Climatic controls on biophysical interactions in the Black Sea under present day conditions and a potential future (A1B) climate scenario

A dynamical downscaling approach has been applied to investigate climatic controls on biophysical interactions and lower trophic level dynamics in the Black Sea. Simulations were performed under present day conditions (1980–1999) and a potential future (2080–2099) climate scenario, based on the Intergovernmental Panel for Climate Change A1B greenhouse gas emission scenario. Simulations project a 3.7 °C increase in SST, a 25% increase in the stability of the seasonal thermocline and a 37 day increase in the duration of seasonal stratification. Increased winter temperatures inhibited the formation of Cold Intermediate Layer (CIL) waters resulting in near complete erosion of the CIL, with implications for the ventilation of intermediate water masses and the subduction of riverine nutrients. A 4% increase in nitrate availability within the upper 30 m of the water column reflected an increase in the retention time of river water within the surface mixed-layer. Changes in thermohaline structure, combined with a 27% reduction in positive wind stress curl, forced a distinct change in the structure of the basin-scale circulation. The predominantly cyclonic circulation characteristic of contemporary conditions was reversed within the southern and eastern regions of the basin, where under A1B climatic conditions, anticyclonic circulation prevailed. The change in circulation structure significantly altered the horizontal advection and dispersion of high nutrient river waters originating on the NW self. Net primary production increased by 5% on average, with much spatial variability in the response, linked to advective processes. Phytoplankton biomass also increased by 5% and the higher nutrient environment of the future scenario caused a shift in species composition in favour of larger phytoplankton. No significant change in zooplankton biomass was projected. These results constitute one of many possible future scenarios for the Black Sea, being dependent on the modelling systems employed in addition to the choice of emission scenario. Our results emphasise in particular the sensitivity of dynamical downscaling studies to the regional wind forcing fields extracted from global models (these being typically model dependent). As atmospheric warming is projected with a high degree of confidence warming of the Black Sea upper layer, increased water column stability, and erosion of the CIL are believed to be robust results of this study

Understanding the limits to generalizability of experimental evolutionary models.

Post print version of article deposited in accordance with SHERPA RoMEO guidelines. The final definitive version is available online at: http://www.nature.com/nature/journal/v455/n7210/abs/nature07152.htmlGiven the difficulty of testing evolutionary and ecological theory in situ, in vitro model systems are attractive alternatives; however, can we appraise whether an experimental result is particular to the in vitro model, and, if so, characterize the systems likely to behave differently and understand why? Here we examine these issues using the relationship between phenotypic diversity and resource input in the T7-Escherichia coli co-evolving system as a case history. We establish a mathematical model of this interaction, framed as one instance of a super-class of host-parasite co-evolutionary models, and show that it captures experimental results. By tuning this model, we then ask how diversity as a function of resource input could behave for alternative co-evolving partners (for example, E. coli with lambda bacteriophages). In contrast to populations lacking bacteriophages, variation in diversity with differences in resources is always found for co-evolving populations, supporting the geographic mosaic theory of co-evolution. The form of this variation is not, however, universal. Details of infectivity are pivotal: in T7-E. coli with a modified gene-for-gene interaction, diversity is low at high resource input, whereas, for matching-allele interactions, maximal diversity is found at high resource input. A combination of in vitro systems and appropriately configured mathematical models is an effective means to isolate results particular to the in vitro system, to characterize systems likely to behave differently and to understand the biology underpinning those alternatives

Mesoscale eddies in the Black Sea: Characteristics and kinematic properties in a high-resolution ocean model

Mesoscale eddies are ubiquitous features of oceanic circulation and important contributors to the transport of water and heat as well as chemical and biological constituents. In the Black Sea, mesoscale eddies, filaments and meanders are recognized as main agents facilitating the transport and distribution of nutrients and biomass between coastal regions and the open, deep sea. In this study, a high-resolution ocean model, Nucleus for a European Model of the Ocean (NEMO), is implemented for the Black Sea and used to create a hindcast simulation of circulation dynamics for the 1985–2014 period. This hindcast simulation is validated and then used to produce a detailed statistical investigation of the occurrence and behavior of mesoscale eddies in the Black Sea. For this purpose, an eddy identification and tracking algorithm (EddyScan) is applied and the kinematic properties of all eddies are detected, including eddy number, size, lifetime, excursion distance and their spatial distribution. The analysis shows that, on average, anticyclonic eddies are larger in diameter, have a longer lifetime and travel farther distances from the generation site than cyclonic eddies. However, the number of anticyclonic eddies generated is less than cyclones. Spatial distribution of eddies shows that cyclonic and anticyclonic eddies occupy much of the open Black Sea but few are found on the northwestern shelf. The density of anticyclonic eddies is especially high in the Sevastapol, Sinop, Kizilirmak and Batumi regions; while cyclonic eddy densities are high in the northern Black Sea along the Rim Current, north of the Batumi region, as well as in the center of the western and eastern Black Sea gyres. The number of eddies generated increases in spring and summer and decreases again in fall and winter due to changes in wind stress curl and its impact on Rim Current strength. The temporal evolution of long-lived eddies (>30 days) shows that after their creation, the diameters of cyclonic eddies increase for a period of 2–3 months, after which they reach a stable diameter. On the other hand, anticyclonic eddy diameters increase, on average, for a 5–6-month period and then reach a stable value. The vertical effects of these long-lived eddies generated in the Black Sea generally reach down to 150-200 m and hence intersect with the nitrate maximum and oxygen minimum zone. A first estimation shows that the simulated anticyclonic eddies in the Black Sea may have transported up to four times more water than cyclonic eddies over one year. The mean vertical flux induced by all cyclones generated in one year upwell ~ 0.63 Sv of water, while all anticyclones generated in one year downwell two times as much water or ~ 1.27 Sv over the top 100 m of the water column. This highlights the importance of eddies for the vertical transport of water and associated biochemical properties. In addition, eddies are able to connect different regions of the Black Sea as well as offshore/onshore regions along their paths and are of great importance for nutrient distribution and availability in the Black Sea

Liraglutide and Renal Outcomes in Type 2 Diabetes.

BACKGROUND: In a randomized, controlled trial that compared liraglutide, a glucagon-like peptide 1 analogue, with placebo in patients with type 2 diabetes and high cardiovascular risk who were receiving usual care, we found that liraglutide resulted in lower risks of the primary end point (nonfatal myocardial infarction, nonfatal stroke, or death from cardiovascular causes) and death. However, the long-term effects of liraglutide on renal outcomes in patients with type 2 diabetes are unknown. METHODS: We report the prespecified secondary renal outcomes of that randomized, controlled trial in which patients were assigned to receive liraglutide or placebo. The secondary renal outcome was a composite of new-onset persistent macroalbuminuria, persistent doubling of the serum creatinine level, end-stage renal disease, or death due to renal disease. The risk of renal outcomes was determined with the use of time-to-event analyses with an intention-to-treat approach. Changes in the estimated glomerular filtration rate and albuminuria were also analyzed. RESULTS: A total of 9340 patients underwent randomization, and the median follow-up of the patients was 3.84 years. The renal outcome occurred in fewer participants in the liraglutide group than in the placebo group (268 of 4668 patients vs. 337 of 4672; hazard ratio, 0.78; 95% confidence interval [CI], 0.67 to 0.92; P=0.003). This result was driven primarily by the new onset of persistent macroalbuminuria, which occurred in fewer participants in the liraglutide group than in the placebo group (161 vs. 215 patients; hazard ratio, 0.74; 95% CI, 0.60 to 0.91; P=0.004). The rates of renal adverse events were similar in the liraglutide group and the placebo group (15.1 events and 16.5 events per 1000 patient-years), including the rate of acute kidney injury (7.1 and 6.2 events per 1000 patient-years, respectively). CONCLUSIONS: This prespecified secondary analysis shows that, when added to usual care, liraglutide resulted in lower rates of the development and progression of diabetic kidney disease than placebo. (Funded by Novo Nordisk and the National Institutes of Health; LEADER ClinicalTrials.gov number, NCT01179048 .)