The acclimative biogeochemical model of the southern North Sea

Ecosystem models often rely on heuristic descriptions of autotrophic growth that fail to reproduce various stationary and dynamic states of phytoplankton cellular composition observed in laboratory experiments. Here, we present the integration of an advanced phytoplankton growth model within a coupled three-dimensional physical-biogeochemical model and the application of the model system to the southern North Sea (SNS) defined on a relatively high resolution (∼1.5-4.5 km) curvilinear grid. The autotrophic growth model, recently introduced by Wirtz and Kerimoglu (2016), is based on a set of novel concepts for the allocation of internal resources and operation of cellular metabolism. The coupled model system consists of the General Estuarine Transport Model (GETM) as the hydrodynamical driver, a lower-trophic-level model and a simple sediment diagenesis model. We force the model system with realistic atmospheric and riverine fluxes, background turbidity caused by suspended particulate matter (SPM) and open ocean boundary conditions. For a simulation for the period 2000-2010, we show that the model system satisfactorily reproduces the physical and biogeochemical states of the system within the German Bight characterized by steep salinity; nutrient and chlorophyll (Chl) gradients, as inferred from comparisons against observation data from long-term monitoring stations; sparse in situ measurements; continuous transects; and satellites. The model also displays skill in capturing the formation of thin chlorophyll layers at the pycnocline, which is frequently observed within the stratified regions during summer. A sensitivity analysis reveals that the vertical distributions of phytoplankton concentrations estimated by the model can be qualitatively sensitive to the description of the light climate and dependence of sinking rates on the internal nutrient reserves. A non-acclimative (fixed-physiology) version of the model predicted entirely different vertical profiles, suggesting that accounting for physiological flexibility might be relevant for a consistent representation of the vertical distribution of phytoplankton biomass. Our results point to significant variability in the cellular chlorophyll-to-carbon ratio (Chl : C) across seasons and the coastal to offshore transition. Up to 3-fold-higher Chl : C at the coastal areas in comparison to those at the offshore areas contribute to the steepness of the chlorophyll gradient. The model also predicts much higher phytoplankton concentrations at the coastal areas in comparison to its non-acclimative equivalent. Hence, findings of this study provide evidence for the relevance of physiological flexibility, here reflected by spatial and seasonal variations in Chl : C, for a realistic description of biogeochemical fluxes, particularly in the environments displaying strong resource gradients. © 2017 Author(s)

Interactive impacts of meteorological and hydrological conditions on the physical and biogeochemical structure of a coastal system

The German Bight was exposed to record high riverine discharges in June 2013, as a result of flooding of the Elbe and Weser rivers. Several anomalous observations suggested that the hydrodynamical and biogeochemical states of the system were impacted by this event. In this study, we developed a biogeochemical model and coupled it with a previously introduced high-resolution hydrodynamical model of the southern North Sea in order to better characterize these impacts and gain insight into the underlying processes. Performance of the model was assessed using an extensive set of in situ measurements for the period 2011–2014. We first improved the realism of the hydrodynamic model with regard to the representation of cross-shore gradients, mainly through inclusion of flow-dependent horizontal mixing. Among other characteristic features of the system, the coupled model system can reproduce the low salinities, high nutrient concentrations and low oxygen concentrations in the bottom layers observed within the German Bight following the flood event. Through a scenario analysis, we examined the sensitivity of the patterns observed during July 2013 to the hydrological and meteorological forcing in isolation. Within the region of freshwater influence (ROFI) of the Elbe–Weser rivers, the flood event clearly dominated the changes in salinity and nutrient concentrations, as expected. However, our findings point to the relevance of the peculiarities in the meteorological conditions in 2013 as well: a combination of low wind speeds, warm air temperatures and cold bottom-water temperatures resulted in a strong thermal stratification in the outer regions and limited vertical nutrient transport to the surface layers. Within the central region, the thermal and haline dynamics interactively resulted in an intense density stratification. This intense stratification, in turn, led to enhanced primary production within the central region enriched by nutrients due to the flood but led to reduction within the nutrient-limited outer region, and it caused a widespread oxygen depletion in bottom waters. Our results further point to the enhancement of the current velocities at the surface as a result of haline stratification and to intensification of the thermohaline estuarine-like circulation in the Wadden Sea, both driven by the flood event

Threshold indicators of primary production in the north-east Atlantic for assessing environmental disturbances using 21 years of satellite ocean colour

Primary production (PP) is highly sensitive to changes in the ecosystem and can be used as an early warning indicator for disturbance in the marine environment. Historic indicators of good environmental status of the north-east (NE) Atlantic and north-west (NW) European Seas suggested that daily PP should not exceed 2–3gCm−2 d−1 during phytoplankton blooms and that annual rates should be <300 g C m−2 yr−1 . We use 21 years of Copernicus Marine Service (CMEMS) Ocean Colour data from September 1997 to December 2018 to assess areas in the NE Atlantic with similar peak, climatology, phenology and annual PP values. Daily and annual thresholds of the 90th percentile (P90) of PP are defined for these areas and PP values above these thresholds indicate disturbances, both natural and anthropogenic, in the marine environment. Two case studies are used to test the validity and accuracy of these thresholds. The first is the eruption of the volcano Eyjafjallajökull, which deposited large volumes of volcanic dust (and therefore iron) into the NE Atlantic during April and May 2010. A clear signature in both PP and chlorophyll-a (Chl a) was evident from 28th April to 6th May and from 18th to 27th May 2010, when PP exceeded the PP P90 threshold for the region, which was comparatively more sensitive than Chl a P90 as an indicator of this disturbance. The second case study was for the riverine input of total nitrogen and phosphorus, along the Wadden Sea coast in the North Sea. During years when total nitrogen and phosphorus were above the climatology maximum, there was a lag signature in both PP and Chl a when PP exceeded the PP P90 threshold defined for the study area which was slightly more sensitive than Chl a P90. This technique represents an accurate means of determining disturbances in the environment both in the coastal and offshore waters in the NE Atlantic using remotely sensed ocean colour data

Effect of Coenzyme Q10 on ischemia and neuronal damage in an experimental traumatic brain-injury model in rats

<p>Abstract</p> <p>Background</p> <p>Head trauma is one of the most important clinical issues that not only can be fatal and disabling, requiring long-term treatment and care, but also can cause heavy financial burden. Formation or distribution of free oxygen radicals should be decreased to enable fixing of poor neurological outcomes and to prevent neuronal damage secondary to ischemia after trauma. Coenzyme Q₁₀(CoQ₁₀), a component of the mitochondrial electron transport chain, is a strong antioxidant that plays a role in membrane stabilization. In this study, the role of CoQ₁₀in the treatment of head trauma is researched by analyzing the histopathological and biochemical effects of CoQ₁₀administered after experimental traumatic brain injury in rats. A traumatic brain-injury model was created in all rats. Trauma was inflicted on rats by the free fall of an object of 450 g weight from a height of 70 cm on the frontoparietal midline onto a metal disc fixed between the coronal and the lambdoid sutures after a midline incision was carried out.</p> <p>Results</p> <p>In the biochemical tests, tissue malondialdehyde (MDA) levels were significantly higher in the traumatic brain-injury group compared to the sham group (<it>p </it>< 0.05). Administration of CoQ₁₀after trauma was shown to be protective because it significantly lowered the increased MDA levels (<it>p </it>< 0.05). Comparing the superoxide dismutase (SOD) levels of the four groups, trauma + CoQ₁₀group had SOD levels ranging between those of sham group and traumatic brain-injury group, and no statistically significant increase was detected. Histopathological results showed a statistically significant difference between the CoQ₁₀and the other trauma-subjected groups with reference to vascular congestion, neuronal loss, nuclear pyknosis, nuclear hyperchromasia, cytoplasmic eosinophilia, and axonal edema (<it>p </it>< 0.05).</p> <p>Conclusion</p> <p>Neuronal degenerative findings and the secondary brain damage and ischemia caused by oxidative stress are decreased by CoQ₁₀use in rats with traumatic brain injury.</p

Effects of Nutrient Management Scenarios on Marine Eutrophication Indicators: A Pan-European, Multi-Model Assessment in Support of the Marine Strategy Framework Directive

A novel pan-European marine model ensemble was established, covering nearly all seas under the regulation of the Marine Strategy Framework Directive (MSFD), with the aim of providing a consistent assessment of the potential impacts of riverine nutrient reduction scenarios on marine eutrophication indicators. For each sea region, up to five coupled biogeochemical models from institutes all over Europe were brought together for the first time. All model systems followed a harmonised scenario approach and ran two simulations, which varied only in the riverine nutrient inputs. The load reductions were evaluated with the catchment model GREEN and represented the impacts due to improved management of agriculture and wastewater treatment in all European river systems. The model ensemble, comprising 15 members, was used to assess changes to the core eutrophication indicators as defined within MSFD Descriptor 5. In nearly all marine regions, riverine load reductions led to reduced nutrient concentrations in the marine environment. However, regionally the nutrient input reductions led to an increase in the non-limiting nutrient in the water, especially in the case of phosphate concentrations in the Black Sea. Further core eutrophication indicators, such as chlorophyll-a, bottom oxygen and the Trophic Index TRIX, improved nearly everywhere, but the changes were less pronounced than for the inorganic nutrients. The model ensemble displayed strong consistency and robustness, as most if not all models indicated improvements in the same areas. There were substantial differences between the individual seas in the speed of response to the reduced nutrient loads. In the North Sea ensemble, a stable plateau was reached after only three years, while the simulation period of eight years was too short to obtain steady model results in the Baltic Sea. The ensemble exercise confirmed the importance of improved management of agriculture and wastewater treatments in the river catchments to reduce marine eutrophication. Several shortcomings were identified, the outcome of different approaches to compute the mean change was estimated and potential improvements are discussed to enhance policy support. Applying a model ensemble enabled us to obtain highly robust and consistent model results, substantially decreasing uncertainties in the scenario outcom

Atmospheric stilling leads to prolonged thermal stratification in a large shallow polymictic lake

To quantify the effects of recent and potential future decreases in surface wind speeds on lake thermal stratification, we apply the one-dimensional process-based model MyLake to a large, shallow, polymictic lake, Võrtsjärv. The model is validated for a 3-year period and run separately for 28 years using long-term daily atmospheric forcing data from a nearby meteorological station. Model simulations show exceptionally good agreement with observed surface and bottom water temperatures during the 3-year period. Similarly, simulated surface water temperatures for 28 years show remarkably good agreement with long-term in situ water temperatures. Sensitivity analysis demonstrates that decreasing wind speeds has resulted in substantial changes in stratification dynamics since 1982, while increasing air temperatures during the same period had a negligible effect. Atmospheric stilling is a phenomenon observed globally, and in addition to recent increases in surface air temperature, needs to be considered when evaluating the influence of climate change on lake ecosystems

Sodium Alginate Microneedle Arrays Mediate the Transdermal Delivery of Bovine Serum Albumin

BACKGROUND: The "poke and release" strategy for the delivery of macromolecules using polymeric microneedle (MN) is of great importance because it eliminates microneedle reuse, the risks of biohazardous sharps and cross contamination, and it requires no special disposal mechanism. The main objective of this study was the determination of the stability and delivery of bovine serum albumin (BSA) that was transported across human skin via sodium alginate (SA) microneedle arrays (MNs) and SA needle free patches using two different analytical methods. METHODOLOGY AND FINDINGS: The capability of two analytical methods, the bicinchoninic acid (BCA) assay and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), to precisely detect and quantify BSA within different types of polymeric MNs was assessed. The ex vivo protein release of BSA across dermatomed human abdominal skin from 10 w/w SA MNs was compared to that from needle-free patches using Franz diffusion cells. The developed applicator was mechanically characterized using a Texture Analyzer. The patch mold and its components were fabricated using a rapid prototyping machine. CONCLUSIONS/SIGNIFICANCE: The BCA method was able to precisely detect BSA that had been loaded into SA MNs. However, the use of SDS-PAGE as the analytical method resulted in significantly different amounts of BSA recovered from differently conditioned polymeric MNs. The permeation of BSA across dermatomed human abdominal skin by SA MNs, which were composed of 100 pyramidal needles, increased by approximately 15.4 fold compared to the permeation obtained with SA needle-free patches. The ease of use of the applicator during the release studies was also demonstrated, as was its mechanical characterization

Characterization of Polymeric Microneedle Arrays for Transdermal Drug Delivery

Microfabrication of dissolvable, swellable, and biodegradable polymeric microneedle arrays (MNs) were extensively investigated based in a nano sensitive fabrication style known as micromilling that is then combined with conventional micromolding technique. The aim of this study was to describe the polymer selection, and optimize formulation compounding parameters for various polymeric MNs. Inverse replication of micromilled master MNs reproduced with polydimethylsiloxane (PDMS), where solid out of plane polymeric MNs were subsequently assembled, and physicochemically characterized. Dissolvable, swellable, and biodegradable MNs were constructed to depth of less than 1 mm with an aspect ratio of 3.6, and 1/2 mm of both inter needle tip and base spacing. Micromolding step also enabled to replicate the MNs very precisely and accurate. Polymeric microneedles (MN) precision was ranging from ± 0.18 to ± 1.82% for microneedle height, ± 0.45 to ± 1.42% for base diameter, and ± 0.22 to ± 0.95% for interbase spacing. Although dissolvable sodium alginate MN showed less physical robustness than biodegradable polylactic-co-glycolic acid MN, their thermogravimetric analysis is of promise for constructing these polymeric types of matrix devices

Bilateral non-traumatic acetabular and femoral neck fractures due to pregnancy-associated osteoporosis

PubMed ID: 17828410Pregnancy-associated osteoporosis is a rare disorder and its pathophysiology remains unknown. We report a case of pregnancy-associated osteoporosis in a 27-year-old primiparous patient who revealed bilateral hip pain during early postnatal period. The plain radiographs and computarized tomography showed bilateral femoral neck and asetabular fractures. The diagnosis of osteoporosis was established by bone mineral density. Diagnostic work-up excluded a secondary osteoporosis. The case was treated successfully by bilateral cementless total hip arthroplasty. Bone mineral density increased after 2 years of treatment with calcium - vitamin D, calcitriol and alendronate. Diagnosis of pregnancy-associated osteoporosis should be suspected when hip pain occurs during pregnancy or in the post-partum period as it can lead to acetabular and femoral neck fractures. © Springer-Verlag 2007