DETECTION OF LIMITING OR SURPLUS NITROGEN IN ALGAE AND AQUATIC WEEDS1

The rate of NH₄+-N absorption by algae and aquatic weeds in the dark has been shown to be 4-5 times greater for plants which are N-limited as compared to plants with sufficient available N. Eight species of green algae, 2 blue-green algae, 2 diatoms, and 3 aquatic weeds were used to demonstrate the usefulness of the test in determining if available N was in surplus or limited supply in a particular environment. The test was shown not to differentiate between blue-green algae capable of fixing N (4 species) from media with NO₃-N or without combined nitrogen. The factors influencing the results of NH4⁺-N absorption tests have been investigated. In order to differentiate between plants with sufficient available N and those which are N limited, the rate of NH₄⁺-N absorption (0.1 mg N) over 1-hr incubation in the dark by 10-20 mg of algae or aquatic weed tissues is measured. The relatively simple analysis for NH₄⁺-N in the samples makes it very easy to follow the changing N nutrition of plants in cultures with a limited N supply or in the presence of possible N sources.     

Hydrocarbons in green and blue-green algae

Liquid column chromatography and thin-layer chromatography were used to determine the total content of hydrocarbons and gas chromatography was used to evaluate composition of hydrocarbons in green algae (Chlorella kessleri, C. vulgaris, Chlorella sp.,Scenedesmus acutus, S. acuminatus, S. obliquus) and the blue-green alga (Spirulina platensis) cultivated under autotrophic or heterotrophic conditions. InC. kessleri cultivated under heterotrophic conditions the content of hydrocarbons was found to be about 10^-2 % (per dry mass), whereas under autotrophic conditions it was about 10^-3 % (per dry mass). The highest content of hydrocarbons was detected in species of the genusScenedesmus cultivated autotrophically (10^-1 %). Heptadecane and hexacosane were found as major alkanes, 1-heptadecene was detected among alkenes.     

Seasonal variation of phytoplankton community in Thale Sap Songkhla, a lagoonal lake in southern Thailand

The phytoplankton in Thale Sap Songkhla was investigated at 2–3 month intervals from August 1991 to October 1993. The abundance of phytoplankton ranged from 1.4×10⁶ to 1.3×10⁹ cells m^–3. A total of 6 divisions with 103 genera were identified as Bacillariophyta: 49 genera, Chlorophyta: 21 genera, Pyrrhophyta: 15 genera, Cyanophyta: 12 genera, Chrysophyta: 3 genera and Euglenophyta: 3 genera. Although phytoplankton abundance was distinctly greater in the first year of study (August 1991–June 1992) than in the second year (August 1992–October 1993), their patterns are similar: 2 peaks yearly. The peaks of phytoplankton occurred in the heavy rainy season (northeast monsoon) and the light rainy season (southwest monsoon). The main bloom was found during December–January, with a predominance of blue-green algae (e.g. Aphanizomenon andPhormidium) and green algae (e.g. Eudorina). Their species composition also increased, an effect of the large amount of rainfall resulting in low salinity during the northeast monsoon. The minor bloom was produced by diatoms during June–July when water salinity was moderate to seawater. Both phytoplankton numbers and species composition were high. However, unpredictably heavy rainfall during the southwest monsoon period may reduce diatom production due to rapid immediate replacement by blue-green species. Besides salinity concentration, a low total nitrogen: total phosphorus (TN: TP) ratio tended to support the growth of blue-green algae. The diversity of phytoplankton was lowest in the heavy rainy period.     

Efficiency of using green algae as biological controllers against toxic algal taxa in cultured Nile tilapia Oreochromis niloticus,based on histopathological examinations

The incidence of harmful cyanobacterial blooms in surface waters has increased in frequency and outbreaks have become more severe. This research aimed at studying the effect of a culture of two green algal species as biological control of the growth of toxic blue-green algae. Nile tilapia of an initial mean weight of 55 g fish^?1 (SE 5) were used for each of four treatments in triplicate. All algal seedings were done at 4 × 10³ cells ml^?1. Treatment I (untreated) served as a control, Treatment II was seeded with Microcystis aeruginosa, Treatment III was seeded with green algae Chlorella ellipsoidea and Scenedesmus bijuga, and Treatment IV was seeded with a mixture of M. aeruginosa and C. ellipsoidea and S. bijuga. After 10 days, Treatment IV showed 3.4% viable cell survival, compared to 35% and 55% in Treatments II and III, respectively. Histopathological examination revealed mild degenerative changes and focal necrosis, as well as a depletion of haematopoietic tissues in Treatment IV compared to Treatment II. These findings suggest the efficacy of C. ellipsoidea and S. bijuga in controlling the growth of M. aeruginosa and minimising its side effects on cultured Nile tilapia.     

Algal nitrogen fixation in the tropics

Summary a)Nitrogen fixation in rice fields. Nitrogen-fixing blue-green algae grow abundantly in tropical regions and are particularly common in paddy fields. Their possible role in the nitrogen accumulation of soil has been studied. The most vigorous nitrogen-fixing blue-green algae have been assessed for use as green manure in rice fields and favorable effects have been reported in India and other countries. b)Nitrogen fixation by algae in water. The planktonic blue-green algae occur abundantly at certain time of the year in sea water and lake water, and some of them are known to be nitrogen fixers. Certain Japanese species of blue-green algae can withstand high temperatures including ten nitrogen-fixing species from hot-spring waters. c)Nitrogen fixation by symbiotic blue-green algae. Certain species of blue-green algae form associations with other organisms such as fungi, liverworts, ferns and seed plants. The relationship between these two organisms is on one occasion commensal and on others symbiotic. Certain symbiotic blue-green algae are provided with the ability to fix the atmospheric nitrogen.     

Screening of algal strains for metal removal capabilities

Eight algal species were tested for their ability to remove five toxic metalsduring 30-min exposures to single-metal (1 mg L^-1) solutions at pH7. Efficacy of metal bioremoval varied according to algal species and metal. Al⁺³ was best removed by the thermophilic blue-green alga(cyanobacterium) Mastigocladus laminosus, Hg⁺² and Zn⁺² by the thermophilic and acidophilic red alga Cyanidiumcaldarium, and Cd⁺² by C. caldarium and the green alga Scenedesmus quadricauda. All of these alga/metal combinations resultedin >90% metal removal. However, none of the eight algal speciesremoved more than 10% of Cr⁺⁶. Results indicate that some toxicmetals are more readily removed than others are by algae and that selectionof appropriate strains could potentially enhance bioremoval of specificmetals from wastewater at neutral pH.     

Cyclic adenosine-3': 5'-mono phosphate: Production and extracellular release from green and blue-green algae

Cellular and extracellular levels of cAMP were analyzed in the blue-green algae Microcystis aeruginosa, Anabaena flos-aquae, and Synechococcus leopoliensis and the green algae Chlorella pyrenoidosa, Cosmarium botrytis, Pandorina morum, Scenedes-mus communis, and Pediastrum biradiatum. On the basis of chromatographic analyses, and several biochemical assays, each alga produced cAMP and released it into the medium. Cellular cAMP (92–394 pmol g^?1) and extracellular cAMP (8–440 pmol liter^?1) varied greatly among species.     

Winter phytoplankton communities in different depths of three mesotrophic lakes (Łęczna-Włodawa Lakeland, Eastern Poland)

Phytoplankton samples were collected from three mesotrophic lakes: Piaseczno, Rogóźno and Krasne during winter seasons (from January to March). The samples were analyzed for species analysis and abundance of planktonic algae in relation to different depths of water column (0–7 m). Selected water physical-chemical parameters were also measured. Abundance of phytoplankton depended strongly on the thickness of snow and ice cover or mixing conditions. The maximal phytoplankton total number reached about 5 × 10⁶ ind. L⁻¹ beneath the clear ice in the Krasne Lake, minimal numbers were recorded under the thick snow and ice layers in the Piaseczno Lake (2 × 10³ ind. L⁻¹). The winter phytoplankton communities were dominated by flagellates principally cryptomonads (Cryptomonas spp. Rhodomonas minuta), euglenophytes (Trachelomonas volvocina, T. volvocinopsis), dinoflagellates (Peridinium bipes, Gymnodinium helveticum) and chrysophytes (Mallomonas elongata, M. akrokomos, Dinobryon sociale) or non-motile small species of blue-green algae (e.g. Rhabdoderma lineare, Limnothrix redekei), diatoms (Stephanodiscus spp., Asterionella formosa), and green algae (e.g. Scenedesmus spp., Monoraphidium spp.). Phytoplankton abundance and structure showed differentiation during the winter season and along the water column as well.     

Effect of larval fish and nutrient enrichment on plankton dynamics in experimental ponds

The hypotheses that larval fish density may potentially affect phytoplankton abundance through regulating zooplankton community structure, and that fish effect may also depend on nutrient levels were tested experimentally in ponds with three densities of larval walleye, Stizostedion vitreum (0, 25, and 50 fish m^–3), and two fertilizer types (inorganic vs organic fertilizer). A significant negative relationship between larval fish density and large zooplankton abundance was observed despite fertilizer types. Larval walleye significantly reduced the abundances of Daphnia, Bosmina, and Diaptomus but enhanced the abundance of various rotifer species (Brachionus, Polyarthra, and Keratella). When fish predation was excluded, Daphnia became dominant, but Daphnia grazing did not significantly suppress blue-green algae. Clearly, larval fish can be an important regulator for zooplankton community. Algal composition and abundance were affected more by fertilizer type than by fish density. Inorganic fertilizer with a high N:P ratio (20:1) enhanced blue-green algal blooms, while organic fertilizer with a lower N:P ratio (10:1) suppressed the abundance of blue-green algae. This result may be attributed to the high density of blue-green algae at the beginning of the experiment and the fertilizer type. Our data suggest that continuous release of nutrients from suspended organic fertilizer at a low rate may discourage the development of blue-green algae. Nutrient inputs at a low N:P ratio do not necessarily result in the dominance of blue-green algae.     

Nitrogenase Activity in Relation to Intracellular Organisms in Sphagnum Mosses

Electron microscopic studies of Sphagnum lindbergii (Schimp.) and S. riparium (Ångstr.) have revealed the presence of intracellular organisms such as blue-green algae, green algae, bacteria and fungi. Nitrogenase activities of these Sphagnum mosses were found to be related mainly to the presence of intracellular Nostoc filaments. The appearance of nitrogen-fixing blue-green algae within bryophytes is thus not restricted to liverworts. The association is likely to be of ecological importance as it seems to occur in very acid habitats generally lacking blue-green algae. Possible interrelations between the moss, the blue-green algae and different types of bacteria are discussed.     

LIGHT AND ELECTRON MICROSCOPY OF GRAZING BY POTERIOOCHROMONAS MALHAMENSIS (CHRYSOPHYCEAE) ON A RANGE OF PHYTOPLANKTON TAXA1

Grazing of fluorescent latex beads, bacteria, and various species of phytoplankton by Poterioochromonas malhamensis (Pringsheim) Peterfi (about 8.0 μm in diameter) was surveyed. The alga ingested fluorescent beads and various live or killed and nomnotile or motile organisms including bacteria, blue-green algae, green algae, diatoms, and chrysomonads. The size range of grazed prey was from 0.1 to 6.0 μm for latex beads and from 1.0 μm (bacteria) to about 21 μm (Carteria inverse) for organisms. As many as 17 latex beads (2.0 μm) or more than 10 Microcystis cells (5–6 μm) were ingested by a single P. malhamensis cell. Following such grazing, the cell increased in volume by up to about 30-fold. The range of cell volume of ingested prey was from 0.52 μm³ (bacteria) to about 3178 μm³(Carteria inversa). This study demonstrates for the first time that P. malhamensis is capable of grazing algae 2–3 times larger in diameter than its own cell and of grazing intact motile algae. Poterioochromonas malhamensis is an omnivorous grazer. Food vacuole formation and digestion processes were examined. The membrane that was derived from the plasma membrane and surrounded the prey disappeared sometime after ingestion. The food vacuole was then formed by successive fusion of numerous homogeneous vesicles accumulated around the prey. The prey was enclosed in a single membrane-bound food vacuole and then digested.     

Algal nitrogen fixation on the lava field of Heimaey,Iceland

Summary Nitrogen fixation (C₂H₂ reduction) by blue-green algae occurring on the juvenile lava field of Heimaey, Iceland was examined both in the laboratory (potential at 20° C and 39° C) and in the field, three and a half years after the volcanic eruption.Already at this early stage of colonization representatives of unicellular and filamentous heterocystous and non-heterocystous blue-green algae were commonly observed. The predominating algae were Nostoc sp. (20° C) and Schizothrix sp. — Microcoleus chthonoplastes, (39° C), the former often in association with the protonemata-rhizoids of moss plants.The potential for nitrogen fixation was recorded at an average rate of 109.2 (20° C) and 138.1 (39° C) ng N g^-1 h^-1 in soil collected from localities randomly distributed over the lava field.Tests for nitrogen fixation performed in situ revealed significant fixation activities in all the eleven localities subject to examination. The activities ranged from 2.8 to 63.4 (mean 21.5) ng N g^-1 h^-1 and 1.9 to 17.7 (mean 7.9) ng N cm^-2 h^-1.All the nitrogen fixation data noted imply that blue-green algae contribute a substantial part of the nitrogen input to the lava. Further, it was found that material incubated under micro-aerophilic conditions exhibited considerably enhanced nitrogenase activity.The role of nitrogen-fixing blue-green algae in general and Nostoc muscorum in particular in being suitable as pioneering organisms preparing the bare lava for ingress of other plants is also discussed.     

Concentration of 137Cs, 65Zn,and 85Sr by fresh-water algae

Differences in the concentration and retention of ¹³⁷Cs by unicellular diatoms, filamentous green algae, and filamentous blue-green algae were demonstrated under both batch and continuous-flow culture conditions. ¹³⁷Cs concentration factors were generally higher by a factor of 2 in batch tests than in continuous flow tests. In retention studies, ¹³⁷Cs was desorbed more rapidly from algae under continuous-flow conditions. Studies with blue-green algae indicate that ¹³⁷Cs concentrations in the various species were more closely related to the surface-to-volume ratios of algal cells than to the systematic relationships of the three species. Continuous-flow studies indicated no differences among three species of filamentous green algae in the concentration of ¹³⁷Cs, ⁶⁵Zn, and ⁸⁵Sr. However, the average concentration factors of the radionuclides were considerably different: 3800 for ⁶⁵Zn, 460 for ¹³⁷Cs, and 230 for ⁸⁵Sr. These radionuclides were rapidly desorbed following the transfer of algae to nonradioactive media. The desorption rate was inversely related to the concentration rate.     

Benthic algal populations respond to aluminum,acid, and aluminum-acid mixtures in artificial streams

Elevated aluminum (Al) concentrations are often associated with acid-stressed aquatic ecosystems, so it has been unclear whether acidic water or elevated Al is more responsible in changing community composition. Experiments were done to investigate effects of acidification and increased Al on the abundance of benthic algae in artificial streams supplied with natural water and nominal treatments of (a) pH 4.8, (b) 500 µg l^-1 Al, or (c) the mixture of pH 4.8 and 500 µg l^-1 Al compared to a control without added Al or acid. These treatments are referred to as Acid, Al-only, Acid + Al, and the control, respectively. In the Acid treatment the abundance of two diatoms, two green algae, dry weight biomass, and chlorophyll a decreased; one diatom and one filamentous blue-green alga increased. In the Al-only treatment, densities of two diatoms, one green alga, one blue-green alga, dry weight biomass, and chlorophyll a increased. In the Acid + Al treatment, abundances of one green alga, two blue-green algae, and concentrations of chlorophyll a decreased below the levels observed in the Acid treatment. Acid and Al concentrations were altered by each other and by chemical and biological processes in the stream system. Species of diatoms, green algae, and blue-green algae responded individually to treatments and mixtures of acid and Al. Shifts in the abundance of species may change food web relationships for higher-level consumers, and algae may be useful biomonitors of ecological stress.     

The Comparative Boron Nutrition of Several Green and Blue-Green Algae

The boron requirements of filamentous and non-filamentous species of green and blue-green algae have been investigated. A primary feature of this study was the quantitative analysis of the cells for boron. This permitted expression of the degree of purification of the environment and the boron requirements of the organisms in terms of cell content. Three species of green algae were shown neither to require boron nor to absorb it in appreciable amounts. In contrast, three species of blue-green algae readily absorbed boron and nitrogen fixing species showed a marked growth response to boron when nitrate was omitted from the culture medium. The response to boron was less with nitrate in the medium, probably due to increased contamination from the nitrate salt rather than an involvement of boron in the fixation process. The boron content of the deficient blue-green algae was 1–2 μg/g, suggesting a requirement below dicot angiosperms and comparable to monocots. In agreement with other reports, the fungus Penicillium chrysogenum neither required nor absorbed boron.     

ALGAL BIOMASS AND PRIMARY PRODUCTION WITHIN A TEMPERATE ZONE SANDSTONE

The use of dimethyl sulfoxide (DMSO) to extract chlorophyll a and ^l4C-labelled photosynthate from endolithic algae of sparsely vegetated, cold temperate grasslands on the Colorado Plateau in Arizona has yielded the first estimates of biomass and photosynthesis for this unusual community. These subsurface microorganisms are found widespread in exposed Coconino Sandstone, a predominant formation in this cold temperate region. The endolithic community in Coconino Sandstone, composed primarily of coccoid blue-green and coccoid/sarcinoid green algae, yielded a biomass value (as chlorophyll a content) of 87 mg m^-2 rock surface area and a photosynthetic rate of 0.37 mg CO₂ dm ² hr^-1 or 0.48 mg CO₂ mg^-1 chl a hr^-1. The endolithic algal community contributes moderate biomass (5–10%) and substantial photosynthesis (20–80%) to the sparse grassland ecosystem.     

Measurement of photorespiration in algae

The rates of true and apparent photosynthesis of two unicellular green algae, one diatom and four blue-green algae were measured in buffer at pH 8.0 at subsaturating concentrations of dissolved inorganic carbon (13-27 micromolar). Initial rates of depletion from the medium of inorganic carbon and ¹⁴C activity caused by the algae in a closed system were measured by gas chromatography and by liquid scintillation counting, respectively. The rate of photorespiration was calculated as the difference between the rates of apparent and true photosynthesis. The three eucaryotic algae and two blue-green algae had photorespiratory rates of 10 to 28% that of true photosynthesis at air levels of O₂. Reduction of the O₂ level to 2% caused a 52 to 91% reduction in photorespiratory rate. Two other blue-green algae displayed low photorespiratory rates, 2.4 to 6.2% that of true photosynthesis at air levels of O₂, and reduction of the O₂ concentration had no effect on these rates.     

The distribution and abundance of algae in saline lakes of Saskatchewan,Canada

Collections of algae, mainly planktonic, were made from 41 saline lakes in southern Saskatchewan ranging in salinity from 3.2 to 428 g l^-1. Algae in 7 phyla, 8 classes, 42 families, 91 genera and 212 species and varieties were identified. Fourteen species were restricted to hypersaline (50 g l^-1) waters and eleven of these were diatoms. In general, species diversity was inversely related to lake salinity. Algae that were important community constituents over a broad spectrum of salinities were the green algae Ctenocladus circinnatus, Dunaliella salina and Rhizoclonium hieroglyphicum, the blue-green Lyngbya Birgei, Microcystis aeruginosa, Oscillatoria tenuis, O. Utermoehli and Nodularia spumigena and the diatoms Melosira granulata, Stephanodiscus niagarae and Chaetoceros Elmorei. In general green algae were dominant when lake salinity exceeded 100 g l^-1 although diatoms played important roles in most of these highly saline lakes except for Patience Lake.     

Seasonal succession of the phytoplankton in the upper Mississippi River

Species composition and seasonal succession of the phytoplankton were investigated on the upper Mississippi River at Prairie Island, Minnesota, U.S.A. Both the numbers and volume of individual species were enumerated based on cell counts with an inverted microscope. A succession similar to algal succession in the local lakes occurred. The diatoms were dominant during the spring and fall and blue-green algae were dominant during the summer. The algal concentrations have increased up to 40 fold the concentrations of the 1920's, since the installation of locks and dams. The maximum freshweight standing crop was 4 mg · l^–1 in 1928 (Reinhard 1931), 13 mg · l^–1 in 1975 a wet year, and 47 mg · l^–1 in 1976, a relatively dry year with minimal current discharge. The diatoms varied from 36–99%, the blue-green algae from 0–44% and the cryptómonads from 0–50% of the total standing crop. The green algae were always present but never above 21% of the biomass. The dominant diatoms in recent years were centric -Stephanodiscus andCyclotella spp. (maximum 50,000 ml^–1). The dominant blue-green algae wereAphanizomenon flos-aquae (L.) Ralfsex Born.et Flahault andOscillatoria agardhii Gomont (maximum 800 ml^–1). These algal species are also present in local lakes. Shannon diversity values indicated greatest diversity of algae during the summer months.     

Dynamics of phytoplankton growth in the Waikato River,North Island,New Zealand

The Waikato River (latitude 38°S, longitude 176°E, North Island, New Zealand) is overwhelming y dominated by diatoms (mainly Melosira species) while blue-green and green algae are of minor importance. Both laboratory and in situ nutrient enrichment experiments showed enhanced growth of natural and index blue-green and green algae by addition of phosphate and nitrate. These algae were also shown to require higher temperature and light intensity than the diatoms. On the other hand, Waikato River with its higher silica content, moderate range of temperature and running water habitat was more favourable an environment for diatoms.