Pinnularia

Abstract: A review is presented of 28 studies in the literature of diatoms in environments at pH ≤35, including natural and anthropogenic acid sources A total of 124 diatom taxa have been reported, but many are likely to have been accidental occurrences, because only a few specimens were found Approximately 19 taxa abundant in at least one study or common in several studies are considered true inhabitants of highly acidic waters These include: Achnanthes minutissima, Eunotia exigua, E tenella, E septentrionalis, E osoresanensis, E arcus, E glacialis, E pectinalis, Frustulia rhomboides, F rhomboides var saxonica, Nitzschia capitellata/subcapitellata, Nitzschia communis, Nitzschia pusilla, Nitzschia vasta, Pinnularia acoricola, P obscura, P braunii var amphicephala, P subcapitata and P terminitina There are inconsistencies in the taxonomy of several of these species and possible synonymies could lower the number of taxa to less than 9 Compared to diatom species richness in environments at pH 45–50, there are many fewer taxa in environments ≤ pH 35, suggesting a threshold between pH 45 and 35 below which many species are unable to maintain a population

Abstract: Diatom floras were examined from geothermal environments in three contrasting tectonic settings. These included subduction-related acid and alkaline springs in New Zealand; alkaline springs along a divergent plate boundary on Iceland; and alkaline springs in the Kenya Rift. These shallow (<1 cm) aquatic environments vary considerably (e.g., temperature: 21.3–99°C; pH: 2.1–9.65; 56.41–643 mg l−1 SiO2). Diatoms form an important component of geothermal floras at temperatures of <45°C. The floras from New Zealand are distinguished by the common occurrence of Pinnularia. Icelandic springs have a variety of Fragilariaceae. Navicula and Anomoeoneis are most common in the Kenyan springs. Statistical analyses suggest that the diatoms cluster into seven major groups. The most common taxa include: Achnanthidium exiguum v. heterovalvum (Kras.) Czarn., Anomoeoneis sphaerophora (Ehrenb.) Pfitz, Brachysira brebissonii f. thermalis Grun., Caloneis bacillum (Grun.) Cl., Craticula cuspidata (Kutz.) Mann, Diadesmis confervacea Kutz., Epithemia argus (Ehrenb.) Kutz., Frustulia rhomboides (Ehrenb.) DeT., Hantzschia amphioxys (Ehrenb.) Grun., Navicula tenelloides Hust., Nitzschia amphibia Grun., Nitzschia inconspicua Grun., Nitzschia invisitata Hust., Nitzschia frustulum (Kutz.) Grun., Nitzschia sigma (Kutz.) W, Smith., Pinnularia chapmaniana Fog., Pinnularia appendiculata (Ag.) Cl., Pinnularia molaris (Grun.) Cl., Pinnularia acoricola Hust., Rhopalodia gibberula (Ehrenb.) O. Mull., Staurosira construens v. venter (Ehrenb.) Ham., Staurosira elliptica (Schum.) Will. & Round, and Staurosirella pinnata (Ehrenb.) Will. & Round. Canonical correspondence analysis shows clear correlations between species, alkalinity, pH, and conductivity, with less strong correlations for silica and temperature. Other factors include substrate type, current velocity, and light conditions. The preservation potential of host deposits varies considerably, being lowest for springs on clastic deltas and highest where travertine or sinter is accumulating.

Abstract: High-resolution LM images of diatoms from remote regions of western Canada are presented as a contribution to our knowledge of diatom floristics, ecology and biogeography in North America. Approximately 600 taxa are imaged in 132 plates. Genera with the most taxa are Cymbella (19 taxa), Cymbopleura (29), Encyonema (23), Encyonopsis (15), Eunotia (77), Gomphonema (42), Navicula (47), Neidium (20), Nitzschia (35), Pinnularia (50) and Stauroneis (34). Diatoms were collected from diverse habitats in four of North America's major biomes: Arctic tundra, taiga, Rocky Mountains and Pacific rainforest. Many of the photographed taxa could not be identified to species and are likely new to science. Other taxa may represent new records for North America or Canada. Images of voucher specimens are keyed to individual collection sites. Detailed descriptions of the collection sites include GPS coordinates, colour photographs, vegetation, algal substrates, elevations, pH, temperature and conductivity. Samples were collected from natural substrates in fresh to brackish, flowing and standing waters. Voucher slides are deposited in the Montana Diatom Collection (Helena) and the University of Montana Herbarium (Missoula). Cleaned diatom frustules have been deposited in the Diatom Herbarium of the Academy of Natural Sciences of Philadelphia.

Abstract: During the ongoing revision of the non-marine diatom flora of Livingston Island (South Shetland Islands, Maritime Antarctic Region) the taxonomy and morphology of all Pinnularia taxa, excluding the section Distantes , present in the samples from Livingston Island, have been analysed. Seventeen different Pinnularia taxa have been recorded. Apart from those previously described from the Antarctic Region ( P. subcapitata var. elongata , P. gemella , P. austroshetlandica ) and the Andes ( P. strictissima ), thirteen unknown taxa have been found. Based on their unique morphological features, twelve are described as new in this paper: P. australodivergens sp. nov., P. australoglobiceps sp. nov., P. australomicrostauron sp. nov., P. australoschoenfelderi sp. nov., P. hamiltonii sp. nov., P. livingstonensis sp. nov., P. magnifica sp. nov., P. microstauroides sp. nov., P. pseudolaucensis sp. nov., P. sergiplaiana sp. nov., P. subcarteri sp. nov. and P. subaltiplanensis sp. nov. For one, only a few specimens have been found and at present they cannot be identified with 100% certainty.