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The paper presents data regarding two larvae insect populations – Gomphus (Stylurus) flavipes (Charpentier, 1825) and Palingenia longicauda (Olivier, 1791), inhabiting in the communities existing at the water/sediment interface along the Danube River. The dragonfly Gomphus (Stylurus) flavipes (Charpentier, 1825) is one of the most important indicator species, listed in Annex IV of the EU Habitats Directive (EU Directive 92/43/EEC) and included in the IUCN Red List of Threatened Species, 2014. This species of dragonfly has become an endangered species in most Western European countries due to water pollution and river regulation. The other important larvae species, mayfly Palingenia longicauda (Olivier, 1791), listed in Annex II of the Bern Convention, is considered critically endangered in Europe. Both require a specific habitat conditions in order to complete their life cycle. During the spring campaigns conducted during 2012-2015, the presence of the two species was reported in 26 profiles from the Lower Danube Sector, Gomphus (Stylurus) flavipes in 18 profiles, and Palingenia longicauda in 10 profiles. The most abundant occurrences were recorded in 2015, at Km 4 – Măcin Arm (59.2 ind/m2) for Gomphus (Stylurus) flavipes, respectively, in 2012, at Km 8 – Sf. Gheorghe) (125.8 ind/m2) for Palingenia longicauda. The presence or absence of larvae in samples, as well as their abundance, are strictly dependent on ecological conditions, the type of substrate representing the decisive factor in the microdistribution of the two larvae., {"references":["Bálint, M., MálnáS, k., Nowak, C., Geismar, j., Váncsa, e., Polyák, l., Lengyel, S., Haase, P. (2012). Species history masks the effects of human– Induced range loss – unexpected. Genetic diversity in the endangered giant mayfly Palingenia longicauda. In: PLoS ONE Vol. 7(3): e31872. 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International audience; In this article we document the evolution of the internal area of the Danube Delta (i.e. the blocked delta) starting from the geo-archaeological and geomorphological investigations performed at Mila 23 district, following the discovery of the oldest human settlement in the Delta. The in-site and out-site field work and coring allowed us to specify the delta's early stages of evolution from 5600 to 4000 CAL BC. During this period, the site evolves as a freshwater bay-head delta flowing into a huge lagoon isolated from the open sea by Letea-Caraorman spits. The rapid sedimentation rate in the lagoon is interpreted as a response to base-level rise and overflooding as a result of humid conditions during 6-5 ky RCC, leading to the partial submersion of the site and probably to its abandonment around 4450 CAL BC.

This paper aims to localize areas along the Danube where erosion is predominant. It starts with an analysis of previous evaluations of riverbed changes in time, suggesting methods of investigation based on interpreting textural and hydrologic parameters. Making use of grain size analysis performed on 140 sediment samples from the Danube riverbed, the skewness/kurtosis diagram is applied identifying the main points in which erosion or deposition are predominant. Given the lack of data, the method of identifying points where erosion is predominant on the basis of the sediment transport capacity/suspension concentration ratio is only applied for demonstration purposes.

The paper is based on grain size analyses as well as on the macroscopic lithologic description of a large number of samples collected from the bottom of the Danube. Unlike previous papers on sedimentology, which were limited to the textural characterisation of sediments from the various sectors of the Danube, this paper attempts a new approach of the sediment dynamics. The interpretation of histograms, of cumulative curves or of the Passega diagram is used in the attempt to explain the dynamic and genetic reasons for the presence of a particular type of sediment in locations characterised by different environmental energy conditions.

Tuzla Lake emerged in the 70’s as an extension of Techirghiol Lake. The forming of the lake occurred due to human factors (intensive irrigations) and was favoured by natural factors (years of intense pluvial regime). The periodical increase of the Tuzla Lake level produced flooding in the area; the most recent ones (September 2005) significantly affected the buildings and the land around Tuzla Town. In order to evaluate the geo-ecological state of Tuzla Lake, including the impact from the last flooding events on the morphology of the lacustrine basin, the following investigations were performed: bathymetry measurements, sedimentological evaluations, and determination of the physico-chemical, chemical and microbiological parameters of the water. These investigations were performed during 2005 and 2006, and they consisted of the periodical sampling of the water and sediments as well as of bathymetry measurements sensu stricto before and after the 2005 flooding events. The central area of Tuzla Lake has a positive morphological element directed N-S, which divides the basin of the lake in two distinct areas: a western area, maximum 2m deep, and an eastern area, over 1.5m deep. Following the September 2005 floods, a decrease in the depth of the lake by 60-70cm in the southern part of the lake and by 30cm in the northern part occurred. Probably, one of the effects of the flood was the partial clogging of the lake. The lithology of the samples analyzed (mud, silt) indicates that the Tuzla Lake sediments are specific to a lacustrine environment. The aquatic environment is eutrophic (high level of nutrients and reduced oxygen level), an environment suggested by the blackish colour and the oily consistency which is specific to the sapropelic muds. The laboratory analysis results indicate low values for dissolved oxygen, and values significantly above the standards for PO4 2, SO4 2-, as well as high salinity values (30-40 ‰). Therefore, it was concluded that the water in Tuzla Lake is polluted. This observation, along with the fact that there was an excess of lake vegetation that favoured an increase in anophelic habitats, indicates the fact that Tuzla Lake presents a hazard for the human health of the communities in the area.

This paper is based on grain size analyses performed on 250 sediment samples collected with the Van Veen grab from water depths of 0 to 20 meters in the littoral area of the Black Sea situated between Sfântu Gheorghe village and Gura Portiţa. As a result of analyzing the distribution of the types of depth sediments, it has been noted that along the entire length of the area under study littoral sediments consisting of well-sorted sands with skewness levels ranging from –0.41 to 0.60 are to be found between 0 and 7 meters. At water depths between 7 and 20 meters there are frequent sediments consisting of clayey silt, followed by clay, poorly sorted and with skewness values ranging from 0.10 to 0.85. The percentage of sand in the composition ofsediments (closely connected to the average diameter of the particles) decreases in a linear fashion with depth, suggesting a possible direction of transport of the sand particles from the littoral area out towards the open sea. By interpreting the grain size parameters it was noted that sandy sediments tended to move from North to South, East of Sakhalin Island. South of Sakhalin Island it is impossible to estimate in which direction sediment is being transported based on the sizes of the sand grains. This is due to the presence of organogenous particles resulted from shells, whose larger dimensions upset the normal distribution of textural parameters.