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We present the first experimental results on salinity tolerance and regulation mechanisms in the genus Tolypella. The two species investigated, T. nidifica and T. glomerata, regulate turgor pressure with almost complete effectiveness by adjustment of K+ and CT concentrations. Sucrose is also involved. The mechanism is basically identical to the mechanism of turgor pressure regulation previously identified in representatives of the genera Chara and Lamprothamnium. Since Chara and Lamprothamnium on the one hand and Tolypella on the other belong to different phylogenetic branches that separated early in the geological history of the Characeae, the K+ regulation mechanism can be assumed to represent an ancient pattern derived from a salt‐tolerant common ancestor. Furthermore, our experiments provide evidence that salinity is a limiting factor for fertility in both T. nidifica and T. glomerata. Although the onset of gametangia covers the whole range of salinities tested here (0–29 psu), 12psu was the inhibitory level for the formation of mature oospores. Fertilization is probably disturbed by an increase in salinity. An inability to reproduce sexually under euryhaline conditions could explain why the distribution of the two species is restricted to oligo‐ and mesohaline environments, despite the wide range of salinity tolerance of their vegetative apparatus.

The archaeological sites in the open-cast mine of Schöningen, Germany, represent outstanding archives for understanding Middle Pleistocene interglacial-glacial transitions and human adaption. Aquatic microfossil and pollen assemblages from the 'Reinsdorf sequence', likely correlated to Marine Isotope Stage 9, document environmental changes from a thermal maximum to succeeding glacial conditions recorded in two sequences of excavation sites 12 II and 13 II. Multi-proxy analyses enable detailed reconstruction of lake-shore and landscape developments despite variable microfossil preservation in changing carbonate-and organic-rich deposits. Rich aquatic vegetation with abundant charophytes suggests repeated phases with water depths of 0.5-2 m at site 13 II, while even greater temporary depths are deduced for 12 II DB. Mesorheophilic and mesotitanophilic ostracod species indicate stream inflows with medium-low calcium contents of >18 mg Ca L -1 originating from nearby springs. Diatoms point to meso-eutrophic conditions and an alkaline pH of the lake water. Interglacial conditions with thermophile forests but no aquatic microfossils preserved, suggesting a dry or only temporarily flooded site, mark the beginning of the sequence. Continuous presence of aquatic organisms and overall dominance of small tychoplanktonic diatoms during a subsequent cool steppe phase provide evidence for increasedwater depths and unstable habitats characterized by erosion and probably prolonged periods of lake ice cover. During the succeeding boreal forest-steppe phase, surface runoff into the productive, shallow lake decreased due to a more extensive vegetation cover. Concurrently, intensified groundwater input in contact with the nearby salt wall caused elevated salinities. Following a lake level drop, stream inflows and lake levels increased again towards the end of the Reinsdorf sequence and promoted development of a diverse fauna and flora at the lake shore; thereby maintaining an attractive living and hunting environment for early humans during a phase of generally cooler temperatures and landscape instability at the transition into a glacial period.

International audienceWater level fluctuations of Lake Afourgagh (Middle-Atlas Mountains, Morocco) over the last 2500 years (Late Holocene) have been reconstructed using charophyte remains in the lake sediment archives. The study involved 22 pits (1-3 m deep) dug along a transect across the lake shore terrace. Biogenic activity appears to be a dominant contributor to the accumulation of the lake sediments, as the thickest deposits are tufas composed of charophyte-encrusted stems with numerous gyrogonites (termed "charophyte tufas"). The gyrogonites were identified as Chara aspera and Chara hispida remains. The spatial distribution of these two species, measured vertically within a single core and horizontally along the shore terrace, varies according to bathymetry. Shallow proximal environments are characterized by the development of C. aspera, whereas C. hispida remains are mostly observed in distal sediments. Moreover, according to their ecological characteristics, the C. hispida belt migrated proximally when the water level rose, whereas the C. aspera belt migrated distally when the water level fell. These trends were observed successively in a single charophyte tufa layer which records the rise, highstand, and fall of lake level in a single depositional sequence. The late Holocene palaeobathymetry of Lake Afourgagh was inferred by comparing data on charophyte remains and deposit geometry. Data provide evidence for four major low lake level phases (estimated in terms of amplitude) which induced the development of palaeosols in proximal settings at 2191 cal. BP, 1769 BP, 1515 cal. BP and 1062 cal. BP. These results confirm the accuracy of charophyte-based palaeobathymetry studies

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