Pliocaenicus nipponicus sp. nov. is d e scribed from a Pliocene freshwater diatomite of the Kabutoiwa Formation in Gunma Prefecture, central Japan. The species is characterized by wide mantle interstriae with fultoportula openings on the lower part and an external ligula-like segment covering the valvocopula slit. Internally, each costa has a mantle fultoportula, and both mantle fultoportulae and valve face fultoportulae have two satellite pores. The new species is compared to similar species of Pliocaenicus: p costatus (Lupikina)Flower et al. (sensu lato), P. jilinensis G. Wang and P. omarensis (Kuptseva) Round et Håk. Observations of the external ligula-like segment have been included as recent research suggests its usefulness as an identifying characteristic.
Diatomite outcrops at three sites, Oto r i, Noharu and Matsuo of Yamaga Town in Oita Prefecture, Kyushu, Japan, were investigated, and 94 taxa in 39 genera of freshwater diatoms were found from 7 samples taken at the three sites. Every sample contained a high frequency of the same centric diatoms, and the dominant species were Stephanodiscus komoroensis, Cyclostephanos kyushuensis and Aulacoseira sp. of which taxonomic information is presented here. The diatom assemblages of the 7 samples suggest that the d iatomite of all three sites were deposited in the same paleo-lake. This supports the result of a previous geological study that all of the three sites are from the same stratum.
New records of diatoms were observ e d from the River Alaknanda-Ganga,32 from the Alaknanda and 26 from the Ganga amounting to 58 taxa. The tally of diatom taxa from the Alaknanda-Ganga has risen from 193 reported earlier to 251. Recently,77 new records of diatom taxa were found among 200 species, varieties and forms from the Mandakini basin drained by River Mandakini, a tributary of the Alaknanda, thus increasing the count to 328 of 30 genera in Garhwal Himalaya. Three of the new records were Cyclotella (centrales)and remaining 325 were pennales. The pennate flora was dominated by biraphids (210 taxa) represented by 18 genera. Navicula (50), Cymbella (39), Gomphonema (29) and Nitzschia (28), while Pinnularia (12) dominated among the rest 13 genera that represented 52 species, showing richness at generic level. The remaining components included 45 araphids of 6 genera, largely Synedra (19), Fragilaria (14) and Diatoma (9) and only 13 raphidioids (Eunotia 12 and Peronia 1). Notably,57 monoraphids belonged to just 3genera. Achnanthes (49) dominated them. Navicula and Achnanthes were the most species rich genera. Achnanthes (33,38) was species rich than Navicula (25,28) in the Alaknanda-Ganga and Mandakini basin, respectively. There was an overall decrease in the raphidioids (12 to 2), monoraphids (45 to 34) and biraphids (115 to 103) from high (Mandakini basin) to low elevation (Ganga), while araphids (32), were comparably higher at mid elevations (Alaknanda).
The National Water-Quality Assessm e nt (NAWQA) Program of the U. S. Geological Survey uses algal data together with other physical, chemical, and biological variables to assess the quality of rivers and streams throughout the United States. Pilot NAWQA studies (1987-1990) led to the development of methods for collecting algal samples from various instream habitats and to the publication of protocols for the identification and enumeration of algal samples to ensure nationally consistent data. During the first decade of the Program, more than 7,000 algal samples were analyzed from more than 1,500 river reaches throughout the United States. These data from the NAWQA Program and related studies have been incorporated into more than 70 publications,50 of which are cited in this paper. Determinations of algal biomass (algal biovolume, chlorophyll a, ash-free dry mass), autecological-guild and pollution-tolerance metrics, indicator taxa, physiognomy, and weighted-average optima and tolerance were used in evaluations of stream-water quality, depending onthe focus of each study. Relations of the biological datawith trophic condition, hydrologic disturbance, geochemistry, and land use were examined. Although species optima and tolerance values for diatoms differ depending on the scale of assessment (national and regional), species optima determined for indicators of alkalinity, water hardness, specific conductance, chloride, and sulfate were consistent with qualitative, autecological classifications for those taxa in western Europe. The ecological studies summarized here are part of nationally guided studies addressing selected water-quality issues, such as the effects of watershed urbanization and agricultural land use on nutrient enrichment and stream ecosystems. The algal data and related physical, chemical, and biological data are released (after quality reviews) and made available to the public online through the NAWQA website http://wate.usgs.gov/nawqa/.
Attached diatoms and water samples were seasonally collected from Szu-Tsao mangrove wetlands, in southwestern Taiwan, from autumn of October 1999 to summer of July 2001. In the 48 micro-algal samples collected from six sites,35 diatom taxa were identi-Red, and mainly were divided into eight dominant or codominant diatom groups for comparing with the ecological factors by statistical analysis. The eight groups in these wetlands were (1) Achnanthes spp. including A. brevipes and A. exilis, (2) Amphora spp. including A. granulata, A. holsatica, A. normanii, A. exigua and A. strigosa, (3) Cocconeis spp. including C. placentula var. euglypta and C. scutellum, (4) Mastogloia exigua, (5)Haslea sp., (6) Navicula spp. including N. angusta, N. cryptocephala var. veneta, N cincta and N. margalithii, (7) Pleurosigma normanii and (8) Nitzschia longissima. The results showed that mangrove dominant diatoms could do as bioindicators of water condition, for example, Amphora spp, Navicula spp. and Pleurosigma normanii were regarded as the most adapted to the pH value from 7.4 to 9.0. In addition, statistical analysis showed that environmental variables of salinity and nutrient resources of nitrogen and phosphate were the important factors which impacted the growth of diatom groups.
Encyonopsis leei Krammer 2003, prob a bly a common freshwater diatom in East Asia but so far very little known, is taxonomically examined by using both scanning electron microscopy (SEM) and light microscopy (LM). SEM reveals that this species has ultrastructures which is typical of Encyonema, and therefore we propose a new combination, Encyonema leei (Krammer) Ohtsuka, Hanada et Yus. Nakam. nov. comb. Although it is similar to Encyonema lacustre (C. Agardh) Mills in LM, they are apparently different from each other in the raphe structures. In total 102 specimens collected from four localities in Japan are morphometrically examined based on LM photographs. Four morphometric measurements, i. e. length, width, striae- and areolae densities, are significantly correlated with each other except the combination of striae- and areolae densities. Analysis of scores produced by principal component analysis (PCA) shows as a whole the measures approximately follow multivariate lognormal distribution irrespective of the heterogeneity between localities. The extrapolated PC scores of E. leei var. leei's type specimens are within the 99% interval of those of Japanese specimens with one exception of PC1 which might shift with the size reduction after the initial cell formation. In contrast, the extrapolated scores of E. leei var. sinensis' type specimens are in total out of the 99% boundary of the multivariate lognormal distribution mainly because of their wider valve in proportion to the length. Therefore, this variety can still be separated from E. var. leei in spite of the fact that areolae density, which is the chief criterion for their separation suggested in Krammer (2003), is in fact not much different between the two varieties' type specimens.
We have performed a statistical anal y sis on the pH tolerance of 485 diatom taxa in epilithic algal assemblages, collected from 215 freshwater sites, representing a pH gradient ranging from 1.0 to 12.5. In this study,45 Nitzschia taxa occurred. Among them 22 belong to alkaliphilous (16 taxa) or alkalibiontic (6 taxa) taxa, while 21 are circum-neutral taxa. Only two taxa were recognized as acidobiontic taxa. In this paper, we report on the ecological and morphological features of these two strange Nitzschia taxa occurring in the strong acid waters from pH 1.0 to 3.9 in Japan.
This study presents new information on the morphology of the brackish water species Achnanthes brevipes var. intermedia Kütz. based on the type slide and material. This taxon has been difficult to identify compared with A. brevipes C. Agardh var. brevipes because they resemble each other in the shape of the valve face. A. brevipes var. brevipes has valves that are usually more or less linear, slightly constricted at the centre and cuneate at the apices, and both valve faces are quite flat. On the other hand, var. inter-media has valves that are usually more or less elliptical with a rounder valve face. Furthermore, valve size of var. intermedia is smaller than var. brevipes. However, var. intermedia is not considered an independent species but should remain a variety of A. brevipes at this time because several structures that resemble each other are more than the differences between these two taxa. More observations are required about this taxon and the other species of A. brevipes complex to propose its specific rank.
Three new Eunotia taxa, Eunotia osoresanensis var. cuneata, E. raphidioides, E. pseudosoresanensis, and a new Navicula taxon Navicula acidobiontica were described. Among them three Eunotia taxa are thought to be acidobiontic and endemic to Lake Usoriyama, Aomori, Japan.
This study examined the relationship between the change of water temperature and the distribution of cold-water diatom species. This study uses data from 1973 to 2002 of the auto measurement system at continuous monitoring sites and the studies of periphytic algal assemblages in the urban rivers in long-term monitoring of aquatic organisms. In the rivers receiving sewage effluent, water temperatures have risen markedly since the mid-1980s at the downstream sites of the sewage discharge points. These environments contained few cold-water diatoms. Recently, in the rivers without a sewage treatment plant in the basin area and upstream part of the sewage discharge points, the water temperature has tended to drop. In these environments, cold-water diatom species were observed in each-study after the average water temperature -in winter-had dropped below 10°C over 4-5 years. Nevertheless, the relative abundance of these species in the periphytic diat om assemblage was low. These phenomena indicate the start of the recovery of seasonality.
The ultrastructure of the sporic diatom Muelleriopsis limbata (Ehrenb. ) Hendey is observed by SEM. Complete frustules recovered from the Miocene marine formations have shown trilayered wall and complicate attachment of opposed valves within a frustule. The epivalve always has a compressed bowl-shape and hypovalve is highly vaulted with the valvar edge extended to a broad circumferential flange. Preliminary considerations are given to affiliation and vegetative/sporic problems of this enigmatic fossil.
A new model describing the valve outline of pennate diatom, arc-constitutive model is here advocated. We measured the outline of 30 valves belonging to ten Navicula species using an arc-gauge, and found out that the outline can be resolved into arcs. Dividing the valve by apical- and transapical axis into four quadrant, the outline in each quadrant can be resolved in maxiMurfno u r 'arcs; main arc from the transapical axis, terminal arc from the apical axis, and two or less supplemental arcs smoothly connecting main- and polar axis. The valves were classified into six types based on the number and convexity/concavity of the supplemental arcs. After averaging the diameters and lengths of each corresponding arc in four quadrants, the valve outline was drawn as a combination of the arcs by using computer aided design (CAD). The drawn outlines were almost agreed with that of the original micrographs. We therefore conclude that the arc-constitutive model well explains valve outline of some pennate diatoms, at least of ten Navicula species evaluated in the present study.
The relationships between diatoms and water supplies are discussed.1) Diatoms give sever damages to water works: clogging both slow and rapid sand filters, mechanisms of clogging are different between them, though. Clogging of slow sand filter is caused by accumulation of diatom on the surface of sand layer, while that of rapid sand filter is caused chiefly by difficulty of coagulation-sedimentation of special diatom, e. g. Synedra acus.2) Diatoms have, on the other hand, very useful aspect to water works, e. g. diatom can be used as a tracer of water current in lake and reservoir, and as a indicator of leakage of impounded or supplied water, too. Several examples of both cases are shown.3)Three types are distinguished in precipitation patterns of dead or weakened diatom. And the mechanisms and application to water works are studied while precipitation rates of two species are measured in natural condition.
The history, type of diatom assemblages, sampling methods and statistical methods of biological monitoring for acidification, were studied. We examined published papers and discussed the problem of applying this monitoring to eastern Asia including Japan. Though, a technical challenge was thought to exist, a data set for this study did not exist in Japan and eastern Asia, and so we could not evaluate this problem. The construction of a data set for application to eastern Asia and Japan, is clearly needed.
Diatom assemblages of dystrophic water, Lake Ara-numa, Aomori Prefecture, were studied in August 2003. A total of 89 taxa among 25 genera were recorded. The dominant taxon was Fragilaria crotonensis var. binodis (61.3%).
The study focuses on applying the d iatom flora to evaluate environmental conditions of the Szczecin Lagoon. A total of 521 taxa (diatom species and varieties) of 74 genera were identified in the samples. Light microscope (LM) counts were processed with OMNIDIA software to yield diatom indices. The diatom flora structure and relations between assemblages at individual sites were explored with multivariate analyses. Applicability of diatom indices in assessing the state of the Szczecin Lagoon was confirmed. The inferences produced by diatom indices were compared with those derivedfrom directly measuring physico-chemical water parameters and from using the diatom bioindicative characteristics. Diatom indices produced conclusions similar to those resulting from conventional application of diatom bioindicative potential. Both methods showed the Szczecin Lagoon to be eutrophic and moderately polluted.
The types of pore occlusions found i n raphid diatoms were reviewed and their terminology was reassessed. In particular, the application of the term vola was questioned. Its usage within the raphid diatoms, and the Cymbellales in particular, is in conflict with its original designation. It was concluded that a new term should be adopted for flap-like occlusions with a broad attachment area, and the term foricula (window shutter) is proposed. Comparisons between different shapes of external opening in the Cymbellales suggest that these are formed similarly by the outgrowth of thin flanges of silica, but the final slit shape is dependent on the primary direction(s) of growth. A new form of pore occlusion was also recorded for the genus Placoneis. This comprises a roundish disc of silica, attached internally by a number of regularly arranged props. The term tectulum (little roof) is proposed. The importance of applying terminology consistently is discussed.
Gyrosigma prolongatum var. closterioi d es is raised to specific status as G. closterioides (Grunow) G. Reid stat. nov. The ultra-structure of G. closterioides, G. fasciola (Ehrenb. ) J. W. Griff. & Henfr., G. prolongatum (WSm. ) J. WGriff. & Henfr. and G. macrum (W. Sm. ) J. W. Griff. & Henfr. is investigated using light and electron microscopy.
A new species of Synedra from Urugu a y is described. Comparison with other species from the genus Synedra sensu lato suspected to be either auxospores or initial cells are made. We describe the new species with reference to its auxospore and initial cell structure as well as its vegetative valves.
The fossil marine genus Isodiscus Rattray presently comprises three species, I. debyi (E. Grove & G. Sturt) Rattray, I. mirificus Rattray and I. coronalis Brun; all are rare. One new species I. watanabei is described here. The genus is confined to the middle to late Eocene and its morphological features present difficulties in assigning it to a family or order. A new family Isodiscaceae is proposed and relationships discussed.
Fossil marine diatom resting spore morpho-genus Dispinodiscus gen. nov. is described using samples from DSDP Site 338 in the Norwegian Sea, Sites 436 and 438 in the northwest Pacific and from the Newport Beach Section, California. Dispinodiscus gen. nov. is characterized by having a valve with two bristles or spines near each apex. This genus includes four new taxa: D. stimulus sp. nov., D. pilusus sp. nov., D. pilusus var. montanus var. nov. and D. rugosus sp. nov.
Some brief thoughts on the considerable progress made to fit diatom distribution to the pH scale and some suggestions for further discussion on carrying the work forward are presented in appreciation of Dr Toshiharu Watanabe's contribution to this topic.
Fossil marine diatom resting spore m orpho-genus Coronodiscus gen. nov. is described using samples from DSDP Site 338 in the Norwegian Sea, Sites 436 and 438 in the northwest Pacific and from the Newport Beach Section, California. Coronodiscus is characterized by having sheathes surrounding the epivalve and hypovalve which possess rows of elongate simple pores. This genus contains two species: C. collarius sp. nov. and C. trigonus sp. nov. Coronodiscus trigonus is differentiated from C. collarius by having a sheath possessing a triangular process.