Distribution of non-marine diatoms in surface sediments of streams in Socotra Island, Yemen

Abundance and species composition of non-marine benthic diatom assemblages were studied from surface sediments samples of 11 streams distributed in Socotra Island, located in the northwest Indian Ocean. A total of 145 diatom species, representing 44 genera, were identified. The overall diatom communities appear to be the first recorded off the island. Pennales and non-planktonic taxa were most dominant over centrales and planktonic forms, both in diversity of genera and species. The majority of recognized diatoms are of cosmopolitan distribution. The predominant diatom flora in the surface sediment samples follow: Synedra ulna, Synedra longissima, Encyonema caespitosum, Encyonema silesiacum, Encyonemopsis microcephala, Mastogloia braunii, Mastogloia dansei, Mastogloia elliptica, Navicula cryptocephala, Navicula cryptotenella, Navicula rhynchocephala, Navicula cincta, Nitzschia amphibian, Nitzschia frustulum, Nitzschia perminuta, Cocconeis placentula, Pleurosira laevis and Staurosirella pinnata. These are found in addition to the common occurrence of Amphora coffeaeformis, Amphora Montana, Anomoeoneis sphaerophora, Cyclotella meneghiniana, Cymbella affinis, Diploneis elliptica, Encyonema mesianum, Diploneis smithii, Gomphonema gracile, Gomphonema parvulum, Kobayasia subtilissima, Mastogloia smithii, Navicula minuscule, Navicula notha, Navicula tenelloides, Nitzschia obtuse, Nitzschia palea, Nitzschia scalaris, Synedra nana, Tryblionella acuminate, Tryblionella granulate and Tryblionella punctata. Multivariate statistical techniques including detrended correspondence and cluster analyses were used to summarize changes in the diatom assemblages present in the examined streams. The results indicated six major diatom assemblages with a variation in dominant species. Each assemblage reflects distinctive environmental conditions based on salinity preference of the recognized and dominant

Recent and fossil freshwater diatoms of Poland : taxonomy, distribution and their significance in the environmental reconstruction, Part 1, Coscinodiscophyceae, Mediophyceae and Fragilariophycidae

High-resolution diatom investigation from the Polish ecosystem is presented as a contribution to our knowledge of diatom floristics, ecology, biogeography, and their significance in environmental and climate reconstruction in Poland. The study is based on the analysis of 821 sediment samples taken from different lakes in northern Poland, besides 8 borehole-originated from the Eemian paleolakes sites in central Poland. The preceding diatom results in published papers included the diatom flora that were recorded from different habitats in Poland are mentioned in the present work to complete the Polish diatoms list. The current work is the first part in a series of monographs dealing with the diatom taxa belonging to classes Coscinodiscophyceae, Mediophyceae and subclass Fragilariophycidae. A total of 269 diatom species and varieties belonging to 38 genera are recognized. The checklist is comprising 86 entries of Coscinodiscophyceae that includes all radial centric diatoms and 183 taxa of Fragilariophyceae that includes araphid pennate diatoms. Of these 97 diatom taxa are represented as a new record for Poland and 12 new combinations and new varieties. A detailed diatom description, distribution in Poland, andautecological information are presented to round up the content of this volume and documented with 120 plates including 2423 excellent light micrographs of diatom taxa, which allows for a better understanding of morphology to aid in the identification. This work is proposed to contribute towards a general view of the high diatom biodiversity that characterizes Polish ecosystems and provides a revised diatom checklist from Poland. Additionally, it offers the first taxonomic and autecological catalog, which will be significant in the assessment of the water quality monitoring, paleoenvironmental interpretation, and construct the paleoclimate changes.This research was financially supported by the National Science Centre in Poland (NCN) throughout research project No. UMO-2016/21/B/ST10/03059 and research project No. 2017/27/B/ST10/01905. The authors acknowledge with deep gratitude and appreciation to the Faculty of Technical Sciences John Paul II University of Applied Sciences in Biala Podlaska and the Geology Department, Faculty of Science, Tanta University, Egypt for providing all available facilities in the environmental and paleobotany lab including slide preparation, microscopic observations, identification, and photography consequent work