ALBERT

Description: This study investigated photosynthetic and oxidative stress-related responses to moderate (500 μmol photons m −2 s −1 ) and high irradiances (1500 μmol photons m −2 s −1 ) in two tropical intertidal seagrasses, Halophila ovalis and Thalassia hemprichii . Exposure to high irradiance for 3 h resulted in a large decline in the maximum quantum yield of photosystem II (Fv/Fm) and in the effective quantum yield of photosystem II (ΦPSII) but induced non-photochemical quenching (NPQ) and chloroplast clumping in H. ovalis . Thalassia hemprichii , however, showed only a minor decrease in Fv/Fm and ΦPSII, and no change in either NPQ or the intracellular arrangement of chloroplasts. The irradiance did not affect reactive oxygen species (ROS) or superoxide dismutase (SOD) activity in either seagrass, whereas high irradiance enhanced ascorbate peroxidase (APX) activity in H. ovalis . The results from a subsequent experiment using an oxidative stress inducer, methyl viologen (MV), also showed a higher degree of Fv/Fm inhibition in H. ovalis . These results show that H. ovalis is much more physiologically responsive to high irradiances and oxidative stress than T. hemprichii and that its photoprotective mechanisms involve NPQ, APX and reduction of the amount of light absorbed through the clumping of its chloroplasts.

Description: El Niño events are characterized by surface warming of the tropical Pacific Ocean and weakening of equatorial trade winds that occur every few years. Such conditions are accompanied by changes in atmospheric and oceanic circulation, affecting global climate, marine and terrestrial ecosystems, fisheries and human activities. The alternation of warm El Niño and cold La Niña conditions, referred to as the El Niño–Southern Oscillation (ENSO), represents the strongest year-to-year fluctuation of the global climate system. Here we provide a synopsis of our current understanding of the spatio-temporal complexity of this important climate mode and its influence on the Earth system.

Description: Green infrastructures play an essential role in urban planning, namely with their potential to reduce the impact from air pollution episodes together with extreme weather events. This chapter focuses on the assessment of green infrastructures’ benefits on current and future microclimate and air quality patterns in Porto’s urban area (Portugal). The effects of green infrastructures on flow dynamics are evaluated for the baseline scenarios by means of numerical and physical simulations, using the computational fluid dynamics (CFD) model VADIS and the wind tunnel of the University of Aveiro. The baseline morphological (BM) scenario focuses on the current morphological characteristics of Porto’s urban area, while a baseline green (BG) scenario comprises the replacement of built-up areas by green areas and parks. In addition, the benefits of green infrastructures on air quality are assessed for the baseline and under future climate scenarios. The air quality simulations focus on particulate matter, one of the most critical air pollutants with severe impacts on human health. For the BM scenario, the simulated concentrations are compared with hourly averaged PM10 concentrations measured during a weekday at the air quality station located within the study domain.

Description: The principles of responsibility and accountability have increasingly become a significant concept for the political capability to act independently and make decisions without superior authorization.

Description: Exposure to nitrogen dioxide (NO2) is associated with negative human health effects, both for short-term peak concentrations and from long-term exposure to a wider range of NO2 concentrations. For the latter, the European Union has established an air quality limit value of 40 µg m−3 as an annual average. However, factors such as proximity and strength of local emissions, atmospheric chemistry and meteorological conditions means that there is substantial variation in the hourly NO2 concentrations contributing to an annual average concentration. The aim of this analysis was to quantify the nature of this variation at thousands of monitoring sites across Europe through the calculation of a standard set of chemical climatology statistics. Specifically, at each monitoring site that satisfied data capture criteria for inclusion in this analysis, annual NO2 concentrations, as well as the percentage contribution from each month, hour of the day, and hourly NO2 concentrations divided into 5 µg m−3 bins were calculated. Across Europe, 2010–2014 average annual NO2 concentrations (NO2AA) exceeded the annual NO2 limit value at 8 % of 〉 2500 monitoring sites. The application of this chemical climatology approach showed that sites with distinct monthly, hour of day, and hourly NO2 concentration bin contributions to NO2AA were not grouped in specific regions of Europe, and within relatively small geographic regions there were sites with similar NO2AA, but with differences in these contributions. Specifically, at sites with highest NO2AA, there were generally similar contributions from across the year, but there were also differences in the contribution of peak vs moderate hourly NO2 concentrations to NO2AA, and from different hours across the day. Trends between 2000 and 2014 for 259 sites indicate that, in general, the contribution to NO2AA from winter months has increased, as has the contribution from the rush-hour periods of the day, while the contribution from peak hourly NO2 concentrations has decreased. The variety of monthly, hour of day and hourly NO2 contribution bin contributions to NO2AA, across cities, countries and regions of Europe indicate that within relatively small geographic areas different interactions between emissions, atmospheric chemistry and meteorology produce variation in NO2AA and the conditions that produce it. Therefore, measures implemented to reduce NO2AA in one location may not be as effective in others. The development of strategies to reduce NO2AA for an area should consider i) the variation in monthly, hour of day and hourly NO2 concentration bin contributions to NO2AA within that area, and ii) how specific mitigation actions will affect variability in hourly NO2 concentrations.

Description: The Cretaceous with extremely high atmospheric pCO2 is one of the warmest periods in the Phanerozoic, providing an endmember to test climate models. Repeated periods of widespread dysoxic / anoxic conditions (Oceanic Anoxic Events; OAEs) were characterized by enhanced burial of organic matter and different degrees of marine faunal turnovers, that can be seen as extreme equivalents for the already observed trend of expanding Oxygen Minimum Zones (OMZ) in modern oceans caused by anthropogenic climate warming. One of the largest OAEs occurring at the Cenomanian / Turonian boundary is OAE2. This thesis presents results from Core SN°4 drilled in the Tarfaya Basin (SW Morocco). This continuous record spanning the time from the late Albian to early Turonian allowed 1) to reconstruct climatic and paleoceanographic variability during this period in the Tarfaya Basin, 2) to unravel climate processes and biospheric changes during the onset of OAE2 and 3) to study phosphorus dynamics during the Cenomanian and early Turonian.

Description: The transition from high to low and zero oxygen content in deep sea sediments provokes many important redox reactions in sedimentary pore waters, which are of high interest for geochemists. However, opening a sediment core yields the danger of introducing atmospheric O2, thus potentially compromising the measurements of pore water O2. Preparing a transparent sediment core with oxygen sensitive foils allows for fast and undisturbed measurements of the O2 content of sedimentary pore waters through the core wall once the core is recovered, but before atmospheric oxygen can exert an influence.