Climate Change, Coral Reef Ecosystems, and Management Options for Marine Protected Areas

Marine protected areas (MPAs) provide place-based management of marine ecosystems through various degrees and types of protective actions. Habitats such as coral reefs are especially susceptible to degradation resulting from climate change, as evidenced by mass bleaching events over the past two decades. Marine ecosystems are being altered by direct effects of climate change including ocean warming, ocean acidification, rising sea level, changing circulation patterns, increasing severity of storms, and changing freshwater influxes. As impacts of climate change strengthen they may exacerbate effects of existing stressors and require new or modified management approaches; MPA networks are generally accepted as an improvement over individual MPAs to address multiple threats to the marine environment. While MPA networks are considered a potentially effective management approach for conserving marine biodiversity, they should be established in conjunction with other management strategies, such as fisheries regulations and reductions of nutrients and other forms of land-based pollution. Information about interactions between climate change and more “traditional” stressors is limited. MPA managers are faced with high levels of uncertainty about likely outcomes of management actions because climate change impacts have strong interactions with existing stressors, such as land-based sources of pollution, overfishing and destructive fishing practices, invasive species, and diseases. Management options include ameliorating existing stressors, protecting potentially resilient areas, developing networks of MPAs, and integrating climate change into MPA planning, management, and evaluation

Exploration of Shared Genetic Architecture Between Subcortical Brain Volumes and Anorexia Nervosa

In MRI scans of patients with anorexia nervosa (AN), reductions in brain volume are often apparent. However, it is unknown whether such brain abnormalities are influenced by genetic determinants that partially overlap with those underlying AN. Here, we used a battery of methods (LD score regression, genetic risk scores, sign test, SNP effect concordance analysis, and Mendelian randomization) to investigate the genetic covariation between subcortical brain volumes and risk for AN based on summary measures retrieved from genome-wide association studies of regional brain volumes (ENIGMA consortium, n = 13,170) and genetic risk for AN (PGC-ED consortium, n = 14,477). Genetic correlations ranged from − 0.10 to 0.23 (all p > 0.05). There were some signs of an inverse concordance between greater thalamus volume and risk for AN (permuted p = 0.009, 95% CI: [0.005, 0.017]). A genetic variant in the vicinity of ZW10, a gene involved in cell division, and neurotransmitter and immune system relevant genes, in particular DRD2, was significantly associated with AN only after conditioning on its association with caudate volume (pFDR = 0.025). Another genetic variant linked to LRRC4C, important in axonal and synaptic development, reached significance after conditioning on hippocampal volume (pFDR = 0.021). In this comprehensive set of analyses and based on the largest available sample sizes to date, there was weak evidence for associations between risk for AN and risk for abnormal subcortical brain volumes at a global level (that is, common variant genetic architecture), but suggestive evidence for effects of single genetic markers. Highly powered multimodal brain- and disorder-related genome-wide studies are needed to further dissect the shared genetic influences on brain structure and risk for AN

The Ecological Importance of Unregulated Tributaries to Macroinvertebrate Diversity and Community Composition in a Regulated River

In regulated rivers, dams alter longitudinal gradients in flow regimes, geomorphology, water quality and temperature with associated impacts on aquatic biota. Unregulated tributaries can increase biodiversity in regulated environments by contributing colonists to the main channel and creating transitional habitats at a stream junction. We assessed whether unregulated tributaries influence macroinvertebrate communities in two mainstem rivers during summer low-flows. Three tributary junctions of upland cobble-gravel bed streams were surveyed in an unregulated and a regulated river in the Sierra Nevada Mountains, California, USA. We found distinct physical habitat conditions and increased macroinvertebrate abundance and diversity in unregulated tributaries on the regulated river, but macroinvertebrate diversity did not increase downstream of tributary junctions as predicted. On the unregulated river, macroinvertebrate diversity was similar in upstream, downstream and unregulated tributary sites. Our findings highlight that unregulated tributaries support high macroinvertebrate diversity and heterogeneous communities compared to the mainstem sites in a regulated river, and thus likely support ecological processes, such as spillover predation, breeding and refugia use for mobile taxa. We suggest unregulated tributaries are an integral component of river networks, serving as valuable links in the landscape for enhancing biodiversity, and should be protected in conservation and management plans

Calculations of NLO Response in Langmuir-Blodgett Films

Organic materials are attractive for nonlinear optics because they offer the possibility of tailoring the molecules to modify their properties. However, this implies also that one understands how the desired material properties arise from the molecular properties. The basic understanding is well established: the material response is given by the molecular response transformed from molecular to material axes, modified by local-field factors that relate the polarizing field in the material to the macroscopic electric field at the relevant frequencies. 1 Often the local-field factors are approximated by the Lorentz local-field factor using the mean refractive index, in the spirit of the oriented-gas model. 2 In crystals, this approximation is known to be reasonable for compact molecules but not for elongated ones, 3 and hence care needs to be taken in interpreting and predicting NLO response of ordered materials composed of markedly anisotropic molecules. These reservations clearly apply to Langmuir-Blodgett films, formed from amphiphilic molecules with a hydrophilic" head" and a long hydrophobic" tail". The effect of the elongated structure on the local field is not obvious, particularly if the molecular axis is tilted away from the normal to the film, as often seems to occur. 4 Previous algebraic results show how a planewise approach can be used to calculate the linear and nonlinear optical response of layered materials such as LB films. 5 Here we report numerical calculations for simplified model LB films in order to explore how the response varies with molecular tilt and lattice distortion. This work forms part of a coordinated programme to design, prepare and

Calculations of nonlinear optical properties of model Langmuir‐Blodgett films

Calculations have been performed on models of Langmuir‐Blodgett LB films to explore how molecular nonlinear response expresses itself in film response. The molecules are treated as a string of s beads initially arranged normal to the film with their long axes forming a close‐packed hexagonal array, but they are then allowed to tilt away from the vertical. The molecular polarizability α and first hyperpolarizability β are represented by one‐dimensional models in which the axial components are s times the perpendicular ones. Because of the layer structure of the films, the dipolar interactions are calculated as planewise sums between one molecule and all the molecules in a given layer. The sums have been calculated for various values of s as a function of tilt; they are negligible except for interactions of a molecule with its own layer. They have been used to calculate the local electric field, refractive index and

Theory of Non-linear Optical Response in Molecular Layers

Nonlinear optics has provided a useful testing ground for the concept of molecular engineering. One seeks to design and synthesize molecules of high nonlinear optical response, and then to fabricate a molecular material in which this response is effectively expressed. In many such materials the active region is limited in thickness. Obvious examples are Langmuir-Blodgett films1 and polymer films. 2 Less obvious are molecular crystalline thin films or crystalline cored fibres, 3 or active species diffused into the surface of an optical polymer. 4 Finally, centrosymmetric materials lacking any bulk quadratic nonlinearity may display surface nonlinearity5 or pyroelectricity. 6 Molecular theories of nonlinear optical response in thin layers are not well developed. As in theories of bulk nonlinear response, a common approach has been to approximate the local electric field by the Lorentz expression. The Lorentz approximation is known to be poor for crystals of elongated molecules such as p.-terphenyl7 and the polydiacetylenes, 8 so that its reliability is questionable in Langmuir-Blodgett films, at least