Modelling coral calcification accounting for the impacts of coral bleaching and ocean acidification

© Author(s) 2015. Coral reefs are diverse ecosystems that are threatened by rising CO2 levels through increases in sea surface temperature and ocean acidification. Here we present a new unified model that links changes in temperature and carbonate chemistry to coral health. Changes in coral health and population are explicitly modelled by linking rates of growth, recovery and calcification to rates of bleaching and temperature-stress-induced mortality. The model is underpinned by four key principles: the Arrhenius equation, thermal specialisation, correlated up- and down-regulation of traits that are consistent with resource allocation trade-offs, and adaption to local environments. These general relationships allow this model to be constructed from a range of experimental and observational data. The performance of the model is assessed against independent data to demonstrate how it can capture the observed response of corals to stress. We also provide new insights into the factors that determine calcification rates and provide a framework based on well-known biological principles to help understand the observed global distribution of calcification rates. Our results suggest that, despite the implicit complexity of the coral reef environment, a simple model based on temperature, carbonate chemistry and different species can give insights into how corals respond to changes in temperature and ocean acidification

Tracing differences in iron supply to the Mid-Atlantic Ridge valley between hydrothermal vent sites: implications for the addition of iron to the deep ocean

Supply of iron (Fe) to the surface ocean supports primary productivity, and while hydrothermal input of Fe to the deep ocean is known to be extensive it remains poorly constrained. Global estimates of hydrothermal Fe supply rely on using dissolved Fe (dFe) to excess He (xs3He) ratios to upscale fluxes, but observational constraints on dFe/xs3He may be sensitive to assumptions linked to sampling and interpolation. We examined the variability in dFe/xs3He using two methods of estimation, for four vent sites with different geochemistry along the Mid-Atlantic Ridge. At both Rainbow and TAG, the plume was sampled repeatedly and the range of dFe/xs3He was 4 to 63 and 4 to 87 nmol:fmol, respectively, primarily due to differences in plume age. To account for background xs3He and shifting plume position, we calibrated He values using contemporaneous dissolved Mn (dMn). Applying this approach more widely, we found dFe/xs3He ratios of 12, 4–8, 4–44, and 4–86 nmol fmol−1 for the Menez Gwen, Lucky Strike, Rainbow, and TAG hydrothermal vent sites, respectively. Differences in plume dFe/xs3He across sites were not simply related to the vent endmember Fe and He fluxes. Within 40 km of the vents, the dFe/xs3He ratios decreased to 3–38 nmol fmol−1, due to the precipitation and subsequent settling of particulates. The ratio of colloidal Fe to dFe was consistently higher (0.67–0.97) than the deep N. Atlantic (0.5) throughout both the TAG and Rainbow plumes, indicative of Fe exchange between dissolved and particulate phases. Our comparison of TAG and Rainbow shows there is a limit to the amount of hydrothermal Fe released from vents that can form colloids in the rising plume. Higher particle loading will enhance the longevity of the Rainbow hydrothermal plume within the deep ocean assuming particles undergo continual dissolution/disaggregation. Future studies examining the length of plume pathways required to escape the ridge valley will be important in determining Fe supply from slow spreading mid-ocean ridges to the deep ocean, along with the frequency of ultramafic sites such as Rainbow. Resolving the ridge valley bathymetry and accounting for variability in vent sources in global biogeochemical models will be key to further constraining the hydrothermal Fe flux.</p

Tracing differences in iron supply to the Mid-Atlantic Ridge valley between hydrothermal vent sites: implications for the addition of iron to the deep ocean

Supply of iron (Fe) to the surface ocean supports primary productivity, and while hydrothermal input of Fe to the deep ocean is known to be extensive it remains poorly constrained. Global estimates of hydrothermal Fe supply rely on using dissolved Fe (dFe) to excess He (xs³He) ratios to upscale fluxes, but observational constraints on dFe/xs³He may be sensitive to assumptions linked to sampling and interpolation. We examined the variability in dFe/xs³He using two methods of estimation, for four vent sites with different geochemistry along the Mid-Atlantic Ridge. At both Rainbow and TAG, the plume was sampled repeatedly and the range of dFe/xs³He was 4 to 63 and 4 to 87 nmol:fmol, respectively, primarily due to differences in plume age. To account for background xs³He and shifting plume position, we calibrated He values using contemporaneous dissolved Mn (dMn). Applying this approach more widely, we found dFe/xs³He ratios of 12, 4–8, 4–44, and 4–86 nmol fmol−1 for the Menez Gwen, Lucky Strike, Rainbow, and TAG hydrothermal vent sites, respectively. Differences in plume dFe/xs³He across sites were not simply related to the vent endmember Fe and He fluxes. Within 40 km of the vents, the dFe/xs³He ratios decreased to 3–38 nmol fmol−1, due to the precipitation and subsequent settling of particulates. The ratio of colloidal Fe to dFe was consistently higher (0.67–0.97) than the deep N. Atlantic (0.5) throughout both the TAG and Rainbow plumes, indicative of Fe exchange between dissolved and particulate phases. Our comparison of TAG and Rainbow shows there is a limit to the amount of hydrothermal Fe released from vents that can form colloids in the rising plume. Higher particle loading will enhance the longevity of the Rainbow hydrothermal plume within the deep ocean assuming particles undergo continual dissolution/disaggregation. Future studies examining the length of plume pathways required to escape the ridge valley will be important in determining Fe supply from slow spreading mid-ocean ridges to the deep ocean, along with the frequency of ultramafic sites such as Rainbow. Resolving the ridge valley bathymetry and accounting for variability in vent sources in global biogeochemical models will be key to further constraining the hydrothermal Fe flux

Effective practices of international volunteering for health : perspectives from partner organizations

Abstract: The demand for international volunteer experiences to promote global health and nutrition is increasing and numerous studies have documented the experiences of the international volunteers who travel abroad; however, little is known about effective practices from the perspective of partner organizations. This study aims to understand how variables such as the skill-level of volunteers, the duration of service, cultural and language training, and other key variables affect partner organizations’ perceptions of volunteer effectiveness at promoting healthcare and nutrition..

GEO 600 and the GEO-HF upgrade program: successes and challenges

The German-British laser-interferometric gravitational wave detector GEO 600 is in its 14th year of operation since its first lock in 2001. After GEO 600 participated in science runs with other first-generation detectors, a program known as GEO-HF began in 2009. The goal was to improve the detector sensitivity at high frequencies, around 1 kHz and above, with technologically advanced yet minimally invasive upgrades. Simultaneously, the detector would record science quality data in between commissioning activities. As of early 2014, all of the planned upgrades have been carried out and sensitivity improvements of up to a factor of four at the high-frequency end of the observation band have been achieved. Besides science data collection, an experimental program is ongoing with the goal to further improve the sensitivity and evaluate future detector technologies. We summarize the results of the GEO-HF program to date and discuss its successes and challenges

Local Prediction of Laser Powder Bed Fusion Porosity by Short-Wave Infrared Imaging Thermal Feature Porosity Probability Maps

Local thermal history can significantly vary in parts during metal Additive Manufacturing (AM), leading to local defects. However, the sequential layer-by-layer nature of AM facilitates in-situ part voxelmetric observations that can be used to detect and correct these defects for part qualification and quality control. The challenge is to relate this local radiometric data with local defect information to estimate process error likelihood in future builds. This paper uses a Short-Wave Infrared (SWIR) camera to record the temperature history for parts manufactured with Laser Powder Bed Fusion (LPBF) processes. The porosity from a cylindrical specimen is measured by ex-situ micro-computed tomography (μCT). Specimen data from the SWIR camera, combined with the μCT data, are used to generate thermal feature-based porosity probability maps. The porosity predictions made by various SWIR thermal feature-porosity probability maps of a specimen with a complex geometry are scored against the true porosity obtained via μCT. The receiver operating characteristic curves constructed from the predictions for the complex sample demonstrate the porosity probability mapping methodology\u27s potential for in-situ based porosity detection

Seismicity and Pn Velocity Structure of Central West Antarctica

We have located 117 previously undetected seismic events mainly occurring between 2015 and 2017 that originated from glacial, tectonic, and volcanic processes in central West Antarctica using data recorded on Polar Earth Observing Network (POLENET/ANET) and UK Antarctic Network (UKANET) seismic stations. The seismic events, with local magnitudes (ML) ranging from 1.1 to 3.5, are predominantly clustered in four geographic regions; the Ellsworth Mountains, Thwaites Glacier, Pine Island Glacier, and Mount Takahe. Eighteen of the events are in the Ellsworth Mountains and can be attributed to a mixture of glacial and tectonic processes. The largest event noted in this study was a mid‐crustal (∼19 km focal depth; ML 3.5) normal mechanism earthquake beneath Thwaites Glacier. We also located 91 glacial events near the grounding zones of Thwaites Glacier and Pine Island Glacier that are predominantly associated with time periods of significant calving activity. Eight events, likely arising from volcano‐tectonic processes, occurred beneath Mount Takahe. Using Pn travel times from the seismic events, we find laterally variable uppermost mantle structure in central West Antarctica. On average, the Ellsworth Mountains are underlain by a faster mantle lid (VPn = ∼8.4 km/s) compared to the Amundsen Sea Embayment region (VPn = ∼8.1 km/s). Within the Amundsen Sea Embayment itself, we find mantle lid velocities ranging from ∼8.05 to 8.18 km/s. Laterally heterogeneous uppermost mantle structure, indicative of variable thermal and rheological structure, likely influences both geothermal heat flux and glacial isostatic adjustment spatial patterns and rates within central West Antarctica

Neural sensing and control in a kilometer-scale gravitational-wave observatory

Suspended optics in gravitational-wave (GW) observatories are susceptible to alignment perturbations, particularly slow drifts over time, due to variations in temperature and seismic levels. Such misalignments affect the coupling of the incident laser beam into the optical cavities, degrade both the circulating power and optomechanical photon squeezing, and thus decrease the astrophysical sensitivity to merging binaries. Traditional alignment techniques involve differential wave-front sensing using multiple quadrant photodiodes but are often bandwidth restricted and limited by the sensing noise. We present a successful implementation of neural-network-based sensing and control at a GW observatory and demonstrate low-frequency control of the signal-recycling mirror at the GEO 600 detector. Alignment information for three critical optics is simultaneously extracted from the interferometric dark-port camera images via a convolutional neural net-long short-term memory network architecture and is then used for multiple-input-multiple-output control using soft actor-critic-based deep reinforcement learning. The overall sensitivity improvement achieved using our scheme demonstrates the capabilities of deep learning as a viable tool for real-time sensing and control for current and next-generation GW interferometers

First demonstration of neural sensing and control in a kilometer-scale gravitational wave observatory

Suspended optics in gravitational wave (GW) observatories are susceptible toalignment perturbations and, in particular, to slow drifts over time due tovariations in temperature and seismic levels. Such misalignments affect thecoupling of the incident laser beam into the optical cavities, degrade bothcirculating power and optomechanical photon squeezing, and thus decrease theastrophysical sensitivity to merging binaries. Traditional alignment techniquesinvolve differential wavefront sensing using multiple quadrant photodiodes, butare often restricted in bandwidth and are limited by the sensing noise. Wepresent the first-ever successful implementation of neural network-basedsensing and control at a gravitational wave observatory and demonstratelow-frequency control of the signal recycling mirror at the GEO 600 detector.Alignment information for three critical optics is simultaneously extractedfrom the interferometric dark port camera images via a CNN-LSTM networkarchitecture and is then used for MIMO control using soft actor-critic-baseddeep reinforcement learning. Overall sensitivity improvement achieved using ourscheme demonstrates deep learning's capabilities as a viable tool for real-timesensing and control for current and next-generation GW interferometers.<br

Complexity-Based Measures Inform Effects of Tai Chi Training on Standing Postural Control: Cross-Sectional and Randomized Trial Studies

Background: Diminished control of standing balance, traditionally indicated by greater postural sway magnitude and speed, is associated with falls in older adults. Tai Chi (TC) is a multisystem intervention that reduces fall risk, yet its impact on sway measures vary considerably. We hypothesized that TC improves the integrated function of multiple control systems influencing balance, quantifiable by the multi-scale “complexity” of postural sway fluctuations. Objectives: To evaluate both traditional and complexity-based measures of sway to characterize the short- and potential long-term effects of TC training on postural control and the relationships between sway measures and physical function in healthy older adults. Methods: A cross-sectional comparison of standing postural sway in healthy TC-naïve and TC-expert (24.5±12 yrs experience) adults. TC-naïve participants then completed a 6-month, two-arm, wait-list randomized clinical trial of TC training. Postural sway was assessed before and after the training during standing on a force-plate with eyes-open (EO) and eyes-closed (EC). Anterior-posterior (AP) and medio-lateral (ML) sway speed, magnitude, and complexity (quantified by multiscale entropy) were calculated. Single-legged standing time and Timed-Up–and-Go tests characterized physical function. Results: At baseline, compared to TC-naïve adults (n = 60, age 64.5±7.5 yrs), TC-experts (n = 27, age 62.8±7.5 yrs) exhibited greater complexity of sway in the AP EC (P = 0.023), ML EO (P<0.001), and ML EC (P<0.001) conditions. Traditional measures of sway speed and magnitude were not significantly lower among TC-experts. Intention-to-treat analyses indicated no significant effects of short-term TC training; however, increases in AP EC and ML EC complexity amongst those randomized to TC were positively correlated with practice hours (P = 0.044, P = 0.018). Long- and short-term TC training were positively associated with physical function. Conclusion: Multiscale entropy offers a complementary approach to traditional COP measures for characterizing sway during quiet standing, and may be more sensitive to the effects of TC in healthy adults. Trial Registration ClinicalTrials.gov NCT0134036