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Present study dealt with the relative influence of environmental factors on phytoplankton assemblage pattern and diversity in Indian Sundarbans. Analysis revealed, five parameters (temperature, DO, salinity, PO4−P and transparency) varied significantly between seasons (p ≤0.05). Out of 84 species (62 genera), diatoms dominated across the seasons with maximum contribution from pennales (22 genera). Coscinodiscophyceae exhibited prominence in terms of abundance (2.501 × 103±1.04 × 103 org.L−1) and Bacillariophyceae in diversity (29 species). ANOVA (post-hoc test) showed the significant spatio-temporal heterogeneity (p≤0.05) of phytoplankton distribution in the system. Seasonal abundance revealed maximum in monsoon (3.347 × 103±1.948 × 103 org.L−1). Cluster analysis showed three clusters among the stations with maximum similarity between Jharkhali and Nischintapur. NMDS portrayed overall 40% similarity among all the stations. Furthermore, the resemblance of community compositions was observed between Pathar Pratima and Frazerganj, which might be due to geographical proximity between the stations and similar magnitude of salinity throughout the study period. Water parameters viz., temperature, total alkalinity, salinity, PO4−P, SiO4−Si and SO42− were the deterministic parameters influencing the distribution of phytoplankton, which was evident from BIO-ENV and Marginal test. Furthermore, the distance based linear model (DistLM) model explained two variables viz., PO4−P and total alkalinity were the controlling variables that could explain the phytoplankton community compositions in Sundarbans. Shannon diversity index indicated moderately rich phytoplankton diversity in the system with a calculated value >2.78. Index of multivariate dispersion (IMD) value also depicted increase in the community variability with the dispersion value of – 0.431.

Phytoplankton, as one of the most important primary producers in aquatic ecosystems, has been widely used to indicate the health of ecosystems. Nine physico-chemical parameters of water, as well as the phytoplankton community, of Al-Chibayish marsh were studied. Samples were collected from four sites and analyzed every two months from January to October 2019. Seasonal variations in physical and chemical properties were observed at all sites during the study period. The results indicated that 154 species of phytoplankton were recorded. The highest percentage of species was recorded to be 64.28% for Bacillariophyceae (diatoms) (Centrales 3.24% and Pennales 61.03%), followed by Chlorophyceae (16.23%), Cyanophyceae (11.68%), and Charophyceae and Euglenophyceae (3.24%), while Pyrrophyceae recorded the lowest value (1.29%) The numbers of phytoplankton species were 102, 94, 102, 99 in sites 1, 2, 3 and 4 ,respectively, during the study period. The total density of phytoplankton ranged from 223.769 cells x103 during January to 2784.693 cells x103 during September in site 2, with a clear increase during March and September, while the lowest number was 223.796 - 237.248 cells x103 in January and May, respectively. The dominance of diatoms was observed in all sites by 49.07% of the total density of phytoplankton, while the lowest abundance was 0.04% for the Pyrrophyceae. The results of the statistical analysis showed significant differences among sites and months, concerning the physical, chemical, and biological factors measured during the study period, at p-value

The number of diatomaceous genera that were isolated and diagnosed was about 20 genera, including 15 genera belonging to the order of lateral symmetry Pennales, all of which are benthic or epilithic diatoms, of which 4 genera are motile, and 5 genera belonging to the order of radial symmetry were isolated and diagnosed, all of them plankton diatoms. The highest numbers of isolated benthic diatoms ,were at the D7 sampling station site, about 17 species , while the lowest numbers were at the D2 site, about 13 species. The highest numbers of plankton diatoms were located at the D6 and D8 sampling stations, with 3 types. The highest total values of Palmer Pollution Index were within the sampling stations on the Diyala River section D7, D8, D4 and D6, about 33, 29, 25 and 23, respectively. Which indicates that the Diyala River water in those sites suffers from high confirm organic pollution. While the highest values of the TDI were 80.9 and 77.6, respectively, and the percentage of diatoms tolerant of organic pollution PTV was 49.8% and 47.8%, respectively, indicating the presence of a hypertrophy state in the river waters within those sites resulting from the presence of high confirm organic pollution. Especially with a decrease in the DQI values that were recorded in sites D7 and D4, which about 19.1 and 22.4, respectively.

The water quality characteristics and phytoplankton at a domestic waste polluted site at Oworonsoki, Lagos Lagoon in relation to environmental factors were investigated for six months (October, 2012 – March, 2013). Plankton samples were collected horizontally with plankton hauls on each trip using standard plankton net of 55µm mesh size tied unto a motorized boat and towed slowly (≤4m/s) for 10 mins. The water quality characteristics showed monthly variation linked to hydrological flow conditions, namely the rainfall pattern and tidal seawater inflow. Air temperature (28.3 – 32˚C), Water temperature (29 - 31˚C), Transparency (12.95 – 101.5cm), Total suspended solid (8 – 35mg/L), Total dissolved solid (553.0 – 20712.66mg/L), Conductivity (1069.0 – 31100.0µS/cm), Salinity (0.50 – 17.11 %), Acidity (4.9 – 6.3mg/L), Total hardness (102.0 – 3811.0 mg/L), Dissolved oxygen (4.8 – 5.2 mg/L), Chemical oxygen demand (14 – 23 mg/L) recorded higher values in the dry than in the wet season. High nutrients, especially nitrates and heavy metal levels between December and February points to the inflow of domestic wastes. The water quality characteristics reflected freshwaters situation in October and November (0.52 – 0.82 ‰) while December through March were increasingly brackish (9.42 – 17.11 %). The phytoplankton diversity (S) and abundance (N) were notably higher in the dry than the wet season. The phytoplankton spectrum (Bacillariophyta, Cyanophyta and Chlorophyta) were dominated by the Bacillariophyta (Diatoms) (93.47% - Centrales – 69.77 % and Pennales – 30.23%). Notable species of were Aulacoseira granulata var. angustissima, Odontella laevis, Coscinodiscus radiatus, Skeletonema coastasum, Chaetoceros convolutes, Bacillaria paxillifer, Gyrosigma balticum, Nitzschia sigmoidea, Synedra crystallina, Thalasiothrix fraunfeldii, Synedra ulna, Microcystis aeruginosa and Oscillatoria limnosa. The phytoplankton diversity at each time was reflective of the water chemistry situation. Comparatively, low phytoplankton diversity, and the occurrence of indicators of organic waste pollution are noteworthy.

The present paper was communicated with the morpho-taxonomic description of three diatom taxa belonging to the order Pennales of the class Bacillariophyceae namely Fragilariopsis cylindrus, Achnanthidium lineare and Rhopalodia gibba var. ventricosa. Among them, the former species is rare in occurrence within freshwater ecosystem while the latter two species are found sparsely to abundant in pond, water reservoirs and other types of aquatic bodies. The limnological characteristics that supported their occurrences in water bodies were recorded and found to be congenial for their growth. The pH of water in studied aquatic bodies was observed alkaline and acceptable quantity of phosphate, nitrate-nitrogen and silica along with other physico-chemical parameters of waters were also noted. The above mentioned all three diatom taxa are new taxonomic reports from this district of West Bengal, India.

Diatom test is an important tool in diagnosis death in drowning cases. As the typical features of ante-mortem drowning disappeared very rapidly with commencement of putrefaction and hence diatom test plays an important role for diagnosis and confirmation of drowning deaths. Diatoms have number of characteristic like their widespread presence in water, high diversity in species, habitat specificity and have a good potential for preservation and thus this group can be used in forensic geosciences for criminal investigations. Extraction and identification of diatoms present in the tissue samples can be used as supportive evidence in drowning and also for site specific diatoms. Temperature and pH variations also play important role in the distribution of diatoms in a particular location. Diatoms species detection in both water and tissue samples gave a reliability of the diatom test in solving cases pertaining to drowning deaths. Hence the possible means and methods must be practiced on a regular basis by the forensic examiner as well practitioners so that new possibilities must always be explored for extraction and identification of diatoms in near future. This paper reviews the recent year’s progress on diatom test and its application in forensic science.

Seasonal variations in the composition and abundance of phytoplankton were investigated fortnightly at 3 different regions along the Mandovi estuary from June 2007 to May 2008 in relation to salinity and nutrients. A total of 209 species belonging to 7 divisions were identified during the study period. The highest phytoplankton cell density (5.17 × 104 cells L-1) and biomass (7.68 mg m-3 chlorophyll a) were observed in the upper sections during the nonmonsoon period, while the highest diversity (3.46) was observed in the upper section during the monsoon period. Bacillariophyta was the dominant phytoplankton group at 71% of the total species identified. This group was dominated by Pennales (88) over Centrales (60) at all 3 stations. Contributions of Dinophyta, Chlorophyta, Cyanophyta, Haptophyta, Chromophyta, and Chrysophyta to the total species were 25%, 0.5%, 1%, 0.5%, 1%, and 1%, respectively. Dinophyta did not show significant variations in percentage distribution among the 3 sections and seasons. Twenty-six dominant species of phytoplankton, representing all seasons with cell density of >1000 cells L-1, showed spatial adaptability patterns with respect to salinity. Protoperidinium acbromaticum and Alexandrium ostenfeldii were found to grow only during nonmonsoon periods in upper sections and were reported for first time in the present study. Euryhaline Skeletonema costatum and Thalassiothrix frauenfeldii were present throughout the study period. A total of 36 harmful algal bloom-forming species, with 11 toxin-producing species, have been identified. The presence of Streptotheca thamensis acts as an indicator to evaluate water quality.

Although the method of seedling production of Haliotis discus hannai is well known, the optimum benthic diatom species as a live food at early larval stage are not fully developed. In this study three Pennales diatom species, Caloneis schroederi, Rhaphoneis sp., and Cocconeis californica were examined on settlement, metamorphosis, survival, and growth of Haliotis discus hannai larvae. The larvae fed Raphoneis sp. or C. californica showed high settlement rate with 80-82% within 48 hrs, which was significantly higher than those fed C. schroederi or mixed diets with three diatom species. The larvae fed the former microalgal species also showed higher metamorphosis rate with 32-34% than the latter species with 10-12% within 4 days. With regard to survival and growth of the larvae, single diet with Rhaphoneis sp. or C. californica had better dietary value than the mixed diets for the early larvae of H. discus hannai.

Terenko L., Terenko G., 2012: Dominant Pseudo-nitzschia (Bacillariophyta) species in the Black Sea (Ukraine) [Vyraujančios Pseudo-nitzschia (Bacillariophyta) rūšys Juodojoje jūroje (Ukraina)]. - Bot. Lith., 18(1): 27-34. Diatoms of the genus Pseudo-nitzschia (order Pennales) are persistent component of the phytoplankton community in the Black Sea and may reach bloom level during some periods in summer and autumn. Six potentially toxic and non-toxic Pseudo-nitzschia species were recorded up to date in the Ukrainian waters. Since 1980s, several mass developments of Pseudo-nitzschia spp. have been observed. Morphological analysis revealed Pseudo-nitzschia delicatissima, P. pseudodelicatissima, P. pungens, P. seriata as the dominant species in the blooms. Pronounced bloom of Pseudo-nitzschia spp. reaching up to 80 % of total phytoplankton abundance and occupying wide area of the Black Sea was observed in June 2001. The summer density peak of P. delicatissima and P. seriata was observed at 16.0-17.5 °С and salinity 15.2-15.7 ‰ in the coastal waters of Odessa Bay. In December 2005, the density of Pseudo-nitzschia spp. in the bottom layers in Odessa region reached 3.0·106 cells l-1. In June 2008, a single species P. pseudodelicatissima bloomed in the Danube region. The density of the species came up to 12.0·106 cells l-1. At the end of May 2009, P. delicatissima showed short-term and lower magnitude density peak (3.1·106 cells l-1) in the coastal zone of Odessa Bay. Thus, the Pseudo-nitzschia spp. blooms are frequent phenomena in the Black Sea and may occur in any season of a year. These species are indicators of trophic state in marine waters.

The phytoplankton functional group concept is successfully used to assess ecological status in lakes (Q index), and also provides a method for lotic ecosystems (Q(r) index). Here, we examine the Q(r) composition metric to demonstrate local to regional scale human effects on natural distribution of phytoplankton along the River Loire. Distribution of phytoplankton functional groups coupled with chemical and physical parameters are described at whole river scale (19 stations, between March and November 2009). Natural longitudinal changes were reflected by the switch from benthic Pennales (TB) towards meroplanktic greens (J) via unicellular centric diatoms (D/C). While upstream human pressure was mostly associated to species indicating eutrophic, stagnant environments (coda P, M, H1, Y), downstream attenuation of the Q(r) reflected enriched, shallow environments with prolonged residence time (coda J, X2, X1). Occurrence of minimum Q(r) index values were synchronized to late summer, but the longer was the distance from the source, the earlier was the seasonal decrease of Q(r). Increasing downstream co-dominance of codon F evidenced an ascending light availability in summer. The longitudinal distribution of functional groups allowed us to conclude that functional diversity might be able to sign human-affected richness, while simply species diversity does not.

Diatoms are considered the most successful and widespread group of photosynthetic eukaryotes. Their contribution to primary production is remarkably significant to the earth's ecosystems. Diatoms are composed of two orders: Centrales and Pennales. Thus far, viruses infecting centric diatom species have been isolated and characterized; however, viruses infecting pennates have not been reported. Here, we describe the first isolations and preliminary characterizations of two distinct pennate diatom viruses, AglaRNAV (31 nm in diameter, accumulates in the host cytoplasm) and TnitDNAV (35 nm in diameter, accumulates in the host nuclei) infecting Asterionellopsis glacialis and Thalassionema nitzschioides, respectively. Their genomes contain a single-stranded RNA of approximately 9.5 kb, and a closed, circular single-stranded DNA of approximately 5.5 kb harboring a partially double-stranded region, respectively. Further analysis of these viruses may elucidate many aspects of diatom host-virus relationships.

We introduce the German multi-metric assessment method PhytoFluss for large rivers, based on phytoplankton, which can be used to implement the European Water Framework Directive (WFD). First, we examined the response of chlorophyll a concentration to total phosphorus (TP) at 220 German river sites. Rivers could be assigned to one of four groups, based on the response curves: a) streams with high specific run-off (Rhine, Danube) had the lowest yield of chlorophyll a per unit of TP, followed by b) low yield in small lowland rivers (Trave, Stepenitz), c) medium-sized lowland rivers (Spree) and large central mountain rivers (Main) had intermediate yields of chlorophyll a, and d) streams with low specific run-off (Elbe, Weser) and Baltic tributaries (Penne, Warnow) had the highest yield of chlorophyll a per unit of TP. To define the five trophic status classes of phytoplankton biomass according the WFD, the chlorophyll a boundaries were derived from these response curves at the 75% percentile level. All selected sites were pre-classified with the combined trophic boundaries for TP and chlorophyll a to create the new four taxa composition metrics: The proportions of Chlorophytes, Cyanobacteria, or Pennales and of indicator taxa were selected as indicative parameters. When applying the final PhytoFluss method to 418 years of investigation from 150 German river sites, the percentages in each status according to the bio- component phytoplankton were: high 3%, good 19%, moderate 42%, poor 30%, and bad 5%. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Major nutrients (N and P) and phytoplankton from 19 large lakes from southern (61°) to northern (69°) Finland were analyzed to detect long-term trends and regional differences. The data sets from June, July and August cover the period from the early 1980s to the present. Altogether >700 phytoplankton and >4000 N, P and Chl a results were used for the study. In 40% of the lakes, the total phosphorus (TP) concentration decreased significantly and in >25% of the lakes a significant reduction was found in the total nitrogen (TN) concentration. At the same time, the phytoplankton biomass declined only in 15% of the lakes and the long-term trends in chlorophyll a more often increased than decreased. A clear gradient from southern to northern Finland and western to eastern Finland was found in the phytoplankton biomass. During the study period, the biomasses of cyanobacteria and centrales (diatoms) decreased whilst there was an increase in the biomass of pennales (diatoms) in one-third of the lakes. The proportion of chlorophytes in the total biomass also increased in >20% of the study lakes. In southern and western Finland, the total biomass and the contribution of cyanobacteria were higher. Centrales made a higher contribution to the total biomass in the north. Pennales and chlorophytes were less abundant and chrysophytes more abundant in the east. Differences in the community composition reflected the gradients in the total nutrients, and particularly in TP. The observations support the assumed role of phosphorus as the key limiting nutrient in large Finnish lakes irrespective of lake′s location. The N:P ratio proved to be a poor predictor of cyanobacteria occurrence in the study lakes.

Investigation of bodies recovered in water comprises an important proportion of medico-legal cases, but is affected by relevant limits concerning the specific decomposition processes and the cause of death. Few indications are provided by literature concerning the post mortem modification of corpses in water, but for a general variability in decomposition degree, and only few experimental projects have been performed in order to verify the influence of water on the decomposition process. On the other hand, in order to reconstruct the cause of death, at present, the diatom test is considered as the "golden standard" for the diagnosis of drowning, although recent literature has pointed out its relative reliability and the frequent problems of contamination. This pilot study was performed to observe the changes of animal remains in aquatic environments. The following experimental system was set up: three piglet corpses, who died by natural causes independent from the study, were immerged in water rich in diatoms (Navicola, Order Pennales) in a tank exposed to the open air; macroscopic, histochemical and diatoms analysis were performed after 1, 2 and 3 months. Decomposition effects were fast: since the first month the skin appeared colliquated with exposure of the underlying bone surface, whereas at the second and third month the inner viscera were no longer recognizable; histology revealed that the skin was well preserved at 1 month, but morphology was completely altered at the second month, whereas at the third month epidermis was no longer visible. Diatom testing showed the presence of contamination both in the first and second piglet; the finding of a sea-diatom, on the other hand, was completely unexpected. This study performed for the first time histochemical testing on animal models submerged in water: although the results became negative after the second month, some microscopic structure could still be recognized at the end of the experimental project; on the other hand, the search for diatoms in the samples proved the high possibility of post mortem contamination.

Discovery of obligate benthic diatoms living as deep as 191 m substantially extends the known depth range of these primary producers and holds significant implications for oceanic productivity and biogeochemical cycling. Species of the epipsammic, monoraphid genus Cocconeis dominated the ≥35 species of living benthic diatoms identified from the North Carolina continental margin in samples collected at bottom depths from 67 to 191 m. A total of 126 species were identified from prepared samples, more than 90% of which are obligate benthic forms. Mid-day, near bottom, photosynthetically active radiation values recorded at the 191 m site averaged 0.106 µmol photons m -2 s -1 , representing about 0.028% of surface incident radiation and resulting from a water column attenuation coefficient of 0.0446 m -1 . The presence of active benthic microalgae in these extremely low light conditions suggests the development of special light-harvesting adaptations including elevated levels of the blue-light absorbing accessory pigment, fucoxanthin. Extending the limit of benthic microalgal production to upper slope depths offshore from North Carolina increases the estimated total benthic primary production in that area of the continental margin by about 14%. At present, extrapolating potential increases in benthic microalgal biomass and production resulting from extending the depth limits of viable benthic microalgae to a larger, global, oceanic scale is limited by paucity of data.

Diatoms are unicellular microscopic organisms with silicon dioxide-based cylindrical-shaped skeletons, enveloped with an organic material composed of essentially polysaccharides and proteins. By removing the organic compounds from the diatom, we present an alternative method for the preparation of insulating nanocapillaries. The lengths of the capillaries are about 100 µm and the diameters of the regularly structured pores are about 200 nm. Moreover, we confirm with measurements by XPS that the shell of the Pennales diatoms contains mostly SiO2 .C opyrightc � 2008 John Wiley & Sons, Ltd.

Diatoms have been classified historically as either centric or pennate based on a number of features, cell outline foremost among them. The consensus among nearly every estimate of the diatom phylogeny is that the traditional pennate diatoms (Pennales) constitute a well-supported clade, whereas centric diatoms do not. The problem with the centric‐pennate classification was highlighted by some recent analyses concerning the phylogenetic position of Toxarium, whereby it was concluded that this ‘‘centric’’ diatom independently evolved several pennate-like characters including an elongate, pennate-like cell outline. We performed several phylogenetic analyses to test the hypothesis that Toxarium evolved its elongate shape independently from Pennales. First, we reanalyzed the original data set used to infer the phylogenetic position of Toxarium and found that a more thorough heuristic search was necessary to find the optimal tree. Second, we aligned 181 diatom and eight outgroup SSU rDNA sequences to maximize the juxtapositioning of similar primary and secondary structure of the 18S rRNA molecule over a much broader sampling of diatoms. We then performed a number of phylogenetic analyses purposely based on disparate sets of assumptions and found that none of these analyses supported the conclusion that Toxarium acquired its pennate-like outline independently from Pennales. Our results suggest that elongate outline is congruent with SSU rDNA data and may be synapomorphic for a larger, more inclusive clade than the traditional Pennales.

The purpose of this study was to clarify the differences of the community structure and the diversity of aquatic organisms (i) among sampling sites that the distances from inlets or outlets were different each other, and (ii) between the floodwater and the irrigation water during the crop season in a paddy field. The irrigation water was sampled from one inlet. The taxonomical groups and the number of aquatic organisms ranging in size from 30 µm to 2 cm in the floodwater and the irrigation water were surveyed approximately every 10 days during the growth period of the rice plant. Aquatic organisms were classified mainly at the order level. Thirty-eight taxonomical groups of aquatic organisms were found in the floodwater, while 18 groups were found in the irrigation water. We were not able to find the differences of the community structure of aquatic organisms among the sites. In the floodwater, the number of taxonomical group increased and the community structure changed during the late flooding period (over 50 days after the onset of flooding) at any site, while those in the irrigation water hardly changed. Although the community structure of aquatic organisms differed between the floodwater and the irrigation water throughout the flooding period, the differences became especially bigger during the late flooding period. Principal component analysis showed that three groups (Pennales, Dinoflagellida, Choreotrichida) characterized the community structure in the irrigation water. Their population densities tended to be the highest at the site near inlets and the lowest at the site far from inlets.

In present study water sample from four sites of Yamuna River were collected for identification of diatom. Collected water sample were digested with acid digestion and examined under high power microscope after slide preparation. After examination it was found that total 41 diatom species was found at four sites of river. Out of 41 diatom species 10 diatom species were found as site specific. These site specific diatoms can be used as marker for site identification in cases of suspected drowning as well as for other forensic purposes. I. Introduction: Diatoms are microscopic unicellular eukaryotic organisms ranging in size from approximately 5 microns to 1000 microns and of the most common types of phytoplankton. The word 'diatom' means 'cut in two' and is derived from the Greek :(dia) = 'through' + (temnein) = ' to cut', i.e. 'cut in half'. A characteristic feature of diatoms cell is that they are encased within a cell wall made of silica (hydrated silicon dioxide) called a Frustule and is found in almost aquatic environment including fresh and marine waters, soils, in fact almost anywhere in moist environment. There are more than 200 genera of living diatoms and it is estimated that there are approximately 100,000 extant species (Hasle et al., 1997), either free-floating, planktonic forms or attached to substrate. Diatoms grow as single cells, or form simple filaments/colonies. They form the base of aquatic food webs in marine and fresh water habitats. Diatoms are divided into two orders. The Centrales (now called the Biddulphiales) which have valve striae arranged basically in relation to a point, an annulus or a centrals areola and tend to appear radially symmetrical, and the Pennales (now called Bacillariales) which have valve striae arranged in relation to a line and tend to appear bilaterally symmetrical. The valve face of diatom frustules is ornamented with pores (areolae),spines, hyaline areas and other distinguishing morphological features. It is these skeletal features, which are used to classify and describe diatoms, which is an advantage in terms of paleontology since the same features are used to define extant species as extinct ones. Diatoms have several as a unique forensic marker in deciding the cause of death as drowning and in solving drowning related cases where medical officers fail ascertain the cause of death especially in cases when skeletonised and putrefied dead bodies are recovered. II. Methodology: 500ml to 1000ml water sample were collected in thoroughly washed bottle and then bottles were tightly fitted with cap & labelled with the location of sampling site, along with the date, time, and month. Water samples were collected at the bank, mid & across the river. Water samples were collected in different month continuously at month February to May .The water samples were collected from 4-different sites (Site1 (old bridge), Site2 (new bridge), Site3 (boat club) and Site4 (Sangam)) of Yamuna River at Allahabad. The collected water samples were brought to the laboratory for examination of diatoms. 500ml water sample was taken into the beaker from each bottles and 10 ml of Lugol's iodine was added in beaker .Lugol's iodine was used as preservative of water sample and left it for overnight. According to Ludes et al., (1996), 50ml of Conc. HNO3, KMnO4 & H2O2 was added in 500ml water sample in 5:2:3 ratios. They oxidize the organic matter present in the water sample except diatom cell wall because cell wall is resistant to them. The next day samples were taken in Tarson tubes & centrifuged at 1500rpm for 5-7 minutes and the supernant were discarded. This step was repeated till full of the water sample contained in the beaker was centrifuged. The Pellets were formed at the bottom of Tarson tube, the pellets were taken with the dropper and transferred on microscopic slide, left it for drying on the hot plate and cover it with cover slip then observed under compound microscope at 10x ,45x and 100x (oil immersion) magnification Taylor et al.,(2007). The same steps were repeated for all the samples from sites S1 to S4 for morphological examination of diatoms.

The epipellic algae of Qua Iboe Estuary was studied in late summer (between January and February) of 1999. Physicochemical analysis of the tidal mud flats of the Estuary revealed a mixohaline habitat characterized by its high acidity (pH 4.72±0.02) and rich nutritive salts content. The results of the phytoplankton studies revealed variation in the density of the microalgae within the microalgal Orders. The epipellic algae community was predominated by pinnate diatoms. The mean densities of the phytoplanktons ranged from 102.75 organism/ha, 34.25 organism/ha, 21.25 organism/ha to 1.00 organism/ha of Pennales, Centrales, Zygnematales and Blue-Green algae, respectively. Their densities, however, decreased with increase in sampling distance from the low tide level. At the species level, Actinoptychus undulatus and Tabellaria sp. predominate the microalgae community. The occurrence of the freshwater diatom, A. undulatus, in an otherwise “harsh” salty epipellic habitat confirms the adaptive potential of some freshwater phytoplankton to marine ecosystem. Other phytoplankter present in the epipellic habitat of the estuary were Amphora ovalis, Campylodis cibrosus, Cymbella lanceolata, Navicular radiosa, N. rhynocephala, Pleurosignma sp., Pinnularia viridis, Stephanodiscus sp., Closterium sp., Oscillatoria nigroviridis and Nodularia spumigena.

Sedimentary diatoms were collected from 62 New Jersey lakes and correlated with limnological and land use variables. Four diatom attributes (species richness, percentage dominance by a single diatom species, percentage acidobiontic species, percentage eutraphentic species) and 4 diatom indices, Centrales:Pennales (C/P), Araphidinaea:Centrales (A/C), Generic Diatom (GI), and diatom index of biotic integrity (DIBI), were compared to the environmental variables. Lakes were classified as forested lakes (±80% the watershed in forests), mixed land use lakes (21–79% forests), or deforested lakes (≤20% forests) based on the satellite imagery. Forested lakes had significantly lower specific conductance and pH, greater ZSD and hypo limnetic DO, and less urban land use within their watersheds than either mixed land use or deforested lakes. Forested lakes also had greater species richness, lesser dominance by single species, more acidobiontic diatoms, fewer eutraphentic diatoms, lower C/P, and higher DIBI sc...

A molecular phylogeny of the diatoms has been constructed from the nucleotide sequence of two domains of the nuclear-encoded large subunit ribosomal RNA in four centric and four pennate species. Distance and parsimony analyses support the monophyly of the diatoms and their closeness to the chrysophytes. The Centrales (radially symmetrical) appear to be paraphyletic: the centric Lithodesmium undulatum Ehrenberg (Lithodesmiales, Lithodesmiaceae) is associated with the pen-nate lineage. In the Pennales (bilaterally symmetrical), the araphids also appear to be paraphyletic. These phylogenetic inferences are in close congruence with those previously obtained from 18S rRNA data (Bhattacharya et al. 1992; Medlin et al. 1993). The evolutionary relationships of diatom families inferred from the ribosomal RNA data are discussed in relation to the fossil record.

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.

Diatoms, a class of heterokont algae, are among the most important primary producers. They may live attached to the ground as part of the benthos or buoyant in the oceans, in brackish water and in freshwater habitats. Their ability to stay in the water column as well as their propensity to adhere to structures is a result of secretion, even locomotary activity of pennate diatoms is a consequence of secretion. Diatoms make a cell wall of glass-like silicate. This feature, which sets diatoms apart from most other algae, also entails secretory activity. Secretion in diatoms has been studied by biochemical and immunological means, by histochemistry, light and electron microscopy and by physical methods. Recently, the genomes of two diatom species, one of the order Centrales and the other of the order Pennales, have been sequenced and transformation techniques have become available for the establishment of transgenic lines in some species. This has given diatom research an additional push forward, so that not surprisingly, tremendous progress has been made, particularly in the field of silica polycondensation and frustule morphogenesis. In trying to bring together classical biochemical, cell biological and structural work with modern molecular studies, the role of secretory processes in the diatoms is illuminated with particular emphasis on cell wall morphogenesis and locomotion.

Diatoms are unicellular photosynthetic eurkaryotes within the class Bacillariophyceae whose peculiarity amongst other microalgae is a siliceous cell wall (Round et al., 1990). Traditionally, diatoms have been subdivided into two major groups based upon their symmetry: the centrales have radial symmetry, whilst the pennales have bilateral symmetry. Diatoms are found in both freshwater and marine environments, as well as in soil, and on moist surfaces. Individual diatoms vary in size from 2 nm up to several mm in size, although only a few species are larger than 200 mm.

The lipid class and total fatty acid compositions of 14 species of diatom (class Bacillariophyceae) were examined. The major lipid class in these microalgae was polar lipid (50.1-90.8%), although in some species, triacylglycerols (0.3-47.7%) and free fatty acids (0-29.2%) were also abundant in the logarithmic phase cultures. The major fatty acids in most species were 14:0, 16:0, 16:1 (n-7) and 20:5(n-3). The polyunsaturated fatty acids 16:2(n-4), 16:3(n-4), 16:4(n-1), 18:4(n-3) and 22:6(n-3) also comprised a significant proportion (>4% each) of the total fatty acids in some species. The characteristic fatty acid composition of diatoms is readily distinguishable from those of other classes of microalgae. The mean proportion of 22:6(n-3) was significantly higher in representatives from the order Centrales (4.9%) than the Pennales (1.6%), but there was no consistent difference in the proportions of the other fatty acids. Four of the pennate diatoms contained significant proportions of arachidonic acid, 20:4(n-6) (3.5-5.6%), but most species examined contained very low proportions of (n-6) polyunsaturated fatty acids. Based on the lipid compositions, all of the diatom species studied are potentially suitable sources of some of the longer chain polyunsaturated fatty acids.

Biomass and community structure of phytoplankton have been analysed in the eutrophic, shallow, polymictic Muggelsee and in the inflowing Spree since 1980. In both lake and river, mean biomass and vitality of phytoplankton were similar. A regular annual succession of planktonic algae was found in both the river and the lake. The same species were found to be dominant, although the actual biomass of single phytoplankton populations differed normally from inflow to lake. Lake phytoplankton was characterized by higher proportions of Cyanobacteria (45.9 ± 11.3% resp. 34.5 ± 8.2%) and lower proportions of centric diatoms (35.1 ± 9.5% resp. 41.9 ± 10.3%, average April-October, 1980–90). The less abundant Pennales, Chlorophytes, and unidentified planktonic algae < 10 μm had attained a relatively higher importance in the river than in the lake. In the last decade, a pronounced shift from Cyanobacteria to diatoms (mainly Centrales) has been observed in the river.

Benthic suspension feeders are very important in coupling and energy transfer between benthos and plankton. Hence, it becomes essential to know which factors regulate the feeding activity of suspension feeders. In an in situ experiment seasonal variability in the biodeposition of Mytilus trossulus was related to temperature, salinity, current velocity, total chlorophyll a (Chl a equivalent), and the biomass of phytoplankton species in the northern Baltic Sea. The biodeposition was explained by current velocity interacting with ambient Chl a and temperature. The biodeposition increased curvilinearly with ambient concentration of Chl a eq suggesting that the saturation reduction occurred above 10 µg Chl a eq l-1. The biomass of benthic diatoms (Pennales) better described the biodeposition of M. trossulus than the other studied variables. The result suggests that a significant part of its diet consists of benthic microalgae. The population of M. trossulus could remove on an average less than 3% of phytoplankton stock daily and, hence, had a minor effect on phytoplankton populations in the study area.

The phytoplankton of the River Lujan (Buenos Aires, Argentina) was studied for a period of 18 months, together with physical and chemical variables, in relation to a pollution gradient. 167 taxa were recorded within a seasonal succession characterized by dominance of diatoms with a brief summer green algae facies. A combination of several biotic indices and multivariate analysis was employed to assess the impact of pollution on the phytoplankton community. The biotic indices used were species diversity and richness, algal quotients (green algae/diatom ratio, Centrales/Pennales ratio) and the SD succession rate index. Multivariate procedures included cluster analysis and ordination by PCA of both species and samples, stepwise discriminant analysis and multiple discriminant analysis of variance (MANOVA). Results indicate that community dynamism is attenuated at the more polluted sites, concomitant with an increased predominance of a broad-tolerance algal assemblage, co-dominated by Cyclotella meneghiniana and Nitzschia stagnorum. The changes in the community structure and dynamics described herein involved alterations in the distribution and relative proportions of the algae, rather than modifications in the basic species composition. These changes may not be readily detectable by methods which over-simplify the ecological information, such as systems of indicator species and biotic indices, designed to assess the degree of pollution. The suitability of multivariate analysis and biotic indices in river phytoplankton studies is further discussed.

Sterols were identified from seven species of axenically cultured diatoms which may be used for oyster food. Five species contained 24-methylenecholesterol as the major sterol. Stigmasterol was the principal sterol in Amphora coffaeformis while 24-ethylcholesterol was the major sterol in Navicula pelliculosa . Each of the four species of the order Centrales had 24-methylcholesterol, which was all 22-dihydrobrassicasterol (24β-methyl epimer). The 24-methylcholesterol from Nitzschia brevirostris (order Pennales) was all campesterol (24α-methyl epimer). From this and previously published works on diatom sterols, it appears that sterols from the order Centrales are 24β-oriented and those from the order Pennales are 24α-oriented.

Quaternary lacustrine deposits were identified and studied for the first time in a 1.2 m core test (PED-92/T-15) on the Precambrian Shield of Rio Grande do Sul at Encruzilhada do Sul. The area of the deposit is about one kilometer square. Sedimentologic and micropaleontologic study identified the following sequence: sand (base) → non laminated, silty black clay → slightly sandy/silty black clay → silty black clay with organic matter and some pebbles. Diatoms of the Order Pennales are the dominant microfossils. The sedimentary sequence shows that an initial shallow, sandy lake eutrophied and became filled with organic-rich clays.

The nuclear encoded large and small-subunit ribosomal RNA indicate that diatoms originated sometime between 400 and 330 million years ago. This time interval is clearly in disagreement with a Late Precambrian or Early Paleozoic origin (Round 1981 a,b; Round and Crawford 1981, 1984) and with Pyxidicula representing a diatom form associated with the first evolutionary appearance of the group. Considering the fact that the slowest possible nucleotide substitution rates within Pennales and the largest distance values between the pennate diatoms and the outgroup/basal diatom taxa were used to infer the origination time interval, there is a possibility that the obtained values are overestimated.

On the basis of results of stratigraphic and comparative morphological studies on the diatom frustule, the Surirellaceae is generally assumed to be the endpoint of the evolution of the Pennales. The present study shows that a line of development, based on frustule construction and which parallels the search for optimum design of comparable elements in engineering, can be traced from the Naviculaceae to the Surirellaceae. In both cases lightweight construction is achieved through economy of material and energy expenditure. This leads to structural stability and in the case of the diatom valve, a larger area for metabolic exchange. From the functional-morphological point of view, three construction principles can be distinguished in the genus Surirella: 1. valves with pennate costal framework, raphe keels and fibulae (Surirella gemma group); 2. frustules where all supporting elements are in the form of corrugations, with raphe keel and fibulae (Pinnatae, Fastuosae, Surirella striatula group); and 3. as in 2, but with true alae with alar canals (Robustae) instead of keels with fibulae.

The “double thecae” or “internal septa” of Eunotia soleirolii (Kutz.) Rabenh, are shown to represent the thecae of resting spores, as characterized by their physiology, as well as morphology. They differ from all resting spores of centric diatoms by the formation of both their valves as a result of unequal cell divisions; and, from the majority of centric spores by the presence of several girdle bands in both their thecae. Spore formation can be induced by high or low pH, high temperature (24 C), and iron, silica, phosphate or nitrate deficiencies, whereas low temperatures defer it. Spores do not germinate directly, but dormancy can be removed by dark treatments (–2 to 15 C) for a minimum of 4–5 wk. Longer dark treatments result in higher germination rates. At 15 C, a minimum of 2 mo is required and 4 mo is better. Heat treatments (27–42 C) are ineffective, but may shorten the dormancy-breaking subsequent cold period. Instances of secondary dormancy, as well as relative dormancy, were observed. Germination usually occurs in the light between 2 and 21 C. An equal division of the spore is followed by unequal divisions of both new cells with only the two resulting large cells being viable. The experiences in the laboratory aided the discovery of stages of spore germination in nature.

The diatom flora of a district in Jebel Marra, Sudan, has been qualitatively analysed. The periphyton is related to the type of substratum with which the various diatoms associated. Certain diatoms were found to be restricted to one habitat, while others were common to more than one. All species recorded belong to the Pennales. Comparison with regions in the Southern and Northern hemisphere is made.

Phytoplankton, submerged macrophytes, zoobenthos and zooplankton communities were studied concurrently in three lochs which progressively increased in trophic state. The phytoplankton showed a change in dominance from Bacillariophyceae (Pennales) and Desmidaceae in the mesotrophic Loch of the Lowes to Bacillariophyceae (Pennales) and Cyanobacteria in eutrophic Balgavies Loch and to Bacillariophyceae (Centrales) and Chlorophyceae in hypertrophic Forfar Loch. The Nygaard Compound phytoplankton quotient rose from 1.2 in the Lowes to 12 in Forfar. There was a decrease in number of species of submerged macrophytes, and in depth of colonisation from 5 m in the Lowes to 2 m in Forfar which was proportional to the decrease in mean transparency. Macrophyte biomass, however, increased in proportion to the concentration of total phosphorus in the lochs. There was a decrease in species of littoral zoobenthos, but an increase in density of profundal benthos from the Lowes to Forfar. Zooplankton also showed an increase in density with enrichment, accompanied by changes in dominance. Calanoida were dominant in the Lowes; Cladocera in Balgavies and Cyclopoda in Forfar. The importance of these differences in understanding the effects of progressive enrichment and to the management of the lochs is discussed.

The epipelic diatoms from various water bodies from the south-western part of the Hornsund fiord area are presented. Altogether, 157 taxa (127 species together with their variants and forms) have been identified. The flora consists almost entirely of diatoms from the order Pennales which is represented predominantly Biraphidineae, chiefly by the genera Navicula, Pinnularia and Cymbella. Also some information about the ecology and phytogeography of the diatom flora analysed is given. Most of the species are typical indifferent or alkaliphilous freshwater forms with low trophic requirements. Nearly 55% of the diatoms examined are arctic-alpine or nordic-alpine species.

The analysis of gut contents ofAmphichaeta leydigii, found for the first time in Italy in sandy shores of Lake Vico (Central Italy), proved grazing of the species on diatoms (Centrales and Pennales). Detritus and organic particles, abundant in the substratum, were observed only in small amounts.

Interactions between fish species and their effect on the ecological conditions in the fish pond were studied in ten ponds of 0.1 ha each. The ponds were stocked with bottom-feeding fish: common carp, Cyprinus carpio L., and male hybrid tilapia Oreochromis niioticus (L.) x O. aureus (Steindachner). and a filter-feeder: silver carp, Hypophthalmichtys molitrix (Valenciennes), in various combinations. This paper deals with the effect of different assemblages of these fishes on the phytoplankton populations in the ponds. A Principal Component Analysis of the data showed that only 20% of the phytoplanktonic variability is accounted for by the fish combination present in the pond (treatment). The first principal component (PCI) groups the species of phytoplankton which responded to treatment. This component is formed by small size species; Scenedesmus spp., small Chlorophytes (mainly Chlorella), Selenastrum minutum, Ankistrodesmus setigerus, Merismopedia minima and Diatoms of the order Pennales. The presence of silver carp led to an increase in total phytoplankton numbers, concurrently with a decrease in their dominant size. This was due to the predominance in the water of the small size species of the PCI group, which could not be retained by the gill filtering apparatus of the fish. Reduction in zooplankton abundance by silver carp also contributed to this situation. The presence of bottom-feeding fish resulted in a decrease in total phytoplankton numbers, and in the importance of the small-size species of the PCI group, and hence in the dominance of larger algae. The interactions between these two trophic types of fish and algae size are discussed.

The digestive tracts of newly metamorphosed juvenile abalone were examined, every 2 days after settlement on plates, for the presence of ingested diatoms. Samples of five juveniles were rinsed with filtered seawater, immersed in a saturated EDTA disodium salt solution to decalcify the shell, and tissue was dissolved with 6% sodium hypochlorite to reveal gut contents. The presence of diatoms was first noted 2 to 6 days after settlement. All diatoms found within abalone digestive tracts were of the Order Pennales and usually smaller than 10 μm. This technique contributes to the examination of certain aspects of feeding in larval and juvenile molluscan species.

Antialgal (allelopathic) activity of the mucilage excreted by a brown alga Sargassum horneri to various diatom species was examined. The growth of all diatoms examined was completely in-hibited by the crude mucilage at the concentrations, 3->30%, depending on the species. The lag phases of growth of these diatoms were influenced at the lower concentrations, however, their maximum growth rates were not affected at these concentration levels. The sensitivity of each diatom to the mucilage was related ot its ecological status (eiphyte or plankter), that is, epiphytic diatoms were generally more resistant than planktonic ones. But taxonomical difference (Pennales or Centrales) was not related to the sensitivity. The antialgal substances contained in the mucilage were non-dialyzable (>M. W. 25000) and heat-stable. The epiphytic diatom flora on S. horneri seems to be influenced by the allelochemicals pyoduced by their host.

The Pennales are diplonts and possess sexual, parthenogenetic or apogamous auxospore formation. Fusion is either isogamous or physiologically anisogamous. Sexual reproduction among the Centrales, with the exception ofMelosira, is not fully understood. It is probable, however, that the Centrales are also diplonts. Contradicting claims of various authors can be explained through the assumption that the microspores are spermatozoids which fertilize the undivided contents of female cells (egg cells) and that the resulting zygotes develop into auxospores. Conclusive proof of this claim is lacking for neither do cytological investigations of reduction divisions which occur during microspore formation suffice in the matter, nor has fusion of the gametes been observed. InMelosira, which has no microspores, reduction division takes place in the mother cells before auxospore formation; two of the four nuclei fuse and the zygote develops into an auxospore. The problems concerning sexual reproduction and alternation of nuclear phases among Centrales still remain unsolved except forMelosira. The Pennales, on the other hand, are definitely diploid.

Botanical expedition to the Sundarban Mangrove Forests in the Bangladesh part revealed the presence of 14 diatom taxa not recorded so far from Bangladesh territory. The taxa are Amphiprora alata Kutz., Chaetoceros pendulus Karsten, Chaetoceros socialis Lauder, Cyclotella comta (Ehr.) Kutz. Thalassionema nitzschioides (Grun.) Meresch, Thalassiosira rotula Meunier, Thalassiosira weisflogii Grun., Lioloma delicatula (Cupp) Hasle, Navicula brekkaensis Petersen fa, Nitzschia inconspicua Grun. fa, Nitzschia romana Grun. , Surirella fastuosa var. recedens (Schm.) Cl. Besides these, unidentified species of Chaetoceros sp. and an unidentified centric diatom have been recorded. These newly recorded taxa are described and illustrated. Key words: Phytoplankton; Diatoms; Mangrove; Estuarine algae; Centrales; Pennales DOI: http://dx.doi.org/10.3329/bjb.v40i2.9772 Bangladesh J. Bot. 40 (2): 163-169, 2011 (December)

Diatoms are armored with a rigid cell wall which consists of two thecae overlapping in the girdle region and resembling a bipartite box (Fig. 1). Cell division occurs by binary fission parallel to the valvar plane. Each daughter cell inherits one part of the mother cell wall, which in both cells becomes the epitheca, while the hypotheca is newly created (Figs. 2, 7, 8). This causes a decrease in size for some of the daughter cells during successive divisions (Fig. 2). At a certain stage this is compensated by sexual reproduction, resulting in a large auxospore, within which the initial valves are laid down (Fig. 3). The initial valves are rounded and do not exhibit the surface pattern characteristics of the species. The species-specific surface form of the vegetative valves is created with the first division (Fig. 3). Each individual part of the wall is composed of an inorganic opaline silica component that is enveloped by an organic coat (ref. in Schmid et al. 1981). The enormous variety and complexity of valve shapes and particularly their patterns induces the question of “how” and “why” they are formed in such a remarkable way; and what determines their outline, their topography, and their pattern? With respect to overall frustule pattern, why is there always a geometric center from which it fans out, forming a ring, or central area, in Centrales, while in Pennales it lies along an axial rib, which in a number of genera is penetrated by a slit, the raphe (Fig. 4)?

Analysis of the diatom content of limnic sediments from Linton Loch, Roxboroughshire, allowed a subdivision of the sequence into six diatom assemblage zones. Palynological evidence from the same core has been used to relate the sequence to the Late Quaternary chronozones of Din Moss. Fragilaria spp. are the dominant pioneer taxa in the basal clays of Late Devensian age, when a minerogenic environment persisted. With the onset of the Flandrian, biogenic precipitation of marl commenced and a planktonic community developed, together with an epiphytic flora dominated by Epithemia spp. Productivity, as indicated by diatom concentrations, remained low throughout the period of marl deposition, though the rate of accumulation was in excess of that for other Late Quaternary sediments in Britain. Consequent on anthropogenic disturbance in the catchment, productivity increased as muds and finally peat were deposited in the basin with a diatom flora dominated by Fragilaria spp. Possible reasons for the apparent competition between Epithemia spp. and Fragilaria spp. are discussed. The persistence of an alkaliphilous/alkalibiontic diatom flora suggests the maintenance of waters of high base-status throughout the Late Quaternary. The limited application of Centrales:Pennales and Araphidineae:Centrales ratios in a marl deposit and in a palaeoenvironmental context are discussed. The Linton Loch diatoms are compared with other sites. There are unique characteristics, which appear to relate to the existence of a marl environment, and do not conform with general trends of Late Quaternary lake evolution in Britain.