Bottom mixed layer oxygen dynamics in the Celtic Sea

The seasonally stratified continental shelf seas are highly productive, economically important environments which are under considerable pressure from human activity. Global dissolved oxygen concentrations have shown rapid reductions in response to anthropogenic forcing since at least the middle of the twentieth century. Oxygen consumption is at the same time linked to the cycling of atmospheric carbon, with oxygen being a proxy for carbon remineralisation and the release of CO2. In the seasonally stratified seas the bottom mixed layer (BML) is partially isolated from the atmosphere and is thus controlled by interplay between oxygen consumption processes, vertical and horizontal advection. Oxygen consumption rates can be both spatially and temporally dynamic, but these dynamics are often missed with incubation based techniques. Here we adopt a Bayesian approach to determining total BML oxygen consumption rates from a high resolution oxygen time-series. This incorporates both our knowledge and our uncertainty of the various processes which control the oxygen inventory. Total BML rates integrate both processes in the water column and at the sediment interface. These observations span the stratified period of the Celtic Sea and across both sandy and muddy sediment types. We show how horizontal advection, tidal forcing and vertical mixing together control the bottom mixed layer oxygen concentrations at various times over the stratified period. Our muddy-sand site shows cyclic spring-neap mediated changes in oxygen consumption driven by the frequent resuspension or ventilation of the seabed. We see evidence for prolonged periods of increased vertical mixing which provide the ventilation necessary to support the high rates of consumption observed

Will the declining sea ice extent in the Arctic cause a reversal of net benthic-pelagic exchange directions?

In the Arctic, loss of sea ice due to climate change and the northward shift of the Polar Front are predicted to affect many ecosystem processes such as the ecologically important process of particulate and dissolved matter exchange between the seafloor and the water column. In this study, we show for the first time that a change from an ice-covered, Arctic water-dominated system to an Atlantic -dominated ice-free one is likely to reverse seafloorwater exchange directions. A north – south transect across the Barents Sea was studied over two years with differing sea ice cover conditions, recording biological, biogeochemical, hydrographic, geophysical, and oceanographic data. There was a clear difference between the direction and magnitude of key benthic-pelagic fluxes present at Atlantic-dominated environments, and those in Arctic water – dominated ones. Currently, the southern Barents Sea exhibits a net downward flux of dissolved matter and a net upward flux of particulates, while in the northern region solutes fluctuate upwards and particulates downward, making the North a more depositional region that promotes near-surface primary productivity. Broad scale assessments of net fluxes in rapidly changing ecosystems should be employed to monitor impacts of climate change and anthropogenic activities

The UK needs an open data portal dedicated to coastal flood and erosion hazard risk and resilience

In the UK, coastal flooding and erosion are two of the primary climate-related hazards to communities, businesses, and infrastructure. To better address the ramifications of those hazards, now and into the future, the UK needs to transform its scattered, fragmented coastal data resources into a systematic, integrated portal for quality-assured, publicly accessible open data. Such a portal would support analyses of coastal risk and resilience by hosting, in addition to data layers for coastal flooding and erosion, a diverse array of spatial datasets for building footprints, infrastructure networks, land use, population, and various socio-economic measures and indicators derived from survey and census data. The portal would facilitate novel combinations of spatial data layers to yield scientifically, societally, and economically beneficial insights into UK coastal systems

Microbial Diversity of a Brazilian Coastal Region Influenced by an Upwelling System and Anthropogenic Activity

BACKGROUND: Upwelling systems are characterised by an intense primary biomass production in the surface (warmest) water after the outcrop of the bottom (coldest) water, which is rich in nutrients. Although it is known that the microbial assemblage plays an important role in the food chain of marine systems and that the upwelling systems that occur in southwest Brazil drive the complex dynamics of the food chain, little is known about the microbial composition present in this region. METHODOLOGY/PRINCIPAL FINDINGS: We carried out a molecular survey based on SSU rRNA gene from the three domains of the phylogenetic tree of life present in a tropical upwelling region (Arraial do Cabo, Rio de Janeiro, Brazil). The aim was to analyse the horizontal and vertical variations of the microbial composition in two geographically close areas influenced by anthropogenic activity (sewage disposal/port activity) and upwelling phenomena, respectively. A lower estimated diversity of microorganisms of the three domains of the phylogenetic tree of life was found in the water of the area influenced by anthropogenic activity compared to the area influenced by upwelling phenomena. We observed a heterogenic distribution of the relative abundance of taxonomic groups, especially in the Archaea and Eukarya domains. The bacterial community was dominated by Proteobacteria, Cyanobacteria and Bacteroidetes phyla, whereas the microeukaryotic community was dominated by Metazoa, Fungi, Alveolata and Stramenopile. The estimated archaeal diversity was the lowest of the three domains and was dominated by uncharacterised marine Crenarchaeota that were most closely related to Marine Group I. CONCLUSIONS/SIGNIFICANCE: The variety of conditions and the presence of different microbial assemblages indicated that the area of Arraial do Cabo can be used as a model for detailed studies that contemplate the correlation between pollution-indicating parameters and the depletion of microbial diversity in areas close to anthropogenic activity; functional roles and geochemical processes; phylogeny of the uncharacterised diversity; and seasonal variations of the microbial assemblages

Inter-comparison between five devices for determining erodability of intertidal sediments

Five erosion devices were compared using five intertidal estuarine sites covering a range of sediment stability from newly settled mud to very cohesive mud at the margins of a saltmarsh. The erosion devices use different methods of fluid shearing from horizontal currents/bed shear stresses to vertical water jets, and have different ‘footprint’ areas. The devices included: (1) the annular flumes (AFs—diameter 64 cm; footprint area 0.17 m2) of the Plymouth Marine Laboratory (PML); (2) PML's mini-annular flume (MAF—diameter 19 cm; area 0.026 m2); (3) the annular mini-flume (AMF—diameter 30.5 cm; area 0.032 m2) of the National Oceanography Centre Southampton (NOC); (4) NOC's Cohesive Strength Meter (CSM—diameter 3 cm; area 0.0007 m2); (5) NOC's EROMES (ER—diameter 10 cm; area 0.0079 m2). The quantification of threshold shear stress for bed erosion (?e) and sediment erosion rate was complemented by the measurement of physical, chemical and biological properties of the sediment (grain size, bulk density, water content, organic content, chlorophyll a, carbohydrates, macrofauna). The results demonstrated a significant correlation (r2=0.98) between the PML AF (laboratory measurement of undisturbed cored sediment) and PML MAF (in situ) for measurement of erosion thresholds for bed sediment. However, there were no significant correlations between AFs, the CSM and EROMES. There were no consistent correlations with physical or biological sediment properties due to the spatially unrelated sites and the marked differences in benthic assemblages. The sources of differences and the lack of correlations between erosion devices were due to several factors, including operational procedures (e.g., sediment resuspension during filling with water), definition of erosion threshold, the nature of the force applied to the bed, and method of calibration. In contrast to the CSM and EROMES, both types of AFs were able to record significant differences in the erodability of soft sediments from four sites. This indicates that the CSM and EROMES may not be very effective at measuring the differences in erosion thresholds of soft estuarine sediments. <br/

Micro-abrasion of flint artefacts by mobile sediments: a taphonomic approach

Fluvial redeposition of stone artifacts is a major complicating factor in the interpretation of Lower Palaeolithic open-air archaeological sites. However, the microscopic examination of lithic surfaces may provide valuable background information on the transport history of artifacts, particularly in low energy settings. Replica flint artifacts were therefore abraded in an annular flume and examined with a scanning electron microscope. Results showed that abrasion time, sediment size, and artifact transport mode were very sensitive predictors of microscopic surface abrasion, ridge width, and edge damage (p < 0.000). These results suggest that patterns of micro-abrasion of stone artifacts may enhance understanding of archaeological assemblage formation in fluvial context

Major Self-mutilation in the First Episode of Psychosis

Major self-mutilation (MSM) is a rare but catastrophic complication of severe mental illness. Most people who inflict MSM have a psychotic disorder, usually a schizophrenia spectrum psychosis. It is not known when in the course of psychotic illness, MSM is most likely to occur. In this study, the proportion of patients in first episode of psychosis (FEP) was assessed using the results of a systematic review of published case reports. Histories of patients who had removed an eye or a testicle, severed their penis, or amputated a portion of a limb and were diagnosed with a schizophrenia spectrum psychosis were included. A psychotic illness was documented in 143 of 189 cases (75.6%) of MSM, of whom 119 of 143 (83.2%) were diagnosed with a schizophrenia spectrum psychosis. The treatment status of a schizophrenia spectrum psychosis could be ascertained in 101 of the case reports, of which 54 were in the FEP (53.5%, 95% confidence interval = 43.7%–63.2%). Patients who inflict MSM in FEP exhibited similar symptoms to those who inflict MSM later in their illness. Acute psychosis, in particular first-episode schizophrenia, appears to be the major cause of MSM. Although MSM is extremely uncommon, earlier treatment of psychotic illness may reduce the incidence of MSM

Value-based modulation of memory encoding involves strategic engagement of fronto-temporal semantic processing regions

A number of prior fMRI studies have focused on the ways in which the midbrain dopaminergic reward system co-activates with hippocampus to potentiate memory for valuable items. However, another means by which people could selectively remember more valuable to-be-remembered items is to be selective in their use of effective but effortful encoding strategies. To broadly examine the neural mechanisms of value on subsequent memory, we used fMRI to examine how differences in brain activity at encoding as a function of value relate to subsequent free recall for words. Each word was preceded by an arbitrarily assigned point value, and participants went through multiple study-test cycles with feedback on their point total at the end of each list, allowing for sculpting of cognitive strategies. We examined the correlation between value-related modulation of brain activity and participants’ selectivity index, a measure of how close participants were to their optimal point total given the number of items recalled. Greater selectivity scores were associated with greater differences in activation of semantic processing regions, including left inferior frontal gyrus and left posterior lateral temporal cortex, during encoding of high-value words relative to low-value words. Although we also observed value-related modulation within midbrain and ventral striatal reward regions, our fronto-temporal findings suggest that strategic engagement of deep semantic processing may be an important mechanism for selectively encoding valuable items