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1
Bradbury, J. P., and W. N. Krebs. "Fossil Continental Diatoms: Paleolimnology, Evolution, and Biochronology." Short Courses in Paleontology 8 (1995): 119–38. http://dx.doi.org/10.1017/s2475263000001458.
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Diatoms are golden brown algae (class Bacillariophyceae) whose cellular contents are enclosed between two valves or shells of silica. They are classified into groups with radial symmetry (centric diatoms) and axial symmetry (pennate diatoms). The latter are subdivided as raphid and araphid diatoms according to the presence or absence of raphes (slit-like structures) that allow diatoms to move along firm surfaces. Many centric and some araphid diatoms are planktonic, maintained by turbulence in the limnetic region of a lake, whereas raphid diatoms live on the lake bottom or are attached to objects in the illuminated zone.
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Sato, Shinya, and Linda K. Medlin. "MOTILITY OF NON-RAPHID DIATOMS." Diatom Research 21, no. 2 (2006): 473–77. http://dx.doi.org/10.1080/0269249x.2006.9705686.
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Harwood, David M., Vladimir A. Nikolaev, and Diane M. Winter. "Cretaceous Records of Diatom Evolution, Radiation, and Expansion." Paleontological Society Papers 13 (October 2007): 33–59. http://dx.doi.org/10.1017/s1089332600001455.
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New information and discussions regarding Mesozoic diatoms presented over the last decade advanced our knowledge of their origin and early history. The oldest confirmed centric diatom fossils are presented here from the earliest Cretaceous, and araphid and raphid pennate diatoms now date from the Late Cretaceous; all from terrestrial sediments. Molecular sequencing helped clarify relationships between diatom lineages, and verify the position of diatoms within the heterokontophytes. Molecular clock approaches estimate a diatom origin near ~135 Ma, but not before 240 Ma. Biomarkers in marine sediments are able to trace a diatom presence back to the mid-Cretaceous, even when siliceous fossils are absent. Seasonal growth and encystment cycles in Late Cretaceous planktonic marine diatoms are now well documented. A biostratigraphic framework for the Late Cretaceous Arctic will aid regional and global biostratigraphic correlations. The systematic position of many new taxonomic groups is now included within a more natural classification scheme that better reflects phylogenetic relationships evident in molecular data and affirmed by biostratigraphic micropaleontology. Discussions regarding the impact of diatoms on several global systems are maturing, as more information becomes available. Four stages in diatom evolution are proposed to explain the history of radiation, extinction, and expansion into new environments and habitats during the Mesozoic.
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Klapper, Franziska, Sien Audoor, Wim Vyverman, and Georg Pohnert. "Pheromone Mediated Sexual Reproduction of Pennate Diatom Cylindrotheca closterium." Journal of Chemical Ecology 47, no. 6 (2021): 504–12. http://dx.doi.org/10.1007/s10886-021-01277-8.
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AbstractBenthic diatoms dominate primary production in marine subtidal and intertidal environments. Their extraordinary species diversity and ecological success is thought to be linked with their predominantly heterothallic sexual reproduction. Little is known about pheromone involvement during mating of pennate diatoms. Here we describe pheromone guided mating in the coastal raphid diatom Cylindrotheca closterium. We show that the two mating types (mt+ and mt−) have distinct functions. Similar to other benthic diatoms, mt+ cells are searching for the mt− cells to pair. To enhance mating efficiency mt− exudes an attraction pheromone which we proved by establishing a novel capillary assay. Further, two more pheromones produced by mt− promote the sexual events. One arrests the cell cycle progression of mt+ while the other induces gametogenesis of mt+. We suggest that C. closterium shares a functionally similar pheromone system with other pennate diatoms like Seminavis robusta and Pseudostaurosira trainorii which synchronize sexual events and mate attraction. Remarkably, we found no evidence of mt+ producing pheromones, which differentiates C. closterium from other pennates and suggests a less complex pheromone system in C. closterium.
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Siver, Peter A., and Alexander P. Wolfe. "Eunotia spp. (Bacillariophyceae) from Middle Eocene lake sediments and comments on the origin of the diatom raphe." Canadian Journal of Botany 85, no. 1 (2007): 83–90. http://dx.doi.org/10.1139/b06-143.
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Freshwater diatoms belonging to the genus Eunotia Ehrenberg 1837 are well preserved in Middle Eocene lake sediments from the Northwest Territories, Canada. Although two distinct valve morphologies are recognized, both have features that are entirely compatible with modern congeneric taxa, including dorsiventral valve morphology, striae spanning the valve face and extending onto the mantle, raphe structures on the mantle that extend distally onto the valve face, two helictoglossae per valve, and one apical rimoportula per valve. These findings establish that the genus Eunotia, and likely freshwater raphid diatoms as a whole, are more ancient than previously believed, dating back to at least 40 Ma. One of the observed morphotypes has a raphe spanning more than 80% of the valve length as well as a narrow hyaline area extending between proximal raphe endings and interrupting mantle striae. These features imply that the raphe system among certain ancient representatives of Eunotia was more developed relative to modern counterparts. The notion of progressive degeneration of the raphe within Eunotia is supported by several extant species. Collectively, these observations confirm molecular phylogenetic arguments that position Eunotia as a basal raphid diatom.
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Bonneure, Eli, Amber De Baets, Sam De Decker, et al. "Altering the Sex Pheromone Cyclo(l-Pro-l-Pro) of the Diatom Seminavis robusta towards a Chemical Probe." International Journal of Molecular Sciences 22, no. 3 (2021): 1037. http://dx.doi.org/10.3390/ijms22031037.
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As a major group of algae, diatoms are responsible for a substantial part of the primary production on the planet. Pennate diatoms have a predominantly benthic lifestyle and are the most species-rich diatom group, with members of the raphid clades being motile and generally having heterothallic sexual reproduction. It was recently shown that the model species Seminavis robusta uses multiple sexual cues during mating, including cyclo(l-Pro-l-Pro) as an attraction pheromone. Elaboration of the pheromone-detection system is a key aspect in elucidating pennate diatom life-cycle regulation that could yield novel fundamental insights into diatom speciation. This study reports the synthesis and bio-evaluation of seven novel pheromone analogs containing small structural alterations to the cyclo(l-Pro-l-Pro) pheromone. Toxicity, attraction, and interference assays were applied to assess their potential activity as a pheromone. Most of our analogs show a moderate-to-good bioactivity and low-to-no phytotoxicity. The pheromone activity of azide- and diazirine-containing analogs was unaffected and induced a similar mating behavior as the natural pheromone. These results demonstrate that the introduction of confined structural modifications can be used to develop a chemical probe based on the diazirine- and/or azide-containing analogs to study the pheromone-detection system of S. robusta.
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Merino-Virgilio, Fany Del Carmen, Yuri B. Okolodkov, Ana C. Aguilar-Trujillo, and Jorge A. Herrera- Silveira. "Phytoplankton of the northern coastal and shelf waters of the Yucatan Peninsula, southeastern Gulf of Mexico, Mexico." Check List 9, no. 4 (2013): 771. http://dx.doi.org/10.15560/9.4.771.
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Based on long-term monitoring (2001-2012) and four oceanographic cruises (2010-2012) in the coastal and shelf waters of the Yucatan Peninsula, SE Gulf of Mexico, a list of 306 strictly phytoplanktonic and tychoplanktonic species from 131 genera is presented: centric diatoms (83 species), raphid diatoms (47), araphid diatoms (22), Dinoflagellata (124), Cyanoprokaryota (18), Ebriacea (2), Chlorophyceae (3), Dictyochophyceae (2), Euglenophyceae (2), Cryptophyceae (1), Prymnesiophyceae (1), and Raphidophyceae (1). Diatoms also dominated the number of genera (80) followed by dinoflagellates (39) and cyanobacteria (11). The genera most abundant in species were Chaetoceros Ehrenb. (23 species), Protoperidinium Bergh (23) and Ceratium Schrank (17). The relative richness in species of the genus Oxytoxum (11 species) is related to the tropical affiliation of the phytoplankton community. Most of the tychoplanktonic diatoms (57 species out of a total of 152 diatoms, or 37.5%) were observed principally from coastal samplings. Eighteen potentially toxic species were found.
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Merino-Virgilio, Fany, Yuri Okolodkov, Ana Aguilar-Trujillo, and Silveira Jorge Herrera-. "Phytoplankton of the northern coastal and shelf waters of the Yucatan Peninsula, southeastern Gulf of Mexico, Mexico." Check List 9, no. (4) (2013): 771–79. https://doi.org/10.15560/9.4.771.
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Based on long-term monitoring (2001-2012) and four oceanographic cruises (2010-2012) in the coastal and shelf waters of the Yucatan Peninsula, SE Gulf of Mexico, a list of 306 strictly phytoplanktonic and tychoplanktonic species from 131 genera is presented: centric diatoms (83 species), raphid diatoms (47), araphid diatoms (22), Dinoflagellata (124), Cyanoprokaryota (18), Ebriacea (2), Chlorophyceae (3), Dictyochophyceae (2), Euglenophyceae (2), Cryptophyceae (1), Prymnesiophyceae (1), and Raphidophyceae (1). Diatoms also dominated the number of genera (80) followed by dinoflagellates (39) and cyanobacteria (11). The genera most abundant in species were <em>Chaetoceros </em>Ehrenb. (23 species), <em>Protoperidinium </em>Bergh (23) and <em>Ceratium </em>Schrank (17). The relative richness in species of the genus <em>Oxytoxum </em>(11 species) is related to the tropical affiliation of the phytoplankton community. Most of the tychoplanktonic diatoms (57 species out of a total of 152 diatoms, or 37.5%) were observed principally from coastal samplings. Eighteen potentially toxic species were found.
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Tan, Ling, Pengbin Wang, In-Hwan Cho, Eun-A. Hwang, Hyuk Lee, and Baik-Ho Kim. "Morphology and phylogenetic position of three new raphid diatoms (Bacillariophyceae) from Hangang River, South Korea." Phytotaxa 442, no. 3 (2020): 153–82. https://doi.org/10.11646/phytotaxa.442.3.3.
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Tan, Ling, Wang, Pengbin, Cho, In-Hwan, Hwang, Eun-A, Lee, Hyuk, Kim, Baik-Ho (2020): Morphology and phylogenetic position of three new raphid diatoms (Bacillariophyceae) from Hangang River, South Korea. Phytotaxa 442 (3): 153-182, DOI: 10.11646/phytotaxa.442.3.3, URL: http://dx.doi.org/10.11646/phytotaxa.442.3.3
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Kaczmarska, Irena, and James M. Ehrman. "Auxospore wall structure and postsexual valve morphology in Rhabdonema minutum Kützing." Plant and Fungal Systematics 64, no. 1 (2019): 33–40. http://dx.doi.org/10.2478/pfs-2019-0005.
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AbstractSeveral decades ago, three members of the araphid pennate genus Rhabdonema (R. adriaticum, R. arcuatum, R. minutum) were the first araphid diatoms studied using cultures and electron microscopical methods to determine auxospore structure and development. Of these, R. minutum was the least documented at that time. None have been reinvestigated until now. Here we present the structural elements of the mature auxospore and the initial and postsexual valve characteristics of R. minutum. Although in general the auxospore wall of this diatom is similar to that of the two other species examined (to the extent that they were documented), there are intriguing differences. Most unanticipated is the structure of the primary band of the longitudinal perizonium, which shows remarkable similarities to the raphid pennate diatom valve. The evolutionary implications of such a similarity are considered.
11
Kennedy, Bryan, and Norman Allott. "A review of the genus Brachysira in Ireland with the description of Brachysira praegeri and Brachysira conamarae, new raphid diatoms (Bacillariophyceae) from high status waterbodies." Phytotaxa 326, no. 1 (2017): 1–27. https://doi.org/10.11646/phytotaxa.326.1.1.
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Kennedy, Bryan, Allott, Norman (2017): A review of the genus Brachysira in Ireland with the description of Brachysira praegeri and Brachysira conamarae, new raphid diatoms (Bacillariophyceae) from high status waterbodies. Phytotaxa 326 (1): 1-27, DOI: 10.11646/phytotaxa.326.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.326.1.1
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Khademalrasool, Marzieh, and Mohammad Davoud Talebzadeh. "Dez River Araphid/Bi-raphid diatoms for nano-optic applications." Applied Materials Today 41 (December 2024): 102427. http://dx.doi.org/10.1016/j.apmt.2024.102427.
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Solak, Cüneyt Nadir, Batni Alakananda, Maxim Kulikovskiy, Saul Blanco, Aydin Kaleli, and Elif Yilmaz. "Distribution of nitzschioid diatoms in Kütahya waters." Oceanological and Hydrobiological Studies 48, no. 2 (2019): 140–64. http://dx.doi.org/10.1515/ohs-2019-0014.
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Abstract The family of Bacillariaceae Ehrenberg is a group of well-known raphid diatoms, associated with water quality. Our current knowledge of the species diversity of this group in Turkey is still incomplete. There are three river basins in the Kütahya region in Turkey, located in the eastern part of the country, including the Gediz, Sakarya and Susurluk basins, thus the region is rich in lotic waters. We present each taxon based on our observations of specimens collected in the Kütahya region. A total of 53 sites were surveyed in this study and a total of 65 taxa from Bacillariaceae were identified. Of these 65 taxa, 15 are recognized as the first records for Turkey. For each taxon, we indicate the reference(s) used for its identification. To facilitate the identification by others working on the Turkish freshwater diatom flora, we also present dimensions of the taxa identified, the distribution of each taxon in the Kütahya region, the distribution of each taxon in Turkey as well as one or more figures for each taxon.
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Chudaev, D. A., M. A. Gololobova та M. S. Kulikovskiy. "Оn taxonomic position of two species of achnanthoid diatoms (Achnanthidiaceae, Bacillariophyceae)". Novosti sistematiki nizshikh rastenii 49 (2015): 110–16. http://dx.doi.org/10.31111/nsnr/2015.49.110.
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Results of light and scanning electron microscopy investigations of valves of two freshwater achnanthoid diatoms are provided. Based on the structure of external terminal raphe endings, represented by simple pores, and cocconeoid habitus Achnanthes joursacensis Hérib. is transferred to the genus Platessa. Achnanthes rostellata A. Cleve is transferred to the genus Lemnicola due to presence of stauros on raphid valve and external terminal raphe fissures curved in opposite directions.
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Mann, David G., and Alan J. Stickle. "Sporadic evolution of dorsiventrality in raphid diatoms, with special reference to Lyrella amphoroides sp. nov." Nova Hedwigia 65, no. 1-4 (1997): 59–77. http://dx.doi.org/10.1127/nova.hedwigia/65/1997/59.
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MANN, D. G. "In vivo Observations of Plastid and Cell Division in Raphid Diatoms and Their Relevance to Diatom Systematics." Annals of Botany 55, no. 1 (1985): 95–108. http://dx.doi.org/10.1093/oxfordjournals.aob.a086882.
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Stickle, Alan J. "MASTOGLOIA SMITHIIHAS A METHOD OF SEXUAL REPRODUCTION HITHERTO UNKNOWN IN RAPHID DIATOMS." Diatom Research 1, no. 2 (1986): 271–82. http://dx.doi.org/10.1080/0269249x.1986.9704973.
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Gogorev, R. M., and E. K. Lange. "Amphoroid and canal-raphid diatoms (Bacillariophyta) of relict Lake Mogilnoye (Kildin Island, Barents Sea)." Novosti sistematiki nizshikh rastenii 53, no. 1 (2019): 15–38. http://dx.doi.org/10.31111/nsnr/2019.53.1.15.
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New data on morphology of eleven pennate diatoms from four orders (Thalassiophysales, Rhopalodiales, Bacillariales, Surirellales) found in the subpolar meromictic Lake Mogilnoye with the level of salinity up to 4 ‰ and the water temperature at about 10 °С are presented. Halamphora cf. dubiosa and Nitzschia soratensis are recorded for the first time for the flora of Russia, Halamphora turgida, Cymbellonitzschia diluviana, Epithemia adnata var. saxonica are found for the first time for the flora of the Murmansk Region and eight new taxa are listed for the first time for Lake Mogilnoye.
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Wetherbee, Richard, Jan L. Lind, Jo Burke, and Ralph S. Quatrano. "MINIREVIEW-THE FIRST KISS: ESTABLISHMENT AND CONTROL OF INITIAL ADHESION BY RAPHID DIATOMS." Journal of Phycology 34, no. 1 (1998): 9–15. http://dx.doi.org/10.1046/j.1529-8817.1998.340009.x.
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CHEN, WEI, PAN YU, GAOFEI SONG, and REDIAT ABATE. "A new freshwater species Achnanthes licunese sp. nov. (Achnanthaceae, Bacillariophyta) from pebbles of Licun River, Shandong Province, China." Phytotaxa 649, no. 1 (2024): 69–82. http://dx.doi.org/10.11646/phytotaxa.649.1.4.
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A new freshwater diatom species, Achnanthes licunese sp. nov., was found on pebble samples collected from Licun River in Shandong Province, China. The various taxonomic characteristics of Achnanthes licunese sp. nov. is observed under light and scanning electron microscope. The living cells of A. licunese sp. nov. possesses two chloroplasts. Its valves exhibit a linear to linear-lanceolate outline, slightly constricted in the middle part, with uniseriate striae. The central area of the raphid valves is expanded into a linear and thickened stauros, and the raphe is filiform. On the araphid valves, there is no central area, and the axial area (sternum) is located in the valve margin. The valve of the A. licunese sp. nov. possesses the marginal spines, but no marginal ridge and terminal orbiculi. By comparing the new species with similar Achnanthes species, A. licunese sp. nov. was confirmed to be sufficiently different regarding valve size, striae density, and the presence of marginal spines. The discovery of this species increases the diversity of freshwater diatoms.
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Cox, Eileen. "Morphogenetic information and the selection of taxonomic characters for raphid diatom systematics." Plant Ecology and Evolution 143, no. (3) (2010): 271–77. https://doi.org/10.5091/plecevo.2010.403.
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<b>Background</b> – The traditional approach to diatom systematics assumed that structure and morphology were stable within a taxon and replicated faithfully down the generations, but wall structure is the end-product of biological processes, potentially modified by environment and over time. Electron microscopy revealed additional structural characters that may be taxonomically informative, but homology continues to be inferred primarily on morphological similarity, without reference to ontogeny. <b>Review</b> – Morphogenetic data reveal that similar structures can be derived in different ways, and that dissimilar end-products may be produced by a single ontogenetic pathway. This paper discusses the importance of understanding valve morphogenesis before wall characters and character states are chosen and described, with particular reference to dorsiventrality, solid areas of silica, raphe and pore structure. <b>Conclusions</b> – A better understanding of character formation will inform the use and development of terminology, which is critical to comparative studies and phylogenetic analyses of morphological data.
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TAN, LING, PENGBIN WANG, IN-HWAN CHO, EUN-A. HWANG, HYUK LEE, and BAIK-HO KIM. "Morphology and phylogenetic position of three new raphid diatoms (Bacillariophyceae) from Hangang River, South Korea." Phytotaxa 442, no. 3 (2020): 153–82. http://dx.doi.org/10.11646/phytotaxa.442.3.3.
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Epilithic diatoms were isolated and cultured during ecological investigations of the Hangang River, South Korea. Three species belonging to the genera Fragilaria, Nitzschia, and Encyonema were investigated using morphological and molecular data. Their morphological characteristics were analyzed using light microscopy (LM) and scanning electron microscopy (SEM). The nuclear small subunit (SSU) rRNA and ribulose-1, 5-bisphosphate carboxylase/oxygenase (rbcL) genes were used to study the molecular characteristics of these taxa. We herein describe three new species: 1) Fragilaria thornata, which has spatulate spines tapering towards their tips; 2) Nitzschia hantanense, which has a small-sized frustule with convex margins and parallel striae in the central part of the valve that become strongly radial towards the poles; 3) Encyonema equalis, which has a space between projections, located on the upper siliceous struts, that is consistent whether near the margin or near the raphe. According to the molecular analysis of three species, there also give a strong evidence to separate these three species as new species based on the phylogenetic tree and genetic distance of SSU rRNA and rbcL gene. The result of all analyses support that Fragilaria thornata, Nitzschia hantanense and Encyonema equalis are new to science.
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Goessling, JW, S. Frankenbach, L. Ribeiro, J. Serôdio, and M. Kühl. "Modulation of the light field related to valve optical properties of raphid diatoms: implications for niche differentiation in the microphytobenthos." Marine Ecology Progress Series 588 (February 8, 2018): 29–42. http://dx.doi.org/10.3354/meps12456.
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Kim, Byoung-Seok, Andrzej Witkowski, Jong-Gyu Park, et al. "Taxonomy and diversity of a little-known diatom genus Simonsenia (Bacillariaceae) in the marine littoral: novel taxa from the Yellow Sea and the Gulf of Mexico." Plant Ecology and Evolution 152, no. 2 (2019): 248–61. http://dx.doi.org/10.5091/plecevo.2019.1614.
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Background and aims – The diatom genus Simonsenia has been considered for some time a minor taxon, limited in its distribution to fresh and slightly brackish waters. Recently, knowledge of its diversity and geographic distribution has been enhanced with new species described from brackish-marine waters of the southern Iberian Peninsula and from inland freshwaters of South China, and here we report novel Simonsenia from fully marine waters.
 Methods – New isolates of Simonsenia species were obtained from marine waters, the littoral zone of the Korean Yellow Sea coast and the Gulf of Mexico in Corpus Christi (Texas), and documented in LM, SEM and with DNA sequence data (plastid-encoded rbcL and psbC). Phylogenetic trees of raphid diatoms were constructed to assess the relationships of the new species and of the genus as a whole.
 Key results and conclusions – Two novel species of Simonsenia (S. eileencoxiae and S. paucistriata) are described and a further putative taxon is characterized morphologically. The molecular phylogeny of the new Simonsenia species and previously sequenced species supports both the monophyly of the genus and its place within the Bacillariaceae. The Simonsenia clade clusters with clades composed of Cylindrotheca, Denticula and some Nitzschia spp. (including N. amphibia, N. frustulum, N. inconspicua). Hence Simonsenia is firmly positioned within the Bacillariaceae by molecular phylogenies, confirming its position within this group based on the possession of a canal raphe and its ultrastructure, and rejecting its classification within the Surirellaceae. Morphological data from the new Simonsenia species is typical for the genus, with a “simonsenioid” canal raphe type supported over the valve face with fenestral braces, alar canals connecting the canal raphe with the cell lumen, and the presence of fenestrae between the alar canals externally. Our results indicate unequivocally that the biogeography and the biodiversity of Simonsenia remain highly underestimated.
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Yildirim, Vesile, and Selda Demirkapu. "Taxonomic composition of epilithic diatoms and indicator role in freshwater pools and the effect of pollution in the Keban Dam lake, Turkey." Acta Scientiarum. Biological Sciences 46 (December 5, 2024): e70839. https://doi.org/10.4025/actascibiolsci.v46i1.70839.
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The aim of this study is to determine the epilithic diatom flora of stations exposed to pollutants of different characteristics, to test the relationships of these diatoms with water quality and the suitability of environmental quality indicators, and to determine different indicators of various quality pollutants for the rapid assessment of ecological pollution. Additionally, determining the ecological impact of both industrial and domestic waste on the reservoir in the region and determining whether the diatom community changes when exposed to various pollutants (including potential mortality), especially its role as an indicator of metal pollution; Samples taken from stations where domestic and industrial wastes were discharged with different chemical properties were evaluated and investigated. A total of 100 species were identified for Bacillariophyta. Although there was no significant change in the number of the species among the stations, significant changes were observed in the community structure. While Achnanthidium minutissimum, Fragilaria capucina, Gomphonema parvulum, Nitzschia palea and Surirella angustatum were the dominant diatoms in the impermeable artificial pool where the industrial wastewater of the factory was collected, Nitzschia amphibia, N. palea, N. recta and Ulnaria ulna were the dominant diatoms of the station where domestic wastewater was discharged. In the dam area where domestic wastewater is discharged, Fragilaria capucina Ulnaria ulna and Diatoma vulgaris are the dominant diatoms. Achnanthidium minutissimum, Gomphonema parvulum Navicula cinta and Nitzschia amphibia, N. angustata were the dominant diatoms of the station where both domestic and industrial wastewater was discharged. It was determined that benthic diatoms responded to different types of waste by changing their species composition, and that the change in the benthic community was not due to seasonal differences in stations under the influence of pollutants with different chemical properties. Diatom taxa which are known to tolerate metal concentrations, diatom diversities, and teratologies were determined.
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Vodeneeva, Ekaterina, Yulia Pichugina, Darja Zhurova, et al. "Epiplastic Algal Communities on Different Types of Polymers in Freshwater Bodies: A Short-Term Experiment in Karst Lakes." Water 16, no. 22 (2024): 3288. http://dx.doi.org/10.3390/w16223288.
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The increasing amount of plastic debris in water ecosystems provides a new substrate (epiplastic microhabitats) for aquatic organisms. The majority of research about epiplastic communities has focused on seawater environments, while research is still quite limited and scattered concerning freshwater systems. In this study, we analyze the first stages of colonization on different types of plastic by a periphytic algae community (its composition and dominant species complex) in freshwater bodies located in a nature reserve (within the Middle Volga Basin). A four-week-long incubation experiment on common plastic polymers (PET, LDPE, PP, and PS), both floating and dipped (~1 m), was conducted in two hydrologically connected karst water bodies in July 2023. The composition of periphytic algae was more diverse (due to the presence of planktonic, benthic, and periphytic species) than the phytoplankton composition found in the water column, being weakly similar to it (less than 30%). Significant taxonomic diversity and the dominant role of periphytic algae were noted for diatoms (up to 60% of the total composition), cyanobacteria (up to 35%), and green (including Charophyta) algae (up to 25%). The composition and structure of periphytic algae communities were distinct between habitats (biotope specificity) but not between the types of plastic, determined primarily by a local combination of factors. Statistically significant higher values of abundance and biomass were demonstrated for some species, particularly for Oedogonium on PP and Nitzschia on LDPE (p-value ≤ 0.05). As colonization progressed, the number of species, abundance, and dominance of individual taxa increased. In hydrologically connected habitats, different starts of colonization are possible, as well as different types of primary succession (initiated by potentially toxic planktonic cyanobacteria or benthic cyanobacteria and mobile raphid diatoms). Within the transparency zone, colonization was more active on the surface (for example, in relation to green algae on PP (p-value ≤ 0.05)). These results indicate a tendency for microalgae communities to colonize actively submerged plastic materials in freshwater, and they may be useful in assessing the ecological status of these aquatic ecosystems.
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KENNEDY, BRYAN, and NORMAN ALLOTT. "A review of the genus Brachysira in Ireland with the description of Brachysira praegeri and Brachysira conamarae, new raphid diatoms (Bacillariophyceae) from high status waterbodies." Phytotaxa 326, no. 1 (2017): 1. http://dx.doi.org/10.11646/phytotaxa.326.1.1.
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The genus Brachysira is frequently encountered in the algal flora of oligotrophic freshwaters. In order to re-evaluate its diversity in Irish waters, light and scanning electron microscopy was used to examine populations at 209 river sites and in 85 lakes. The full range of morphological variation of all common and sometimes challenging Brachysira populations was investigated. The study revealed two new species, Brachysira praegeri sp. nov. and Brachysira conamarae sp. nov. and compared them to all closely related taxa. The study also recorded B. intermedia and B. neglectissima which are new records for Ireland. Further taxonomic clarification is required for a diatom resembling B. intermedia and the complex of taxa around the polymorphic B. microcephala. Individual Brachysira taxa differed with respect to their optima along an alkalinity-pH gradient, but the trophic requirements of all forms were comparable, suggesting that species may be merged for routine water quality assessment. Nevertheless, it is recommended that Brachysira morphotypes be enumerated separately until their taxonomy is more fully resolved and their significance for the biodiversity of epilithic communities has been clearly established.
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Kim, Byoung-Seok, Andrzej Witkowski, Jong-Gyu Park, et al. "Taxonomy and diversity of a little-known diatom genus Simonsenia (Bacillariaceae) in the marine littoral: novel taxa from the Yellow Sea and the Gulf of Mexico." Plant Ecology and Evolution 152, no. (2) (2019): 248–61. https://doi.org/10.5091/plecevo.2019.1614.
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<b>Background and aims</b> – The diatom genus <em>Simonsenia</em> has been considered for some time a minor taxon, limited in its distribution to fresh and slightly brackish waters. Recently, knowledge of its diversity and geographic distribution has been enhanced with new species described from brackish-marine waters of the southern Iberian Peninsula and from inland freshwaters of South China, and here we report novel <em>Simonsenia</em> from fully marine waters.<b>Methods</b> – New isolates of <em>Simonsenia</em> species were obtained from marine waters, the littoral zone of the Korean Yellow Sea coast and the Gulf of Mexico in Corpus Christi (Texas), and documented in LM, SEM and with DNA sequence data (plastid-encoded <em>rbc</em>L and <em>psb</em>C). Phylogenetic trees of raphid diatoms were constructed to assess the relationships of the new species and of the genus as a whole.<b>Key results and conclusions</b> – Two novel species of <em>Simonsenia</em> (<em>S. eileencoxiae</em> and <em>S. paucistriata</em>) are described and a further putative taxon is characterized morphologically. The molecular phylogeny of the new <em>Simonsenia</em> species and previously sequenced species supports both the monophyly of the genus and its place within the Bacillariaceae. The <em>Simonsenia</em> clade clusters with clades composed of <em>Cylindrotheca</em>, <em>Denticula</em> and some <em>Nitzschia</em> spp. (including <em>N. amphibia</em>, <em>N. frustulum</em>, <em>N. inconspicua</em>). Hence <em>Simonsenia</em> is firmly positioned within the Bacillariaceae by molecular phylogenies, confirming its position within this group based on the possession of a canal raphe and its ultrastructure, and rejecting its classification within the Surirellaceae. Morphological data from the new <em>Simonsenia</em> species is typical for the genus, with a "simonsenioid" canal raphe type supported over the valve face with fenestral braces, alar canals connecting the canal raphe with the cell lumen, and the presence of fenestrae between the alar canals externally. Our results indicate unequivocally that the biogeography and the biodiversity of <em>Simonsenia</em> remain highly underestimated.
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Lin, Hung-Yun, Chung-Hsiao Liu, Yong-Ting Kang, et al. "Enhancing the Spermidine Synthase-Based Polyamine Biosynthetic Pathway to Boost Rapid Growth in Marine Diatom Phaeodactylum tricornutum." Biomolecules 14, no. 3 (2024): 372. http://dx.doi.org/10.3390/biom14030372.
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Diatoms, efficient carbon capture organisms, contribute to 20% of global carbon fixation and 40% of ocean primary productivity, garnering significant attention to their growth. Despite their significance, the synthesis mechanism of polyamines (PAs), especially spermidine (Spd), which are crucial for growth in various organisms, remains unexplored in diatoms. This study reveals the vital role of Spd, synthesized through the spermidine synthase (SDS)-based pathway, in the growth of the diatom Phaeodactylum tricornutum. PtSDS1 and PtSDS2 in the P. tricornutum genome were confirmed as SDS enzymes through enzyme-substrate selectivity assays. Their distinct activities are governed primarily by the Y79 active site. Overexpression of a singular gene revealed that PtSDS1, PtSDS2, and PtSAMDC from the SDS-based synthesis pathway are all situated in the cytoplasm, with no significant impact on PA content or diatom growth. Co-overexpression of PtSDS1 and PtSAMDC proved essential for elevating Spd levels, indicating multifactorial regulation. Elevated Spd content promotes diatom growth, providing a foundation for exploring PA functions and regulation in diatoms.
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Puccinelli, Camilla, Stefania Marcheggiani, and Laura Mancini. "A Patented Rapid Method for Identification of Italian Diatom Species." International Journal of Environmental Research and Public Health 16, no. 20 (2019): 3933. http://dx.doi.org/10.3390/ijerph16203933.
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The study of diatoms—unicellular algae of the class Bacillariophyceae—has several applications, first and foremost the evaluation of freshwater ecosystem quality according to the Water Frame Directive 2000/60/EC (WFD). Identification at the species level is a crucial step in diatom studies, considering that species belonging to the same genus have different geographical distributions and different ecological requirements. The Rapid Method for Identification of Italian Diatom Species is aimed at guiding users in the classification of freshwater diatom species. It consists of a digitized flow chart that leads, step by step, to the identification, starting with an image capture by light or electron microscopy. This rapid and easy tool could be useful to workers of an environmental agency when performing the operational monitoring required by the WFD to classify surface waters. It will also expand the application of diatoms in numerous fields. This method has been patented in Italy.
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Gemmell, Brad J., Genesok Oh, Edward J. Buskey, and Tracy A. Villareal. "Dynamic sinking behaviour in marine phytoplankton: rapid changes in buoyancy may aid in nutrient uptake." Proceedings of the Royal Society B: Biological Sciences 283, no. 1840 (2016): 20161126. http://dx.doi.org/10.1098/rspb.2016.1126.
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Phytoplankton sinking is an important property that can determine community composition in the photic zone and material loss to the deep ocean. To date, studies of diatom suspension have relied on bulk measurements with assumptions that bulk rates adequately capture the essential characteristics of diatom sinking. However, recent work has illustrated that individual diatom sinking rates vary considerably from the mean bulk rate. In this study, we apply high-resolution optical techniques, individual-based observations of diatom sinking and a recently developed method of flow visualization around freely sinking cells. The results show that in both field samples and laboratory cultures, some large species of centric diatoms are capable of a novel behaviour, whereby cells undergo bursts of rapid sinking that alternate with near-zero sinking rates on the timescales of seconds. We also demonstrate that this behaviour is under direct metabolic control of the cell. We discuss these results in the context of implications for nutrient flux to the cell surface. While nutrient flux in large diatoms increases during fast sinking, current mass transport models cannot incorporate the unsteady sinking behaviour observed in this study. However, large diatoms appear capable of benefiting from the enhanced nutrient flux to their surface during rapid sinking even during brief intervening periods of near-zero sinking rates.
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Agustí, Susana, Jeffrey W. Krause, Israel A. Marquez, Paul Wassmann, Svein Kristiansen, and Carlos M. Duarte. "Arctic (Svalbard islands) active and exported diatom stocks and cell health status." Biogeosciences 17, no. 1 (2020): 35–45. http://dx.doi.org/10.5194/bg-17-35-2020.
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Abstract. Diatoms tend to dominate the Arctic spring phytoplankton bloom, a key event in the ecosystem including a rapid decline in surface-water pCO2. While a mass sedimentation event of diatoms at the bloom terminus is commonly observed, there are few reports on the status of diatoms' health during Arctic blooms and its possible role on sedimentary fluxes. Thus, we examine the idea that the major diatom-sinking event which occurs at the end of the regional bloom is driven by physiologically deteriorated cells. Here we quantify, using the Bottle-Net, Arctic diatom stocks below and above the photic zone and assess their cell health status. The communities were sampled around the Svalbard islands and encompassed pre- to post-bloom conditions. A mean of 24.2±6.7 % SE (standard error) of the total water column (max. 415 m) diatom standing stock was found below the photic zone, indicating significant diatom sedimentation. The fraction of living diatom cells in the photic zone averaged 59.4±6.3 % but showed the highest mean percentages (72.0 %) in stations supporting active blooms. In contrast, populations below the photic layer were dominated by dead cells (20.8±4.9 % living cells). The percentage of diatoms' standing stock found below the photic layer was negatively related to the percentage of living diatoms in the surface, indicating that healthy populations remained in the surface layer. Shipboard manipulation experiments demonstrated that (1) dead diatom cells sank faster than living cells, and (2) diatom cell mortality increased in darkness, showing an average half-life among diatom groups of 1.025±0.075 d. The results conform to a conceptual model where diatoms grow during the bloom until resources are depleted and supports a link between diatom cell health status (affected by multiple factors) and sedimentation fluxes in the Arctic. Healthy Arctic phytoplankton communities remained at the photic layer, whereas the physiologically compromised (e.g., dying) communities exported a large fraction of the biomass to the aphotic zone, fueling carbon sequestration to the mesopelagic and material to benthic ecosystems.
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Ashworth, Matt P., Christopher S. Lobban, Andrzej Witkowski, et al. "Molecular and Morphological Investigations of the Stauros-bearing, Raphid Pennate Diatoms (Bacillariophyceae): Craspedostauros E.J. Cox, and Staurotropis T.B.B. Paddock, and their Relationship to the Rest of the Mastogloiales." Protist 168, no. 1 (2017): 48–70. http://dx.doi.org/10.1016/j.protis.2016.11.001.
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Martínez-Carreras, N., C. E. Wetzel, J. Frentress, et al. "Hydrological connectivity inferred from diatom transport through the riparian-stream system." Hydrology and Earth System Sciences 19, no. 7 (2015): 3133–51. http://dx.doi.org/10.5194/hess-19-3133-2015.
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Abstract. Diatoms (Bacillariophyta) are one of the most common and diverse algal groups (ca. 200 000 species, ≈ 10–200 μm, unicellular, eukaryotic). Here we investigate the potential of aerial diatoms (i.e. diatoms nearly exclusively occurring outside water bodies, in wet, moist or temporarily dry places) to infer surface hydrological connectivity between hillslope-riparian-stream (HRS) landscape units during storm runoff events. We present data from the Weierbach catchment (0.45 km2, northwestern Luxembourg) that quantify the relative abundance of aerial diatom species on hillslopes and in riparian zones (i.e. surface soils, litter, bryophytes and vegetation) and within streams (i.e. stream water, epilithon and epipelon). We tested the hypothesis that different diatom species assemblages inhabit specific moisture domains of the catchment (i.e. HRS units) and, consequently, the presence of certain species assemblages in the stream during runoff events offers the potential for recording whether there was hydrological connectivity between these domains or not. We found that a higher percentage of aerial diatom species was present in samples collected from the riparian and hillslope zones than inside the stream. However, diatoms were absent on hillslopes covered by dry litter and the quantities of diatoms (in absolute numbers) were small in the rest of hillslope samples. This limits their use for inferring hillslope-riparian zone connectivity. Our results also showed that aerial diatom abundance in the stream increased systematically during all sampled events (n = 11, 2011–2012) in response to incident precipitation and increasing discharge. This transport of aerial diatoms during events suggested a rapid connectivity between the soil surface and the stream. Diatom transport data were compared to two-component hydrograph separation, and end-member mixing analysis (EMMA) using stream water chemistry and stable isotope data. Hillslope overland flow was insignificant during most sampled events. This research suggests that diatoms were likely sourced exclusively from the riparian zone, since it was not only the largest aerial diatom reservoir, but also since soil water from the riparian zone was a major streamflow source during rainfall events under both wet and dry antecedent conditions. In comparison to other tracer methods, diatoms require taxonomy knowledge and a rather large processing time. However, they can provide unequivocal evidence of hydrological connectivity and potentially be used at larger catchment scales.
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Martínez-Carreras, N., C. E. Wetzel, J. Frentress, et al. "Hydrological connectivity as indicated by transport of diatoms through the riparian–stream system." Hydrology and Earth System Sciences Discussions 12, no. 2 (2015): 2391–434. http://dx.doi.org/10.5194/hessd-12-2391-2015.
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Abstract. Diatoms (Bacillariophyta) are one of the most common and diverse algal groups (ca. 200 000 species, ≈10–200 μm, unicellular, eukaryotic). Here we investigate the potential of terrestrial and aerophytic diatoms (i.e. diatoms nearly exclusively occurring outside water bodies, on wet, moist or temporarily dry places) to infer surface hydrological connectivity between hillslope–riparian–stream (HRS) landscape units during storm runoff events. We present data from the Weierbach catchment (0.45 km2, NW Luxembourg) that quantifies the relative abundance of terrestrial and aerophytic diatom species on hillslopes and in riparian zones (i.e. surface soils, litter, bryophytes and vegetation) and within streams (i.e. stream water, epilithon and epipelon). We tested the hypothesis that different diatom species assemblages inhabit specific moisture domains of the catchment (i.e. HRS units) and, consequently, the presence of certain species assemblages in the stream during runoff events offers the potential for recording if there was or not hydrological connectivity between these domains. We found that a higher percentage of terrestrial and aerophytic diatom species was present in samples collected from the riparian and hillslope zones than inside the stream. However, diatoms were absent on hillslopes covered by dry litter, limiting their use to infer hillslope–riparian zone connectivity in some parts of the catchment. Our results also showed that terrestrial and aerophytic diatom abundance in the stream increased systematically during all sampled events (n = 11, 2010–2011) in response to incident precipitation and increasing discharge. This transport of terrestrial and aerophytic diatoms during events suggested a rapid connectivity between the soil surface and the stream. Diatom transport data was compared to two-component hydrograph separation, and end-member mixing analysis (EMMA) using stream water chemistry and stable isotope data. This research suggests that diatoms were likely sourced exclusively from the riparian zone, since it was not only the largest terrestrial and aerophytic diatom reservoir, but also riparian zone water was a major streamflow source during rainfall events under both wet and dry antecedent condition.
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Michelutti, Neal, Marianne S. V. Douglas, Alexander P. Wolfe, and John P. Smol. "Heightened sensitivity of a poorly buffered high arctic lake to late-Holocene climatic change." Quaternary Research 65, no. 3 (2006): 421–30. http://dx.doi.org/10.1016/j.yqres.2006.02.001.
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AbstractA diatom-based paleolimnological investigation was conducted on late Holocene sediments from a poorly buffered lake, informally named “Rock Basin Lake”, on Ellesmere Island, Arctic Canada. The fossil diatom record is unlike any other obtained thus far from high arctic regions, exhibiting dynamic assemblage shifts over the entire ∼3300 yr sedimentary record. Multiple proxies (i.e., diatoms, pH reconstructions, biogenic silica, C/N ratios, total organic carbon) appear to sensitively track rapid limnological changes, which are associated with distinct climate intervals as inferred from other regional proxy records. The highly responsive nature of the diatom assemblages in Rock Basin Lake, relative to those recorded from nearby alkaline sites, appears to be related to this lake's limited ability to buffer changes in pH. The dynamic species responses suggest that the diatoms in Rock Basin Lake are faithfully tracking climatic changes, and that low-alkalinity lakes may provide the most sensitive diatom-based paleolimnological records from high arctic regions.
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Pestana-Nobles, Roberto, Reynaldo Villarreal-González, Nataly J. Galan-Freyle, et al. "Cross-Correlation and Fractal Analysis in the Images Diatoms Symmetry." Applied Sciences 13, no. 8 (2023): 4909. http://dx.doi.org/10.3390/app13084909.
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Diatoms are one of the main species of interest due to their possible impact on the maintenance of ecosystems, as well as their photosynthetic capacity and biotechnological applications. Reliable, easy, rapid identification of diatoms remains a highly desirable goal to avoid the difficulty for experts in the visual analysis of frustules; a method commonly used to compare the distinctive traits of diatoms, such as ornaments and the marks from images taken by optical and electronic microscopy for identification. This study proposed three simple morphometric methods based on fractal dimension measurements in conjunction with 2D cross-correlation parameters to analyze diatom images. This novel approach demonstrates the differentiation feasibility between a wide variety of diatom species with heterogeneity in their structures and shapes, which could possibly expand the application of this preprocessing process for the identification of new types of images or other biological species.
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Pfister, Laurent, Carlos E. Wetzel, Núria Martínez-Carreras, et al. "Examination of aerial diatom flushing across watersheds in Luxembourg, Oregon and Slovakia for tracing episodic hydrological connectivity." Journal of Hydrology and Hydromechanics 63, no. 3 (2015): 235–45. http://dx.doi.org/10.1515/johh-2015-0031.
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Abstract Hydrological processes research remains a field that is severely measurement limited. While conventional tracers (geochemicals, isotopes) have brought extremely valuable insights into water source and flowpaths, they nonetheless have limitations that clearly constrain their range of application. Integrating hydrology and ecology in catchment science has been repeatedly advocated as offering potential for interdisciplinary studies that are eventually to provide a holistic view of catchment functioning. In this context, aerial diatoms have been shown to have the potential for detecting of the onset/cessation of rapid water flowpaths within the hillslope-riparian zone-stream continuum. However, many open questions prevail as to aerial diatom reservoir size, depletion and recovery, as well as to their mobilisation and transport processes. Moreover, aerial diatoms remain poorly known compared to freshwater species and new species are still being discovered. Here, we ask whether aerial diatom flushing can be observed in three catchments with contrasting physiographic characteristics in Luxembourg, Oregon (USA) and Slovakia. This is a prerequisite for qualifying aerial diatoms as a robust indicator of the onset/cessation of rapid water flowpaths across a wider range of physiographical contexts. One species in particular, (Hantzschia amphioxys (Ehr.) Grunow), was found to be common to the three investigated catchments. Aerial diatom species were flushed, in different relative proportions, to the river network during rainfall-runoff events in all three catchments. Our take-away message from this preliminary examination is that aerial diatoms appear to have a potential for tracing episodic hydrological connectivity through a wider range of physiographic contexts and therefore serve as a complementary tool to conventional hydrological tracers.
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Olsen, Brianna K., Michael F. Chislock, Anja Rebelein, and Alan E. Wilson. "Nutrient enrichment and vertical mixing mediate 2-methylisoborneol and geosmin concentrations in a drinking water reservoir." Water Supply 17, no. 2 (2016): 500–507. http://dx.doi.org/10.2166/ws.2016.159.
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Few ecosystem-level studies have experimentally determined the physicochemical and biological factors that mediate concentrations of off-flavor compounds in drinking water reservoirs. Consequently, the watershed-scale mechanisms determining production of these compounds are still poorly understood. In a recent study, the addition of both nitrogen and phosphorus significantly increased 2-methylisoborneol (MIB). Not surprisingly, MIB was correlated with cyanobacterial abundance (a well-known producer of off-flavor compounds); however, MIB was most strongly correlated with diatom abundance. To empirically test for differences in the production of two important off-flavor compounds, specifically MIB and geosmin, by either cyanobacteria or diatoms, we conducted a fully factorial experiment that manipulated two factors that typically promote cyanobacteria (nitrogen and phosphorus fertilization) or diatoms (vertical mixing of the water column). As predicted, fertilization promoted cyanobacteria, and vertical mixing favored diatoms. Interestingly, the production of geosmin was rapid and consistent with an increase in cyanobacteria while MIB production increased later in the experiment when cyanobacterial biovolume tended to decline and diatom biovolume increased. Based on our current and previous studies, MIB and geosmin production is associated with cyanobacteria, but the direct or indirect influence of diatoms on production should not be ignored.
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Fan, Yong, Xiao-Ting Ding, Li-Juan Wang, Er-Ying Jiang, Phung Nghi Van, and Fu-Li Li. "Rapid Sorting of Fucoxanthin-Producing Phaeodactylum tricornutum Mutants by Flow Cytometry." Marine Drugs 19, no. 4 (2021): 228. http://dx.doi.org/10.3390/md19040228.
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Fucoxanthin, which is widely found in seaweeds and diatoms, has many benefits to human health, such as anti-diabetes, anti-obesity, and anti-inflammatory physiological activities. However, the low content of fucoxanthin in brown algae and diatoms limits the commercialization of this product. In this study, we introduced an excitation light at 488 nm to analyze the emitted fluorescence of Phaeodactylum tricornutum, a diatom model organism rich in fucoxanthin. We observed a unique spectrum peak at 710 nm and found a linear correlation between fucoxanthin content and the mean fluorescence intensity. We subsequently used flow cytometry to screen high-fucoxanthin-content mutants created by heavy ion irradiation. After 20 days of cultivation, the fucoxanthin content of sorted cells was 25.5% higher than in the wild type. This method provides an efficient, rapid, and high-throughput approach to screen fucoxanthin-overproducing mutants.
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Kumar, Santosh, Katya Rechav, Ifat Kaplan-Ashiri, and Assaf Gal. "Imaging and quantifying homeostatic levels of intracellular silicon in diatoms." Science Advances 6, no. 42 (2020): eaaz7554. http://dx.doi.org/10.1126/sciadv.aaz7554.
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Diatoms are an abundant group of microalgae, known for their ability to form an intricate cell wall made of silica. Silicon levels in seawater are in the micromolar range, making it a challenge for diatoms to supply the rapid intracellular silicification process with the needed flux of soluble silicon. Here, we use three-dimensional cryo–electron microscopy and spectroscopy to quantitatively analyze, at submicrometer spatial resolution and sensitivity in the millimolar range, intracellular silicon in diatom cells. Our results show that the internal silicon concentration inside the cell is ~150 mM in average, three orders of magnitude higher than the external environment. The cellular silicon content is not compartmentalized, but rather unevenly distributed throughout the cell. Unexpectedly, under silicon starvation, the internal silicon pool is not depleted, reminiscent of a constitutive metabolite. Our spatially resolved approach to analyze intracellular silicon opens avenues to investigate this homeostatic trait of diatoms.
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Blinn, Dean W., Richard H. Hevly, and Owen K. Davis. "Continuous Holocene Record of Diatom Stratigraphy, Paleohydrology, and Anthropogenic Activity in a Spring-Mound in Southwestern United States." Quaternary Research 42, no. 2 (1994): 197–205. http://dx.doi.org/10.1006/qres.1994.1069.
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AbstractThis study presents the first continuous record of fossil diatoms taken from an open spring-mound in southwestern United States. Diatoms were analyzed from a radiocarbon-dated core taken from Montezuma Well, a near thermally constant spring in northcentral Arizona. Fluctuations in total diatom density, oscillations in the relative abundance of Anomoeoneis sphaerophora, and intermittent deposition of calcite suggest that water levels in Montezuma Well underwent dramatic fluctuations to the degree of being intermittently dry, or at least very shallow, during the middle Holocene (∼8000-5000 yr B.P.). The fluctuations in water level probably correspond to oscillations in regional temperature and precipitation, which regulate hydrologic input and evaporation rates. The dramatic fluctuations in water level during the middle Holocene suggest that the endemic biota of Montezuma Well underwent relatively rapid speciation within the past ∼5000 yr. The appearance of endemic species (Gomphonema montezumense and Cyclotella pseudostelligera f. parva ) at ∼5000-3000 yr B.P. supports this hypothesis. Diatom indicators for organic enrichment (Aulacoseira granulata and A. islandica) closely coincide with the prehistoric native occupation of Montezuma Well.
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Luo, Junlong, Jun Cai, De Gong, Aoping Guo, Jaw-Kai Wang, and Jiangtao Zhang. "Diatom-Based Artificial Anode—Uniform Coating of Intrinsic Carbon to Enhance Lithium Storage." Materials 17, no. 18 (2024): 4473. http://dx.doi.org/10.3390/ma17184473.
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Pursuing improved electrode materials is essential for addressing the challenges associated with large-scale Li-ion battery applications. Specifically, silicon oxide (SiOx) has emerged as a promising alternative to graphite anodes, despite issues related to volume expansion and rapid capacity degradation. In this study, we synthesized carbon-coated SiOx using diatom biomass derived from artificially cultured diatoms. However, the inherent carbon content from diatoms poses a significant challenge for the electrochemical performance of diatom-based anodes in large-scale applications. Subsequently, we conducted further research and demonstrated excellent performance with a carbon content of 33 wt.% as anodes. Additionally, real-time characterization of the carbonization process was achieved using thermogravimetry coupled with infrared spectroscopy and gas chromatography mass spectrometry (TG-FTIR-GCMS), revealing the emission of CO and C3O2 during carbonization. Furthermore, electrochemical tests of the processed diatom and carbon (PD@C) anode exhibited outstanding rate capability (~500 mAh g−1 at 2 A g−1), high initial Coulomb efficiency (76.95%), and a DLi+ diffusion rate of 1.03 × 10−12 cm2 s−1. Moreover, structural characterization techniques such as HRTEM-SAED were employed, along with DFT calculations, to demonstrate that the lithium storage process involves not only reversible transport in Li2Si2O5 and Li22Si5, but also physical adsorption between the PD and C layers. Exploring the integration of diatom frustules with the intrinsic carbon content in the fabrication of battery anodes may contribute to a deeper understanding of the mechanisms behind their successful application.
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Archibald, C. G. M., and J. C. Taylor. "The assessment of diffuse pollution from acid-mine drainage using an updated and revised diatom assessment procedure as an added-value bio-monitoring tool." Water Science and Technology 55, no. 3 (2007): 151–60. http://dx.doi.org/10.2166/wst.2007.083.
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Three data sources (physico-chemistry, bio-monitoring and eco-toxicology) are currently used in South Africa to establish environmental water quality conditions. Environmental water quality in turn is key information required for the “ecological reserve determination” of river reaches. Bio-monitoring in South Africa has been limited in recent times mostly to the use of the SASS procedure which relies on invertebrates only. This paper describes the re-introduction of a diatom-based water quality assessment as an added-value bio-monitoring tool. A specific example is discussed citing the response of diatom assemblages to diffuse pollution from acid mine drainage and how effective diatoms are as indicators of ecological integrity and river recovery measured downstream of the area of impact. The advantages of applying this bio-monitoring technique over other biological measures are presented in the context of technological advances in rapid image processing, species identification and software applications of diatom-based water quality indices. The valuable records of the diatom assemblages of the past, held in the South African Diatom Collection at the CSIR (KwaZulu-Natal), can now be accessed and interpreted as historical environmental water quality reference points for several rivers in South Africa.
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Sherrod, Brian L., Robert C. Bucknam, and Estella B. Leopold. "Holocene Relative Sea Level Changes along the Seattle Fault at Restoration Point, Washington." Quaternary Research 54, no. 3 (2000): 384–93. http://dx.doi.org/10.1006/qres.2000.2180.
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At a marsh on the hanging wall of the Seattle fault, fossil brackish water diatom and plant seed assemblages show that the marsh lay near sea level between ∼7500 and 1000 cal yr B.P. This marsh is uniquely situated for recording environmental changes associated with past earthquakes on the Seattle fault. Since 7500 cal yr B.P., changes in fossil diatoms and seeds record several rapid environmental changes. In the earliest of these, brackish conditions changed to freshwater ∼6900 cal yr B.P., possibly because of coseismic uplift or beach berm accretion. If coseismic uplift produced the freshening ∼6900 cal yr B.P., that uplift probably did not exceed 2 m. During another event about 1700 cal yr B.P., brackish plant and diatom assemblages changed rapidly to a tidal flat assemblage because of either tectonic subsidence or berm erosion. The site then remained a tideflat until the most recent event, when an abrupt shift from tideflat diatoms to freshwater taxa resulted from ∼7 m of uplift during an earthquake on the Seattle fault ∼1000 cal yr B.P. Regardless of the earlier events, no Seattle fault earthquake similar to the one ∼1000 cal yr B.P. occurred at any other time in the past 7500 years.
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Armbrust, E. Virginia, and H. M. Galindo. "Rapid Evolution of a Sexual Reproduction Gene in Centric Diatoms of the Genus Thalassiosira." Applied and Environmental Microbiology 67, no. 8 (2001): 3501–13. http://dx.doi.org/10.1128/aem.67.8.3501-3513.2001.
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ABSTRACT Sexual reproduction is commonly assumed to occur in the vast majority of diatoms due to the intimate association of this process with cell size control. Surprisingly, however, little is known about the impact of sexual events on diatom population dynamics. TheSig1 gene is strongly upregulated during sexual reproduction in the centric diatom Thalassiosira weissflogii and has been hypothesized to encode a protein involved in gamete recognition. In the present study, degenerate PCR primers were designed and used to amplify a portion ofSig1 from three closely related species in the cosmopolitan genus Thalassiosira, Thalassiosira oceanica, Thalassiosira guillardii, andThalassiosira pseudonana. Identification ofSig1 in these three additional species facilitated development of this gene as a molecular marker for diatom sexual events. Examination of the new sequences indicated that multiple copies of Sig1 are probably present in the genome. Moreover, compared to the housekeeping geneβ -tubulin, the Sig1genes of isolates of T. weissflogii collected from different regions of the Atlantic and Pacific oceans displayed high levels of divergence. The Sig1 genes of the four closely related Thalassiosira species also displayed high levels of sequence divergence compared to the levels observed with a second gene, Fcp, probably explaining why Sig1could not be amplified from more distantly related species. The high levels of sequence divergence both within and between species suggest that Sig1 is rapidly evolving in a manner reminiscent of the manner observed in other genes that encode gamete recognition proteins. A simple model is presented for Sig1 evolution and the implications of such a rapidly evolving sexual reproduction gene for diatom speciation and population dynamics.
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Siver, Peter, Alexander Wolfe, and Mark Edlund. "Taxonomic descriptions and evolutionary implications of Middle Eocene pennate diatoms representing the extant genera Oxyneis, Actinella and Nupela (Bacillariophyceae)." Plant Ecology and Evolution 143, no. (3) (2010): 340–51. https://doi.org/10.5091/plecevo.2010.419.
Full textAbstract:
<b>Background and aims</b> – The majority of freshwater diatom lineages appear to have evolved before or during the Eocene, with rapid radiation occurring in the Miocene. However, only a few accurately dated fossil localities are available to test this assertion, resulting in an overall poor understanding of the biostratigraphy and early evolution of these organisms. Exquisitely preserved diatoms have been uncovered from Eocene lake sediments deposited post-eruptively in the Giraffe kimberlite pipe (Northwest Territories, Canada). We describe three new pennate diatoms from this deposit and discuss their evolutionary implications. <b>Methods</b> – Both oxidized preparations and whole-rock mudstone samples from the Giraffe Pipe core were examined with light and scanning electron microscopy for diatom remains. <b>Key results</b> – Species belonging to the genera <i>Actinella</i> F.W.Lewis, <i>Oxyneis</i> Round and <i>Nupela</i> Vyverman & Compère are described from the Giraffe Pipe sediments. <i>Oxyneis apporrecta</i> is a unique species with valves that are centrally constricted, inflations midway between the center and apices, and protracted and rostrate apices. <i>Actinella giraffensis</i> is a small taxon that lacks a highly complex head pole, and is most closely related to a species known today only from the highlands of New Zealand. <i>Nupela mutabilis</i> has variably shaped valves possessing a raphe and unique areolae characteristic of this genus. These findings represent the first known fossils for both <i>Oxyneis</i> and <i>Nupela</i>, and the oldest record for <i>Actinella</i>. <b>Conclusions</b> – None of the species are known from extant floras and are therefore considered extinct. However, the morphological features they present, including the structure of the areolae, raphe, rimoportula and girdle bands, share pronounced affinities with modern congeneric taxa. The well-developed raphe found on <i>Nupela mutabilis</i> confirms that the evolution of this structure dates to at least the Middle Eocene, and supports the hypothesis that it may be older than the Paleocene.
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Wang, Liang-Chi, Hong-Chun Li, and Liang-Jian Shiau. "Impacts of Anthropogenic Disturbances on Diatom Diversity in a Shallow Spring-Fed Pool." Diversity 14, no. 3 (2022): 166. http://dx.doi.org/10.3390/d14030166.
Full textAbstract:
Human impacts cause significant problems for shallow lakes in the karst regions of South China. In recent years, the ecological issues related to managing and restoring these critical aquatic ecosystems have come to the fore. Lingshui Pool (LSP) is one of the most-studied spring-fed lake ecosystems in south China, and it has well-preserved chronological profiles. The LSP was a very shallow lake before dam construction in 1962. Due to the dam’s construction, rapid development and urbanization, this important freshwater ecosystem has suffered severe eutrophication and environmental degradation. In order to determine the environmental effects of recent anthropogenic disturbances and establish conservation recommendations for this lake ecosystem, we analyzed diatoms and weak-acid leachable elements from a well-dated sediment core from LSP to reconstruct the changes in aquatic conditions and diatom diversity during the period AD 1960–2013. This revealed shifts in diatom assemblages, diversity, and geochemistry that were strongly linked to the construction of a dam in 1962 and rapid eutrophication after 1990. Diatom diversity was stable and relatively high when submerged macrophytes were present between 1962 and 1990. Thus, the reintroduction of endemic macrophytes could benefit the ecological stability and diversity of this shallow lake.
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Avramenko, A. S., та V. S. Pushkar. "Изменения климата в Южном Приморье на границе плиоцен-плейстоцена как важнейшего стратиграфического рубежа позднего кайнозоя". Bulletin of the North-East Science Center, № 3 (30 вересня 2024): 8–18. http://dx.doi.org/10.34078/1814-0998-2024-3-8-18.
Full textAbstract:
The study of diatoms from Southern Primorye's Pliocene deposits permitted to comprehensively reconstruct the climate of the region during the cooling increase at the border of the late Pliocene and Pleistocene. The ecological composition of the diatom flora recorded a trend of rapid decrease of temperatures and water levels in the range of 3.6-2.58 Ma, while the dominant Aulacoseira flora changing to a flora dominated by predominantly benthic taxa (Ellerbeckia, Tetracyclus, Alveolophora) marked a transition from lacustrine to alluvial sedimentogenesis, as well as the evolutionary extinction of ancient representatives of the genus Aulacoseira and their replacement by modern taxa.
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Starratt, Scott W. "Long-Term Records of Continental Diatoms Paleolimnology and Biochronology." Paleontological Society Papers 13 (October 2007): 111–20. http://dx.doi.org/10.1017/s1089332600001480.
Full textAbstract:
The great abundance and diversity of diatoms in lacustrine sediments and their ability to adjust to rapid changes in physical, chemical, and biological conditions makes them ideal for the study of lake history. Continuous diatom records from long-lived lakes have the potential to answer questions of basin history, climate variability, ecological change, and evolution. Isolated Tertiary outcrops provide a more limited record of environmental conditions, but as the ability to correlate individual exposures improves through the use of techniques such as tephrochronology, it is becoming possible to evaluate the timing of environmental or evolutionary changes on a regional basis.