SCHIZOMERIS—A GROWTH FORM OF STIGEOCLONIUM TENUE (CHLOROPHYTA:CHAETOPHORACEAE)1

Schizomeris leibleinii Kütz. was found as an ecophene of Stigeoclonium tenue (Ag.) Kütz. in Centennial Lake, Palmerston North, New Zealand. The Schizomeris form occurred in autumn when the water was polluted by a large number of ducks. Sampling of the plant population of the lake and culture work showed that S. tenue has a high degree of polymorphism. Other forms of it which developed both in the lake and in culture were indistinguishable from Protoderma Kütz. emend. Borzi, from Uronema Lagerheim, or from Pearsoniella Fritsch and Rich, respectively.     

The distribution of Stigeoclonium tenue Kütz. in South Wales in relation to its use as an indicator of organic pollution

The distribution and frequency of Stigeoclonium tenue Kütz. in some South Wales rivers were studied for 12 months to assess the value of the alga as an indicator of organic pollution. It colonised organically polluted areas at most times of the year, and generally in greater abundance as compared with cleaner stations. Tolerance was observed over a wide range of a number of environmental factors: pH, water temperature, suspended solids content, flow, nitrate, nitrite and ammonia nitrogen, phosphate phosphorus, dissolved oxygen, B.O.D., electrical conductivity, chloride, total hardness, magnesium hardness and calcium hardness. Greatest tolerance was expressed mainly in the spring months when the organism became widely distributed in diverse habitats ranging from organically polluted to fairly clean conditions. Some precautions in the use of S. tenue as an indicator of organic pollution are therefore suggested. In particular, the frequency of the organism should be noted especially in spring, since organic conditions are suspect only when the alga is highly abundant.     

Trace metal biomonitoring in the soil and the leaves ofQuercus ilex in the urban area of Naples

The concentrations of Pb, Cu, Fe, and Mn were analyzed in surface deposit and tissue ofQuercus ilex leaves from several sites of the urban area of Naples, exposed to different degrees of air pollution. These included some major roads with heavy traffic loads, squares, and three urban parks. The soil from the trunk base area ofQ. ilex trees in the same sites was also analyzed for total and available metal contents. Pb, Cu, and Fe contents in the surface deposit and leaf tissue were significantly higher (p<0.01) in leaves from roadside sites than in leaves from parks; significant correlations were found between deposit- and tissue-contents of Pb, Cu, and Fe. Mn content in leaves from roadside sites and in leaves from parks were similar and Mn content in the leaf deposit was irrelevant. Significant differences (p<0.001) in both total and available Pb and Cu soil content were found between sampling sites. Also for available Fe and Mn soil content differences among sites were relevant, although the highest values were measured in soil from urban parks. A positive correlation between leaf and soil metal content was found only for Pb, thus suggesting that trace metal contents of leaves directly depend on atmospheric depositions. Seasonal variations of Pb, Cu, and Fe were pronounced at a polluted site, whereas no relevant seasonal variation was observed at a control site; moreover, metal accumulation was high at the polluted site. Mn content and seasonal dynamics were comparable at control and polluted sites.     

BENTHIC MARINE DIATOM ASSOCIATIONS: UPPER FLORIDA BAY (FLORIDA) AND ASSOCIATED SOUNDS1

Models of the diatom associations found in upper Florida Bay and adjoining sounds have been constructed utilizing Q modal factor-vector analysis and ecologic diversity indices (Shannon index, number of species, evenness). Four distinct associations were defined using Q-mode factor-vector analysis. Two associations were epiphytic, occurring on Thalassia testudinum König—Association I was characterized by Cocconeis placentula Ehr., Association III by Cylindrotheca closterium (Ehr.) Reim. & Lewin and Cocconeis placentula Ehr. The other two associations were epipelic, occurring on the carbonate mud substratum—Association II was characterized by Cyclotella striata (Kütz.) Grun., Rhopalodia gibberula (Ehr.) O. Müller and Surirella fastuosa (Ehr.) Kütz., Association IV by Fragilaria crotonensis Kitton and Cyclotella striata (Kütz.) Grun. The majority of the 161 species identified were present in both the epiphytic and epipelic assemblages. Only 33 species were restricted to the epiphyton, and 18 species restricted to the epipelon. The epipelic assemblage was significantly more diverse than was the epiphytic assemblage. A general trend of increased diversity away from terrestrial environs toward more open areas of water in both the epipelon and epiphyton was also found.     

COMMUNITY STRUCTURE DYNAMICS OF EPILITHIC AND EPIPHYTIC DIATOMS IN A MISSISSIPPI STREAM1

Epilithic and epiphytic diatoms were collected monthly from 18 June 1979 through 19 May 1980 from both shaded and unshaded sites of Sessums Creek, a shallow, oligotrophic and strongly alkaline stream in northeastern Mississippi. The dominant macroalgae were filamentous green algae belonging to the non-mucilage producing genera Cladophora and Rhizoclonium. Ninety taxa were identified with Navicula minima Grun. and Nitzschia dissipata (Kütz.) Grun. accounting for 50% of all valves counted. Other important taxa were Navicula menisculus var. upsaliensis (Grun.) Grun., N. cryptocephala var. veneta (Kütz.) Rabh., Achnanthes minutissima Kütz. and Cymbella turgida (Greg.) Cl. With few exceptions, the more dominant taxa were equally abundant in the shaded and unshaded sites and also in the epilithon and epiphyton. Species diversity (H') and the number of taxa in a sample in all four habitats showed an identical pattern, being lowest in winter and highest in fall. No one pair of habitats was more structurally similar than any-other pair when compared by a similarity index (SIMI). Apparently, differences in light intensity and substrate type had little effect on diatom distribution in Sessums Creek and it was concluded that the locality sampled supported a single, nearly homogeneous diatom community.     

SCANNING ELECTRON MICROSCOPY OBSERVATIONS OF DEFORMITIES IN SMALL PENNATE DIATOMS EXPOSED TO HIGH CADMIUM CONCENTRATIONS1

Different types of malformations are likely to affect the morphology of diatoms when exposed to particularly unstable environmental conditions, the most easily identifiable being distortion of the whole frustule. In the present study, we investigated, by means of SEM, valve abnormalities induced by high cadmium contamination (100 μg · L^?1) in small pennate diatoms. Changes in the shape of Amphora pediculus (Kütz.) Grunow and anomalous sculpturing of the cell wall of many species, such as Encyonema minutum (Hilse) D. G. Mann, Mayamaea agrestris (Hust.) Lange‐Bert., Gomphonema parvulum (Kütz.) Kütz., or Eolimna minima (Grunow) Lange‐Bert., were observed, which were not, or almost not, noticeable in the LM. With consideration to current knowledge of diatom morphogenesis, metal uptake by the cell would induce, directly or indirectly, damage to many cytoplasmic components (e.g., microtubules, cytoskeleton, Golgi‐derived vesicles) involved in the precisely organized silica deposition. This study confirms that many species, whatever their size, are likely to exhibit morphological abnormalities under cadmium stress, and that this indicator may be valuable for the biomonitoring of metal contamination, even if SEM observations are not necessary for routine studies.     

NOTES ON CLADOPHORA (CHLOROPHYCEAE). II. CLADOPHORA CATENATA (LINNAEUS) KÜTZ., 1843, EMEND. V. D. HOEK, 1963

The species name Cladophora catenata (L.) Kütz. emend, van den Hoek has priority over Cladophora fuliginosa Kütz.     

Examination of the type material of Synedra rumpens =Fragilaria rumpens, Bacillariophyceae

Fragilaria rumpens (Kütz.) G. W. F. Carlson is assumed to be a cosmopolitan species, and is often reported from ponds and lakes. Nevertheless, this species is similar to both Fragilaria capucina Desm. and Fragilaria vaucheriae (Kütz.) J. B. Petersen and, as a consequence, the taxonomy of all three species has been confusing. In an attempt to solve the taxonomic problems within this group, we have examined the type material of Synedra rumpens and discuss the differences between it and some of those species said to be similar.     

Metal Phytoremediation by the Halophyte Limoniastrum monopetalum (L.) Boiss: Two Contrasting Ecotypes

The phytoremediation potential of the halophyte Limoniastrum monopetalum for the removal of Cd and Pb from polluted sites is assessed in this work. Two pot experiments were conducted; the first with wild L. monopetalum grown on soil polluted with Cd and Pb irrigated at different salinities, and the second with commonly cultivated ornamental L. monopetalum grown on soil polluted with Cd irrigated also at different salinities. The data revealed that wild L. monopetalum is a Cd and Pb tolerant plant able to accumulate at least 100 ppm of cadmium in its shoots without showing any significant decrease in terms of biomass production, chlorophyll content or water content suggesting that it could be an accumulator of Cd. Pb above-ground accumulation was kept at low levels with the majority of Pb localized in the roots. On the other hand, contrasting results were obtained for ornamental L. monopetalum which although it was found to be also Cd tolerant, Cd accumulation in its tissues was kept at significantly lower levels especially compared to that of the wild ecotype. In addition for ornamental L. monopetalum salinity did not have a positive effect on Cd accumulation and translocation as observed in the wild type and in other halophytes. Analysis of the salt excretion crystals on the leaf surface confirmed that wild and cultivated ornamental L. monopetalum excrete cadmium and lead through their salt glands as a possible metal detoxification mechanism, although the amount excreted by the ornamental L. monopetalum is significantly less.     

POLYMORPHISM IN THE DESMID MICRASTERIAS PINNATIFIDA AND ITS TAXONOMICAL IMPLICATIONS1

A case of polymorphism in the desmid Micrasterias pinnatifida (Kütz.) Ralfs is described. It is based on material collected from the overflow channel of a dam in Caeté, Minas Gerais State. After careful examination of nearly 500 specimens, 26 different morphological expressions of the alga were found which led the authors to make the following deductions: (1) for delimitation of species and infraspecific taxa in desmids it is absolutely necessary to analyze sample populations; (2) the morphological characteristics presently used, for delimination of some varieties of M. Pinnatifida (Kütz.) Ralfs seem to have no taxonomical value if only isolated individuals are examined; (3) the varieties granulata, inflata, and tridentata must be considered with some caution, until further studies are carried out, because they can be merely distinct morphological expressions of M. pinnatifida (Kütz.) Ralfs var. pinnatifida.     

Strategies providing success in a variable habitat: I. Relationships of environmental factors and dominance of Cladophora glomerata

Dominance of macrophytes and their response to environmental factors were studied in the river Ilm, Thuringia/ Germany with special reference to Cladophora glomerata (L.) Kütz. Macroalgae showed a growth peak in spring with C. glomerata, Ulothrix zonata Kütz., Lemanea fluviatilis (L.) C. Agardh and Audouinella sp. being the dominant species. Shortly after this peak, a rapid decline of macrophyte substrate coverage was observed. Only C. glomerata revealed a second growth peak in late summer/early autumn. Frequent disturbances of the macrophyte assemblage by floods resulted repeatedly in an almost complete wash out of benthic organisms. After summer floods C. glomerata was the species that recolonized the substrate. At high‐light sites, faster recovery of C. glomerata was observed as compared to low‐light sites. This is discussed in relation to the life cycle of C. glomerata. Among the physical and chemical parameters that were analysed, irradiance, current velocity, pH, soluble reactive phosphorus and ammonia‐nitrogen accounted for most of the observed patterns of dominance of C. glomerata.     

GENETIC ADAPTATION AND ACCLIMATION OF PHYTOPLANKTON ALONG A STRESS GRADIENT IN THE EXTREME WATERS OF THE AGRIO RIVER–CAVIAHUE LAKE (ARGENTINA)1

We tested if different adaptation strategies were linked to a stress gradient in phytoplankton cells. For this purpose, we studied the adaptation and acclimation of Dictyosphaerium chlorelloides (Naumann) Komárek et Perman (Chlorophyta) and Microcystis aeruginosa (Kütz.) Kütz. (Cyanobacteria) to different water samples (from extremely acid, metal‐rich water to moderate stressful conditions) of the Agrio River–Caviahue Lake system (Neuquén, Argentina). Both experimental strains were isolated from pristine, slightly alkaline waters. To distinguish between physiological acclimation and genetic adaptation (an adaptive evolution event), a modified Luria‐Delbrück fluctuation analysis was carried out with both species by using as selective agent sample waters from different points along the stress gradient. M. aeruginosa did not acclimate to any of the waters tested from different points along the stress gradient nor did D. chlorelloides to the two most acidic and metal‐rich waters. However, D. chlorelloides proliferated by rapid genetic adaptation, as the consequence of a single mutation (5.4 × 10^?7 resistant mutants per cell per division) at one locus, in less extreme water and also by acclimation in the least extreme water. It is hypothesized that the stress gradient resulted in different strategies of adaptation in phytoplankton cells from nonextreme waters. Thus, very extreme conditions were lethal for both organisms, but as stressful conditions decreased, adaptation of D. chlorelloides cells was possible by the selection of resistant mutants, and in less extreme conditions, by acclimation.     

Observations on the structure of some forms of Gomphonema parvulum Kütz

Isolates from four sites were identified as varieties of the diatom Gomphonema parvulum Kütz. The material was examined by light and electron microscopical techniques. A detailed account of the morphology of this species is given.

No fundamental differences between the varieties were found apart from cell shape. It is considered that cell size is of no importance to classification below the species level since reduction in size occurred in all the isolates during normal growth.     

Geothermal diatoms: a comparative study of floras in hot spring systems of Iceland,New Zealand,and Kenya

Diatom floras were examined from geothermal environments in three contrasting tectonic settings. These included subduction-related acid and alkaline springs in New Zealand; alkaline springs along a divergent plate boundary on Iceland; and alkaline springs in the Kenya Rift. These shallow (<1 cm) aquatic environments vary considerably (e.g., temperature: 21.3–99°C; pH: 2.1–9.65; 56.41–643 mg l⁻¹ SiO₂). Diatoms form an important component of geothermal floras at temperatures of <45°C. The floras from New Zealand are distinguished by the common occurrence of Pinnularia. Icelandic springs have a variety of Fragilariaceae. Navicula and Anomoeoneis are most common in the Kenyan springs. Statistical analyses suggest that the diatoms cluster into seven major groups. The most common taxa include: Achnanthidium exiguum v. heterovalvum (Kras.) Czarn., Anomoeoneis sphaerophora (Ehrenb.) Pfitz, Brachysira brebissonii f. thermalis Grun., Caloneis bacillum (Grun.) Cl., Craticula cuspidata (Kütz.) Mann, Diadesmis confervacea Kütz., Epithemia argus (Ehrenb.) Kütz., Frustulia rhomboides (Ehrenb.) DeT., Hantzschia amphioxys (Ehrenb.) Grun., Navicula tenelloides Hust., Nitzschia amphibia Grun., Nitzschia inconspicua Grun., Nitzschia invisitata Hust., Nitzschia frustulum (Kütz.) Grun., Nitzschia sigma (Kütz.) W, Smith., Pinnularia chapmaniana Fog., Pinnularia appendiculata (Ag.) Cl., Pinnularia molaris (Grun.) Cl., Pinnularia acoricola Hust., Rhopalodia gibberula (Ehrenb.) O. Müll., Staurosira construens v. venter (Ehrenb.) Ham., Staurosira elliptica (Schum.) Will. & Round, and Staurosirella pinnata (Ehrenb.) Will. & Round. Canonical correspondence analysis shows clear correlations between species, alkalinity, pH, and conductivity, with less strong correlations for silica and temperature. Other factors include substrate type, current velocity, and light conditions. The preservation potential of host deposits varies considerably, being lowest for springs on clastic deltas and highest where travertine or sinter is accumulating. Handling editor: J. Padisak     

PERIPHYTON COLONIZATION OF ROCK SURFACES IN A BOREAL FOREST STREAM STUDIED BY SCANNING ELECTRON MICROSCOPY AND TRACK AUTORADIOGRAPHY1

Periphyton colonization of natural rock surfaces and granite tiles was followed experimentally in the Matamek River, an acidic (pH 5.5) sixth order boreal stream in northeast Quebec, Canada. Accumulation of chlorophyll a and freshweight algal biomass was logarithmic over a 25 day colonization period. The major colonizers were Tabellaria flocculosa (Roth) Kütz., T. fenestrata (Lyngb.) Kütz., Mougeotia sp., and Eunotia pectinalis (Kütz) Rabh., and its varieties. The microcolonization sequence on granite tiles, followed over 27 days with scanning electron microscopy, showed an initial accumulation of algal cells on the upstream and downstream margins and in depressions, followed by a gradual filling-in of the flat surfaces. It is hypothesized that the observed slow rate of colonization was due to the high surface tension of the granite substratum and the absence of preconditioning by an organic film. It is further hypothesized that the increase in cellular carbon fixation rates of T. flocculosa measured over a 23 day period using nuclear track autoradiography parallels the development of an algal-detrital microcosm on the granite tile, and is evidence for the establishment of localized tight nutrient spiralling. It is suggested that the periphyton community may be regarded as a nutrient recycling system at a microenvironmental level which may be especially important in oligotrophic systems.     

Genetic and ecophysiological diversity of Cladophora (Cladophorales,Ulvophyceae) in various salinity regimes

Although Cladophora species frequently appear in brackish environments, their genetic diversity, phenological patterns and physiological properties have not been well investigated in these environments. Cladophora is distributed throughout Mikata‐goko, an area consisting of five coastal lakes that are directly or indirectly connected to the sea, resulting in a salinity gradient ranging from fully marine to freshwater. To elucidate genetic and ecological variation in Cladophora, we monthly compared ribosomal internal transcribed spacer sequences of Cladophora specimens across six study sites characterized by different salinity regimes for a year. A total of 12 ribotypes were detected and assigned to six species, four of which were restricted to the marine habitat. Ribotype I of C. vagabunda (L.) Hoek was distributed in high‐salinity brackish waters (mean salinity ≤13 psu; maximum salinity ≤31 psu), whereas C. vagabunda ribotype II and C. glomerata were abundant in low‐salinity brackish waters (mean salinity ≤5 psu; maximum salinity ≤10 psu). Although Cladophora albida (Nees) Kütz. and C. glomerata (L.) Kütz. were collected during all four seasons, C. laetevirens (Dillwyn) Kütz., C. oligocladoidea Hoek and Chihara, C. opaca Sakai and C. vagabunda displayed marked seasonal variation. Culture experiments revealed that optimal salinity conditions for vegetative growth vary among ribotypes collected from different salinity regimes, suggesting that Cladophora distributions are controlled by ribotype‐specific ecophysiological adaptations. In contrast, temperature optima and tolerance were similar among ribotypes showing different seasonalities, and thus their phenologies may be controlled by other environmental factors or biotic conditions, such as reproductive maturity and spore germination.     

STRUCTURE,LIFE HISTORY AND SYSTEMATICS OF RHOICOSPHENIA (BACILLARIOPHYTA). IV. CORRELATION OF SIZE REDUCTION WITH CHANGES IN VALVE MORPHOLOGY OF RH. GENUFLEXA1

Rhoicosphenia Grun. is a relatively isolated genus among the biraphid diatoms. Morphological changes in an isopolar member of the genus, Rh. genuflexa (Kütz.) Medlin, were investigated using light and scanning electron microscopy. The fully raphid valve showed changes in its flexure that could be correlated with size reduction during its life history from the initial cells to the smallest cells found in the population. Bands showed changes in number (from three to one) related to size reduction. Rh. genuflexa is morphologically similar to Rh. abbreviata (C. Ag.) Lange-Bert. (=Rh. curvata (Kütz.) Grun.), although the two are distinct taxa. These observations support previous contentions that Rhoicosphenia is a natural taxonomic grouping.     

Life history of Cladophora surera sp. nov. (Cladophorales, Ulvophyceae)

The life history of Cladophora surera sp. Nov., described from the south of the province of Buenos Aires, Argentina, was found to be diplobiontic and isomorphic with haploid gametophytic (n= 24) and sporophytic (2n= 48) plants. Other freshwater species, namely C, suhriana Kutz, and C. callicoma Kütz. have also been reported to be diplobiontic and isomorphic but differing from C. surera by their ploidy level. Plants exhibit great morphological variation, as the number of branches/mm² tends to increase with higher water velocity, thus adopting morphotypes that resemble very different species, that is, C. vagabunda (L.) Hoek, C. glomerata (L.) Kutz., C, laetevirens (Dillw.) Kutz., C. brasiliana Martens, C. dalmatica Kütz., C. vadorum (Aresch.) Kütz. and C. rivularis (L.) Hoek., but clearly differing from them by other morphological parameters; apical cell diameters, The ploidy level 24/48 has not been established for a species of Cladophora. Autogamy is the normal conjugation method and can take place even inside the gametangia before the gametes are released. Isogametes conjugate in a slow behavioral anisogamy, in which the contents of one migrate to the other. Tetra-flagellate zoospores result from meiosis.     

INFLUENCE OF VARIOUS EXPOSURE PERIODS ON THE BIOMASS AND CHLOROPHYLL A OF CLADOPHORA GLOMERATA (CHLOROPHYTA)1

The biomass of Cladophora glomerata (L.) Kütz. was estimated at selected sites in the Colorado River between Glen Canyon Dam, Arizona, and River Kilometer 354. C. glomerata biomass was significantly higher at sites above Lees Ferry (25 km downstream from the Dam) than sites below the Ferry. Biomass and chlorophyll a were significantly reduced when C. glomerata was subjected to one-time exposures to the atmosphere for 12 daylight h in more. Repeated 12/12 h and 24/24 h (exposure/submergence) cycles over a two-week period also showed a significant reduction in biomass. The adaptations of C. glomerata to “stranding” during regulated flows are discussed.     

ABSOLUTE CONFIGURATION ANALYSIS OF THE FLAGELLAR APPARATUS IN CLADOPHORA AND CHAETOMORPHA MOTILE CELLS,WITH AN ASSESSMENT OF THE PHYLOGENETIC POSITION OF THE CLADOPHORACEAE (ULVOPHYCEAE,CHLOROPHYTA)

Absolute configurational analyses of flagellar apparatus components were performed on the motile cells produced by three species of Cladophora, Cl. dalmatica Kütz., Cl. flexuosa (Dillw.) Harv., and Cl. glomerata (L.) Kütz., and by Chaetomorpha aerea (Dillw.) Kütz. There was little variation among the species. All of the flagellar apparatuses demonstrated the ulvophyceous features of 180° rotational symmetry, counterclockwise absolute orientation, and basal body overlap, as well as the alignment of the basal bodies perpendicular to the long axis of the cell. Diagnostic features included the nearly complete absence of C tubules from the basal bodies and the presence of a coarsely striated component dorsal to the two-membered rootlets in all cells, as well as, in quadriflagellate cells, a tetralobate distal fiber, the coaxial arrangement of the lowermost pair of basal bodies, and the presence of a characteristic array of basal-body-associated striated bands. The distal fiber architecture, the presence of a “wing” in the X-membered rootlets, and the “flattening” of the flagellar apparatus components suggests a close relationship of the Cladophoraceae to the Dasycladales, and indicates that these two groups may have shared a common ancestor, possibly ancient in terms of the geological time scale but relatively recent in the context of ulvophyceous evolution. A sizeable phylogenetic gap exists between the Cladophoraceae and uninucleate-celled, presumably primitive members of the Ulvophyceae.