Description / Table of Contents: "The option of disposing of radioactive waste deep underground has been studied in Belgium by SCK CEN since the 1970s. This led in 1980 to the construction of the HADES underground research laboratory (URL) in a clay formation, the Boom Clay, at a depth of 225 m under the premises of SCK CEN in Mol. Over the last four decades, many in situ experiments have been conducted in the HADES URL. These have made a significant contribution to ONDRAF/NIRAS' research, development and demonstration (RD&D) efforts demonstrating that disposal in Boom Clay can offer a safe solution for the long-term management of high-level and/or long-lived radioactive waste. Moreover, the construction of the HADES URL itself is a demonstration that shafts and galleries can be constructed in clay at that depth. However, the HADES URL did not only contribute to the Belgian programme. Many of the in situ experiments have been part of international research and the laboratory has provided valuable input to the research programmes of other URLs, such as the Meuse/Haute-Marne URL in France and the Mont Terri rock laboratory in Switzerland. This paper gives a brief overview of the main contributions of the HADES URL to both national and international research into geological disposal"--Abstract

Description / Table of Contents: Marine fish play important functional roles within the carbon cycle, including the production and excretion of intestinal carbonates. With fish accounting for at least 3-15% of total marine carbonate production, the global significance of this process is clear. A comprehensive assessment of the drivers of fish carbonate excretion rate and mineralogy is however lacking. Closing this gap is imperative to fully understand the role of fish in the inorganic carbon cycle and to predict how it may change in future. Focusing on tropical and subtropical reefs, this thesis assessed the drivers of fish contributions to the inorganic carbon cycle at different ecological levels and spatial scales. At the individual level, this project compiled intestinal traits for 142 species and carbonate excretion rates and mineralogy for 85 species. A comprehensive modelling approach then identified the species traits and environmental factors that influence individual excretion rates and mineralogy. At the community level and at the global scale, a novel analysis of 〉1,400 reefs mapped distribution patterns in fish carbonate excretion and mineralogy. A causal inference analysis identified the major ecological, environmental, and socio-economic factors driving these community-level patterns. At the regional scale (i.e., in the Australian coral reefs context), structural equation models disentangled the indirect effects of human gravity (i.e., a proxy for human pressure) and fisheries management on fish contributions to inorganic carbon cycling. Findings at the individual level confirmed the long-assumed direct link between fish carbonate excretion and metabolic rate and showed that diet strongly influences intestinal morphology. Relative intestinal length was uncovered as a strong driver of carbonate excretion rates and mineralogy, as were taxonomic identity and temperature. Current global patterns of fish contribution to the inorganic carbon cycle are primarily driven by fish community structure, sea surface temperature, and human gravity. Carbonate excretion rates peaked in highly productive areas supporting high fish biomass, especially within the upper trophic levels, and where human gravity is low. Globally, fish communities predominantly excrete the more soluble carbonates and their proportion increases with increasing temperature. On Australian reefs, fish carbonate excretion was strongly affected by human impact through reduced fish biomass despite the region’s relatively low fishing pressure. In this particular geographic context, current fisheries management is not sufficient to maintain fish carbonate excretion, despite positive effects on fish biodiversity. This thesis advances our understanding of the role of fish in inorganic carbon cycling from the physiological, ecological, biogeographic, chemical, mineralogical, and conservation perspectives. It unravels the complex variability of this function across ecological levels and spatial scales. Coupled with predictive models, this information could yield solid predictions of the future levels of this function in light of anthropogenic impacts and climate-driven range shifts. While fish carbonate excretion may increase with climate change, excreted carbonates will dissolve faster and/or at shallower water depths, thereby changing their influence on seawater chemistry and reducing their sedimentation potential. Protecting large predators would promote inorganic carbonate production and other fish roles within the carbon cycle. However, fisheries management has in places limited capacity to sustain fish inorganic carbon cycling. The need for effective, context-tailored management approaches that address socio-economic factors beyond fishing pressure is strongly emphasised.

Description / Table of Contents: Quantifying species responses to the effects of changing environmental conditions is critical for a better understanding of how climate change affects invasion, expansion, and contraction of marine coastal species. Climate change is leading to modifications in the marine coastal environment, to conditions not experienced before; climate change results in that marine organisms experience simultaneous changes in several environmental variables (=drivers: e.g. temperature, salinity, food). How simultaneous changes in multiple drivers are experienced depend on species-specific traits (e.g. physiological tolerance, developmental time); for instance, co-occurring native and non-native species may experience and respond to climate change in different ways. In addition, within species, responses to multiple drivers may vary across populations and environmental gradients. The general objective of this thesis was to quantify the effects of environmental drivers (temperature, salinity and food limitation) on performance of native and non-native species with focus on larval stages and using crabs as model systems. There were two main objectives, first to compare native and non-native species in the responses to multiple environmental drivers and to quantify larval responses to temperature across their distribution range. I focused on larvae because they play a critical role in population dynamics: larvae are important for the dispersion and connectivity of populations, and are more sensitive to changes in environmental conditions than adults. I used three ecologically relevant species of coastal areas of the North Sea and North Atlantic Ocean as models: Hemigrapsus sanguineus, Carcinus maenas and Hemigrapsus takanoi. C. maenas is native to Europe; Hemigrapsus spp. are both non-native species in the European coast, where they coexist with C. maenas as juveniles and adults in the benthos. I used factorial experiments rearing larvae from hatching to megalopae at different combinations of temperature and other environmental drivers (salinity, food limitation). Larval performance was quantified as survival, duration of development, and growth. The first series of result show that both non-native (Hemigrapsus spp) species had higher performance (high survival, shorter duration of development and high growth rates) than the native C. maenas at higher temperatures and at moderately low salinities (18 – 24 °C, 20 – 25 ‰). These results are comparable to another non-native species in Europe, the Chinese mitten crab Eriocheir sinensis. In H. sanguineus, larvae show moderate level of tolerance to limited access to food at high temperature, which contrasted to the low tolerance shown in native C. maenas. Experiments and modelling show that the nature of the multiple driver response depends strongly on the metric used to measure time, where my emphasis is on biological time (time to metamorphosis). The results from the populations comparisons showed species and gradient-specific responses. For H. takanoi, distributed over a salinity gradient (North Sea -Baltic Sea), larvae from the North Sea populations always showed higher survival and faster development compared with those from the Baltic Sea. The population near the limit of the distribution showed very low survival, suggesting that subsidies or complex ontogenetic migration patterns are needed for population persistence. Results did not show genetic differentiation among the studied populations in the mitochondrial cytochrome c oxidase subunit one gene (COI) suggesting that there is high connectivity among populations. For C. maenas distributed across a latitudinal gradient (South: Vigo, Spain; North: Bergen and Trondheim, Norway) and reared under different temperatures (range 6 to 27 °C in steps of 3 °C), there was little variation in survival and growth among populations. However, larvae from the Norwegian populations had a slightly shorter duration of development at low temperatures than those from Vigo, this response has an adaptive value in that it could sustain survival in scenarios of reduced temperature, by shortening the larval phase, when mortality rates are high. Besides, results from this experiment (as well as for the mentioned above) showed high intrapopulation variability in larval performance which has a potential to affect range expansion of the above-mentioned species. Variation in the responses of larval stages to the effects of different environmental drivers highlights the importance of using physiological descriptors to quantify the performance of marine invertebrates to changing environments. Larval responses vary in rates of survival but also in the duration of time to achieve metamorphosis, as well as the rate at which the organisms grow, with concomitant effects on post-metamorphic success, which in seasonal habitats may strongly depend on temperature. The results from the thesis highlight the importance of quantifying the responses of marine invertebrates to changing environmental conditions, considering different species and species distributed across different gradients as well as variations among and within species.

Description / Table of Contents: The biological carbon uptake, called biological compensation, have been shown to have a huge potential to affect the capacity of the ocean to absorb (anthropogenic) carbon dioxide, and so equilibrate the global carbon budget and hence climate. Since the pelagic calcite flux is made of two fundamentally different components, coccolithophore algae and planktonic foraminifera, understanding of the process of biological compensation requires knowledge of variability of their relative contribution to the total pelagic calcite flux. The aspects of the pelagic carbonate production that have changed through time and the mechanisms explaining the observed carbonate flux variability remain, despite their importance, largely unconstrained. In order to evaluate the orbital and long geological time scale variability of the pelagic carbonate production, I generated new high-resolution records of carbonate accumulation rate, using marine sediments deposited in the equatorial Atlantic Ocean (Ceará Rise) at ODP Site 927, across four warm climates intervals ranging from the Neogene to the Quaternary. I find that the relative contribution of the two groups to the total pelagic carbonate production remains relatively constant on long geological time scales, shows a high orbital time scale variability (factor of two), and is not driving the changes in total pelagic carbonate production. I conclude that at the studied location, the main driver of the pelagic carbonate changes, for both the planktonic foraminifera and the coccoliths were changes in population growth, with a shift in the composition of the communities. The observed dominant periodicities in carbonate accumulation rate indicate that the two groups responded to local changes in factors affecting their productivity, rather than to global climate modulations. On both time scales, the observed changes were large enough to affect the marine inorganic carbon cycle and thus the ocean’s capacity to absorb inorganic carbon.