Incorporating diatoms species and their autecology from reference stream conditions is essential for improving the accuracy of North American diatom bioassessments. This study documents a voucher flora and physicochemical conditions of Upper Three Runs Creek (UTRC), a tributary to the Savannah River that has been protected from heavy human activity for the last 50 years. The algae of UTRC and its watershed have been monitored continuously during this time by the Academy of Natural Sciences in Philadelphia to detect potential impacts from the Savannah River Site and Plant Vogtle. Standard protocols were used to sample and denote substrate types and preferences and to estimate relative abundances of diatom species. Data from artificial substrates (diatometers) were compared to composite samples. Phenotypic plasticity of taxa from Gomphonema parvulum, Eunotia incisa, and Tabellaria flocculosa sensu lato species complexes were considered in biodiversity metrics. We provide documentation of these separations. A total of 297 species/operational taxonomic units (OTUs) were recorded. For 2018 samples, Eunotia rhomboidea accounted for 8.3% for separated taxa methods and G. parvulum sensu lato (16.2%) dominated for combined taxa methods. Luticola goeppertiana (5.4%) was the most abundant taxon in the 1956 samples. The 1956 composite samples species richness means were greater and significantly greater than those for other sample types (ANOVA, df = 3, p = 0.004). The recounted 1956 composite samples had the highest species richness (153) followed by the left diatometer (129). At the same location, the right and left diatometers were not similar. Both methods (diatometers and composite sampling) are useful when assessing species richness. Diatom community composition indicated an acidic and highly oxygenated environment.

Integrative taxonomy is necessary for advancing the field of phycology and understanding regional algal diversity. Collection-based studies for the purposes of providing descriptive voucher flora of living algal communities inform future long-term monitoring and genetic barcoding studies. In this study, littoral composite samples were taken from eight sites (Center Lake, Emerson Bay, Freda Haffner Kettlehole State Preserve, Millers Bay, East Okoboji Lake, West Okoboji Lake, Big Spirit Lake, Upper Gar Lake) in Dickinson County, Iowa, for the purposes of fine level taxonomy. This region has a history of eutrophication, and algal blooms have caused Iowa water resource issues in the past. Micrography for these voucher floras was conducted for taxa representing at least 10% or more of the total estimated algal biomass of evaluated slides. Our voucher floras comprise micrographs of living cells across nine different algal groups and 54 unique taxonomic entities. Unique taxa from these sites include Glaucocystis nostochinearum Itzigsohn, Draparnaldia acuta (C.Agardh) Kützing, and Chaetophoropsis elegans (Roth) B. Wen Liu, Qian Xiong, X.Dong Liu, Z. Yu Hu & G. Xiang Liu. We also document species belonging to toxin-producing Cyanobacteria genera Mycrocystis and Dolichospermum.

Gomphonema parvulum is a cosmopolitan freshwater diatom that is used as an indicator in water quality biomonitoring. In this study, we report the culturing of two geographically separated isolates from southeastern North America, their morphology, and the sequencing and assembly of their mitochondrial and chloroplast genomes. Morphologically, both strains fit G. parvulum sensu lato, but the frustules from a protected habitat in South Carolina were smaller than those cited in the historic data of this species from the same location as well as a second culture from Virginia. Phylogenetic analyses using the rbcL gene placed both within a clade with G. parvulum. Genetic markers, including full chloroplast and mitochondrial genomes and the nuclear small subunit rRNA gene region were assembled from each isolate. The organellar genomes of the two strains varied slightly in size due to small differences in intergenic regions with chloroplast genomes of 121,035 bp and 121,482 bp and mitochondrial genomes of 34,639 bp and 34,654 bp. The intraspecific pairwise identities of the chloroplast and mitochondrial genomes of these two isolates were 97.9% and 95.4%, respectively. Multigene phylogenetic analysis demonstrated a close relationship between G. parvulum, Gomphoneis minuta, and Didymosphenia geminata.