Trading offspring for survival: high duckweed cover decreases reproductive potential and stimulates elongation in the submerged macrophyte Chara globularis Thuillier

Compact blankets of free-floating plants generate stressful aquatic environments. The response of submerged macrophytes remains largely elusive. Will they rush toward the light or rather speed up reproductive efforts and escape using propagules—the macrophyte equivalent of lifeboats? We studied the effects of complete duckweed (Lemna minor) cover on growth and reproductive fitness of macroalga Chara globularis in a pond mesocosm experiment. C. globularis growing in Lemna-covered plots lost biomass and developed longer internodes, indicating an elongative reflex to escape stress. Densities of reproductive organs per biomass unit evolved positively in open plots and negatively in covered plots, suggesting a trade-off between reproductive effort and vegetative elongation. Reproductive potential correlated significantly with incident radiation. Lemna cover, however, did not affect oospore rain—at least within the limited time span of propagule trapping. C. globularis thus displayed an ability to modify phenology in response to floating plant stress, allocating resources to internodes instead of gametangia. Nevertheless, duckweed dominance clearly suppressed the overall reproductive performance of C. globularis. The regenerative capacity of many submerged macrophytes will likely suffer from increased floating plant dominance due to global warming—unless efforts are made to reduce nutrient levels in vulnerable waterbodies.

Revision of the characeae (Charales, Charophyceae) species and their distribution in Lithuania

The current inventory was mainly based on revising herbarium specimens collected since the 19th century and confirmed twenty-one Characeae species in Lithuania. They are representatives of five genera: Chara (12 species), Nitella (5), Tolypella (2), Lychnothamnus and Nitellopsis (by one species each). Thirteen species mentioned in references or labels of herbarium specimens were not confirmed. The occurrence of the Characeae species was recorded in 251 map grid cells (42% of the total number 593). Herbarium specimens were collected from 693 water bodies, mainly lakes. Chara globularis was the most common species, recorded in 150 map grid cells and more than 250 water bodies. Ten species (C. aspera, C. contraria, C. filiformis, C. subspinosa, C. tomentosa, C. virgata, C. vulgaris, Nitella mucronata, N. flexilis, Nitellopsis obtusa) were recorded in the interval from 100 to 50 grid cells and also belong to the group of common species. Chara papillosa and C. strigosa were recorded less than in 50 grid cells and should be considered quite common. Eight species (C. baltica, C. canescens, Lychnothamnus barbatus, Nitella confervacea, N. gracilis, N. syncarpa, Tolypella nidifica, T. prolifera) were recorded in ten or fewer grid cells and belong to the group of rare or very rare species. The occurrence of species that have not been confirmed by the herbarium specimens was discussed.

Charophytes of Gornje Podunavlje ponds: Revitalization process aspect

Unique marshland area in the Danube floodplain - Special Nature Re?serve Gornje Podunavlje is considered to be one of the last aquatic flora and fauna refuges in the region. The revitalization projects in SNP Gornje Podunavlje started in 2011. They were conducted in order to protect biodiversity and to provide the natural ecosystem. The aim of this study was to investigate and compare the present diversity and distribution of the charophytes in five ponds of SNR Gornje Podunavlje, depending on phases of the revitalization process within the ponds. The researched area includes the following ponds: Semenjaca, Sarkanj, Siroki rit, Sakajtas and Ribolov. The Siroki rit pond was under the process of revitalization during the field surveys, Semenjaca and Sarkanj have already been revitalized, and Ribolov and Sakajtas were not exposed to the revitalization processes at all. The field surveys were conducted monthly, from May to September 2016. Water quality parameters were measured in situ and in laboratory. Ponds differed considerably when it comes to water chemistry; Semenjaca and Sarkanj were associated with highest nutrient concentrations, while Siroki rit was characterized by highest conductivity and water hardness. The highest diversity was found in Siroki rit pond, which was still in process of revitalization when the field survey was conducted. Charophytes were not detected within previously revitalized ponds (Semenjaca and Sarkanj). Eight species of charophytes were detected: Chara contraria, Chara globularis, Chara tenuispina, Chara vulgaris, Nitella confervacea, Nitella gracilis, Nitella syncarpa and Tolypella prolifera.

CHEMICAL CONSTITUENTS AND ANTIOXIDANT PERSPECTIVES OF EXTRACTS OF CHARA GLOBULARIS AND CLADOPHORA SPECIES (STRING ALGAE) SPECIES

Objectives: Marine organisms are capable of producing unusual bioactive compounds that are not observed in terrestrial sources. Algae are now drawing a greater interest following the increase in demand for biodiversity in the screening programs seeking therapeutic drugs from natural products.Methods: Hot acid extraction and cold alkali extraction of Chara globularis and Cladophora species (string algae), respectively, were carried out successfully. The extracted materials were tested for the qualitative reactions and subjected for thin-layer chromatography, ultraviolet, and infrared spectral studies so as to characterize the extracted materials of two algae. They were estimated for their antioxidant perspectives by hydrogen peroxide radical scavenging and reducing power assay methods.Results: Percentage yield of the extracts was found to be 80% and 40%, respectively, for the two algal species. The IC50 value of hydrogen peroxide scavenging activity of C. globularis and Cladophora species was found to be 30 μg/ml and 20 μg/ml, respectively, and the same for the standard ascorbic acid was 20 μg/ml. The results were found to be dose dependent, i.e., higher the concentration, and more was the scavenging activity.Conclusion: Despite the widespread uses and claimed advantages of the algae, only a few investigations on the chemical composition have been reported. A good correlation between the structure and activities of these most popular categories can be brought about.

Significance of current velocity gradients for distribution patterns of charophytes versus mosses and vascular plant communities in a lowland stream

The study focused on the relationships between charophytes and the surrounding species composition and environmental factors in a lowland stream (Flinta stream, Western Poland). A total of 32 vegetation plots (4 m × 4 m) and 13 environmental variables were tested. Detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) were used to describe the relationships between the species composition and the selected variables. Dominance curves of aquatic plants, response curves (GAMs model) of charophytes and other macrophytes to the velocity gradient (the most important environmental factor, the Monte Carlo test) were prepared. In this study, 2 species of charophytes were recorded: Chara vulgaris and Chara globularis and 5 other co-occurring macroscopic algae, 2 mosses and 10 vascular plants. In the studied stream, charophytes occupied the separate niche. Chara vulgaris stands with moss vegetation were found in stream sections with the highest velocity of the water current (0.29 m s-1 mean), and the Chara globularis (with dominant Potamogeton species), preferred sections with the smallest water current velocity (0.19 m s-1 mean).Charophytes seem to respond to ecological gradients differently from mosses and vascular plants. These differences are related to current velocity, pH, conductivity and organic matter in bottom sediments, and to the niche differentiation associated with them.

Lychnothamnus Barbatus (Meyen) Leonh. – Rediscovered In Shalow Lake Šventininkai (Lithuania) After 50 Years

Lychnothamnus barbatus, which in Lithuania occurs northernmost in Europe, was identified in 4 lakes: Balsys, Mažasis Gulbinu, Vygris and Šventininkai. The aim of the paper was to present the recent vegetation, habitat conditions, abundance and co-occurring plant species in shallow Lake Šventininkai. L. barbatus population was rediscovered after 50 years. It was recorded in 1823 and 1960, but it has not been detected later on during scattered investigations until now. Recent vegetation of Lake Šventininkai is a typical of eutrophic lakes with the domination of Ceratophyllum demersum, Elodea canadensis and rarely - L. barbatus. The submerged communities are represented by 7 associations. L. barbatus was distrib­uted at the depth of 1.1-2.1 m. Nitellopsis obtusa, Chara globularis, Chara contraria were the most common, co-occurring species of I. barbatus. Lake Šventininkai is a unique, very shallow (average depth <3 m) lake with re-established L. barbatus population after its total decline in strongly polluted lake waters following the lake’s self-purification. The presented data are important for the restoration of the status of the protected area and management of this territory.

The use of morphometric characteristics in the identification of two morphologically similar charophytes: Chara globularis and Chara virgata

The study reports results of morphometric measurements of two morphologically similar charophytes, Chara globularis Thuill. and Chara virgata Kütz.. Although both species differ in ecological spectra, they can co-occur in the same lakes. Morphological differences given in identification keys can be problematic in the field study. Therefore, additional features were tested and suggested as possibly useful, supplementary differences. 10 individuals of both species growing under similar conditions (littoral of a meromictic, mesotrophic lake, mid-Western Poland) were collected in the vegetation season 2005. Statistical tests evidenced that out of 9 features 6 differed the studied species. Axis diameter, the length of internodes and the length of branchlets revealed the most significant differences. Chara virgata is smaller than Chara globularis even in similar or common habitats. The proposed branchlet length: internode length ratio, higher for Chara virgata than for Chara globularis, can be applied as a useful measure for the species differentiation, particularly under conditions where both charophytes co-occur.

Charophytes (Charophyta) in the Zasavica special nature reserve

Floristic and taxonomic diversity, as well as studies of ecological characteristic of Charophyta algae were carried out within the complex biodiversity researches, in the Zasavica Special Nature Reserve. Nine species were recorded: Chara globularis, C. contraria, C. vulgaris, Nitella mucronata, N. capillaris, N. syncarpa, N. confervacea, Tolypella intricata and T. prolifera. The most common charophyte habitats are shallow, often ephemeral, ponds and puddles in diluvial forests and marshy meadow depressions. Charophytes were also found in riparian areas of water flows, springs and channels, in shallow water (0.1 to 1.2 m), neutral to alkaline (pH 7.4-8.8), and on different substrates (silt, peat, bogland mold).