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BACKGROUND: Understanding the consequences of thermal and chemical variations in aquatic habitats is of importance in a scenario of global change. In ecology, the sex ratio is a major population demographic parameter. So far, research that measured environmental perturbations on fish sex ratios has usually involved a few model species with a strong genetic basis of sex determination, and focused on the study of juvenile or adult gonads. However, the underlying mechanisms at the time of gender commitment are poorly understood. In an effort to elucidate the mechanisms driving sex differentiation, here we used the European sea bass, a fish species where genetics and environment (temperature) contribute equally to sex determination. RESULTS: Here, we analyzed the transcriptome of developing gonads experiencing either testis or ovarian differentiation as a result of thermal and/or exogenous estrogen influences. These external insults elicited different responses. Thus, while elevated temperature masculinized genetic females, estrogen exposure was able to override thermal effects and resulted in an all-female population. A total of 383 genes were differentially expressed, with an overall downregulation in the expression of genes involved in both in testicular and ovarian differentiation when fish were exposed to Estradiol-17ß through a shutdown of the first steps of steroidogenesis. However, once the female phenotype was imposed, gonads could continue their normal development, even taking into account that some of the resulting females were fish that otherwise would have developed as males. CONCLUSIONS: The data on the underlying mechanisms operating at the molecular level presented here contribute to a better understanding of the sex ratio response of fish species subjected to a combination of two of the most common environmental perturbations and can have implications in future conservational policies.

In this paper, we discuss the importance of the efficient communication of science results to citizens across the world. In order for people to absorb information, we need to understand the principles and apply the best available means to facilitate the process of increasing global awareness of the changes. This explicitly applies to the verification of how we appeal to people with respect to various environmental issues and, hence, how we can modernize the educational approaches to challenge the global change. We state that, in order to follow the philosophy of sustainable development goals with respect to ocean issues, we need an attractive alternative to the existing areas of consumption. We also state that the ocean issues are at the core of any process aiming to secure sustainability. New methods and tools of education and scientific communication, especially those which are offered by non-formal approaches, are necessary, and we present here some of the activities of the EU4Ocean coalition as best practice examples.

Mean temperature (MTC) and mean trophic level (MTL) spatiotemporal patterns of MEDITS survey catches were examined in 13 geographic statistical areas (GSAs) of the Mediterranean between 1994 and 2016. The study aimed to detect changes in the demersal community structure related to anthropogenic impacts. A generalized additive modelling approach was used to examine the effects of year and GSA on the MTC and MTL indexes and on bottom temperature by haul. For the MTC index, the year was significant only in 4 GSAs, while for MTL it was significant in 5. Higher MTC values were observed in central and eastern areas. Bottom temperature increased after 2010, and also from west to east and from north to south. Our results indicate that the recently observed increase in bottom sea temperature has not resulted in an immediate response by demersal marine communities, but areas with higher warming rates or shallow depths were found to be more susceptible to sea warming. For MTL, decreasing trends were observed in only 2 GSAs, while the temporal trends observed in 5 GSAs may have reflected changes in fishing activity patterns. However, higher MTL values were observed in GSAs with generally higher exploitation rates, indicating that factors other than fishing play an important structuring role in marine communities. The present results indicate differences among Mediterranean subareas in regard to changes in the community structure attributed to environmental conditions and exploitation patterns and have implications for the ecology and dynamics of the stocks.

AbstractFuture projections of global mean sea level change are uncertain, partly because of our limited understanding of the dynamics of Greenland’s outlet glaciers. Here we study Nioghalvfjerdsbræ, an outlet glacier of the Northeast Greenland Ice Stream that holds 1.1 m sea-level equivalent of ice. We use GPS observations and numerical modelling to investigate the role of tides as well as the elastic contribution to glacier flow. We find that ocean tides alter the basal lubrication of the glacier up to 10 km inland of the grounding line, and that their influence is best described by a viscoelastic rather than a viscous model. Further inland, sliding is the dominant mechanism of fast glacier motion, and the ice flow induces persistent elastic strain. We conclude that elastic deformation plays a role in glacier flow, particularly in areas of steep topographic changes and fast ice velocities.

Hydrological alteration caused by dams, changing climates, and land use-cover changes produce pervasive effects on freshwater ecosystems and undermine the delivery of essential ecosystem services. Riverine ecosystems are particularly vulnerable to these stressors, with alarming biodiversity loss rates. In this context, the primary goal of this PhD thesis is to explore spatial biodiversity patterns in Spanish rivers and how dams and reservoirs modify them. Using the taxonomy and traits of diatom, macroinvertebrate, and fish communities, we evaluated the role of key environmental gradients and spatial distances (i.e. dispersal-related processes) in structuring biological communities in near-pristine streams throughout Spain. In streams impacted by irrigation and hydropower dams in the north of the country, we investigated the ecological responses in mountain areas and in a control-impact design. The study's findings provide useful insights into the development of effective conservation efforts directed towards global change drivers and the different dams' operational schemes. La alteración hidrológica provocada por presas, el cambio climático y cambios en el uso del suelo producen efectos generalizados en los ecosistemas de agua dulce y ponen en riesgo servicios ecosistémicos esenciales. Los ecosistemas fluviales son especialmente vulnerables a estos factores de estrés, con tasas de pérdida de biodiversidad alarmantes. En este contexto, el objetivo principal de esta tesis doctoral es explorar los patrones espaciales de biodiversidad en los ríos españoles y cómo las presas y embalses los modifican. Utilizando taxonomía y rasgos de diatomeas, macroinvertebrados y peces, evaluamos el papel de los gradientes ambientales y las distancias espaciales (es decir, procesos relacionados con la dispersión) en la estructura de las comunidades biológicas en ríos prístinos de toda España. En ríos afectados por presas de regadío e hidroeléctricas en el norte del país, investigamos las respuestas ecológicas en zonas de montaña y en un diseño de control-impacto. Las conclusiones del estudio aportan una perspectiva útil para el desarrollo de estrategias de conservación eficaces dirigidos a los impulsores del cambio global y adaptados a los diferentes esquemas operativos de las presas. Finally, the accomplishment of this work has only been possible thanks to the Spanish Ministry for the Ecological Transition for providing the biological monitoring data and the European Union’s Horizon 2020 research and innovation programme, which funded the EuroFlow project under the Marie Skłodowska-Curie grant agreement No 765553.

The deuterium excess of polar ice cores documents past changes in evaporation conditions and moisture origin. New data obtained from the European Project for Ice Coring in Antarctica Dome C East Antarctic ice core provide new insights on the sequence of events involved in Termination II, the transition between the penultimate glacial and interglacial periods. This termination is marked by a north–south seesaw behavior, with first a slow methane concentration rise associated with a strong Antarctic temperature warming and a slow deuterium excess rise. This first step is followed by an abrupt north Atlantic warming, an abrupt resumption of the East Asian summer monsoon, a sharp methane rise, and a CO2overshoot, which coincide within dating uncertainties with the end of Antarctic optimum. Here, we show that this second phase is marked by a very sharp Dome C centennial deuterium excess rise, revealing abrupt reorganization of atmospheric circulation in the southern Indian Ocean sector.