Diatom Community Composition from Low Human Impact Areas in Southeast U.S.

Algal assemblages were evaluated at two Southeastern U.S. streams with reduced human impact, Upper Three Runs Creek and Tobbler Creek. The two sites were collected using standard protocols for stream samplings. The algal community was dominated by diatoms. Community attributes were found to be similar between the two sites, while indicator species varied as determined by Trophic Diatom Index values and the percentage of tolerant taxa to pollutants. Low pH tolerant Eunotia species were dominant in Upper Three Runs Creek while pH neutral, mesotrophic species were dominant in Tobbler Creek. This is the first report on primary producers from both sites and a taxonomic evaluation of the more common taxa is given for future reference

Algal community membership of estuarine mudflats from the Savannah River, United States

Algae represent a large and diverse group of photosynthetic organisms inhabiting all aquatic habitats. Although the traditional assessment of algal diversity relies mainly on microscopy-based morphological identification, certain limitations exist. In this study, we present a combined molecular and morphological assessment of algal diversity in mudflats from the Savannah River Estuary, Georgia. High diversity of diatoms was documented, and less than 20% of the algal community was physiologically active at the time of collection. From the total genomic DNA extracted from the field samples and lab isolates, 18S rDNA sequences were PCR amplified, cloned, sequenced, identified, and then compared to the taxa identified via microscopy. Only a few of the DNA sequences matched documented taxa, and the abundance of particular algal species was limited to morphological analysis. Surprisingly, upon examination of the remaining lysis buffer from the mechanical lysis step of algal cells, diatom species were left intact even in the presence of a detergent indicating that the diatom species resistant to lysis could be easily underrepresented. Generation of additional algal sequences data, tied to accurate taxonomic identification, is essential to current environmental sequencing projects and potentially would allow faster acquisition of algal community structure within these unique environments

Highest composition dissimilarity among phytoplankton communities at intermediate environmental distances across high-altitude tropical lakes

Tropical high-altitude lakes are vital freshwater ecosystems for the functioning and dynamics of tropical high-altitude wetlands called páramos, found at over 3300 m above sea level. They play a major role in the hydrogeological cycle and provide important hydrological services such as water storage, and yet they are understudied. Describing the patterns and processes of community composition in these lakes is required to better understand the consequences of their degradation by human activities. In this study we tested the geographical and environmental components of distance–decay relationships in the phytoplankton structure across 24 tropical high-altitude lakes from Southern Ecuador. Phytoplankton composition at the phyla level showed high among-lake variation in the tropical high-altitude lakes from Tres Lagunas. We found no links, however, between the geographic distance and phytoplankton composition. On the contrary, we observed some environmentally related patterns of community structure like redox potential, altitude, water temperature, and total phosphorus. The absence of support for the distance–decay relationship observed here can result from a conjunction of local niche-based effects and dispersal limitations. Phytoplankton community composition in the Tres Lagunas system or any other ecosystem may be jointly regulated by niche-based and neutral forces that still need to be explored. Despite not proving a mechanistic explanation for the observed patterns of community structure, we hope our findings provide understanding of these vulnerable and vital ecosystems. More studies in tropical high-altitude lakes are urgently required

The chloroplast and mitochondrial genomes of the green algae Pediastrum duplex isolated from Central Georgia (USA)

A Pediastrum duplex (Chlorophyta) strain was isolated from a freshwater system in Milledgeville, Georgia and its chloroplast and mitochondrial genomes sequenced. The chloroplast genome was 199,241 bp with 136 genes and the mitochondrial 40,756 bp with 40 genes, both were circular. Comparison of the ‘Milledgeville’ plastome to other P. duplex isolates revealed a nearly identical sequence identity to archived genes and genomic fragments from the strain UTEX1364 which was isolated from Lake Machovo in 1962. These sequences provide chloroplast and mitochondrial genomes from a wild P. duplex isolate and provide more organelle genomes for a genus with cryptic phylogenetic relationships

Characterization of algal community composition and structure from the nearshore environment, Lake Tahoe (United States)

Periphyton assemblages from the nearshore environment of the west (California) side of Lake Tahoe, were analyzed to determine their taxonomic composition and community structure across habitats and seasons. Lake Tahoe is the second deepest lake in the US and an iconic oligotrophic subalpine lake with remarkable transparency. It has experienced offshore cultural eutrophication since the 1960s with observations of nuisance nearshore algal growth since the mid 2000s attributed to anthropogenic stressors. Samplings from November 2019–September 2020 provide useful snapshots against which older monitoring may be contextualized. A voucher flora, complete with descriptions, photo-documentation and referencing to species concepts employed, was created as a method of providing reproducible identification and enumeration of algal species, and more seamless reconciliation of detailed taxonomic data with future monitoring projects. The eulittoral zone (0–2 m) is seasonally dominated by elongate araphid (Synedra, Ulnaria) and stalked or entubed diatoms (Gomphonema, Cymbella, Encyonema). The sublittoral zone (>2 m) is dominated by a nitrogen-fixing Epithemia-cyanobacteria assemblage with less seasonal changes in dominance and composition that expanded to impinge on the 2 m depths of the eulittoral zone in the Fall. Sublittoral epipsammic samples, despite their proximity to rocks, had a very distinct diatom composition and high species dominance, similar to what was seen in the Fall eulittoral samples, with high numbers of Staurosirella chains and small biraphid diatoms. The deeper samples at 30 and 50 m contained high numbers of live Epithemia, and indicate a thriving sublittoral assemblage at these greater depths, but with less biomass. The 2019–20 data show many of the same diatom taxa observed in the 1970’s and 1980’s but with changes in species dominance. Notably, there was less of the green alga Mougeotia, when compared to the 1970’s data, and a higher dominance by nitrogen fixing Epithemia in the sublittoral zone, persisting year-round. These new data show roughly double the algal species biodiversity that had been documented previously in the Lake Tahoe nearshore, and is largely attributed to the methods employed. Adopting these new methods in future monitoring efforts should improve harmonization of taxonomic data and help advance our knowledge of the contributions to nearshore cultural eutrophication.Fil: Noble, Paula J.. University Of Nevada; Estados UnidosFil: Seitz, Carina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Lee, Sylvia S.. No especifíca;Fil: Manoylov, Kalina M.. No especifíca;Fil: Chandra, Sudeep. University Of Nevada; Estados Unido

Morphotype variations in subfossil diatom species of Aulacoseira in 24 Michigan Lakes, USA

Diatom assemblages preserved in lake sediment records can provide proxy data of past environmental changes in biological conditions. In order to investigate past changes in the environment of north-central Michigan, diatom assemblages were studied in sediment cores retrieved from 24 lakes. Diatoms were analyzed from the \u27top\u27 and \u27bottom\u27 of each core to reconstruct land-use changes in this area. Aulacoseira taxa were identified and evaluated with light and scanning electron microscopy. Results of these observations showed the presence of some variability of the morphological features within North American species populations. Diatom species composition in surface sediments and differences between tops and bottoms corresponded to changes in land use surrounding the lakes, ranging from predominantly forest and rangeland to urban and agriculturally impacted. Diatom-inferred past conditions revealed that the observed morphotypes probably represent taxa with different ecological preferences. The main factors influencing the variability of these morphotypes are changes in the trophic status of the lakes

Diatom milking? A review and new approaches

The rise of human populations and the growth of cities contribute to the depletion of natural resources, increase their cost, and create potential climatic changes. To overcome difficulties in supplying populations and reducing the resource cost, a search for alternative pharmaceutical, nanotechnology, and energy sources has begun. Among the alternative sources, microalgae are the most promising because they use carbon dioxide (CO2) to produce biomass and/or valuable compounds. Once produced, the biomass is ordinarily harvested and processed (downstream program). Drying, grinding, and extraction steps are destructive to the microalgal biomass that then needs to be renewed. The extraction and purification processes generate organic wastes and require substantial energy inputs. Altogether, it is urgent to develop alternative downstream processes. Among the possibilities, milking invokes the concept that the extraction should not kill the algal cells. Therefore, it does not require growing the algae anew. In this review, we discuss research on milking of diatoms. The main themes are (a) development of alternative methods to extract and harvest high added value compounds; (b) design of photobioreactors; (c) biodiversity and (d) stress physiology, illustrated with original results dealing with oleaginous diatoms

Characterization of algal community composition and structure from the nearshore environment, Lake Tahoe (United States)

Periphyton assemblages from the nearshore environment of the west (California) side of Lake Tahoe, were analyzed to determine their taxonomic composition and community structure across habitats and seasons. Lake Tahoe is the second deepest lake in the US and an iconic oligotrophic subalpine lake with remarkable transparency. It has experienced offshore cultural eutrophication since the 1960s with observations of nuisance nearshore algal growth since the mid 2000s attributed to anthropogenic stressors. Samplings from November 2019–September 2020 provide useful snapshots against which older monitoring may be contextualized. A voucher flora, complete with descriptions, photo-documentation and referencing to species concepts employed, was created as a method of providing reproducible identification and enumeration of algal species, and more seamless reconciliation of detailed taxonomic data with future monitoring projects. The eulittoral zone (0–2 m) is seasonally dominated by elongate araphid (Synedra, Ulnaria) and stalked or entubed diatoms (Gomphonema, Cymbella, Encyonema). The sublittoral zone (>2 m) is dominated by a nitrogen-fixing Epithemia-cyanobacteria assemblage with less seasonal changes in dominance and composition that expanded to impinge on the 2 m depths of the eulittoral zone in the Fall. Sublittoral epipsammic samples, despite their proximity to rocks, had a very distinct diatom composition and high species dominance, similar to what was seen in the Fall eulittoral samples, with high numbers of Staurosirella chains and small biraphid diatoms. The deeper samples at 30 and 50 m contained high numbers of live Epithemia, and indicate a thriving sublittoral assemblage at these greater depths, but with less biomass. The 2019–20 data show many of the same diatom taxa observed in the 1970’s and 1980’s but with changes in species dominance. Notably, there was less of the green alga Mougeotia, when compared to the 1970’s data, and a higher dominance by nitrogen fixing Epithemia in the sublittoral zone, persisting year-round. These new data show roughly double the algal species biodiversity that had been documented previously in the Lake Tahoe nearshore, and is largely attributed to the methods employed. Adopting these new methods in future monitoring efforts should improve harmonization of taxonomic data and help advance our knowledge of the contributions to nearshore cultural eutrophication

Taxonomic identification of algae (morphological and molecular): species concepts, methodologies, and their implications for ecological bioassessment

Algal taxonomy is a key discipline in phycology and is critical for algal genetics, physiology, ecology, applied phycology, and particularly bioassessment. Taxonomic identification is the most common analysis and hypothesis-testing endeavor in science. Errors of identification are often related to the inherent problem of small organisms with morphologies that are difficult to distinguish without research-grade microscopes and taxonomic expertise in phycology. Proposed molecular approaches for taxonomic identification from environmental samples promise rapid, potentially inexpensive, and more thorough culture-independent identification of all algal species present in a sample of interest. Molecular identification has been used in biodiversity and conservation, but it also has great potential for applications in bioassessment. Comparisons of morphological and molecular identification of benthic algal communities are improved by the identification of more taxa; however, automated identification technology does not allow for the simultaneous analysis of thousands of samples. Currently, morphological identification is used to verify molecular taxonomic identities, but with the increased number of taxa verified in algal gene libraries, molecular identification will become a universal tool in biological studies. Thus, in this report, successful application of molecular techniques related to algal bioassessment is discussed

On some \u3ci\u3ePsammothidium\u3c/i\u3e species from rivers in the United States

Psammothidium species have wide distribution in the US, co-occur on sandy habitats, and overlap in morphology. Samples from rivers and streams were collected as part of the NAWQA program (U.S. Geological Survey). The following species were included in this study: Psammothidium bioretii (Germain) Bukhtiyarova et Round, P. chlidanos (Hohn et Hellerman) Lange-Bertalot, P. grischunum f. daonensis (Lange-Bertalot) Bukhtiyarova et Round, P. helveticum (Hustedt) Bukhtiyarova et Round, and P. subatomoides (Hustedt) Bukhtiyarova et Round. Several morphological characteristics of the valves are outlined. These features are visible with light microscopy (LM) and should be used in routine microscopic identification