Habitat Model of Eelgrass in Danish Coastal Waters: Development, Validation and Management Perspectives

During the last century, eutrophication significantly reduced the depth distribution and density of the habitat forming eelgrass meadows (Zostera marina) in Danish coastal waters. Despite large reductions in nutrient loadings and improved water quality, Danish eelgrass meadows are currently not as widely distributed as expected from improvements in water clarity alone. This point to the importance of other environmental conditions such as sediment quality, wave exposure, oxygen conditions and water temperature that may limit eelgrass growth and contribute to constraining current distributions. Recently, detailed local models have been set up to evaluate the importance of such regulating factors in selected Danish coastal areas, but nationwide maps of eelgrass distribution and large-scale evaluations of regulating factors are still lacking. To provide such nationwide information, we applied a spatial habitat GIS modeling approach, which combines information on six key eelgrass habitat requirements (light availability, water temperature, salinity, frequency of low oxygen concentration, wave exposure, and sediment type) for which we were able to obtain national coverage. The modeled potential current distribution area of Danish eelgrass meadows was 2204 km2 compared to historical estimates of around 7000 km2, indicating a great potential for further distribution. While validating the modeled eelgrass distribution area in three areas (83–111 km2) that hold large eelgrass meadows, we found an agreement of 67% with in situ monitoring data and 77% for eelgrass areas as identified from summer orthophotos. The GIS model predicted higher coverage especially in shallow waters and near the depth limits. Areas of disagreement between GIS-modeled and observed coverage generally exhibited higher exposure level, mean summer temperature and salinity compared to areas of agreement. A sensitivity analysis showed that the modeled area distribution of eelgrass was highly sensitive to light conditions, with 18–38% increase in coverage following an increase in light availability of 20%. Modeled coverage of eelgrass was also sensitive to wave exposure and temperature conditions while less sensitive to changes in oxygen and salinity conditions. Large regional differences in habitat conditions suggest spatial variation in the factors currently limiting the recovery of eelgrass and, hence, variations in actions required for sustainable management

Anatomy and Pathology/Oncology Retinal Thickness and Axial Length

PURPOSE. To examine the relationships between axial length and foveal and peripheral retinal thickness. METHODS. Using optical coherence tomography, foveal retinal thickness was measured in participants of the population-based Beijing Eye Study without optic nerve or macula diseases. Inner and outer nuclear layer thickness as surrogate for retinal thickness was assessed in the fundus periphery in human globes enucleated due to malignant uveal melanoma or painful glaucoma. RESULTS. The study included 1117 individuals with a mean age of 64.2 6 9.7 years (range: 50-93 years) and mean axial length of 23.4 6 1.04 mm (range: 20.29-28.68 mm). In multivariate analysis, thicker central foveal thickness was associated with male sex (P < 0.001; standardized regression coefficient beta: À0.13; nonstandardized regression coefficient B: À5.84; 95% confidence interval (CI): À8.56, À3.13); urban region of habitation (P ¼ 0.02; beta: 0.07; B: 3.56; 95% CI: 0.55, 6.57); thinner lens thickness (P ¼ 0.01; beta: À0.08; B: À5.11; 95% CI: À9.01, À1.21); thinner subfoveal choroidal thickness (P ¼ 0.04; beta: À0.07; B: À0.01; 95% CI: À0.03, À0.001); and longer axial length (P < 0.001; beta: 0.18; B: 3.79; 95% CI: 2.41, 5.17). In the same multivariate model, superior, inferior, and temporal foveal thickness was not significantly associated with axial length (P ¼ 0.26, P ¼ 0.19, P ¼ 0.08, respectively), while thicker nasal foveal thickness was associated with longer axial length (P ¼ 0.009; beta: 0.09; B: 1.50; 95% CI: 0.37, 2.62). In the histomorphometric part of the study including 32 eyes (sagittal diameter: 27.0 6 4.2 mm; range: 22-37 mm), mean thickness of the inner and outer nuclear layers at the equator and at the midpoint equator/posterior pole decreased with longer axial length (P ¼ 0.004; beta: À0.48; and P ¼ 0.02; beta: À0.44, respectively). CONCLUSIONS. Myopic axial globe elongation was associated with retinal thinning in the equatorial and pre-equatorial region, while foveal retinal thickness was mostly unaffected by axial length. It suggests that axial elongation takes place predominantly in the equatorial and pre-equatorial region of the eye

Peripapillary Arterial Circle of Zinn-Haller: Location and Spatial Relationships with Myopia

Purpose To measure histomorphometrically the location of the peripapillary arterial circle of Zinn-Haller (ZHAC) and assess its associations with axial length. Methods Using a light microscope, we measured the distance from the ZHAC to the peripapillary ring (optic disc border), the merging point of the dura mater with the posterior sclera (“dura-sclera point”), and the inner scleral surface. In the parapapillary region, we differentiated between beta zone (presence of Bruch's membrane, absence of retinal pigment epithelium) and gamma zone (absence of Bruch's membrane). The peripapillary scleral flange as roof of the orbital cerebrospinal fluid space was the connection between the end of the lamina cribrosa and the posterior full-thickness sclera starting at the dura-sclera point. Results The study included 101 human globes (101 patients) with a mean axial length of 26.7±3.7 mm (range: 20.0–39.0 mm). The distance between the ZHAC and the peripapillary ring increased significantly with longer axial length (P<0.001; correlation coefficient r = 0.49), longer parapapillary gamma zone (P<0.001;r = 0.85), longer (P<0.001;r = 0.73) and thinner (P<0.001;r = −0.45) peripapillary scleral flange, and thinner sclera posterior to the equator (P<0.001). ZHAC distance to the peripapillary ring was not significantly associated with length of parapapillary beta zone (P = 0.33). Including only non-highly myopic eyes (axial length <26.5 mm), the ZHAC distance to the disc border was not related with axial length (P = 0.84). In non-highly myopic eyes, the ZHAC was located close to the dura-sclera point. With increasing axial length and decreasing thickness of the peripapillary scleral flange, the ZHAC was located closer to the inner scleral surface. Conclusions The distance between the ZHAC and the optic disc border is markedly enlarged in highly myopic eyes. Since the ZHAC is the main arterial source for the lamina cribrosa blood supply, the finding may be of interest for the pathogenesis of the increased glaucoma susceptibility in highly myopic eyes

Chiral Separation of 3,5-Dinitrobenzoyl-(R,S)-Leucine in Process Intensified Extraction Columns

The countercurrent liquid–liquid extraction of racemic 3,5-dinitrobenzoyl-(R,S)-leucine (DNB-(R,S)-Leu) was experimentally investigated using a process intensified extraction column (PIEC). This column (Øin = 15 mm; Hac = 1100 mm), in which both stirring and pulsation are applied, allows for many equilibrium stages and enables a good separation. DNB-(R)-Leu was obtained with an enantiomeric excess of 98.6% and a yield of 93.7%. The other enantiomer DNB-(S)-Leu was measured with an enantiomeric excess of 85.8% and a yield of 98.0%. A backflow model was developed to describe the concentration profile inside the column and the outlet concentrations. The model was experimentally validated and indicates an accurate calculation of the concentrations with an inaccuracy of less than 10%. Finally, the chiral separation of the counter-current extraction in columns is compared to centrifugal extractors with respect to extraction efficiency and productivity