Girdle View Research Articles

Ulnaria asymmetrica sp. nov. (Bacillariophyta), a new fossil species from the Trout Creek Miocene locality, Oregon, USA

A new species of Ulnaria (Kützing) Compère is described from the Miocene Trout Creek fossil locality, situated in Harney County, Oregon, USA. The rock material from which the new species is described consisted of a subsample taken from the matrix harboring a plant fossil collected in 1932 or 1933 and archived at the Field Museum of Natural History, Chicago, Illinois, USA. The new species differs from all other taxa in the genus by possessing club-shaped valves that are asymmetric about the transverse axis, and frustules that are cuneate-shaped in girdle view. In addition to its unique shape, valves of the new species have a well-developed ocellulimbus (pore field) at each apex, a single rimoportula at one or both poles and closed girdle bands. The virgae are thick relative to the vimines, areolae possess exterior closing plates, and on larger specimens, the uniseriate striae can become biseriate near the valve margins. Material at the Trout Creek locality was deposited approximately 15.6–14 Ma during the Middle Miocene Climatic Optimum (MMCO). Given the diatom species co-occurring with the new Ulnaria species, it likely inhabited the plankton.

Gomphonema incrassata sp. n., a new benthic diatom species (Bacillariophyceae: Gomphonemataceae) from Walayar Dam, Palakkad district, Kerala, India

ABSTRACT A new freshwater benthic diatom species, Gomphonema incrassata sp. n. (Mohan and Prabha), is described from the Walayar Dam, Palakkad district, Kerala, India. The description is based on data derived from light and scanning electron microscopic studies. The main features of Gomphonema incrassata are: valves are weakly heteropolar; linear-lanceolate; head pole is bluntly round; basal or foot pole is sharply rounded; and the frustule is club-shaped and flexed (bent) in the girdle view. In addition, the analysed physicochemical characteristics revealed that Walayar Dam is moderately polluted, due to various human activities. The newly identified freshwater diatom species adds to the knowledge of diatom diversity in the Indian subcontinent.

Morphology and molecular phylogeny of two marine diatom species, Falcula cf. media and F. rectangularis sp. nov. (Bacillariophyta) from Japan

ABSTRACT Two members of the marine diatom genus Falcula, which has been little known for a long time, were found from the surface of some Japanese seaweeds; one was assigned to F. cf. media and the other was described as a new species, F. rectangularis sp. nov. Aside from the arcuate valves and slit-like apical fields, typical of the genus, detailed morphological observations using light and scanning electron microscopy revealed resemblance between F. cf. media and F. rectangularis in areolae, stria density and lack of costae. However, the two species can be distinguished based on several morphological features, including the valve length, plastid arrangement, and frustules in girdle view. A three-gene molecular phylogeny recovered these two species as monophyletic with a high interspecific rbcL difference, which in turn were sister to the clade containing taxa that belong to the orders Cyclophorales and Protoraphidales with low support. The members in this poorly supported assemblage share apical fields composed of slits. The two species of Falcula were phylogenetically distinct from Pseudofalcula hyalina, a member previously assigned to Falcula.

Bimodal Cell Size and Fusing Cells Observed in a Clonal Culture of the Ciguatoxin-Producing Benthic Dinoflagellate Gambierdiscus (WC1/1).

Cells in a clonal culture of the WC1/1 strain of Gambierdiscus that produced ciguatoxin and maitotoxin-3 were observed to spontaneously fuse during the light phase of culture growth. Cells in the process of fusion were indistinguishable from other cells under the light microscope, except that at least one (often both) of the fusing cells displayed an extendible, finger-like protrusion (presumed peduncle) arising from near the sulcul region. Fusion started with one of the cells turning 90° to place the planes of the girdles approximately at right angles to each other, and movement of the transverse flagella ceased in both cells, or in the cell seen in girdle (lateral) view. The cell in girdle view appeared to fuse into the theca of the other cell. The cell that had turned 90° often rounded up and become egg shaped (obovoid) during early fusion. Fusion can be quick (<10 min) or can take more than an hour. We saw no evidence of the theca being shed during fusion. Measurement of the dorsoventral and transdiameters revealed a wide range for cell sizes that were distributed as a bimodal population in the clonal culture. This bimodal cell population structure was maintained in clonal cultures reisolated from a small or large cell from the original WC1/1 culture. Cellular production of ciguatoxins by the WC1/1 clone increased during the first two years in culture with a corresponding decrease in production of maitotoxin-3, but this inverse relationship was not maintained over the following ~1.5 years.

Diatomasinensis: a new diatom species (Bacillariophyta) found in the brackish Lake Qinghai, China.

Lake Qinghai is an ancient brackish water lake in which several endemic diatom species have been discovered. In this study, a species of Diatoma is observed under light and scanning electron microscopy and described as new, Diatomasinensis sp. nov. The living cells of D.sinensis always lie in girdle view due to the cell depth being much larger than valve width (3.3-8.8 vs. 2.0-3.0 μm). The valves of D.sinensis are characterized by their narrow, linear-lanceolate outline, with capitate to subcapitate apices, the presence of two rimoportulae, one at each apex, embedded in the last rib or located among striae and a 4:2 configuration of girdle bands in normal vegetative cells, with four bands assigned to the epivalve and two to the hypovalve. The new taxon is compared with similar species from the genera Diatoma and Distrionella.

Three new Achnanthidium (Bacillariophyceae) species from Lake Salda (Anatolia, Turkey), a deep soda lake

Background and aims – Kützing separated the genus Achnanthidium from the genus Achnanthes based on two species: Achnanthes minutissima and Achnanthidium microcephalum. These two genera were distinguished by the presence of stalks in the Achnanthes genus and their absence in Achnanthidium. Before electron microscopy, the difference between Achnanthes and Achnanthidium was not clear, especially in Achnanthidium minustissimum sensu lato. The aim of the study is to describe three new species of Achnanthidium from Lake Salda. Material and methods – Lake Salda is located in southwestern Anatolia, in Turkey. The diatoms were collected seasonally from four stations in the lake between 2016 and 2020, from different substrata (epipelic, epiphytic, and epilithic). Key results – Three new species belonging to the genus Achnanthidium have been found in Lake Salda, Turkey. Based on the morphological observations, all new taxa are part of the Achnanthidium minutissimum complex. Achnanthidium barlasii sp. nov. and A. dumlupinarii sp. nov. show a high degree of similarity to each other, but can be separated based on valve outline and a denser areolation, especially in striae close to the apices of the raphe valve. Both species can be distinguished from A. minutissimum based on more separate apices and less elliptic valves. In the case of A. dumlupinarii sp. nov., large specimens show slight undulations of the valve, which is a unique feature. Achnanthidium anatolicum sp. nov. is the most characteristic based on its valve width, broadly rounded valve apices, and almost straight valves in girdle view. All newly described Achnanthidium species can be found in lentic environments, with alkaline water and high calcium ion content. Conclusion – The newly described taxa occurred in the unique habitat of a soda lake. The environment of the lake is highly alkaline, rich in magnesium and calcium, and derived from limestone and dolomitic limestone rocks.

Rise of Subgen. Rhoicosphenula Lange-Bert. to the Genus Level, and Description of a New Gomphosphenia s.s. Species from Puerto Rico

The subgenus Rhoicosphenula Lange-Bert. has a unique character combination that differentiates it from Gomphosphenia subgen. Gomphosphenia Lange-Bert. In particular, Rhoicosphenula has striae/areola features that are similar to Gomphosphenia, but is differentiated from that genus by also having pseudosepta present on both poles of the valves, copulae with septa at one of the poles, and frustules almost rectangular in girdle view. Together, this character combination strongly supports it as an independent genus following modern diatom-taxonomy criteria. Moreover, the only species of Rhoicosphenula known so far was collected from a peculiar acidic and dystrophic habitat, whilst most Gomphosphenia s.s. species colonize medium-conductivity, alkaline inland waters. On the basis of LM and SEM studies, we also propose a species of Gomphosphenia (G. patrickiana Cantonati, Lange-Bert., Kociolek & A.A.Saber, sp. nov.) as new to science. The new species is mainly defined by its valve outline and dimensions, length to breadth ratio, striation density, and geographical distribution. It was found in several samples of two streams in Puerto Rico, sometimes with high relative abundance. Gomphosphenia patrickiana Cantonati, Lange-Bert., Kociolek & A.A.Saber, sp. nov. was much more abundant in the stream with lower nutrient (in particular P) concentrations, and higher ecological integrity. The new species seems to prefer moderately alkaline freshwater habitats with medium-high conductivity and oligo- to mesotrophic conditions, with moderate tolerance to N enrichment. Also noteworthy is the occurrence of the new species in streams with above-average magnesium concentrations (due to the local geology). This Neotropical, warm-water species might be a potential indicator of global warming effects.

Analysis of the type material of Gomphosphenia tackei (Bacillariophyceae) and comparison to epizoic diatom populations on freshwater snails

Background and aims – Hustedt (1942) originally described Gomphosphenia tackei from Germany under the name Gomphonema tackei. Because of the small cell size and the lack of scanning electron microscopy (SEM) images from the type material, it is often confused with other species from this genus, especially with G. stoermeri. The aim of this paper was to present detailed morphological characteristics of G. tackei based on the analysis of the type material and of several epizoic populations from Central Europe. Material and methods – The material in this study was collected from the shells of the freshwater snails Lymnaea stagnalis, Planorbarius corneus, and Planorbis planorbis. Additionally, for an unambiguous species identification, the type material for Gomphosphenia tackei was analyzed using light and scanning electron microscopes.Key results – The presence of Gomphosphenia tackei was confirmed in the studied material. The largest population (up to 19%) was recorded on the shell surfaces of living snails, whereas on empty shells, the diatom did not seem to be present or only in very low numbers. Valves are typically clavate with rounded apices. Valves are frequently observed in girdle view, often joint together in pairs. The valves in the studied populations had a valve length of 7–29 µm, a valve width of 3–4 µm, and a stria density of 25–29 striae in 10 µm. In the type population, valve length ranged from 7.5 to 27 µm with a valve width of 3.0–4.0 µm and a stria density of 23–29 striae per 10 µm. Striae were composed of 2–4 elongated to rounded areolae per stria. At the apices, the striae were composed of one single areola. The cells were attached to the substratum by their footpole.Conclusion – Published illustrations of Gomphosphenia tackei do not always correctly represent this species. Individual cells are attached to the substratum by secreted mucilage, probably via their areolae or girdle band pores located on the footpole.

Diversity in the section Compressa of the genus Chaetoceros (Bacillariophyceae), with description of two new species from Chinese warm waters.

Monoclonal strains of Chaetoceros species were collected from Chinese warm waters. Vegetative cells and resting spores were examined using light microscopy as well as scanning and transmission electron microscopy. Combined morphological and DNA sequence data from the hypervariable D1-D3 region of the nuclear ribosomal large subunit showed the presence of two new species within the section Compressa, herein described as Chaetoceros bifurcatus sp. nov. and C.millipedarius sp. nov. Both species possessed features typical of the section Compressa, but C.bifurcatus was characterized by the heavy intercalary setae fusing and extending together for a distance before diverging. The heavy setae were not visually contorted, lacking poroids and spines, in contrast with how the section Compressa has been defined. Chaetoceros millipedarius was characterized by a horizontal stagger of ordinary intercalary setae when the chain was seen in broad girdle view, making the chain look like a millipede. The two new species were supported by molecular phylogenetic analyses with C.bifurcatus sister to C.contortus var. ornatus, while C.millipedarius was sister to C.contortus var. contortus. Based on the morphological features exhibited in C.bifurcatus, the diagnosis of the section Compressa was emended to exclude "contorted" heavy setae and compressed valve faces.

Entomoneis triundulatasp. nov. (Bacillariophyta), a New Freshwater Diatom Species from Dongting Lake, China

The diatom genus Entomoneis includes species with a unique morphology, having panduriform frustules in girdle view, often twisted about its apical axis, with some unique characters such as a sigmoid raphe on elevated bilobate keel, differently shaped junction lines, numerous girdle bands and variously perforated striae. Most of the species belonging to this genus are found to be brackish or marine, with some occurrences in freshwater habitats, but not one species has been described as exclusively freshwater. In this study, the new freshwater diatom species Entomoneis triundulata sp. nov. is described based on a detailed morphological observation using light and scanning electron microscopy. The specific features of E. triundulata are its triundulate valve margin; the shape of the transition between keel and valve body having a proximal U-shaped end, a slightly curved middle segment and a distal V-shaped end; and five sub-compartments to the frustule cavity. Besides morphological features unique to E. triundulata, similarities with other Entomoneis species are reported and discussed.

Chaetoceros coloradensis sp. nov. (Bacillariophyta, Chaetocerotaceae), a new inland species from Little Gaynor Lake, Colorado, North America

Chaetoceros is a large, mostly marine genus of diatoms that contains over five hundred species worldwide. Most species of Chaetoceros form chains, while a small minority are solitary in their growth form. Only seven Chaetoceros species have been reported in inland waters of Western North America, including C. amanita, C. elmorei, C. hohnii, C. muelleri, C. muelleri var. subsalsum, C. simplex and C. transisetus. A new Chaetoceros species, Chaetoceros coloradensis sp. nov. was found in Little Gaynor Lake in Boulder, Colorado, USA. We describe this new species using light and electron microscopy. Chaetoceros coloradensis has two setae per valve. Setae on opposite valves have different orientations in valve view, being offset by 30–45o from one another while all four setae lie in the same focal plane in girdle view. No processes exist on the valve surface of this new species. Individual gene and a concatenated sequence data set of LSU rDNA and SSU rDNA for C. coloradensis show that this species is allied with other solitary species in the genus. We compare and contrast the new species with all other twenty-one solitary species recorded, and comment on the section Simplicia, a group within Chaetoceros comprised exclusively of solitary species.

Morphology and molecular phylogeny of Chaetoceros dayaensis sp. nov. (Bacillariophyceae), characterized by two 90° rotations of the resting spore during maturation.

Recent studies suggest that a high species diversity of Chaetoceros exists in tropical waters. Based on plankton samples from Chinese tropical waters, Daya Bay of the South China Sea, a new species, Chaetoceros dayaensis sp. nov., is described. Vegetative cells and resting spores were examined by light microscopy as well as transmission and scanning electron microscopy. The nuclear rDNA molecular markers SSU, ITS and D1-D3 of LSU, and the chloroplast rbcL gene were sequenced for information on phylogenetic relationships. The species is characterized by the presence of two 90° rotations of the resting spore during maturation. First a rotation in the apical plane of the mother cell resulting in the valvar plane of the resting spore turning from parallel to perpendicular to that of the mother cell, and a second 90° rotation in the valvar plane of the mother cell resulting in the valve faces of the resting spore turning from facing narrow girdle view to broad girdle view of the mother cell. It is the first report of two 90° rotations of resting spores during maturation in Chaetoceros. Based on this, the maturation rotation of the resting spore of C.rotosporus was reevaluated. C.dayaensis belongs to the subgenus Hyalochaete Gran and we suggest placing it in the section Laciniosa, although a new subdivision of Chaetoceros is needed. The description of C.dayaensis was based on analyses of the phylogenetic relationships combined with morphological comparisons with other similar species.

A second species of Microtabella (Grammatophoraceae, Bacillariophyta) from Guam

One species ofMicrotabella,Microtabella interrupta, is widespread and has been known since the 19th Century but it has a convoluted taxonomic history leaving it presently the only species in the genus. The nameinterruptaderives from the chain-forming habit and the plastids being confined to a portion of the cell by a set of distinctively distended septa. This character makes it very easy to identify and very easy to overlook similar species, especially because the tabulate frustules are most often seen in girdle view. I found specimens of a new taxon that had these characters and was distinguished with difficulty in girdle view by the coarser striae on the copulae and the recurved edges of the septa. However, in valve viewMicrotabella rhombican. sp. has a much broader, rhombic outline. Ultrastructural differences include a more elongated apical pore field with a prominent spine, biseriate striae on the copulae and a different form of the ligule (a raised bar on the last copula). LikeMicrotabella interrupta, the mature epitheca ofMicrotabella rhombicacomprises numerous copulae with nearly flat septa, two copulae with distended septa and four hyaline pleurae that lack septa. This species could well be widespread but, as with other monospecific genera in which there is a strong distinguishing character, care must be taken to look beyond the outstanding feature.

Rhoicosigma parvum n. sp., a benthic marine diatom from The Bahamas and Western Pacific

A new diatom species, Rhoicosigma parvum Hein & Lobban, is described from benthic marine macroalgae and seagrasses northwest of Andros Island, The Bahamas, and from macro- and filamentous seaweeds of Guam and Palau. Specimens observed ranged in length from 30 to 70 µm, and in width from 6 to 9 µm, with 29–32 transverse striae in 10 µm. The frustule is slightly sigmoid in valve view and arched in girdle view. The two valves are dissimilar. The convex valve has an almost-straight raphe and the concave valve has a strongly sigmoid raphe. The chloroplasts are deeply lobed plates, one along each side of the girdle. Scanning electron microscopy revealed that the valves have loculate areolae, with the areolae opening to the valve exterior as apically elongated slits. By contrast, the internal areolar openings are rectangular, elongated apically. Externally, the central raphe endings are deflected in the same direction and terminate in pore-like expansions. The terminal fissures are strongly bent in opposite directions and in the same direction as the sigmoid curvature of the valve end. Internally, the central raphe branch endings are simple and straight, whereas the apical raphe endings terminate in well-developed helictoglossae. There are siliceous thickenings (central bars) on both sides of the central nodule. Specimens are similar to R. compactum (Greville) Grunow but are smaller and have finer striae.

A new uncommon epilithic Eunotia (Bacillariophyceae, Eunotiaceae) from the Chapada Diamantina region, Northeast Brazil

A new uncommon epilithic diatom, Eunotia relicta sp. nov., is described from a small oligotrophic, acidic stream in the Chapada Diamantina region, northeast Brazil. Eunotia relicta is a typical eunotioid form with a pronounced arch on the dorsal side of the valve mainly in smaller valves. Contrary to most Eunotia species, Eunotia relicta does not possess rectangular frustules in girdle view. Until now, this characteristic was only observed in a few species such as E. charliereimeri Edlund &amp; Brant, E. sarraceniae E.E. Gaiser &amp; J.R. Johansen and E. arcuoides Foged, all of them considered asymmetric along the valve plane. Some interesting morphological features of the new species are broad copulae on the dorsal side, an inconspicuous single conical spine on the valve face near the margin at both poles, and the irregularly thickened interstriae. Moreover, each valve has irregular projections at the dorsal valve face margin/mantle juncture and up to three rimoportulae per valve located on the mantle. These features associated with the distinct valve outline set it apart from E. charliereimeri, E. sarraceniae and E. arcuoides, which have no spines, smooth valve faces and 1–2 rimoportulae per valve.

Achnanthidium barbei sp. nov. and Achnanthidium costei sp. nov., two new diatom species from French rivers

Two new benthic freshwater species belonging to the genus Achnanthidium Kützing were found in French rivers located in the Languedoc-Roussillon region. Achnanthidium barbei and A. costei are described as new species based on light and scanning electron microscopy observations. These species belong to the ‘A. minutissimum complex’ based on the short, straight distal raphe fissures. Achnanthidium barbei and A. costei were found in rivers characterized by an alkaline pH and high phosphorus. Achnanthidium costei occurs in waters with very high conductivity and sulfate. The most characteristic morphological features of A. barbei are the bent frustule with recurved apices in girdle view, clearly lanceolate valves with convex margins and distinctly protracted apices, and the presence of up to six areolae per stria. Achnanthidium costei is characterized by a linear raphe valve outline and a wide axial area on the rapheless valve. Both species are compared with the most similar species: A. caravelense Novais & Ector, A. ennediense (Compère) Compère & Van de Vijver, A. eutrophilum (Lange-Bertalot) Lange-Bertalot, A. lineare W. Smith, A. minutissimun (Kützing) Czarnecki., A. pseudolineare Van de Vijver, Novais & Ector, A. sublineare Van de Vijver, Novais & Ector and A. tepidaricola Van de Vijver & M. de Haan. The ecological preferences of both species are assessed based on physicochemical analyses carried out on sites that are part of water quality monitoring networks.

Field Emission Scanning Electron Microscopy (FESEM) characterisation of the porous silica nanoparticulate structure of marine diatoms

Diatoms are unicellular algae that synthesize cell wall with silica that has highly ornate features on the nano to microscale. The porous silica nanoparticulate structure of three marine centric and one pennate diatoms namely, Coscinodiscus concinnus, Coscinodiscus sp., Odontella mobiliensis and Navicula directa were investigated by Field Emission Scanning Electron Microscopy (FESEM). Important morphological features like porous pattern, topography, pore size and shape were studied. The external layer (cribellum) of C. concinnus was found to be consisting of a characteristic pentagonal array of pores which were star in shape and irregular in size, with a diameter of 224.7 nm and a pore-to-pore distance of 160.6 nm. The second diatom species investigated, Coscinodiscus sp. showed frustule with radially-oriented pattern of alternating grid-like arrangements of pores with honeycomb topography with pore diameter of 132.1 and distance between arrays were 61.01 nm. The O. mobiliensis images showed well organisation of holes (foramen) showed hexagonal organisation and all the pores are circular with same size and pores of 328.6 nm diameter with pore to pore distance was 252.8 nm. The girdle view of N. directa was about 5 μm in diameter with values showing striae are parallel in whole and porous were observed in N. directa in the range of 278.3 nm, the gaps between regularly arranged pores were 145.6 nm was clearly observed. The internal and external structures of all the diatom frustules were different in pore arrangements. The present study showed that high-resolution FESEM results revealed the silica nanostructure with nanoporous material exhibited interesting application in antireflection, drug delivery and heavy metal adsorbing studies, which should be investigated further research will be a subject of future proposals by a flat form of present investigation.

Chaetoceros rotosporus sp. nov. (Bacillariophyceae), a species with unusual resting spore formation

Li Y., Lundholm N. and Moestrup Ø. 2013. Chaetoceros rotosporus sp. nov. (Bacillariophyceae), a species with unusual resting spore formation. Phycologia 52: 600–608. DOI: 10.2216/13-168.1With more than 400 species, the diatom genus Chaetoceros Ehrenberg is one of the most species-rich genera of marine planktonic diatoms. Although many Chaetoceros taxa are considered to be cosmopolitan, research has mainly focused on polar and temperate areas. Studies on material from tropical waters suggested that a high and undescribed species diversity of Chaetoceros occur here. On the basis of plankton samples collected in Daya Bay, South China Sea, a new species, C. rotosporus sp. nov., is described. Vegetative cells and resting spores were examined by light microscopy as well as transmission and scanning electron microscopy. The most variable part of the nuclear large-subunit ribosomal DNA was sequenced for information on phylogenetic relationships. Characteristic traits of C. rotosporus were a 90° rotation of the resting spore during spore maturation and a nearly rectangular silica wing that extended around the girdle of the immature resting spore. Neither character has been observed in previously described Chaetoceros species. Other distinguishing characters were the very large apertures and the single chloroplast, which formed a shallow bowl with four arms within each cell and appeared H-shaped in broad girdle view. Chaetoceros rotosporus sp. nov. belongs to the subgenus Hyalochaete Gran, but it could not be placed in any of the traditional sections of Chaetoceros, indicating a need for revision of Chaetoceros using a combination of morphological and molecular data.

A bloom-forming freshwater diatom: &lt;i&gt;Achnanthidium catenatum&lt;/i&gt;

作为区域重要饮用水源的浙江绍兴汤浦水库于2010年5月期间暴发以硅藻和蓝藻为主的藻类水华.对库尾、库中和坝前3处浮游植物样品进行采集和分析,结果表明,汤浦水库浮游植物密度在1.13×108~1.56×108cells/L之间,水华优势种之一为我国大陆地区首次报道的羽纹纲硅藻——链状弯壳藻(Achnanthidium catenatum),另一种为丝状蓝藻——湖泊假鱼腥藻(Pseudanabaena limnetica),两者的平均相对丰度分别为65.6%和28.2%;链状弯壳藻是弯壳藻属中唯一适应浮游生长的种类,具有独特的带面观,能以壳面相连形成2~3个细胞的短链状群体;对国内外3次链状弯壳藻为优势种的水华案例进行分析,发现该藻为广温性种类,适应低光强和低磷浓度生长;水华生消机理则需进一步研究.;In May 2010, algal bloom dominated by diatom and blue-green algae broke out in Tangpu Reservoir,which is the drinking water resource of Shao Xing,Zhejiang Province.Phytoplankton samples collected from 3 sites(Kuwei,Kuzhong,and Baqian) along the flow direction were investigated.The phytoplankton density ranged between 1.13×108 and 1.56×108 cells/L.The dominant species Achnanthidium catenatum(Bílý et Marvan) is a pennatae diatom,which was first reported from mainland in China.Another dominant species Pseudanabaena limnetica belongs to filamentous cyanobacteria,and their average relative abundances were 65.6% and 28.2%,respectively.Achnanthidium catenatum is the only planktonic species of the genus Achnanthidium showing distinctive girdle view and colonies consisting of a maximum of 3 frustules.Case studied of three different Achnanthidium catenatum blooms indicated that this species was eurythermal and adapted to lower light intensity and phosphorus concentration.Further study should shed more lights on the formation and disappearance mechanisms of this algal bloom.

Morphological study of the genus Eucampia (Bacillariophyceae) in Korean coastal waters

Regardless of continuous researches, recent researches on the genus Eucampia (Bacillariophyceae) have focused mainly on E. zodiacus f. zodiacus In the present study, species of the genus Eucampia have been studied based on their morphological characteristics. Eucampia species were collected at 24 sites from July 2008 to June 2011 in Korean coastal waters. Species were mainly identified based on the shape of valve, ocellus, and aperture, along with the length and shape of the bipolar elevations. As a result, five Eucampia species were identified: Eucampia cornuta, E. groenlandica, E. zodiacus f. zodiacus, E. zodiacus f. cylindrocornis, and E. zodiacus var. cornigera. E. cornuta and E. groenlandica have long pervalvar axis length, but the others display short or moderate length. Ocellus shape of E. cornuta, E. groenlandica and E. zodiacus f. cylindrocornis are linear ribs, whereas E. zodiacus f. zodiacus and E. zodiacus var. cornigera have radial ribs with central area. E. cornuta and E. zodiacus f. cylindrocornis have long and narrow cylindrical elevations. E. groenlandica and E. zodiacus f. zodiacus have short and broad elevations with blunt tips. E. zodiacus var. cornigera has long and broad conical elevations. In terms of aperture shape, E. cornuta has large elliptical form, E. groenlandica has almost circular to rounded rectangular form, E. zodiacus f. zodiacus has narrow and elliptical rounded rectangular to a narrow lanceolate form, E. zodiacus f. cylindrocornis has almost rectangular form, and E. zodiacus var. cornigera has rounded rhombic form. On the basis of elevations in broad girdle view, 5 Eucampia taxa could be divided into 3 types: `narrow H type`, E. cornuta and E. groenlandica; `regular H type`, E. zodiacus f. cylindrocornis and E. zodiacus var. cornigera (partial); `wide H type`, E. zodiacus f. zodiacus (almost).