Beschreibung: Public fear for environmental and health impacts or potential leakage of CO2 from geological reservoirs is among the reasons why over the past decade CCS has not yet been deployed on a large enough scale so as to meaningfully contribute to mitigate climate change. Storage of CO2 under the seabed moves this climate mitigation option away from inhabited areas and could thereby take away some of the opposition towards this technology. Given that in the event of CO2 leakage for sub-seabed CCS the ocean would function as buffer for receiving this greenhouse gas, rather than the atmosphere, offshore CCS could particularly address concerns over the climatic impacts of CO2 seepage. In this paper we point out that recent geological studies confirm that leakage for individual offshore CCS operations may be highly unlikely from a technical point of view, if storage sites are well chosen, well managed and well monitored. But we argue that on a global long-term scale, for an ensemble of thousands or millions of storage sites, leakage of CO2 could take place in certain cases and/or countries for e.g. economic, institutional, legal or safety cultural reasons. We investigated what the impact could be in terms of temperature increase and ocean acidification if leakage would nevertheless occur, and addressed the question what the relative roles could be of on- and offshore CCS if mankind desires to divert the atmospheric damages resulting from climate change. For this purpose, we constructed a top-down energy-environment-economy model, with which we performed a probabilistic cost-benefit analysis of climate change mitigation with on- and offshore CCS as specific CO2 abatement options. One of our main conclusions is that even if there is non-zero leakage for CCS activity on a global scale, there is high probability that both onshore and offshore CCS could – on economic grounds – still account for anywhere between 20% and 80% of all future CO2 abatement efforts under a broad range of CCS cost assumptions.

Beschreibung: This paper focuses on the marine foundation eelgrass species, Zostera marina, along a gradient from the northern Baltic Sea to the north-east Atlantic. This vast region supports a minimum of 1480 km2 eelgrass (maximum 〉2100 km2), which corresponds to more than four times the previously quantified area of eelgrass in Western Europe. Eelgrass meadows in the low salinity Baltic Sea support the highest diversity (4–6 spp.) of angiosperms overall, but eelgrass productivity is low (〈2 g dw m-2 d-1) and meadows are isolated and genetically impoverished. Higher salinity areas support monospecific meadows, with higher productivity (3–10 g dw m-2 d-1) and greater genetic connectivity. The salinity gradient further imposes functional differences in biodiversity and food webs, in particular a decline in number, but increase in biomass of mesograzers in the Baltic. Significant declines in eelgrass depth limits and areal cover are documented, particularly in regions experiencing high human pressure. The failure of eelgrass to re-establish itself in affected areas, despite nutrient reductions and improved water quality, signals complex recovery trajectories and calls for much greater conservation effort to protect existing meadows. The knowledge base for Nordic eelgrass meadows is broad and sufficient to establish monitoring objectives across nine national borders. Nevertheless, ensuring awareness of their vulnerability remains challenging. Given the areal extent of Nordic eelgrass systems and the ecosystem services they provide, it is crucial to further develop incentives for protecting them.

Beschreibung: Results of the of the present study provide a strong indication that reproductive periods of the bladderwrack Fucus vesiculosus is tuned by environmental conditions, such as day length, although it cannot be entirely ruled out that genetic constitution may play a role, as well. Furthermore results of the present study identified high temperatures as the most challenging condition for alga recruitment. Sea surface temperature rise could therefore be one of the reasons for the decline of F. vesiculosus populations in the Baltic Sea over the last few decades, particularly in the marginal environments (〈 7 psu). Additionally, fertility of F. vesiculosus from the marginal region, in contrast to all other regions, was very low, which also indicates towards a lower capacity to deal with environmental changes. A rather high germination success of some sibling groups (F. vesiculosus) under various environmental conditions, however, is promising in the light of adaptation to climate change.

Beschreibung: Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and a methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates, consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil-fuel combustion and cement production (EFF) are based on energy statistics, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated for the first time in this budget with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models forced by observed climate, CO2 and land cover change (some including nitrogen–carbon interactions). All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2003–2012), EFF was 8.6 ± 0.4 GtC yr−1, ELUC 0.9 ± 0.5 GtC yr−1, GATM 4.3 ± 0.1 GtC yr−1, SOCEAN 2.5 ± 0.5 GtC yr−1, and SLAND 2.8 ± 0.8 GtC yr−1. For year 2012 alone, EFF grew to 9.7 ± 0.5 GtC yr−1, 2.2% above 2011, reflecting a continued growing trend in these emissions, GATM was 5.1 ± 0.2 GtC yr−1, SOCEAN was 2.9 ± 0.5 GtC yr−1, and assuming an ELUC of 1.0 ± 0.5 GtC yr−1 (based on the 2001–2010 average), SLAND was 2.7 ± 0.9 GtC yr−1. GATM was high in 2012 compared to the 2003–2012 average, almost entirely reflecting the high EFF. The global atmospheric CO2 concentration reached 392.52 ± 0.10 ppm averaged over 2012. We estimate that EFF will increase by 2.1% (1.1–3.1%) to 9.9 ± 0.5 GtC in 2013, 61% above emissions in 1990, based on projections of world gross domestic product and recent changes in the carbon intensity of the economy. With this projection, cumulative emissions of CO2 will reach about 535 ± 55 GtC for 1870–2013, about 70% from EFF (390 ± 20 GtC) and 30% from ELUC (145 ± 50 GtC). This paper also documents any changes in the methods and data sets used in this new carbon budget from previous budgets (Le Quéré et al., 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2013_V2.3).

Beschreibung: The Collaborative Research Centre 754 (SFB 754) at GEOMAR in Kiel, Germany is an interdisciplinary research programme, which investigates the threats posed by ocean de-oxygenation and how this is coupled with climate change and the nutrient balance in the tropical oceans. The outreach component of SFB 754 has the task of producing videos with and for school pupils, in which different aspects of the science of the SFB are explained and introduced in a short and entertaining fashion. The goal is to attract pupils to sciences, both by the active involvement in the video production and by the consumption of the videos made by other pupils. So far more than 30 video clips were published on a dedicated website for viewing and download. The process of video production is enjoyable for all parties involved, but it is also time consuming and entails considerably more work for students and teachers, than normal lessons in class. As a result, the project now concentrates on dedicated summer schools and after-school activities as a platform for video production

Beschreibung: Originating from East Asia, the perennial red macroalga Gracilaria vermiculophylla (Ohmi) Papenfuss has successfully invaded several temperate areas of the Northern hemisphere and continues to spread. In its new range, the seaweed tends to form local mass appearances and to dominate the native community. A high tolerance towards both abiotic and biotic environmental stressors could explain the invasion success of this species. I therefore compared the stress resistance of G. vermiculophylla from six native populations from South Korea and China and eight invasive populations from Europe and NW-Mexico. In short-term experiments G. vermiculophylla individuals were exposed to 1) heat shock, 2) UV-C-radiation and 3) elevated copper concentrations in the water. In a long-term experiment the seaweed had to cope with depletion stress (darkness in combination with low temperature and dryness) for several months. All experiments were carried out twice - one time in the native range in Qingdao, China and one time in the invaded range in Kiel, Germany - to rule out local acclimation effects. In order to compare the resistance against herbivory individuals of native and invasive G. vermiculophylla populations were fed to snails from the native (Littorina brevicula) and the invasive (Littorina littorea) range. In the Baltic Sea, G. vermiculophylla might threaten the habitat-forming native brown alga Fucus vesiculosus through direct competition for resources and by providing a shelter for mesograzers, which prefer to feed on F. vesiculosus. Mesocosm-experiments were conducted over one year in the Kiel Fjord in order to test the direct and indirect effects of G. vermiculophylla on F. vesiculosus.

Beschreibung: The main goal of MSM21/4 was the study of gas hydrate system off Svalbard. We addressed this through a comprehensive scientific programme comprising dives with the manned submersible JAGO, seismic and heat flow measurements, sediment coring, water column biogeochemistry and bathymetric mapping. At the interception of the Knipovich Ridge and the continental margin of Svalbard we collected seismic data and four heat flow measurements. These measurements revealed that the extent of hydrates is significantly larger than previously thought and that the gas hydrate system is influenced by heat from the oceanic spreading centre, which may promote thermogenic methane production and thus explain the large extent of hydrates. At the landward termination of the hydrate stability zone we investigated the mechanisms that lead to degassing by taking sediment cores, sampling of carbonates during dives, and measuring the methane turn-over rates in the water column. It turned out that the observed gas seepage must have been ongoing for a long time and that decadal scale warming is an unlikely explanation for the observed seeps. Instead seasonal variations in water temperatures seem to control episodic hydrate formation and dissociation explaining the location of the observed seeps. The water column above the gas flares is rich in methane and methanotrophic microorganisms turning over most of the methane that escapes from the sea floor. We also surveyed large, until then uncharted parts of the margin in the northern part of the gas hydrate province. Here, we discovered an almost 40 km wide submarine landslide complex. This slide is unusual in the sense that it is not located at the mouth of a cross shelf trough such as other submarine landslides on the glaciated continental margins around the North Atlantic. Thus, the most widely accepted explanation for the origin of such slides, i.e. overpressure development due to deposition of glacial sediments on top of water rich contourites, is not applicable. Instead we find gas-hydrate-related bottom simulating reflectors underneath the headwalls of this slide complex, possibly indicating that subsurface fluid migration plays a major role in its genesis.

Beschreibung: Climate change driven by anthropogenic utilization of fossil fuels and deforestation over the past 250 years is leading to ongoing changes in sea surface temperature (i.e. ocean warming) and seawater carbonate chemistry speciation (i.e. ocean acidification, OA) at an unprecedented pace. Both of these environmental stressors are expected to impact marine ecosystem functioning in the near future with consequences for marine biogeochemical cycling. In the context of this doctoral thesis, phytoplankton physiology and biogeochemical dynamics were investigated under the individual and combined effects of OA and warming through experimental work. Chapter I of this thesis presents data on the individual and synergistic effects of OA and warming on coccolithophore physiology. In order to test for possible synergistic effects, two coccolithophore species, Emiliania huxleyi and Gephyrocapsa oceanica, were exposed to a broad range in CO2 concentrations at three different temperatures. The results from this study showed that both species displayed optimum-curve responses for key metabolic processes (i.e. growth, photosynthesis and calcification) at all temperatures, with species-specific sensitivities. Most importantly, increasing temperature modulated the optimum CO2 concentration and sensitivity of metabolic processes. Our results enabled us to propose a conceptual model showing that the temperature sensitivity of metabolic processes in these organisms could help explain the discrepancies found in the literature on coccolithophore physiology in response to OA. Interested by the results from experiments in Chapter I with single species, mesocosm experiments were carried out in Chapters II and III with natural plankton communities. Since most of the literature with natural communities has focused on effects of individual environmental factors, experiments in Chapters II and III investigated the combined effects of OA and warming during a natural spring bloom (Kiel Bight) and a nutrient-induced summer bloom (Thau lagoon, France). During experiments in Chapter II a shift in phytoplankton community composition towards larger diatoms under combined OA and warming conditions (i.e. ‘Greenhouse’ scenario) was observed. Possible explanations for the observed shift in size are discussed in detailed and compared with results in the literature. Furthermore, the shift in species composition significantly increased losses of organic matter at the end of the experiment in the Greenhouse treatment were larger species dominated. Chapter III focused on the temporal development of phytoplankton derived particulate and dissolved organic matter (i.e. POM and DOM, respectively). Increased CO2, individually and in combination with warming, enhanced biomass build-up and modulated the negative effects of warming (i.e. decreased biomass build-up). In summary, the experimental data from the work presented in this doctoral thesis shows the importance of investigating the synergistic effects of changing environmental factors when trying to understand the response of marine ecosystems to climate change and its importance when assessing the future of marine ecosystem functioning. Some suggestions for experimental work are proposed to follow up on the results from experiments presented in this doctoral thesis.