Revision of the global carbon budget due to changing air-sea oxygen fluxes

Carbon budgets inferred from measurements of the atmospheric oxygen to nitrogen ratio (O2/N2) are revised considering sea-to-air fluxes of O2 and N2 in response to global warming and volcanic eruptions. Observational estimates of changes in ocean heat content are combined with a model-derived relationship between changes in atmospheric O2/N2 due to oceanic outgassing and heat fluxes to estimate ocean O2 outgassing. The inferred terrestrial carbon sink for the 1990s is reduced by a factor of two compared with the most recent estimate by the Intergovernmental Panel on Climate Change (IPCC). This also improves the agreement between calculated ocean carbon uptake rates and estimates from global carbon cycle models, which indicate a higher ocean carbon uptake during the 1990s than the 1980s. The simulated decrease in oceanic O2 concentrations is in qualitative agreement with observed trends in oceanic O2 concentrations

The vacuolar proton-ATPase plays a major role in several membrane-bounded organelles in Paramecium

The vacuolar proton-ATPase (V-ATPase) is a multisubunit enzyme complex that is able to transfer protons over membranes against an electrochemical potential under ATP hydrolysis. The enzyme consists of two subcomplexes: V0, which is membrane embedded; and V1, which is cytosolic. V0 was also reported to be involved in fusion of vacuoles in yeast. We identified six genes encoding c-subunits (proteolipids) of V0 and two genes encoding F-subunits of V1 and studied the role of the V-ATPase in trafficking in Paramecium. Green fluorescent protein (GFP) fusion proteins allowed a clear subcellular localization of c- and F-subunits in the contractile vacuole complex of the osmoregulatory system and in food vacuoles. Several other organelles were also detected, in particular dense core secretory granules (trichocysts). The functional significance of the V-ATPase in Paramecium was investigated by RNA interference (RNAi), using a recently developed feeding method. A novel strategy was used to block the expression of all six c- or both F-subunits simultaneously. The V-ATPase was found to be crucial for osmoregulation, the phagocytotic pathway and the biogenesis of dense core secretory granules. No evidence was found supporting participation of V0 in membrane fusion

An Ins(1,4,5)P3 receptor in Paramecium is associated with the osmoregulatory system

In the ciliate Paramecium, a variety of well characterized processes are regulated by Ca2+, e.g. exocytosis, endocytosis and ciliary beat. Therefore, among protozoa, Paramecium is considered a model organism for Ca2+ signaling, although the molecular identity of the channels responsible for the Ca2+ signals remains largely unknown. We have cloned - for the first time in a protozoan - the full sequence of the gene encoding a putative inositol (1,4,5)-trisphosphate (Ins(1,4,5)P3) receptor from Paramecium tetraurelia cells showing molecular characteristics of higher eukaryotic cells. The homologously expressed Ins(1,4,5)P3-binding domain binds [3H]Ins(1,4,5)P3, whereas antibodies unexpectedly localize this protein to the osmoregulatory system. The level of Ins(1,4,5)P3-receptor expression was reduced, as shown on a transcriptional level and by immuno-staining, by decreasing the concentration of extracellular Ca2+ (Paramecium cells rapidly adjust their Ca2+ level to that in the outside medium). Fluorochromes reveal spontaneous fluctuations in cytosolic Ca2+ levels along the osmoregulatory system and these signals change upon activation of caged Ins(1,4,5)P3. Considering the ongoing expulsion of substantial amounts of Ca2+ by the osmoregulatory system, we propose here that Ins(1,4,5)P3 receptors serve a new function, i.e. a latent, graded reflux of Ca2+ to fine-tune [Ca2+] homeostasis

Trends in marine dissolved oxygen: Implications for ocean circulation changes and the carbon budget

Recent measurements and model studies have consistently identified a decreasing trend in the concentration of dissolved O2 in the ocean over the last several decades. This trend has important implications for our understanding of anthropogenic climate change. First, the observed oceanic oxygen changes may be a signal of the beginning of a reorganization of large-scale ocean circulation in response to anthropogenic radiative forcing. Second, the repartitioning of oxygen between the ocean and the atmosphere requires a revision of the current atmospheric carbon budget and the estimates of the terrestrial and oceanic carbon sinks as calculated by the Intergovernmental Panel on Climate Change (IPCC) from measurements of atmospheric O2/N2

LimnoVIS - A Robotic Surface Vehicle for Spectral Measurements in Inland Waters

Spectral measurements in aquatic remote sensing are usually carried out from ships, boats or stationary platforms. While the latter only covers a single location, mobile platforms can introduce significant errors due to unexpected movement (drift and rotation), reflection and shadowing effects from the ship’s hull, superstructures and the personnel conducting the measurements. To overcome these caveats, we developed the low-profile robotic platform LimnoVIS that can be operated autonomously or remotely controlled and is capable of keeping its position and orientation accurately through its omnidirectional maneuverability. The onboard measurement system comprises a VIS/NIR spectrometer (350-880 nm, 1 nm resolution) which is connected to four different optics via a fiber optical switch. This allows for rapid subsequent measurement of upwelling radiance above and under water, sky radiance and downwelling irradiance using reflectance standards or a cosine corrector, all by the same spectrometer. LimnoVIS carries also a profiler, which can be lowered by up to 30 m. It is equipped with a spectrometer and a tiltable diffusor for measuring benthic reflectance, LED and halogen lamps, a laser range finder, a camera, and sensors for temperature and pressure. Multiple onboard cameras with recording and live viewing capabilities are used for navigation, visual supervision and documentation of the measurements and for compiling shallow-water orthomosaics. Furthermore, LimnoVIS is equipped with a sonar for deriving bathymetry in the range of 0.5 to 30 m

Uncertainty and risk in climate projections for the 21st century: comparing mitigation to non-intervention scenarios

Probabilistic climate projections based on two SRES scenarios, an IMAGE reference scenario and five IMAGE mitigation scenarios (all of them multi-gas scenarios) using the Bern2.5D climate model are calculated. Probability distributions of climate model parameters that are constrained by observations are employed as input for the climate model. The sensitivity of the resulting distributions with respect to prior assumptions on climate sensitivity is then assessed. Due to system inertia, prior assumptions on climate sensitivity play a minor role in the case of temperature projections for the first half of the 21st century, but these assumptions have a considerable influence on the distributions of the projected temperature increase in the year 2100. Upper and lower probabilities for exceeding 2°C by the year 2100 are calculated for the different scenarios. Only the most stringent mitigation measures lead to low probabilities for exceeding the 2°C threshold. This finding is robust with respect to our prior assumptions on climate sensitivity. Further, probability distributions of total present-value damages over the period 2000-2100 for the different scenarios are calculated assuming a wide range of damage cost functions, and the sensitivity of these distributions with respect to the assumed discount rate is investigated. Absolute values of damage costs depend heavily on the chosen damage cost function and discount rate. Nevertheless, some robust conclusions are possibl

Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation: Special Report of the Intergovernmental Panel on Climate Change

This Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) has been jointly coordinated by Working Groups I (WGI) and II (WGII) of the Intergovernmental Panel on Climate Change (IPCC). The report focuses on the relationship between climate change and extreme weather and climate events, the impacts of such events, and the strategies to manage the associated risks. The IPCC was jointly established in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), in particular to assess in a comprehensive, objective, and transparent manner all the relevant scientific, technical, and socioeconomic information to contribute in understanding the scientific basis of risk of human-induced climate change, the potential impacts, and the adaptation and mitigation options. Beginning in 1990, the IPCC has produced a series of Assessment Reports, Special Reports, Technical Papers, methodologies, and other key documents which have since become the standard references for policymakers and scientists.This Special Report, in particular, contributes to frame the challenge of dealing with extreme weather and climate events as an issue in decisionmaking under uncertainty, analyzing response in the context of risk management. The report consists of nine chapters, covering risk management; observed and projected changes in extreme weather and climate events; exposure and vulnerability to as well as losses resulting from such events; adaptation options from the local to the international scale; the role of sustainable development in modulating risks; and insights from specific case studies