Precursor cells of the embryonic cortex sequentially generate neurons and then glial cells, but the mechanisms regulating this neurogenic-to-gliogenic transition are unclear. Using cortical precursor cultures, which temporally mimic this in vivo differentiation pattern, we demonstrate that cortical neurons synthesize and secrete the neurotrophic cytokine cardiotrophin-1, which activates the gp130-JAK-STAT pathway and is essential for the timed genesis of astrocytes in vitro. Our data indicate that a similar phenomenon also occurs in vivo. In utero electroporation of neurotrophic cytokines in the environment of embryonic cortical precursors causes premature gliogenesis, while acute perturbation of gp130 in cortical precursors delays the normal timed appearance of astrocytes. Moreover, the neonatal cardiotrophin-1-/- cortex contains fewer astrocytes. Together, these results describe a neural feedback mechanism; newly born neurons produce cardiotrophin-1, which instructs multipotent cortical precursors to generate astrocytes, thereby ensuring that gliogenesis does not occur until neurogenesis is largely complete.

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Integrated sediment multiproxy studies and modeling were used to reconstruct past changes in the Baltic Sea ecosystem. Results of natural changes over the past 6000 years in the Baltic Sea ecosystem suggest that forecasted climate warming might enhance environmental problems of the Baltic Sea. Integrated modeling and sediment proxy studies reveal increased sea surface temperatures and expanded seafloor anoxia (in deep basins) during earlier natural warm climate phases, such as the Medieval Climate Anomaly. Under future IPCC scenarios of global warming, there is likely no improvement of bottom water conditions in the Baltic Sea. Thus, the measures already designed to produce a healthier Baltic Sea are insufficient in the long term. The interactions between climate change and anthropogenic impacts on the Baltic Sea should be considered in management, implementation of policy strategies in the Baltic Sea environmental issues, and adaptation to future climate change.

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Foundation species, and the roles that they play in structuring ecosystems, are threatened by global change. For example, charophytes are a refuge for zooplankton and stabilize sediments, but they are also a food source for various animal species (water birds, fishes, and invertebrates). Particularly, the introduction of new species, such as Gammarus tigrinus, into the Baltic Sea led to yet not understood changes in the food web. Furthermore, future projections point to increased water temperatures and freshwater inputs affecting species capacity to acclimatize to changing abiotic factors. In this study, we investigated the influence of temperature and salinity on the grazing pressure of G. tigrinus on two charophyte species: Chara aspera and Chara tomentosa. The grazing experiments were conducted in a full‐factorial design with the factors salinity (3–13 g kg−1), temperature (5–30°C), and charophyte species. Grazing rates were determined as mass deviation within 48 h considering biomass changes in the presence and absence of gammarids. Grazing rates were further used to calculate charophyte losses in two coastal lagoons with different salinity concentrations for recent and future time periods. Increasing freshwater inputs can buffer charophyte biomass loss at higher temperatures. Gammarids had a higher grazing impact on C. aspera than on C. tomentosa. The potential grazing peak of about 24°C is not yet reached in these coastal waters but may be reached in the near future as shown by our future projection results. However, a temperature increase and decrease in salinity will cause a shift in seasonal individual grazing patterns from summer to spring and autumn. An increase in temperature and freshwater input can lead to a shift in optimal habitats for G. tigrinus in the future. These interactions between abiotic and biotic factors will affect the future spatial distribution that charophytes can exploit as foundation species.