Responses of a eutrophic pond community to separate and combined effects of N:P supply and planktivorous fish: a mesocosm experiment

We conducted an outdoor mesocosm experiment of factorial design consisting of three levels of nutrient supply (no nutrient addition and additions of nitrogen and phosphorus in ratios of 10:1 and 45:1) cross-classified with two levels of bluegill (Lepomis macrochirus) (presence and absence). Nutrient supply significantly affected total phosphorus (TP), total nitrogen (TN), TN: TP ratio, turbidity, Secchi depth, phytoplankton chlorophyll, filamentous blue-green algae, periphyton chlorophyll, Asplanchna and non-predatory rotifers. The presence of bluegill significantly increased TP, turbidity, diatoms, unicellular green algae, colonial blue-green algae, filamentous blue-green algae, periphyton chlorophyll, Asplanchna and non-predatory rotifers, and decreased Secchi depth, cladocerans, cyclopoid copepodids, copepod nauplii and chironomid tube densities. Nutrient supply and fish effects were not independent of each other as shown by significant nutrient × fish interaction effects for TP, Secchi depth, filamentous blue-green algae, periphyton chlorophyll, Asplanchna and non-predatory rotifers.     

Decomposition of Blue-Green Algal (Cyanobacterial) Blooms in Lake Mendota, Wisconsin

Decomposition of natural populations of Lake Mendota phytoplankton dominated by blue-green algae (cyanobacteria) was monitored by using oxygen uptake and disappearance of chlorophyll, algal volume (fluorescence microscopy), particulate protein, particulate organic carbon, and photosynthetic ability (¹⁴CO₂ up-take). In some experiments, decomposition of ¹⁴C-labeled axenic cultures of Anabaena sp. was also measured. In addition to decomposition, mineralization of inorganic nitrogen and phosphorus were followed in some experiments. Decomposition could be described as a first-order process, and the rate of decomposition was similar to that found by others using pure cultures of eucaryotic algae. Nitrogen and phosphorus never limited the decomposition process, even when the lake water was severely limited in soluble forms of these nutrients. This suggests that the bacteria responsible for decomposition can obtain all of their key nutrients for growth from the blue-green algal cells. Filtration of lake water through plankton netting that removed up to 90% of the algal biomass usually did not cause a similar decrease in oxygen demand, suggesting that most of the particulate organic matter used for respiration of the decomposing bacteria was in a small-particle fraction. Short-term oxygen demand correlated well with the particulate chlorophyll concentration of the sample, and a relationship was derived that could be used to predict community respiration of the lake from chlorophyll concentration. Kinetic analysis showed that not all analyzed components disappeared at the same rate during the decomposition process. The relative rates of decrease of the measured parameters were as follows: photosynthetic ability > algal volume > particulate chlorophyll > particulate protein. Decomposition of ¹⁴C-labeled Anabaena occurred at similar rates with aerobic epilimnetic water and with anaerobic sediment, but was considerably slower with anaerobic hypolimnetic water. Of the various genera present in the lake, Aphanizomenon and Anabaena were more sensitive to decomposition than was Microcystis. In addition to providing a general picture of the decomposition process, the present work relates to other work on sedimentation to provide a detailed picture of the fate of blue-green algal biomass in a eutrophic lake ecosystem.     

ALGAL EXCRETION AND BACTERIAL ASSIMILATION IN HOT SPRING ALGAL MATS1

Benthic algal-bacterial mats are present in the effluents of alkaline hot springs at temperatures between 50 and 73 C. The thin surface layer is composed of the unicellular blue-green alga Synechococcus lividus. Also present in the surface layer and forming thick, orange mats beneath it, are filamentous, phototrophic, gliding bacteria of the genus Chloroflexis, also capable of heterotrophic growth. The very low species diversity and the constancy of the hot spring environment, make these mats a good ecosystem for studying the transfer of nutrients from the algae to the bacteria. To determine whether the alga might supply organic materials to the bacterium, excretion by natural populations of S. lividus was studied in the field by means of short-term radioisotope experiments. Under optimal conditions for photosynthesis, between 3 and 12% of the total ¹⁴C fixed was excreted as ¹⁴C-labeled organic compounds. Variations in cell density at concentrations of S. lividus approximating those found in the mat had no effect on the percentage excretion. However, at cell densities below a threshold, level, the percentage excretion increased with diminishing cell density. Except at very low light intensities the percentage of fixed carbon excreted, was very similar for all light intensities tested. Excretion at temperatures approaching the upper limit for growth was not significantly different from the percentage excretion values observed at lower temperatures. ¹⁴C-labeled organic compounds excreted during algal photosynthesis could be subsequently assimilated by natural populations of the bacteria present in the mat.     

Interrelations of photosynthetic behaviour and buoyancy regulation in a natural population of a blue-green alga

The photosynthetic activity of Anabaena cirdnalis and associated changes in buoyancy were determined from prepared suspensions exposed in the natural light field of Crose Mere. The observations are related to variations in subsurface irradiance and temperature. Parallel experiments, aimed at trapping algal colonies undertaking controlled vertical movements within the lake system, are also described. Buoyancy loss and downward migration are clearly associated with specific photosynthetic rates: rates as low as 1.8 mg O₂ (mg chlorophyll a) h⁻¹ are shown to be sufficient to effect buoyancy loss, while movements in the lake tend towards a depth where rates of 5–7 mg O₂ (mg chlorophyll a)⁻¹ h⁻¹ are possible. These rates are significantly less than those possible at light saturation. The effect of increasing temperature is to depress the population in the light-gradient. The significance of this response is discussed in relation to the growth of natural populations of blue-green algae.     

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.     

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.     

Nitrogenase activity in extracts of heterocystous and non-heterocystous blue-green algae

Summary Cell-free extracts capable of acetylene reduction and cyanide reduction have been prepared from heterocystous (Anabaena cylindrica) and non-heterocystous (Plectonema boryanum 594) blue-green algae. Extracts from Anabaena were obtained from cultures grown in blulk under aerobic conditions, while the Plectonema cultures were grown in bulk on nitrate-nitrogen, then washed free from nitrate and sparged with A/CO₂ for 40 h after which time maximum nitrogenase activity was detected. The nitrogenases of both algae are similar and resemble in many respects nitrogenases from bacteria and legumes. Activity is located primarily in a 40,000xgx15 min supernatant fraction and the rate of C₂H₂ reduction observed is about 10 per cent of whole cell activity. ATP and a source of reducing power (Na₂S₂O₄) are required for efficient functioning of the enzyme. ATP-dependent hydrogen evolution occurs, the extracts are cold labile and highly sensitive to oxygen and the oxygen inhibition is irreversible.     

The role of periphyton abundance and quality in the microdistribution of a stream grazer, Helicopsyche borealis (Trichoptera: Helicopsychidae)

SUMMARY. 1. A series of laboratory and field experiments was performed to determine if the preference of larvae of Helicopsyche borealis (Trichoptera: Helicopsychidae) for exposed rock surfaces in streams was related to patchiness of periphyton food.
2. At low current velocities in the laboratory larvae preferred food-saturated as opposed to food-depleted portions of substrata and drifted off the substratum in response to low food levels.
3. When offered a choice of three potential foods—a diatom, a green filamentous or a blue-green filamentous alga—larvae showed no preference.
4. Larval densities on artificial subtrata in field experiments were highest in areas of high algal chlorophyll a .
5. In laboratory experiments more adults emerged from cultures containing green algae or diatoms than cultures with blue-green algae or bacteria alone.
6. Periphyton quality was not as important as abundance in controlling H. borealis microdistribution. By selecting exposed surfaces of rocks, H. borealis larvae place themselves in the microhabitat most likely to contain both abundant and high quality food patches.     

Light-mediated recovery of N2-fixation in the blue-green algae Anabaena spp. in O2 supersaturated waters

Summary It is well known that N₂-fixation in blue-green algae is O₂ sensitive. However, at least two species of the filamentous, N₂-fixing blue-green alga Anabaena possess an indigenous mechanism allowing recovery of nitrogenase activity during O₂ supersaturation. The process is light-mediated and appears to employ photoreduction as a means of overcoming N₂ inhibition. Such recovery should optimize radiant energy utilization and N₂ fixation in freshwater blooms, which are often O₂ supersaturated during peak daylight hours.     

Succession and physiological health of freshwater microalgal fouling in a Tasmanian hydropower canal

Freshwater microalgal biofouling in hydropower canals in Tarraleah, Tasmania, is dominated by a single diatom species, Gomphonema tarraleahae. The microfouling community is under investigation with the aim of reducing its impact on electricity generation. Species succession was investigated using removable glass slides. Fouled slides were examined microscopically and for chlorophyll a biomass. Chl a biomass increased steeply after 8 weeks (0.09–0.87 mg m^?2), but increased much earlier on slides surrounded by a biofouled inoculum. Succession began with low profile diatoms such as Tabellaria flocculosa, progressing to stalked diatoms such as Gomphonema spp. and Cymbella aspera. Few chlorophytes and no filamentous algae were present. Pulse amplitude modulated fluorometry was used to measure the physiological health of fouling on the canal wall. Maximum quantum yield (F _v/F _m) measurements were consistently <0.18, indicating that the fouling mat consisted of dead or dying algae. The succession and physiological health of cells in the fouling community has broad implications for mitigation techniques used.     

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.     

The Utricularia-Cyanophyta association and its nitrogen-fixing capacity

Utricularia inflexa Forsk. growing in a shallow lake near Dar es Salaam, Tanzania was found to be abundantly associated with blue-green algae and other microorganisms, though blue-green algae were not found in the lake water. The epiphytes occurred both on the outer surfaces of the macrophyte and inside its traps. Seven genera of the Cyanophyta were observed, amongst which Anabaena was the most abundantly and consistently associated.Both epiphytes on the outer surfaces of the macrophyte and those inside mature traps fixed nitrogen in situ. Mature parts of the macrophyte fixed nitrogen at higher rates than immature parts, indicating the former was associated with a greater abundance of nitrogen fixers. The Utricularia-Cyanophyta association showed a nitrogen fixation (acetylene reduction) rate of 2012 nmol C₂H₄ g^–1 dry weight h^–1 or, in terms of lake area, of 4 500 nmol C₂H₄ m^–2 h^–1. The relative contributions of blue-green algae and bacteria were not determined.It is proposed that the association may involve a degree of physiological interdependence and that the association has potential as a biofertilizer for rice.Based on an M.Sc. thesis by G. M. Wagner submitted to the Department of Botany, University of Dar es Salaam, 1983.Based on an M.Sc. thesis by G. M. Wagner submitted to the Department of Botany, University of Dar es Salaam, 1983.     

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.     

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.     

Fat metabolism in higher plants. LVI. Distribution and nature of biotin in chloroplasts of different plant species

A number of bacteria, algae, and higher plant chloroplasts were examined to determine the nature of their biotin-protein complexes. In all tissues studied, the major fraction of the total biotin was bound to protein(s) through a lysine bridge and these proteins accepted ¹⁴CO₂ to form carboxybiotinyl protein(s). The biotinyl protein was present in the soluble protein fraction in the procaryotic organisms, Escherichia coli and Rhodospirillum rubrum. In eucaryotic organisms, such as Chlamydomonas reinhardi and chloroplasts from higher plants, biotinyl protein was associated with chloroplast membranes. The blue-green alga, Anacystis nidulans, showed an intermediate condition, while the filamentous blue-green alga, Anabaena flos-aquae, resembled the higher plant chloroplasts. Although on a chlorophyll basis, stroma lamellae fractions enriched in Photosystem I had a higher biotin protein content than did the grana lamellae fractions, on a protein basis, the biotinyl protein content was rather evenly distributed between the different membrane systems. In dormant embryos of barley and wheat acetyl CoA carboxylase was a soluble protein localized in the proplastids. During germination the biotin protein(s) became associated with the lamellar membrane fraction.     

Effect of temperature on chlorophyll stability of some subaerial blue-green algae

Chlorophyll stability index of eight subaerial blue-green algal species, collected from their natural habitats, i.e., bark of trees, soil and roof-tops and from cultures, has been determined. The algae from natural habitats showed greater chlorophyll stability compared to those algae from cultures. Among the natural algae, high chlorophyll stability was observed in the algae inhabiting adverse habitats. A slight modification in the method of Murty and Majumder (1962) for determination of chlorophyll stability index has been made. Here the total percentage loss in the amount of Chl alpha of heated sample in relation to its unheated sample has been considered as chlorophyll stability index.     

The colonial rock-forming microfossils of the Bohemian Upper Proterozoic (Czechoslovakia), “Bohemipora Pragensis’ n.g., n.sp.

Large amounts of well preserved microfossils have been reported from the cherts of the Upper Proterozoic of the Bohemian Massif (Middle Europe). They resemble those described by Cayeux (1894) from the Upper Proterozoic (Brioverian) of Bretagne (France). It is shown, unlike the views of Cayeux and his followers (Deflandre, 1955, and Graindor 1957), that the observed structures did not belong to individuals but to colonies of filamentous prokaryotic organisms, most probably blue-green algae (Cyanophyta). These produced specific crystal-like mineral aggregation round each filament. Scanning microscope examination has revealed that the individual facets of these mineral crystals were perforated by the openings through which the thread-like bodies of these primitive organisms protruded. It is shown that these microorganisms were attached to the cells of other, bigger microorganisms and enveloped them. Some of these substrate organisms might have been eukaryotic algae. The thecae gradually accumulated around the cells of these carrier organisms and after death the colonies disintegrated to constitute the main component of the sediment. The microfossils described are just a major component of a complicated fossil assemblage comprising coccoid and filamentous blue-green algae and bacteria. There are indications that several eukaryotic species might also have been present.The following new taxa are described:Thecophytales, new order,Cayeuxidae (Graindor) family emend.,Bohemipora n. gen.,B. pragensis, n. sp.     

Biomass production,total protein,chlorophylls, lipids and fatty acids of freshwater green and blue-green algae under different nitrogen regimes

Two green algae (Chlorella vulgaris and Scenedesmus obliquus) and four blue-green algae (Anacystis nidulans, Microcystis aeruginosa, Oscillatoria rubescens and Spirulina platensis) were grown in 81 batch cultures at different nitrogen levels. In all the algae increasing N levels led to an increase in the biomass (from 8 to 450 mg/l), in protein content (from 8 to 54 %) and in chlorophyll. At low N levels, the green algae contained a high percentage of total lipids (45 % of the biomass). More than 70 % of these were neutral lipids such as triacylglycerols (containing mainly 16:0 and 18:1 fatty acids) and trace amounts of hydrocarbons. At high N levels, the percentage of total lipids dropped to about 20 % of the dry weight. In the latter case the predominant lipids were polar lipids containing polyunsaturated C₁₆ and C₁₈ fatty acids. The blue-green algae, however, did not show any significant changes in their fatty acid and lipid compositions, when the nitrogen concentrations in the nutrient medium were varied. Thus the green but not the blue-green algae can be manipulated in mass cultures to yield a biomass with desired fatty acid and lipid compositions. The data may indicate a hitherto unrecognized distinction between prokaryotic and eukaryotic organisms.     

Nuisance biomass levels of periphytic algae in streams

Relative coverage of filamentous periphytic algae increased with chlorophyll a (chl a) biomass on natural substrata in 22 northwestern United States and Swedish streams. A biomass range of 100–150 mg chl a m⁻² may represent a critical level for an aesthetic nuisance; below those levels, filamentous coverage was less than 20%. Other indices of water quality (dissolved oxygen content and measures of benthic macroinvertebrate diversity) were apparently unaffected by periphytic biomass or filamentous coverage in these streams. Neither was biomass related to limiting nutrient content (soluble reactive phosphorus, SRP), as has been observed in previous experiments using bare rocks in streams and slides in artificial channels. Ambient SRP concentration may not be a useful predicter of periphyton accrual on natural substrates, due to uptake and recycling of P throughout the stream and undetermined losses such as sloughing and grazing.     

Distribution of benthic algae and macroinvertebrates along a thermal stream gradient

The distribution and abundance of benthic algae and macroinvertebrates were examined along a natural thermal gradient formed by hot springs in Little Geysers Creek, Sonoma Co., California, USA. Maximum water temperatures ranged from 52 °C at the uppermost station to 23 °C at a station 400 m downstream. Benthic chlorophyll a decreased exponentially from 2.5 g m^–2 at 52 °C to less than 0.1 g m^–2 at 23 °C, a pattern of decline also exhibited by algal phaeophytin. Blue-green algae dominated at higher temperatures but were replaced by filamentous green algae and diatoms at lower temperatures.Macroinvertebrates were absent at temperatures 45 °C; the highest density (> 150 000 m^–2, mainly Chironomidae) occurred at 34 °C, whereas biomass was highest (4.6 g m^–2, as dry weight) at 23 °C and species richness (15 species) was highest at 27 °C. The two predominant macroinvertebrate populations (the midge Tanytarsus sp. and the caddisfly Helicopsyche borealis) occurred at sites that were several degrees below their lethal thermal threshold, suggesting that a temperature buffer is maintained.