Dust mediated transfer of phosphorus to alpine lake ecosystems of the Wind River Range,Wyoming, USA

Alpine lakes receive a large fraction of their nutrients from atmospheric sources and are consequently sensitive to variations in both the amount and chemistry of atmospheric deposition. In this study we explored the spatial changes in lake water chemistry and biology along a gradient of dust deposition in the Wind River Range, Wyoming. Regional differences were explored using the variation in bulk deposition, lake water, sediment, and bedrock geochemistry and catchment characteristics. Dust deposition rates in the Southwestern region averaged 3.34 g m^?2 year^?1, approximately three times higher than deposition rates in the Northwestern region (average 1.06 g m^?2 year^?1). Dust-P deposition rates ranged from 87 µg P m² day^?1 in the Northwestern region to 276 µg P m² day^?1 in the Southwestern region. Subalpine and alpine lakes in the Southwestern region had greater total phosphorus (TP) concentrations (5–13 µg L^?1) and greater sediment phosphorus (SP) concentrations (2–5 mg g^?1) than similar lakes elsewhere in the region (1–8 µg L^?1 TP, 0.5–2 mg g^?1 SP). Lake phosphorus concentrations were related to dissolved organic carbon (DOC) across vegetation gradients, but related to the percent of bare rock, catchment area to lake area, and catchment steepness across dust deposition gradients. Modern phytoplankton and zooplankton biomasses were two orders of magnitude greater in the Southwest than in the Northwest, and alpine lakes in the Southwest had a unique diatom species assemblage with relatively higher concentrations of Asterionella formosa, Pseudostaurosira pseudoconstruens, and Pseudostaurosira brevistriata. These results suggests that catchment controls on P export to lakes (i.e. DOC) are overridden in dominantly bare rock basins where poor soils cannot effectively retain dust deposited P.     

Gogorevia,a New Monoraphid Diatom Genus for Achnanthes exigua and Allied Taxa (Achnanthidiaceae) Described on the Basis of an Integrated Molecular and Morphological Approach

A new diatom genus, Gogorevia, is described on the basis of an integrated molecular and morphological investigation. Two species are described from Vietnam: the generitype, G. rinatii sp. nov., and G. ovalis sp. nov. These species share many morphological features with Achnanthes exigua and allied taxa that were previously transferred to the genera Achnanthidium or Lemnicola. Our current molecular investigation shows that Gogorevia is distinct and phylogenetically removed from the above-mentioned genera. Morphologically, Gogorevia differs from Achnanthidium and Lemnicola by the shape of the valves, possessing uniseriate striae, raphe morphology, and the presence of an evident sternum. The recently described species Lemnicola uniseriata is transferred to Gogorevia on the basis that it possesses the same morphological features and phylogenetic position as other members of the genus.     

Description of a new diatom genus Dorofeyukea gen. nov. with remarks on phylogeny of the family Stauroneidaceae

Type material of Navicula kotschyi was studied, and this species was transferred to Dorofeyukea gen. nov. as D. kotschyi comb. nov. Dorofeyukea was described on the basis of DNA sequence and morphological data. Additional species assigned to this genus that were previously included in Navicula include: D. ancisa comb. nov., D. grimmei comb. nov., D. ivatoensis comb. nov., D. orangiana comb. nov., D. rostellata comb. nov. & stat. nov., D. savannahiana comb. nov., D. tenuipunctata comb. nov., and D. texana comb. nov. All Dorofeyukea species share the same morphological features, including having a narrow stauroid fascia surrounded by 1–3 irregularly shortened striae, uniseriate, and weakly radiate striae, circular, or rectangular puncta in the striae that are covered internally by dome‐shaped hymenes, presence of a pseudoseptum at each apex and absence of septa. Partial DNA sequences of SSU and rbcL loci show Dorofeuykae belongs to the clade of stauroneioid diatoms together with Stauroneis, Prestauroneis, Craticula, Karayevia, Madinithidium, Fistulifera, Parlibellus, and, possibly, Schizostauron. A new species from the monoraphid genus Madinithidium, M. vietnamica sp. nov., was described based on valve and chloroplast morphology as well as DNA sequence data.     

Molecular phylogeny of the diatom genera Amphora and Halamphora (Bacillariophyta) with a focus on morphological and ecological evolution

The taxonomic history of the diatom genus Amphora is one of a broad early morphological concept resulting in the inclusion of a diversity of taxa, followed by an extended period of revision and refinement. The introduction of molecular systematics has increased the pace of revision and has largely resolved the relationships between the major lineages, indicating homoplasy in the evolution of amphoroid symmetry. Within the two largest monophyletic lineages, the genus Halamphora and the now taxonomically refined genus Amphora, the intrageneric morphological and ecological relationships have yet to be explored within a phylogenetic framework. Critical among this is whether the range of morphological features exhibited within these diverse genera are reflective of evolutionary groupings or, as with many previously studied amphoroid features, are nonhomologous when examined phylogenetically. Presented here is a four‐marker molecular phylogeny that includes 31 taxa from the genus Amphora and 77 taxa from the genus Halamphora collected from fresh, brackish, and salt waters from coastal and inland habitats of the United States and Japan. These phylogenies illustrate complex patterns in the evolution of frustule morphology and ecology within the genera and the implications of this on the taxonomy, classification, and organization of the genera are discussed.     

A new species of Achnanthes (Bacillariophyceae) from a freshwater habitat in a karst landform from south‐central China

Achnanthes maolanensis nov. sp. is a large diatom collected from subaerial, freshwater habitats in karst landforms in central‐south China. Living cells have two chloroplasts. Valves of this new species are panduriform in outline, slightly constricted in the middle part of the margins, with uniseriate areolae; the raphe is filiform, and there is a linear, thickened stauros in the central area of the RV. On the ARV, there is no central area, and as well there are no terminal orbiculi, marginal ridge, or terminal spine externally. The axial area (rapheless sternum) is located down the center, not offset from the center as in many other species of the genus and is narrow and almost straight. This suite of characters makes the new species easy to distinguish from other species in the genus. Its presence adds further documentation of the unique and diverse freshwater diatom flora from karst habitats in this region of China.