetic microendoliths may be exposed to high levels of both thermal and solar stress. This study explores the consequence of these combined stresses on the phototrophic endoliths inhabiting the skeleton of Montipora monasteriata, growing at Heron Island, on the southern Great Barrier Reef. Endoliths that were exposed to sun after tissue removal were by far more susceptible to thermal photoinhibition and photo-damage than endoliths under coral tissue that contained high concentrations of brown dinoflagellate symbionts. While temperature or light alone did not result in decreased photosynthetic efficiency of the endoliths, combined thermal and solar stress caused a major decrease and delayed recovery. Endoliths protected under intact tissue recovered rapidly and photoacclimated soon after exposure to elevated sea temperatures. Endoliths under naturally occurring bleached tissue of M. monasteriata colonies (bleaching event in March 2004 at Heron Island) acclimated to increased irradiance as the brown symbionts disappeared. We suggest that two major factors determine the outcome of thermal bleaching to the endolith community. The first is the microhabitat and light levels under which a coral grows, and the second is the susceptibility of the coral-dinoflagellates symbiosis to thermal stress. More resistant corals may take longer to bleach allowing endoliths time to acclimate to a new light environment. This in turn may have implications for coral survival.

Phototrophic microendoliths bloom during coral "white syndrome"

Following rapid lesion progression of white syndrome in tabular Acropora spp., the white bare skeleton gradually changes to green, a result of endolithic algae blooms (primarily Ostreobium spp.). Endolithic algal biomass and chlorophyll concentration were found to be an order of magnitude higher in the green zone compared with healthy appearing parts of each colony. Chl b to Chl a ratio increased from 1:1.6 in the healthy area to 1:2 and 1:3.5 in the white exposed skeleton and green zones, respectively. These observations together with pulse amplitude modulated (PAM) fluorometry suggest photoacclimation of the endoliths in the green zone. Histopathological microscopy revealed that the endolithic algal filaments penetrate the coral tissue. This study highlights the interaction of endolithic algae with both the skeleton and host tissue. This may have a critical role in the processes that accompany the post-disease state in reef-building corals.

Flower animals

The coral reefs around the world may be likened to canaries down the mineshaft of global warming. These sensitive plant-like animals have evolved for life in tropical seas. Their needs are quite specific – not too cold, not too hot. A rise of as little as one degree Celsius is enough to cause some bleaching of these colourful jewels of the sea. Many climate models indicate we can expect sea temperature increases of between two and six degrees Celsius. Research - such as that detailed in a 2004 report by the University of Queensland’s Centre for Marine Studies – indicates that by the year 2050 most of the worlds major reef systems will be dead. Many of us have heard this kind of information, but it remains difficult to comprehend. It’s almost impossible to imagine the death of the Great Barrier Reef. Some six to nine thousand years old and visible from space, it is the world’s largest structure created by living organisms. Yet whilst it is hard to believe, this gentle, sensitive giant is at grave risk because it cannot adapt quickly enough to the changes in the environment. This cluster of fluffy felt brain coral sculptures are connected in real time to temperature data collected by monitoring stations within the Great Barrier Reef, that form part of the Australian Institute of Marine Science’s Great Barrier Reed Ocean Observing System. These corals display illumination patterns showing changes in sea temperature at Heron Reef, one of the 2,900 reefs that comprise the Great Barrier Reef. Their spectrum of colour ranges from cool hues, through warm tones to bright white when temperatures exceed those that tropical corals are able to tolerate over sustained periods. The Flower Animals also blush in colour and make sound when people come within close proximity. In a reef, fishes and other creatures generate significant amounts of sound. These cacophonies are considered an indicator of reef health, and are used by reef fish to determine where they can best live and forage.

(Supplement Table S2) Results of 230Th/U-dating

We compared the suitability of two skeletal materials of the Atlantic brain coral Diploria strigosa for 230Th/U-dating: the commonly used bulk material comprising all skeletal elements and the denser theca wall material. Eight fossil corals of presumably Last Interglacial age from Bonaire, southern Caribbean Sea, were investigated, and several sub-samples were dated from each coral. For four corals, both the ages and the activity ratios of the bulk material and theca wall agree within uncertainty. Three corals show significantly older ages for their bulk material than for their theca wall material as well as substantially elevated 232Th content and (230Th/238U) ratios. The bulk material samples of another coral show younger ages and lower (230Th/238U) ratios than the corresponding theca wall samples. This coral also contains a considerable amount of 232Th. The application of the available open-system models developed to account for post-depositional diagenetic effects in corals shows that none of the models can successfully be applied to the Bonaire corals. The most likely explanation for this observation is that the assumptions of the models are not fulfilled by our data set. Comparison of the theca wall and bulk material data enables us to obtain information about the open-system processes that affected the corals. The corals showing apparently older ages for their bulk material were probably affected by contamination with a secondary (detrital) phase. The most likely source of the detrital material is carbonate sand. The higher (230Th/232Th) ratio of this material implies that detrital contamination would have a much stronger impact on the ages than a contaminant with a bulk Earth (230Th/232Th) ratio and that the threshold for the commonly applied 232Th reliability criterion would be much lower than the generally used value of 1 ng g^-1. The coral showing apparently younger ages for its bulk material was probably influenced by more than one diagenetic process. A potential scenario is a combination of detrital contamination and U addition by secondary pore infillings. Our results show that the dense theca wall material of D. strigosa is generally less affected by post-depositional open-system behaviour and better suited for 230Th/U-dating than the bulk material. This is also obvious from the fact that all ages of theca wall material reflect a Last Interglacial origin (~125 ka), whereas the bulk material samples are either substantially older or younger. However, for some corals, the 230Th/U-ages and activity ratios of the bulk material and the theca wall samples are similar. This shows that strictly reliable 230Th/U-ages can also be obtained from bulk material samples of exceptionally well-preserved corals. However, the bulk material samples more frequently show elevated activity ratios and ages than the corresponding theca wall samples. Our findings should be generally applicable to brain corals (Mussidae) that are found in tropical oceans worldwide and may enable reliable 230Th/U-dating of fossil corals with similar skeletal architecture, even if their bulk skeleton is altered by diagenesis. The 230Th/U-ages we consider reliable (120-130 ka), along with a recently published age of 118 ka, provide the first comprehensive dating of the elevated lower reef terrace at Bonaire (118-130 ka), which is in agreement in timing and duration with other Last Interglacial records.

N-syndecan and HB-GAM in neural migration and differentiation : Modulation of growth factor activity in brain

The juvenile sea squirt wanders through the sea searching for a suitable rock or hunk of coral to cling to and make its home for life. For this task it has a rudimentary nervous system. When it finds its spot and takes root, it doesn't need its brain any more so it eats it. It's rather like getting tenure. Daniel C. Dennett (from Consciousness Explained, 1991) The little sea squirt needs its brain for a task that is very simple and short. When the task is completed, the sea squirt starts a new life in a vegetative state, after having a nourishing meal. The little brain is more tightly structured than our massive primate brains. The number of neurons is exact, no leeway in neural proliferation is tolerated. Each neuroblast migrates exactly to the correct position, and only a certain number of connections with the right companions is allowed. In comparison, growth of a mammalian brain is a merry mess. The reason is obvious: Squirt brain needs to perform only a few, predictable functions, before becoming waste. The more mobile and complex mammals engage their brains in tasks requiring quick adaptation and plasticity in a constantly changing environment. Although the regulation of nervous system development varies between species, many regulatory elements remain the same. For example, all multicellular animals possess a collection of proteoglycans (PG); proteins with attached, complex sugar chains called glycosaminoglycans (GAG). In development, PGs participate in the organization of the animal body, like in the construction of parts of the nervous system. The PGs capture water with their GAG chains, forming a biochemically active gel at the surface of the cell, and in the extracellular matrix (ECM). In the nervous system, this gel traps inside it different molecules: growth factors and ECM-associated proteins. They regulate the proliferation of neural stem cells (NSC), guide the migration of neurons, and coordinate the formation of neuronal connections. In this work I have followed the role of two molecules contributing to the complexity of mammalian brain development. N-syndecan is a transmembrane heparan sulfate proteoglycan (HSPG) with cell signaling functions. Heparin-binding growth-associated molecule (HB-GAM) is an ECM-associated protein with high expression in the perinatal nervous system, and high affinity to HS and heparin. N-syndecan is a receptor for several growth factors and for HB-GAM. HB-GAM induces specific signaling via N-syndecan, activating c-Src, calcium/calmodulin-dependent serine protein kinase (CASK) and cortactin. By studying the gene knockouts of HB-GAM and N-syndecan in mice, I have found that HB-GAM and N-syndecan are involved as a receptor-ligand-pair in neural migration and differentiation. HB-GAM competes with the growth factors fibriblast growth factor (FGF)-2 and heparin-binding epidermal growth factor (HB-EGF) in HS-binding, causing NSCs to stop proliferation and to differentiate, and affects HB-EGF-induced EGF receptor (EGFR) signaling in neural cells during migration. N-syndecan signaling affects the motility of young neurons, by boosting EGFR-mediated cell migration. In addition, these two receptors form a complex at the surface of the neurons, probably creating a motility-regulating structure.

Brucite Microbialites in Living Coral Skeletons: Indicators of Extreme Microenvironments in Shallow-Marine Settings

Brucite [Mg(OH)2] microbialites occur in vacated interseptal spaces of living scleractinian coral colonies (Acropora, Pocillopora, Porites) from subtidal and intertidal settings in the Great Barrier Reef, Australia, and subtidal Montastraea from the Florida Keys, United States. Brucite encrusts microbial filaments of endobionts (i.e., fungi, green algae, cyanobacteria) growing under organic biofilms; the brucite distribution is patchy both within interseptal spaces and within coralla. Although brucite is undersaturated in seawater, its precipitation was apparently induced in the corals by lowered pCO2 and increased pH within microenvironments protected by microbial biofilms. The occurrence of brucite in shallow-marine settings highlights the importance of microenvironments in the formation and early diagenesis of marine carbonates. Significantly, the brucite precipitates discovered in microenvironments in these corals show that early diagenetic products do not necessarily reflect ambient seawater chemistry. Errors in environmental interpretation may arise where unidentified precipitates occur in microenvironments in skeletal carbonates that are subsequently utilized as geochemical seawater proxies.

Brain and cognitive development

'The Millennial Adolescent' offers contemporary, stimulating insights for those currently teaching as well as those preparing to teach. This book investigates the characteristics of Generation Y, using students own voices, generational theory and case studies. The text is structured around the principle that effective teachers need to know who they are teaching as well as what to teach, how to teach it, and how to assess the outcome. Using generational theory, 'The Millennial Adolescent' investigates the characteristics of Generation Y, or the Millennial Generation, and points out what all teachers need to know about working with this current generation of students who are described in a number of ways digital natives, team oriented, confident, multi-taskers, high achievers, and a generation unlike any other. The book contains well-known frameworks for developing understandings about adolescents, blended and contrasted with a contemporary socio-cultural construction of adolescence, set in our particular time, era and society. This book reflects the uniqueness of Australian contexts, while connecting with international trends and global patterns. Engaging and full of insights, this book is essential reading for all professionals dealing with adolescents.

Earliest diagenesis in scleractinian coral skeletons : implications for palaeoclimate-sensitive geochemical archives

Live-collected samples of four common reef building coral genera (Acropora, Pocillopora, Goniastrea, Porites) from subtidal and intertidal settings of Heron Reef, Great Barrier Reef, show extensive early marine diagenesis where parts of the coralla less than 3 years old contain abundant macro- and microborings and aragonite, high-Mg calcite, low-Mg calcite, and brucite cements. Many types of cement are associated directly with microendoliths and endobionts that inhabit parts of the corallum recently abandoned by coral polyps. The occurrence of cements that generally do not precipitate in normal shallow seawater (e.g., brucite, low-Mg calcite) highlights the importance of microenvironments in coral diagenesis. Cements precipitated in microenvironments may not reXect ambient seawater chemistry. Hence, geochemical sampling of these cements will contaminate trace-element and stable-isotope inventories used for palaeoclimate and dating analysis. Thus, great care must be taken in vetting samples for both bulk and microanalysis of geochemistry. Visual inspection using scanning electron microscopy may be required for vetting in many cases.

Human brain regions required for the dividing and switching of attention between two features of a single object

This combined PET and ERP study was designed to identify the brain regions activated in switching and divided attention between different features of a single object using matched sensory stimuli and motor response. The ERP data have previously been reported in this journal [64]. We now present the corresponding PET data. We identified partially overlapping neural networks with paradigms requiring the switching or dividing of attention between the elements of complex visual stimuli. Regions of activation were found in the prefrontal and temporal cortices and cerebellum. Each task resulted in different prefrontal cortical regions of activation lending support to the functional subspecialisation of the prefrontal and temporal cortices being based on the cognitive operations required rather than the stimuli themselves.

Brain-derived neurotrophic factor (BDNF) gene : no major impact on antidepressant treatment response

The brain-derived neurotrophic factor (BDNF) has been suggested to play a pivotal role in the aetiology of affective disorders. In order to further clarify the impact of BDNF gene variation on major depression as well as antidepressant treatment response, association of three BDNF polymorphisms [rs7103411, Val66Met (rs6265) and rs7124442] with major depression and antidepressant treatment response was investigated in an overall sample of 268 German patients with major depression and 424 healthy controls. False discovery rate (FDR) was applied to control for multiple testing. Additionally, ten markers in BDNF were tested for association with citalopram outcome in the STAR*D sample. While BDNF was not associated with major depression as a categorical diagnosis, the BDNF rs7124442 TT genotype was significantly related to worse treatment outcome over 6 wk in major depression (p=0.01) particularly in anxious depression (p=0.003) in the German sample. However, BDNF rs7103411 and rs6265 similarly predicted worse treatment response over 6 wk in clinical subtypes of depression such as melancholic depression only (rs7103411: TT

Controversies of prophylactic hypothermia and the emerging use of brain tissue oxygen tension monitoring and decompressive craniectomy in traumatic brain-injured children

Background Despite being the leading cause of death and disability in the paediatric population, traumatic brain injury (TBI) in this group is largely understudied. Clinical practice within the paediatric intensive care unit (PICU) has been based upon adult guidelines however children are significantly different in terms of mechanism, pathophysiology and consequence of injury. Aim To review TBI management in the PICU and gain insight into potential management strategies. Method To conduct this review, a literature search was conducted using MEDLINE, PUBMED and The Cochrane Library using the following key words; traumatic brain injury; paediatric; hypothermia. There were no date restrictions applied to ensure that past studies, whose principles remain current were not excluded. Results Three areas were identified from the literature search and will be discussed against current acknowledged treatment strategies: Prophylactic hypothermia, brain tissue oxygen tension monitoring and decompressive craniectomy. Conclusion Previous literature has failed to fully address paediatric specific management protocols and we therefore have little evidence-based guidance. This review has shown that there is an emerging and ongoing trend towards paediatric specific TBI research in particular the area of moderate prophylactic hypothermia (MPH).

RatSLAM on the edge : revealing a coherent representation from an overloaded rat brain

The RatSLAM system can perform vision based SLAM using a computational model of the rodent hippocampus. When the number of pose cells used to represent space in RatSLAM is reduced, artifacts are introduced that hinder its use for goal directed navigation. This paper describes a new component for the RatSLAM system called an experience map, which provides a coherent representation for goal directed navigation. Results are presented for two sets of real world experiments, including comparison with the original goal memory system's performance in the same environment. Preliminary results are also presented demonstrating the ability of the experience map to adapt to simple short term changes in the environment.