ALBERT

Description: We used data collected at 〉 60 stations over a 10 yr period to build the carbon budget of the plankton community in the euphotic layer of the Eastern North Atlantic Subtropical Gyre (NASE). Autotrophic biomass exceeded microbial heterotrophic biomass by a factor of 1.7. Mean ( SE), integrated chlorophyll a concentration and net particulate primary production (PP) were 17 +/- 1 Mg m(2) and 271 +/- 29 mg C m(-2) d(-1), respectively. Protist grazing on phytoplankton represented 〉 90% of PP. Bacterial production (BP) was 17 +/- 3 mg C m(-2) d(-1). In vitro O-2-evolution experiments indicated that net community production was -65 +/- 16 mmolO(2) m(-2) d(-1), while community respiration (CR) averaged 124 +/- 13 mmolO(2) m(-2) d-1, equivalent to 1324 +/- 142 mg C m(-2) d(-1). However, the sum of the respiration rates by each microbial group, estimated from their biomass and metabolic rates, ranged from 402 to 848 Mg C m(-2) d-1. Therefore, CR could not be reconciled with the respiratory fluxes sustained by each microbial group. Comparison between estimated gross photosynthesis by phytoplankton (481 to 616 mg C m(-2) d-1) and the sum of respiration by each group suggests that the microbial community in the NASE province is close to metabolic balance, which would agree with the observed O-2 supersaturation in the euphotic layer. Taking into account the mean open-ocean values for PP, BP, CR and bacterial growth efficiency, we show that bacteria account for approximately 20% of CR. Our results suggest that the view that bacteria dominate carbon cycling in the unproductive ocean must be reconsidered, or else that in vitro incubations misrepresent the real metabolic rates of one or several microbial groups.

Description: Marine N2 fixing microorganisms, termed diazotrophs, are a key functional group in marine pelagic ecosystems. The biological fixation of dinitrogen (N2) to bioavailable nitrogen provides an important new source of nitrogen for pelagic marine ecosystems and influences primary productivity and organic matter export to the deep ocean. As one of a series of efforts to collect biomass and rates specific to different phytoplankton functional groups, we have constructed a database on diazotrophic organisms in the global pelagic upper ocean by compiling about 12 000 direct field measurements of cyanobacterial diazotroph abundances (based on microscopic cell counts or qPCR assays targeting the nifH genes) and N2 fixation rates. Biomass conversion factors are estimated based on cell sizes to convert abundance data to diazotrophic biomass. The database is limited spatially, lacking large regions of the ocean especially in the Indian Ocean. The data are approximately log-normal distributed, and large variances exist in most sub-databases with non-zero values differing 5 to 8 orders of magnitude. Reporting the geometric mean and the range of one geometric standard error below and above the geometric mean, the pelagic N2 fixation rate in the global ocean is estimated to be 62 (52–73) Tg N yr−1 and the pelagic diazotrophic biomass in the global ocean is estimated to be 2.1 (1.4–3.1) Tg C from cell counts and to 89 (43–150) Tg C from nifH-based abundances. Reporting the arithmetic mean and one standard error instead, these three global estimates are 140 ± 9.2 Tg N yr−1, 18 ± 1.8 Tg C and 590 ± 70 Tg C, respectively. Uncertainties related to biomass conversion factors can change the estimate of geometric mean pelagic diazotrophic biomass in the global ocean by about ±70%. It was recently established that the most commonly applied method used to measure N2 fixation has underestimated the true rates. As a result, one can expect that future rate measurements will shift the mean N2 fixation rate upward and may result in significantly higher estimates for the global N2 fixation. The evolving database can nevertheless be used to study spatial and temporal distributions and variations of marine N2 fixation, to validate geochemical estimates and to parameterize and validate biogeochemical models, keeping in mind that future rate measurements may rise in the future. The database is stored in PANGAEA (doi:10.1594/PANGAEA.774851).

Description: Deutschland will seine Treibhausgasemissionen bis 2050 um 80 bis 95 Prozent vermindern. Die bereits vorgesehenen und umgesetzten Maßnahmen sind jedoch trotz der bisherigen Erfolge nicht ausreichend, um dieses ambitionierte Ziel zu erreichen. Neben dem Sektor der Energiewirtschaft als größter Quelle der Treibhausgasemissionen werden in Deutschland erhebliche Mengen im Industriesektor freigesetzt. Im Klimaschutzplan 2050 hat die Bundesregierung erstmals ein Sektorziel für die Industrie festgelegt. Die vorliegende acatech POSITION analysiert die Optionen der Verwertung und Speicherung von CO2 – Carbon Capture and Utilization (CCU) und Carbon Capture and Storage (CCS) –, die für die Minderung von Treibhausgasemissionen aus Industrieprozessen infrage kommen. Es wird empfohlen, zeitnah Diskussionen über Potenziale und Bedingungen des Einsatzes von CCU und CCS unter Beteiligung einer breiten Öffentlichkeit zu führen. Nur dann können Vorbehalte gegenüber CCU und CCS berücksichtigt, geeignete Technologien rechtzeitig fortentwickelt und zur Marktreife gebracht werden, damit auch die nötige Infrastruktur geplant, genehmigt, finanziert und errichtet werden kann.

Description: Germany wishes to cut its greenhouse gas emissions by 80 to 95 per cent by 2050. However, despite the success to date, the measures which have already been planned and implemented are not sufficient for achieving this ambitious goal. In addition to the energy sector, the largest source of greenhouse gas emissions, German industry is also responsible for releasing considerable volumes of global warming gases. In its Climate Action Plan 2050, the Federal Government has for the first time set a sector target for industry. The present acatech POSITION PAPER analyses the options for (re)utilising and storing CO2 (Carbon Capture and Utilisation (CCU) and Carbon Capture and Storage (CCS)) which come into consideration for reducing greenhouse gas emissions from industrial processes. It is recommended that a wide-ranging public debate about the use of CCU and CCS be conducted in the near future. Only then will it be possible to take account of reservations about CCU and CCS, further develop suitable technology in good time and bring it to market maturity so that the necessary infrastructure can be planned, approved, funded and constructed.