Blue-green Algal Mats Research Articles

Psychrotrophic ~Iydrolytic Bacteria from Antarctica &,Other I. Low Temperature Habitats

Samples of water, soil,llake sediments and blue-green algal mats from Antarctica were'processed for enumeration, isolation and screening of psychrotrophic hydrolytic bacteria. Amylolytic bacteria were preponderant (75 per cent) in the blue-green algal htat samples. Protease, lipase, an1ylase and urerse producing/bacteria were also isolated from the samples. ,Biochemical characteristics indicated that the isolates ;mainly comprised Pseudomonas and Bacillus species. Proteases and lipases of antarctic bacterial strains preferably hydrolysed denatured protein substrate and water soluble monomeric synthetic lipid substrates, respectively.

Blue-green algal mats of the salinas in San-ya, Hai-nan Island (China): structure, taxonomic composition, and implications for the interpretation of Precambrian stromatolites

The study of the algal mats in salinas used for salt production on Hai-nan Island (China) revealed the presence of five morphological types, which are dominated by different blue-green algae: (1) Orange high pinnacle mats dominated by Phormidium hypersalinum and P. hypolimneticum; (2) Pale green, low pinnacle mats dominated by P. hypolimneticum, P. hypersalinum and Aphanothece sp.; (3) Pale green spongy mats dominated by the unicellular blue-green algae Aphanothece sp., Chroococcus minutus, Aphanocapsa concharum; (4) Yellow green gelatinous mats dominated by P. hypolimneticum and Microcoleus tenerrimus; (5) Blue-green flat mats with finger-like projections dominated by M. tenerrimus and M. chthonoplastes. The distribution of these different mats is correlated to the main ecological parameters monitored: salinity, temperature and water depth. The role of the constituent blue-green algae and of the ecological parameters in the control of the composition and morphology of algal mats, as well as the implications of these findings for the interpretation of Precambrian stromatolites are discussed.

The relationship between nitrogen fixation and tidal exports of nitrogen in a tropical mangrove system

Various components (sediments, algal mats, decomposing logs and algal-covered prop roots) of a tropical mangrove forest showed low to moderate nitrogen fixation (acetylene reduction) rates. Measurements carried out in March, May and October 1989 revealed negligible or inconsistent seasonal variation in activity for all components. Prop roots with their associated algae showed much greater activity during night-time, typical of many substrates with associated cyanobacteria, whereas all other components had constant activity over 24 h periods. Extrapolation of the nitrogen fixation rates for each component to a ‘whole-forest’ basis, using field estimates of the densities of each component, indicated that sediments, prop roots and decomposing logs contributed approximately 3·5, 1·6 and 1·0%, respectively, of the nitrogen requirements for forest net primary production (FPPN). Blue-green algal mats on bare saltpan areas showed no significant nitrogen-fixing activity (in excess of that for the bare sediments in the same area). The total nitrogen contribution of the various components (6% of FPPN) closely matches previous esimates of the net nitrogen loss from the system through tidal fluxes of particulate and dissolved materials. The possible relative importance of other nitrogen input and loss mechanisms for this mangrove system is also discussed.

A Unique Freshwater Carbonate from the Upper Devonian Catskill Magnafacies of New York State

ABSTRACT A unique carbonate bed occurs within the dominantly siliciclastic Catskill Magnafacies (Upper Devonian) of southcentral New York. Associated strata comprise interbedded sandstones and mudstones with a variety of burrows, calcareous concretions, desiccation cracks, and remains of plants, fish, and the bivalve Archanodon. They are interpreted as the deposits of river channels, crevasse splays, levees, and floodbasins. The 0.4-0.5-m-thick carbonate bed is composed dominantly of dolomitic mudstone, containing calcispheres, rare ostracodes, and micron-scale algal filament molds. Laminae are disrupted by vertical and horizontal sheet cracks and burrow tubes which are filled with laminated mudstone, peloids and quartz silt, and spar-mosaic cements. The carbonate bed is interpreted as freshwater-marsh/shallow-lake deposit, where mud-sized particles originated by precipitation around filaments within cyanobacterial (blue-green algal) mats. Laminae were deposited mainly from suspension and disrupted by burrowing organisms and periodic desiccation. The Everglades and interior of Andros Island provide modern analogues, the paleoclimatic and paleolatitudinal implications of which are consistent with previous reconstructions of Catskill deposition under a tropical climate, 20°-30° from the paleoequator. The carbonate bed probably represents local reduction in siliciclastic deposition rate (associated with river diversion) superimposed upon a regional, increasing deposition rate. There is no evidence of hypersalinity or marine influence.

Primary Production Potential of Blue-Green Algal Mats on Southern Texas Tidal Flats

Blue-green algal mat biomass, productivity, and nitrogen fixation were determined for two southern Texas tidal flats, and environmental factors affecting productivity rates were assessed. Algal biomass over three seasons ranged from 0.50 to 1.53 g chl a · m-2. The rate of carbon fixation (by '4C technique) ranged from 0.6 g C'm-2 day-' (in fall) to 2.4 g C'm- 2day-' (in spring) on days when flats were flooded. The rate of N2 fixation on the same days varied from 0.09 to 0.5 kg N-ha-'day-'. On days when mats were severely desiccated (mat water 25% but < 60%) were capable of fixing gaseous CO2 in air. Exposure to sunlight equivalent to one-fourth full sunlight (ca. 500 uE'm-2s-') sustained maximum photosynthetic activity. Tidal flats consist of broad, relatively level shorelines of bays, estuaries, or lagoons that are periodically inundated by high tides and storm surges. In the Laguna Madre of southern Texas, this habitat typically comprises the entire leeward barrier island intertidal zone and covers hundreds of km2 (Fig. 1). While an arid, windy climate, high summer temperatures, and subsequent hypersalinity prevent establishment of estuarine salt marsh (Simmons, 1957; Copeland, 1966; Hoese, 1967), these flats are often covered with a 2-4 mm thick blue-green algal mat. Quantitative productivity data for such subtropical Texas mats are unreported. Existing studies of benthic microalgae production have dealt mostly with temperate mudflat diatom communities (Pomeroy, 1959; Pamatmat, 1968; Riznyk et al., 1978) or salt marsh systems containing sparse blue-green mats (Gallagher and Daiber, 1974; Van Raalte et al., 1976). Sage and Sullivan (1978) found very few blue-green mats in a Mississippi salt marsh, and they concluded that mat distribution in eastern Gulf Coast marshes was limited by shading from salt marsh vascular plants. Wanders (1976), as part of a study on tropical coral reefs, found high primary productivity for epilithic blue-green algae, but only over limited areas. Recent work on blue-green mats from southern California marshes (Zedler, 1980) revealed that these subtropical flats had much higher productivity than temperate flats; and blue-green production was equal to the highest values recorded for some mudflat diatoms (Riznyk et al., 1978). Dawes et al. (1978) concluded that intertidal green and red macroalgae were adapted to periodic tidal exposure and were more productive when exposed to air than when continuously submerged. Dawes (1981) emphasized the need for additional studies of production potential of intertidal algae and evaluation of the concept that such algae are under stress due to exposure per se. During the present study, primary

Regional variation in the distribution of trace metals in modern intertidal sediments of northern Spencer Gulf, South Australia

Spencer Gulf, a sheltered marine inlet extending 270 km inland from the Southern Ocean is important to the maintenance of South Australia's commercial fishery. At the northern end of the Gulf, the tidal range of 3 m exposes 40% of the marine sediments at low water. These intertidal flats vary from wide expanses of coarse sand to finer sediments colonized by blue-green algal mats or mangroves. Dissecting channels are tidal, with virtually no terrestrial runoff. Intertidal sediments from industrial and undeveloped shorelines have been analysed to determine the concentration of trace metals in the surface layer, and factors influencing their local distribution. Physical and chemical characteristics of the depositional environment at sampling sites are defined by field measurements of temperature, salinity, pH, and dissolved H 2S in overlying water, and by laboratory determination of the grain size, organic matter and total carbonate content of the sediment samples. Nitric acid soluble metal content of surface sediments is highly variable, with ranges of <0.2–23 ppm Cd, <0.2–50 ppm Cu, 0.1–17% Fe, 20–3000 ppm Mn, <1–600 ppm Pb, and 4–3200 ppm Zn. Generally, high metal concentrations have been found near existing industries, and in sheltered, organic rich muds. The lowest metal concentrations were found in sandy sediments from exposed beaches. The measured ranges of 12–36°C temperature, 19–59‰ salinity, pH 7–9.5, and <0.1–>5 mg 1 −1 dissolved H 2S indicate the highly variable chemical environment in shallow water overlying the sediments. Proximity to a point source, the established pattern of littoral transport, and the physical and chemical features of the depositional environment apparently control the distribution of trace metals in sediments.

Nitrogen isotope biogeochemistry of thermal springs

Distinct biochemical pathways for nitrogen in living organisms can be detected by stable isotope tracers and may be useful in the interpretation of kerogen from ancient, sedimentary rocks. The organic matter in stromatolite growths of thermal springs was studied as a modern analog of these ancient kerogens. Natural variations in the inorganic environment of hydrothermal areas affect the cycling and isotopic composition of nitrogen through organic matter. For example, the nitrogen isotopic composition ( δ 15N) of stromatolites in alkaline springs with a constant flow of water is similar to that of organisms growing in a nutrient limited steady state. A few of these open system hot springs have higher nonlimiting concentrations of combined nitrogen, and the δ 15N of the organic matter reflects the normal isotope fractionation associated with the enzymatic reactions of biological nitrogen metabolism. In quiescent, closed system pools, however, the isotopic composition of similar types of organisms is distinctly different and indicates the importance of internal recycling of ammonia. In certain hot springs populated by nitrogen-fixing organisms such as blue-green algae, stable isotope ratios of the organic matter indicate that nitrogen fixation is occurring in hot springs not only in blue-green algal mats, but at higher temperatures (up to 60°C) by nonphotosynthetic bacteria. Another factor governing the δ 15N of the organic matter includes the presence of bacteria that derive their cellular energy from nitrification or denitrification.

Major-Element Geochemistry of Brines from the Wind Tidal Flat Area, Laguna Madre, Texas

ABSTRACT This research was designed to investigate the origin and chemical evolution of subsurface brines in a modern coastal marine sabkha by assessing the major-element geochemistry of the brines. The study area is in the Wind Tidal Flat area of Laguna Madre, Texas, which is approximately 80 km south of Corpus Christi. This area is an active sabkha composed essentially of quartz sand. Its surface is covered extensively by blue-green algal mats. A system of 20 well sites has been established across the 22-km width of the sabkha. The geochemistry of the subsurface waters was determined at each site from two wells (1.8 m and 3.8 m deep) and from a shallow trench dug to intersect the water table. The chemical data were collected during two sampling periods (August 1979 and March 1980). The essential conclusions of this study are 1) the subsurface brine is a sodium chloride solution of continental and marine origin; 2) recharge of the marine water is through the process of flood recharge during which Laguna Madre waters are driven across the surface of the sabkha by high winds; 3) recharge of the continental waters is apparently by ground-water movement to the coast; and 4) the brine evolves chemically during evaporitic concentration by the precipitation of calcium carbonate and calcium sulfate minerals.

Geochemistry, Hydrology, and Mineralogy of the Sand Bulge Area, Laguna Madre Flats, South Texas

ABSTRACT The Sand Bulge area of the Laguna Madre Flats is a silicoclastic coastal sabkha lying between Padre Island and the Intracoastal Waterway on the Gulf coast of southwest Texas. The sabkha is sporadically inundated by wind-tidal flooding of water from an adjacent lagoon (Laguna Madre). Saline interstitial brines are formed by infiltration of partially evaporated ponded flood water. Manometric data indicate that the brine seeps downward through the sabkha and laterally, west toward the Intracoastal Waterway (ICWW). Some of the brine may flow seaward (east) through incised Pleistocene stream valleys. Most of the sabkha in this area is covered with blue-green algal mat. Precipitation of microcrystalline Mg-calcite (algal micrite) in brine ponds or within the algal mat, induced by algal or bacterial action, removes much of the calcium from recharge water before it reaches the sabkha watertable. Thus, though brine salinities reach 240 per mil, low calcium concentrations prevent the precipitation of gypsum, and thermodynamic calculations indicate that the brines are undersaturated with respect to gypsum. Gypsum does not presently occur in the sabkha sediments in this area, contrary to earlier observations (Fisk, 1959). It is suggested that emplacement of the ICWW altered the rate and direction of water flow through the sabkha, leading to less saline brines and possibly to the dissolution of previously formed gypsum.

In situ nitrogen (C2H2) fixation in lakes of southern Victoria Land, Antarctica

1. Nitrogenase activity as measured by the acetylene reduction assay occurred in a number of habitats in and nearby several Antarctic lakes. 2. Acetelyne reduction was localized in bluegreen algal mats in littoral/moat areas that received maximal sunlight. 3. Benthic bluegreen algal mats beneath 5–6 m of permanent lake ice, in much reduced light and often in waters supersaturated with oxygen, had no detectable nitrogenase activity. 4. The observed nitrogen fixation potential correlated with lower ammonium ion (NH4+) levels and the presence of heterocystous bluegreen algae which are probably the major nitrogen fixing organisms in these habitats. 5. The relatively low acetylene reduction rates and the lack of detectable15N2 fixation suggest that a small but significant contribution of fixed nitrogen occurs in select shallow, brightly lit habitats where low NH4+ concentrations are found.

Modern Stromatolites in Antarctic Dry Valley Lakes

We report here the discovery of the first modern (Holocene) bluegreen algal stromatolites from Antarctica. Several types occur within these permanently ice-covered, dimly lit, nonturbulent, seasonally glacier-fed lakes, where the habitats vary chemically from fresh-to-saline and anoxic to oxygen-supersaturated. The dominant bluegreen alga and principal stromatolite builder in all types is the oscillatoriaceous species, Phormidium frigidum, which can grow under the wide range of microhabitat conditions occurring in these Antarctic lakes and in the absence of competitive exclusion by eukaryotes, or significant browsing or burrowing by Metazoa. Precipitation of calcite and binding or trapping of sediments give the bluegreen algal mats internal laminae, preserving them as stromatolites. We suggest these frigid Antarctic lake stromatolites may be analogs of those that once inhabited deepwater Precambrian ecosystems. (Accepted for publication 22 May 1981)

Soil stabilization by a prokaryotic desert crust: implications for Precambrian land biota.

A cyanophyte dominated mat, desert crust, forms the ground cover in areas measuring hundreds of square meters in Utah and smaller patches in Colorado. The algal mat shows stromatolitic features such as sediment trapping and accretion, a convoluted surface, and polygonal cracking. Sand and clay particles are immobilized by a dense network of filaments of the two dominating cyanophyte species, Microcoleus vaginatus and M. chthonoplastes, which secrete sheaths to which particles adhere. These microorganisms can tolerate long periods of desiccation and are capable of instant reactivation and migration following wetting. Migration occurs in two events: 1. immediately following wetting of dry mat, trichomes are mechanically expelled from the sheath as it swells during rehydration, and 2. subsequently, trichomes begin a self-propelled gliding motility which is accompanied by further production of sheath. The maximum distance traveled on solid agar by trichomes of Microcoleus vaginatus during a 12 hour period of light was 4.8 cm. This corresponds to approximately 500 times the length of the fastest trichome, and provides a measure of the potential for spreading of the mat in nature via the motility of the trichomes. Dehydration resistence of the sheath modifies the extracellular environment of the trichomes and enables their transition to dormancy. Following prolonged wetting and evaporative drying of the mat in the laboratory, a smooth wafer-like crust is formed by the sheaths of Microcleus trichomes that have migrated to the surface. Calcium carbonate precipitates among the algal filaments under experimental conditions, indicating a potential for mat lithification and fossilization in the form of a caliche crust. It is suggested that limestones containing tubular microfossils may, in part, be of such an origin. The formation of mature Precambrian soils may be attributable to soil accretion, stabilization, and biogenic modification by blue-green algal land mats similar to desert crust.

The response of selected terrestrial organisms to the Martian environment: A modeling study

An energy balance model has been developed to investigate how the Martian atmospheric environment could influence a community of photosynthetic microorganisms with properties similar to those of a cyanophyte (blue-green algal mat) and a lichen. Surface moisture and soil nutrients are assumed to be available. The model was developed to approximate equatorial equinox conditions and includes parameters for solar and thermal radiation, convective and conductive energy transport, and evaporative cooling. Calculations include the diurnal variation of organism temperature and transpiration and photosynthetic rates. The influences of different wind speeds and organism size and resistivity are also studied. The temperature of organisms in mats less than a few millimeters thick will not differ from the ground temperature by more than 10°K. Water loss is actually retarded at higher wind speeds, since the organism temperature is lowered, thus reducing the saturation vapor pressure. Typical photosynthetic rates lead to the production of 10 −6 to 10 −7 mole O 2 cm −2 day −1.

Soil algae from a maryland serpentine formation

Algae from serpentine soil samples collected at Soldiers Delight, Maryland (located in the west central portion of Baltimore County) were cultured using an enrichment technique. The algal flora was found to consist of members of the Cyanophyta, Chlorophyta and Chrysophyta (Bacillariophyceae). Composition of the soil flora at the division level is similar to that of more favorable soil types, indicating possible adaptations to high chromium and nickel concentrations and a low Ca: Mg ratio. Among the Cyanophyceae examined were three genera known to contain species which fix N 2. The presence of Cyanophyte genera capable of N 2 fixation suggests possible N input to this generally nitrogen-poor system. Lack of nitrogenase activity in collections of blue-green algal mats during early spring may be due to seasonal variation or Mo deficiency common in serpentine soils.

Stereochemical relationships between phytol and phytanic acid, dihydrophytol and C 18 ketone in Recent sediments

The relative stereochemistry of certain acyclic isoprenoid compounds has been determined from the following sources: two intervals from a core of bottom sediment of a eutrophic lake (Esthwaite Water, U.K.); a marshy shore sediment from a small lake on the watershed of Esthwaite; the bottom sediment of a tropical lagoon (U.S. Virgin Islands); a blue-green algal mat and its underlying reduced sediment (Shark Bay, Australia); a decayed blue-green alga ( Microcystis aeruginosa) from Esthwaite Water and the products of alteration of phytol as sole carbon source by a bacterial culture from Esthwaite sediment. The stereoisomeric distributions indicate that 1. (i) in the earliest stages of diagenesis of phytol in Esthwaite sediment, reduction to the dihydrophytyl skeleton (free, esterified or bound) is biological, probably microbial, 2. (ii) by analogy with earlier studies of Esthwaite, the phytanic acid in the other sedimentary situations is compatible with an origin in phytol via biological processes; the variations in the distributions reflect the differences in the populations bringing about the conversion, 3. (iii) for the samples where 6,10,14-trimethylpentadecan-2-one was examined, the stereochemistry is compatible with an origin in phytol but no distinction can be made between the pathways of oxidation (biological or chemical), and 4. (iv) conversion of phytol by the bacterial isolate under conditions of low oxygen concentration produced 2(RS),6,10,14-trimethylpentadecan-2-ol as the major saturated alcohol; the likely route for its formation is via reduction of the corresponding ketone.

A biogeochemical study of the Abu Dhabi algal mats: A simplified ecosystem

A variety of lipid classes (alkanes, alkenes, carboxylic acids, carotenoids, saturated alcohols, sterols and stanols) in a core from an intertidal, tropical algal mat (Abu Dhabi, Persian Gulf) have been analysed. The n-alkanes and n-alkanoic acids maximise at n-C17 and n-C16, respectively, and show little or no contribution from homologues > C20. No evidence of pollution from petroleum products is apparent in the branched/cyclic alkanes, which have a simple distribution and contain the unresolved mixture of 7- and 8-methylheptadecanes as a relatively abundant component. Among the major carotenoids, components assigned as β-carotene, torulene, echinenone, spirilloxanthin, rhodopin, 3,4-dehydrorhodopin, zeaxanthin and myxoxanthophyll were present. The distributions of these classes show little or no evidence of a higher-plant contribution and are compatible with the most abundant micro-organisms identified in the core, viz., Lyngbya aestuarii and Microcoleus chthonoplastes (blue-greens), and Chromatium and Thiocystis spp. (purple photosynthetic bacteria). The presence of torulene suggests fungal activity.Only Δ5 or Δ5,22 sterols were observed and their distributions cannot be related at present to specific inputs. However, the distributions of all of the compound classes show features which have been observed in similar analyses of other blue-green algal mat situations.

Production of volatile sulfur compounds during the decomposition of algal mats

Blue-green algal mats incubated anaerobically rapidly produce large amounts of volatile sulfur compounds, including hydrogen sulfide, methyl mercaptan, and dimethyl sulfide. The major organic sulfur compound is methyl mercaptan, in contrast to previous results with marine eucaryotic algae. Light inhibited production of volatile sulfur compounds, apparently because the algae then produced O2, rendering the system aerobic.

The Effects of Moisture on Acetylene Reduction by Mats of Blue-green Algae in Sub-tropical Grassland

The Effects of Moisture on Acetylene Reduction by Mats of Blue-green Algae in Sub-tropical Grassland

Acetylene Reduction in the Dark by Mats of Blue-green Algae in Sub-tropical Grassland

Acetylene Reduction in the Dark by Mats of Blue-green Algae in Sub-tropical Grassland

THE MATURE LARVA AND PUPARIUM OF CANACE MACATEEI (DIPTERA: CANACEIDAE)

AbstractMature larvae and puparia of Canace macateei Malloch inhabiting mats of blue-green algae in a Massachusetts intertidal marsh are described and compared with other larvae of the Canaceidae.