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Habitat conditions and spring-associated limestones (SALs) formed by ambient precipitation with the biotic contribution of the desmid Oocardium stratum Naegeli 1843 (Zygnematophyceae) were studied in 5 springs along a north-south transect across the central Eastern European Alps. Spring waters were characterized by permanent flow and temporally almost stable physicochemical conditions, but variable relationships among major ions (especially HCO3-:SO42- and Ca2+:Mg2+) among sites. In most cases, CO2 supersaturation (0.2-1.8 mu M/L) caused in situ depression of pH from near equilibrium (8.3) to <8, with a minimum pH of 7.1. SAL areas dominated by Oocardium growth were greatest some distance downstream of the spring origin where degassing of excess CO2 had occurred and pH had risen to >8.1. The calcified segments of spring streams were limited to areas <300 m from the spring mouth. Within the uppermost segment of larger rheocrenes (CO sub(2) supersaturated areas), extensive weakly calcified bryophyte crops (Eucladium verticillatum, were replaced further downstream by 100-1000 mu m) whose ultrastructural features were best seen with SEM. The distribution of SAL types within and among sites was evaluated in relation to water-chemistry and additional environmental variables. The findings were compared with earlier records from the Alps and other mountain areas of Europe (in particular, Croatia and UK) to facilitate recognition and delimitation of

Corbett Tiger Reserve (CTR) is the first and oldest tiger reserve for biodiversity conservation, which is located in the ecologically significant Bhabar-Terai region, foothills of the Himalayas in the Nainital and Pauri district, Uttarakhand, India. However, because of popular wildlife tourism destination and increased tourism in the CTR has caused alterations in habitat structures leading to temporary or permanent habitat loss. During the algal exploration, the specimen was observed on the metamorphic rock of slow running stream from the reserve forest area. Worldwide desmids are known for their extraordinary ornamental structures and indicators of oligotrophic environments. In the present investigation, the epilithic desmid, Oocardium corbettensis sp. nov. has been observed and reported from the Western Himalayan ranges of Corbett Tiger Reserve, India for the first time from India. This unusual, minute desmid is described and assigned to the genus Oocardium and compared with similar species and varieties of the genus Oocardium . This taxon exhibits certain unique features such as undulated rough, thick cell wall with semi-cells semicircular and varied even in cell dimensions from all existing varieties and species of Oocardium . Based on the morphological variations, a new species Oocardium corbettensis sp. nov . was reported and named after Corbett Tiger Reserve, from where this desmid was collected. The physico-chemical analysis of the water body where O. corbettensis sp. nov. was found revealed slightly alkaline conditions, with a pH of 7.7, conductivity (88.57 µS cm –1 ), total dissolved solids (41.87 mg L –1 ), salinity (0.04‰), water temperature (15°C), dissolved oxygen (8.2 mg L –1 ), free CO 2 (17.47 mg L –1 ), calcium (2.3 mg L –1 ), magnesium (2.3 mg L –1 ), total hardness (5.7 mg L –1 ), alkalinity (102 mg L –1 ), potassium (0.55 mg L –1 ), nitrate nitrogen (0.12 mg L –1 ), soluble reactive phosphorous (0.92 mg L –1 ), and ammonium nitrogen (0.18 mg L –1 ). Based on trophic status score of 1.6, the water quality of the study site was clean (oligotrophic status). Thus, Oocardium corbettensis sp. nov. can be considered as an oligotrophic species.

Benthic algae were used to identify reference conditions of springs for bioassessment purposes. Benthic algae and environmental factors were quantified in 70 springs (nonthermal and mostly near-natural) in the southeastern Alps. Spring types were identified by fuzzy clustering of nondiatom, benthic algal assemblages. Canonical Correspondence Analysis (CCA) and indicator species analysis (IndVal) were used to identify the most relevant environmental determinants of taxonomic composition in springs and to characterize the ecological traits of key taxa. A total of 120 macro- and microscopic benthic pro- and eukaryotic algae (excluding diatoms) were identified. Cyanobacteria (especially Chroococcales and Oscillatoriales) were strongly prevalent. Seven spring types were identified by fuzzy clustering of nondiatom, benthic algal assemblages. IndVal identified 22 taxa that were significant indicators of spring type, and fuzzy clustering based on environmental preferences identified 18 other important taxa associated with spring type. Spring types differed in environmental features, species richness, and diversity. Mid-to-high altitude, oligotrophic, carbonate flowing springs (rheocrenes) with medium conductivity were the most common spring type and were characterized by shade-tolerant (Chroococcales) or rheophilic (Tapinothrix varians) cyanobacteria. Low-altitude, shaded, and slightly NO3-N-enriched carbonate rheocrenes with medium-to-high conductivity supported rheophilic or eutraphentic cyanobacteria and red algae. Siliceous rheocrenes had benthic algal assemblages dominated by soft-water, rheophilic cyanobacteria and by the rheobiontic chrysophyte, Hydrurus foetidus. Mostly siliceous seepages and pool springs supported predominantly chlorophytes, especially filamentous Zygnematales. Xerotolerant cyanobacteria were common on carbonate rock-face seepages. Tufa springs were characterized by cyanobacteria and by the desmid, Oocardium stratum. In iron springs, benthic algae (mainly filamentous green algae and xanthophytes) were poorly developed, whereas iron bacteria were common. The most influential factors were pH and conductivity, shading, NO3-N, temperature, current velocity, and substratum particle size. The spring types identified may prove useful as references for assessments of ecological integrity naturalness value, at least for the Alps ecoregion.

Habitat conditions and spring-associated limestones (SALs) formed by ambient precipitation with the biotic contribution of the desmid Oocardium stratum Nägeli 1843 (Zygnematophyceae) were studied in 5 springs along a north–south transect across the central Eastern European Alps. Spring waters were characterized by permanent flow and temporally almost stable physicochemical conditions, but variable relationships among major ions (especially HCO3−:SO42− and Ca2+:Mg2+) among sites. In most cases, CO2 supersaturation (0.2–1.8 µM/L) caused in situ depression of pH from near equilibrium (8.3) to <8, with a minimum pH of 7.1. SAL areas dominated by Oocardium growth were greatest some distance downstream of the spring origin where degassing of excess CO2 had occurred and pH had risen to >8.1. The calcified segments of spring streams were limited to areas <300 m from the spring mouth. Within the uppermost segment of larger rheocrenes (CO2 supersaturated areas), extensive weakly calcified bryophyte crops (Eucladium verticillatum, Palustriella commutata) were replaced further downstream by Oocardium-spiked calcified coatings. The various morphologies of Oocardium cells (assessed with light microscopy [LM], scanning electron microscopy [SEM], and petrographic thin sections) revealed different types of calcification, from micritic (<1–4 µm) to sparitic calcites (>100–1000 µm) whose ultrastructural features were best seen with SEM. The distribution of SAL types within and among sites was evaluated in relation to water-chemistry and additional environmental variables. The findings were compared with earlier records from the Alps and other mountain areas of Europe (in particular, Croatia and UK) to facilitate recognition and delimitation of Oocardium niches in the environment and to foster protection of these rare habitats.