Deep-water seagrasses in the tropics: resilience, recovery and establishing thresholds and drivers of change

Global seagrass research and assessment efforts have focused on shallow coastal and estuarine seagrass populations. Comparatively little is known about the dynamics of deep-water (>10m) seagrasses despite evidence they form extensive meadows in some parts of the world and may be highly productive compared with their shallow counterparts. Deep-water seagrasses are subject to a similar range of anthropogenic threats as shallow meadows particularly along the Great Barrier Reef (GBR) in Queensland, where they occur close to major population centres and adjacent to the coast. We examine the dynamics of deep-water seagrass populations in the GBR through a range of research studies including long term (>8 years) assessments of change; impacts of major dredging programs; resilience and recovery from severe tropical storms and; targeted research investigating the drivers, thresholds and tolerances behind seasonal and inter-annual change. Collectively these re- search programs have provided new insight into deep-water seagrass dynamics. Despite considerable inter-annual variability deep-water seagrasses had a regular annual pattern of occurrence at some locations, a low level of resilience to reduced water quality, but a high capacity for recolonisation on the cessation of impacts. While susceptible to large scale loss from severe storms these meadows were quick to re-establish compared with nearby shallow coastal seagrasses. The results of the work are establishing a series of key management thresholds and stress indictors that can be applied to ensure greater protection of these seagrasses

Measuring the dynamics and thresholds of tropical deepwater seagrasses

Extensive areas of deepwater (>10m) seagrass meadows are known to occur in many tropical regions. More than 31,000 km2 are found in the Great Barrier Reef Region of Queensland alone and one of the world's largest continuous seagrass meadows has been mapped recently in deeper waters of the Torres Strait. Despite their extensive distribution, little is known about the ecological roles, tolerances and dynamics of these deepwater communities compared with the much more commonly studied shallow seagrass meadows from the same region. Existing information suggests deepwater meadows may be highly productive but also highly dynamic between and within years. Increasingly these meadows are coming under threat from anthropogenic disturbances and it is critical to develop our understanding of the drivers of change and tolerances of these meadows to effectively manage them. We present initial findings from a major research program to establish a better understanding of the drivers of seasonal and interannual dynamics in these seagrass communities, the role of seed banks and seagrass recruitment, and the environmental cues that drive the seasonal patterns of decline and recovery. The research program includes a detailed study of the light requirements of these deepwater species as well as developing a range of tools for monitoring and managing anthropogenic impacts such as dredging

Measuring the dynamics and thresholds of tropical deepwater seagrasses

Extensive areas of deepwater (>10m) seagrass meadows are known to occur in many tropical regions. More than 31,000 km2 are found in the Great Barrier Reef Region of Queensland alone and one of the world's largest continuous seagrass meadows has been mapped recently in deeper waters of the Torres Strait. Despite their extensive distribution, little is known about the ecological roles, tolerances and dynamics of these deepwater communities compared with the much more commonly studied shallow seagrass meadows from the same region. Existing information suggests deepwater meadows may be highly productive but also highly dynamic between and within years. Increasingly these meadows are coming under threat from anthropogenic disturbances and it is critical to develop our understanding of the drivers of change and tolerances of these meadows to effectively manage them. We present initial findings from a major research program to establish a better understanding of the drivers of seasonal and interannual dynamics in these seagrass communities, the role of seed banks and seagrass recruitment, and the environmental cues that drive the seasonal patterns of decline and recovery. The research program includes a detailed study of the light requirements of these deepwater species as well as developing a range of tools for monitoring and managing anthropogenic impacts such as dredging

A comparison of threats, vulnerabilities and management approaches in global seagrass bioregions

Global seagrass habitats are threatened by multiple anthropogenic factors. Effective management of seagrasses requires information on the relative impacts of threats; however, this information is rarely available. Our goal was to use the knowledge of experts to assess the relative impacts of anthropogenic activities in six global seagrass bioregions. The activities that threaten seagrasses were identified at an international seagrass workshop and followed with a web-based survey to collect seagrass vulnerability information. There was a global consensus that urban/industrial runoff, urban/port infrastructure development, agricultural runoff and dredging had the greatest impact on seagrasses, though the order of relative impacts varied by bioregion. These activities are largely terrestrially based, highlighting the need for marine planning initiatives to be co-ordinated with adjacent watershed planning. Sea level rise and increases in the severity of cyclones were ranked highest relative to other climate change related activities, but overall the five climate change activities were ranked low and experts were uncertain of their effects on seagrasses. The experts' preferred mechanism of delivering management outcomes were processes such as policy development, planning and consultation rather than prescriptive management tools. Our approach to collecting expert opinion provides the required data to prioritize seagrass management actions at bioregional scales

Contribution of neural crest-derived cells in the embryonic and adult thymus

Abstract Neural crest (NC)-derived mesenchyme has previously been shown to play an important role in the development of fetal thymus. Using Wnt1-Cre and Sox10-Cre mice crossed to Rosa26eYfp reporter mice, we have revealed NC-derived mesenchymal cells in the adult murine thymus. We report that NC-derived cells infiltrate the thymus before day 13.5 of embryonic development (E13.5) and differentiate into cells with characteristics of smooth muscle cells associated with large vessels, and pericytes associated with capillaries. In the adult organ at 3 mo of age, these NC-derived perivascular cells continue to be associated with the vasculature, providing structural support to the blood vessels and possibly regulating endothelial cell function.</jats:p

Increasing the flexoelastic ratio of liquid crystals using highly fluorinated ester-linked bimesogens

We present experimental results on the bulk flexoelectric coefficients e and effective elastic coefficients K of non-symmetric bimesogenic liquid crystals when the number of terminal and lateral fluoro substituents is increased. These coefficients are of importance because the flexoelastic ratio e/K governs the magnitude of flexoelectro-optic switching in chiral nematic liquid crystals. The study is carried out for two different types of linkage in the flexible spacer chain that connects the separate mesogenic units: these are either an ether or an ester unit. It is found that increasing the number of fluorine atoms on the mesogenic units typically leads to a small increase in e and a decrease in K, resulting in an enhancement of e/K. The most dramatic increase in e/K, however, is observed when the linking group is changed from ether to ester units, which can largely be attributed to an increase in e. Increasing the number of fluorine atoms does, however, increase the viscoelastic ratio and therefore leads to a concomitant increase in the response time. This is observed for both types of linkage, although the ester-linked compounds exhibit smaller viscoelastic ratios compared with their ether-linked counterparts. Highly fluorinated ester-linked compounds are also found to exhibit lower transition temperatures and dielectric anisotropies. As a result, these compounds are promising materials for use in electro-optic devices.11Nsciescopu

Exploring structural and electronic effects in three isomers of tris{bis(trifluoromethyl)phenyl}borane: Towards the combined electrochemical-frustrated Lewis pair activation of H2

Three structural isomers of tris{bis(trifluoromethyl)phenyl}borane have been studied as the acidic com- ponent of frustrated Lewis pairs. While the 3,5-substituted isomer is already known to heterolytically cleave H2 to generate a bridging-hydride; ortho-substituents in the 2,4- and 2,5-isomers quench such reactivity through electron donation into the vacant boron pz orbital and steric blocking of the boron centre; as shown by electrochemical, structural and computational studies. Electrochemical studies of the corresponding borohydrides identify that the two-electron oxidation of terminal-hydrides occurs at more positive potentials than observed for [HB(C6F5)3]−, while the bridging-hydride oxidizes at a higher poten- tial still, comparable to that of free H2

Neuroprotection in a Novel Mouse Model of Multiple Sclerosis

The authors acknowledge the support of the Barts and the London Charity, the Multiple Sclerosis Society of Great Britain and Northern Ireland, the National Multiple Sclerosis Society, USA, notably the National Centre for the Replacement, Refinement & Reduction of Animals in Research, and the Wellcome Trust (grant no. 092539 to ZA). The siRNA was provided by Quark Pharmaceuticals. The funders and Quark Pharmaceuticals had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript