170,079 research outputs found
A comparative study of Cocconeis scutellum Ehrenberg and its varieties (Bacillariophyta)
No full textWe present an ultrastructure-based revision (using light and electron microscopy) of the type species of the genus Cocconeis, C. scutellum var. scutellum, and four often-mentioned but poorly described, morphologically related varieties: C. scutellum var. baldjikiana, C. scutellum var. clinoraphis, C. scutellum var. parva, C. scutellum var. posidoniae. In addition, we introduce three new taxa, C. scutellum var. gorensis var. nov., C. scutellum var. posidoniae f. decussata f. nov. and C. scutellum var. sullivanensis var. nov. The taxonomic relationships between these varieties and the remaining validly described C. scutellum varieties are analyzed on the basis of their ultrastructural differences. We also provide additional information on the geographical distribution of all analyzed C. scutellum taxa. © 2008 by Walter de Gruyter
Composizione biochimica delle foglie di Zostera marina L. e del substrato sedimentario d’impianto
No full textOsservazione del Fitoplancton al microscopio elettronico a scansione (SEM) e a trasmissione (TEM)
No full textQuesto volume rappresenta l’aggiornamento del manuale pubblicato nel 1990 nella rivista Nova Thalassia 11 intitolato “Metodi nell’ecologia del plancton marino” ed è stato curato dal direttivo del comitato plancton della SIBM in carica dal 2007 al 2009. Lo scopo principale del volume è quello di confermare le metodologie ancora valide già proposte nel volume citato e di aggiornare le nuove tecnologie applicate nella moderna oceanografia biologica dedicata all’ambiente di mare aperto ed all’ambiente costiero. Il volume è rivolto alle istituzioni italiane di ricerca che studiano le problematiche legate all’ecologia del plancton marino, ma anche agli enti locali che per legge devono svolgere attività di monitoraggio.
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Revision of the genus Mastogloia, section sulcatae through electron microscopy
No full textThe genus Mastogloia Thwaites ex Smith includes a number of species living as epiphytes on
seaweeds and seagrasses. The genus is highly speciose and quantitatively significant in
benthic communities. It has a tropical to temperate worldwide distribution and is one of the
largest diatom genera.
Mastogloia is the only diatom genus characterized by a specialized valvocopula that
develops into a series of hollow chambers or partecta attached to each other to form a welldeveloped
partectal ring running along the inner side of the girdle band. Hustedt (1933) has
divided this genus into 11 sections of which one comprising the freshwater species.
The section Sulcatae has distinct external valve features including a variously shaped,
elongated median depression between the raphe‐sternum and the valve margin, siliceous
outgrowths (i.e., conopeum, pseudoconopeum, ribs and ridges) and deflected or sinuous
raphe branches. Internally, the valve face shows a lateral sterna and partecta with different
size and shape.
In this study, we present new ultrastructural details on the frustules of 11 species of
Mastogloia, section Sulcatae: M. baldjikiana Grunow, M. borneensis Hustedt, M. hustedtii
Meister, M. mediterranea Hustedt, M. umbra Paddock & Kemp, M. cannii Kemp & Paddock,
M. depressa Hustedt, M. exilis Hustedt, M. jelineckii (Grunow) Grunow, M. macdonaldii
Greville, M. pisciculus Cleve, including three new taxa (M. neoborneensis Pennesi & Totti, M.
oculoides Pennesi & Poulin and M. sergiana Pennesi & Poulin). Specimens were collected
from seagrasses and seaweeds in tropical (Siladen Island, Celebes Sea, Indonesia and Phú
Bài, China Sea, Vietnam), subtropical (Sharm el‐Sheikh, Red Sea, Egypt) and temperate
(Patmos Island, Aegean Sea, Greece) regions. We propose a revision of the Hustedt’s
Sulcatae section by dividing it in two subgroups: (1) one with a median depressions on the
external valve surface between the raphe‐sternum and the margin, and variably developed
siliceous outgrowths (i.e., conopeum and pseudoconopeum) covering the depressions to
various degrees; (2) the other lacking a developed conopeum or pseudoconopeum which
covers the median depression
Effect of salinity, temperature, organic and inorganic nutrients on growth of cultured Fibrocapsa japonica (Raphidophyceae) from the northern Adriatic Sea
No full textThe effects of temperature, salinity, inorganic and organic nutrients on the growth and physiological performance of Fibrocapsa japonica have been investigated in strains isolated from the northern Adriatic Sea, where intense and regular blooms have occurred since 1997 in coastal waters during summer. Strains isolated at different times and from different locations appeared homogeneous in terms of both physiological responses and molecular (ITS-5.8S rDNA) characteristics. Growth rates were higher at temperatures between 20 and 26 °C and a salinity range of 30-35 (0.7 div d-1). The temperature of 16°C inhibited growth, more markedly at the lowest and highest salinity values, a result also confirmed by a lower photosynthetic efficiency and by an increase in cell volume due to impaired division. Higher cell concentrations were obtained with macronutrients at f/2 levels than in a five-fold diluted medium. Comparing the utilization of 200 μM nitrate to that of different N sources (inorganic and organic), F. japonica showed an efficient growth with equivalent amounts of ammonia, urea and amino acids, such as glycine and tryptophan; glutamate was less effective, while methionine had toxic effects. Organic phosphate, administered as glycerophosphate, could also sustain F. japonica growth, probably on account of an alkaline phosphatase whose activity was enhanced in the presence of the organic form. Vitamins were necessary for growth, though no further stimulation was observed when a surplus of vitamin B12 (3 nM) was added. The addition of 11.7 μM iron instead of 2.3 μM, as well as that of humic acid, with or without macronutrients, did not enhance algal growth either. These results led us to hypothesise that F. japonica blooms became more frequent due to a general seawater temperature increase and to the availability of organic forms which, in coastal anthropized areas, are especially abundant in summer periods
Effect of salinity, temperature, organic and inorganic nutrients on growth of cultured Fibrocapsa japonica (Raphidophyceae) from the northern Adriatic Sea
No full textThe effects of temperature, salinity, inorganic and organic nutrients on the growth and physiological performance of Fibrocapsa japonica have been investigated in strains isolated from the northern Adriatic Sea, where intense and regular blooms have occurred since 1997 in coastal waters during summer. Strains isolated at different times and from different locations appeared homogeneous in terms of both physiological responses and molecular (ITS-5.8S rDNA) characteristics. Growth rates were higher at temperatures between 20 and 26 degrees C and in a salinity range of 30-35 (0.7 div day(-1)). The temperature of 16 degrees C inhibited growth, more markedly at the lowest and highest salinity values, a result also confirmed by a lower photosynthetic efficiency and by an increase in cell volume due to impaircd division. Higher cell concentrations were obtained with macronutrients at f/2 levels than in a fivefold diluted medium. Comparing the utilization of 200 mu M nitrate to that of different N sources (inorganic and organic), F japonica showed an efficient growth with equivalent amounts of ammonia, area and amino acids, such as glycine and tryptophan; glutamate was less effective, while methionine had toxic effects. Organic phosphate, administered as glycerophosphate, could also sustain F japonica growth, probably on account of an alkaline phosphatase whose activity was enhanced in the presence of the organic form. Vitamins were necessary for growth, though no further stimulation was observed when a surplus of vitamin B12 (3 nM) was added. The addition of 11.7 mu M iron instead of 2.3 mu M, as well as that of humic acid, with or without macronutrients, did not enhance algal growth either. These results led us to hypothesise that E japonica blooms became more frequent due to a general seawater temperature increase and to the availability of organic forms which, in coastal anthropized areas, are especially abundant in summer periods
Epiphytic diatoms from Terra Nova Bay (Ross Sea, Antarctica)
No full textIn polar waters, microalgal communities associated with macroalgae exhibit
rates of primary production comparable or even higher than those of
phytoplanktonic ones. These benthic communities are mainly represented by
diatoms. Despite to their crucial ecological role, the biodiversity of Antarctic
epiphytic diatoms is poorly studied and greatly underestimated. In the present
study, the diversity of epiphytic diatom communities from coastal waters of Terra
Nova Bay was investigated and described for the first time. Samplings were
made during the 8 Italian Antarctic expeditions in the space of 15 years. Thalli of
Iridaea cordata, Phyllophora antarctica and Plocamium cartilagineum were
collected during the austral summer. Collections were made from different
depths at 5 sampling sites. Taxonomical identification and counting of diatom
cells has been carried out by scanning electron microscope. According to our
results biomass appears to be inversely related to the diversity. The diatom
community composition varied depending on the sampling site as well as on the
morphology of the macroalgal host. Some differences could be observed along a
depth gradient. In terms of growth form in most cases adnate (e.g. Cocconeis,
Amphora) and mobile forms (e.g. Navicula, Nitzschia) dominated. Erect diatom
taxa tended to be associated with animal macrofouling species
Polyunsaturated aldehydes (PUAS) production and toxicity in a benthic environment: the microphytobenthos community of the Conero Riviera (northern Adriatic Sea).
No full textCocconeis distans Gregory and Amphicocconeis debesi (Hustedt) De Stefano comb. nov (Bacillariophyta), an intricate taxonomical history
No full textWe present a taxonomical revision of Cocconeis distans and C. debesi based on historical collections from Hustedt, and live material sampled from leaves of Posidonia oceanica. Our observations clarify the specific morphology of the two taxa, which have been confused by past and modern authors. In addition, we demonstrate that the valve structure of C. debesi deviates from that of the genus Cocconeis, but agrees with that of the genus Amphicocconeis. Therefore, we propose a new nomenclatural combination, Amphicocconeis debesi. The study also provides additional information on the geographical distribution of these taxa. © 2006 by Walter de Gruyter
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