Spatio-temporal insights into microbiology of the freshwater-to-hypersaline, oxic-hypoxic-euxinic waters of Ursu Lake

Ursu Lake is located in the Middle Miocene salt deposit of Central Romania. It is stratified, and the water column has three distinct water masses: an upper freshwater-to-moderately saline stratum (0–3 m), an intermediate stratum exhibiting a steep halocline (3–3.5 m), and a lower hypersaline stratum (4 m and below) that is euxinic (i.e. anoxic and sulphidic). Recent studies have characterized the lake's microbial taxonomy and given rise to intriguing ecological questions. Here, we explore whether the communities are dynamic or stable in relation to taxonomic composition, geochemistry, biophysics, and ecophysiological functions during the annual cycle. We found: (i) seasonally fluctuating, light-dependent communities in the upper layer (≥0.987–0.990 water-activity), a stable but phylogenetically diverse population of heterotrophs in the hypersaline stratum (water activities down to 0.762) and a persistent plate of green sulphur bacteria that connects these two (0.958–0.956 water activity) at 3–3.5 to 4 m; (ii) communities that might be involved in carbon- and sulphur-cycling between and within the lake's three main water masses; (iii) uncultured lineages including Acetothermia (OP1), Cloacimonetes (WWE1), Marinimicrobia (SAR406), Omnitrophicaeota (OP3), Parcubacteria (OD1) and other Candidate Phyla Radiation bacteria, and SR1 in the hypersaline stratum (likely involved in the anaerobic steps of carbon- and sulphur-cycling); and (iv) that species richness and habitat stability are associated with high redox-potentials. Ursu Lake has a unique and complex ecology, at the same time exhibiting dynamic fluctuations and stability, and can be used as a modern analogue for ancient euxinic water bodies and comparator system for other stratified hypersaline systems

Present status of water mite species (Acari, Hydrachnidia) described by Motaş, Tanasachi and Orghidan from Romania

The present paper investigates the validity of the water mite species (Acari, Hydrachnidia) described from Romania by Motaş, Tanasachi and Orghidan. The Romanian researchers from the “Emil Racoviţă” Speleology Institute, Romanian Academy, Bucharest, had a prolific activity between 1939 and 1963: among the taxa new to science described by these authors, 34 species and 3 subspecies had their type localities in Romania. More than 50 years later, 23 species and one subspecie described by the team coordinated by Motaş are still valid. 17 of these taxa were found all over Europe, while 7 were not recorded outside Romania until present day.W niniejszym artykule zbadano aktualność gatunków wodopójek (Acari, Hydrachnidia) opisanych z terenu Rumunii przez Motaşa, Tanasachi i Orghidana. Główna aktywność rumuńskich badaczy z Instytutu Speleologii "Emil Racoviţă", Akademii Rumuńskiej w Bukareszcie, przypadała na lata 1939-1963. Spośród nowych gatunków opisywanych przez tych autorów locus typicus 34 gatunków i 3 podgatunków znajdowały się na terenie Rumunii. Ponad 50 lat później, 23 gatunki i jeden podgatunek opisane przez zespół prowadzony przez Motaş są nadal aktualne. 17 z tych taksonów odnotowano na terenie całej Europy, a 7 innych do dnia dzisiejszego stwierdzonych jest jedynie na terenie Rumunii

Same karstic substratum, different aquatic communities? Case study: three water bodies from western Romania

We investigated the phytoplankton, periphyton and microcrustacean communities developing on similar limestone substratum, in three karstic lakes: Iezerul Ighiel (Alba County), Dracului and Ochiul Beiului (Caraș-Severin County), during 2014 and 2016. Species richness was significantly higher in the lake greater in size for both algae and microcrustaceans, consistent with the species-area hypothesis. Forty algal taxa and only one microcrustacean species were common in all three lakes, even if comparable physico-chemical characteristics were recorded. Relatively similar saprobic conditions were shown by indicator species, while trophic state differed at some extent. Since current factors existing in the three environments were relatively similar (limestone substratum, physico-chemical parameters, water source etc.), the dissimilarities found in the plankton and periphytic communities were best explained by long-term factors like geographical isolation or the strength of disturbances. Ciorca et al (PDF

Contributions to the knowledge of amphipod fauna (Crustacea, Amphipoda) from the Danube Delta, Romania

The amphipod species Pontogammarus maeoticus (Sovinskij, 1894) was identified in two locations from the Danube Delta, Romania (Sfântu Gheorghe and Sulina beaches) in July 2019. This is an eurybiont species, able to withstand high salinity variations characteristic to mixing fresh and sea waters. The individuals presented a special character in their morphology, a depression on the basis of pereiopod V.  The present paper contributes to the knowledge of existing amphipod fauna from the Danube Delta, in the Black Sea coast area. Purcari et al sc (PDF) Article history: Received 8 April 2020; Revised 7 December 2020; Accepted 10 December 2020; Available online 20 December 2020

Multiple impact assessment and water quality based on diatom, benthic invertebrate and fish communities in the Arieș River catchment area (Transylvania, Romania)

The present paper represents an assessment of human impacts affecting the Arieș River catchment area, a region heavily affected by the mining  industry documented in the middle river course (Roșia Montană, Abrud, Roșia Poieni) since the Roman period. Other important impacts in the study area were: eutrophication / organic pollution due to discharges of untreated domestic wastes of villages and towns from the region; river regularization works, wood exploitation and processing facilities and industrial wastes downstream Turda and Câmpia Turzii localities. Water quality evaluation was carried out using river biotic communities recommended by the European legislation (Water Framework Directive, WFD): diatoms, benthic invertebrates and fish. Twenty-three sampling sites were considered along the Arieș River main course and its main tributaries, and standardized methods were employed for sampling and processing of biological data. Benthic invertebrates prooved to be the most sensitive community, indicating disturbed ecological status downstream the mining-affected region mainly due to high contamination of river sediments. While ichthyofauna responses were moderate (with water quality classes usually ranging from high to moderate), diatoms reflected better the effects of eutrophication / organic pollution caused by human settlements. Battes et al 2018 (PDF

Flash-Floods Influence Macroinvertebrate Communities Distribution in Lotic Ecosystems

Stream dwelling invertebrate populations are facing an ample array of stressors including the habitat imbalance caused by important floods. In this research we used a novel way to estimate the impact of floods upon the substrate, by utilising a remote variable named “flash-flood potential” (FFP), which accounts for the site slope and the average slope of the upstream catchment. The results showed that certain groups are sensitive to the influence of the FFP whereas other are not. We propose this remote variable as a surrogate for assessing stress imposed by floods and sediment scouring for lotic macroinvertebrates

Spatio-temporal insights into microbiology of the freshwater-to-hypersaline, oxic-hypoxic-euxinic waters of Ursu Lake

Ursu Lake is located in the Middle Miocene salt deposit of Central Romania. It is stratified, and the water column has three distinct water masses: an upper freshwater-to-moderately saline stratum (0–3 m), an intermediate stratum exhibiting a steep halocline (3–3.5 m), and a lower hypersaline stratum (4 m and below) that is euxinic (i.e. anoxic and sulphidic). Recent studies have characterized the lake's microbial taxonomy and given rise to intriguing ecological questions. Here, we explore whether the communities are dynamic or stable in relation to taxonomic composition, geochemistry, biophysics, and ecophysiological functions during the annual cycle. We found: (i) seasonally fluctuating, light-dependent communities in the upper layer (≥0.987–0.990 water-activity), a stable but phylogenetically diverse population of heterotrophs in the hypersaline stratum (water activities down to 0.762) and a persistent plate of green sulphur bacteria that connects these two (0.958–0.956 water activity) at 3–3.5 to 4 m; (ii) communities that might be involved in carbon- and sulphur-cycling between and within the lake's three main water masses; (iii) uncultured lineages including Acetothermia (OP1), Cloacimonetes (WWE1), Marinimicrobia (SAR406), Omnitrophicaeota (OP3), Parcubacteria (OD1) and other Candidate Phyla Radiation bacteria, and SR1 in the hypersaline stratum (likely involved in the anaerobic steps of carbon- and sulphur-cycling); and (iv) that species richness and habitat stability are associated with high redox-potentials. Ursu Lake has a unique and complex ecology, at the same time exhibiting dynamic fluctuations and stability, and can be used as a modern analogue for ancient euxinic water bodies and comparator system for other stratified hypersaline systems

Introducing Spatial Variation to Ecological Risk Assessment

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