Algal Mat Communities Research Articles

Diurnal chemistry of two contrasting stream types, Taylor Valley, McMurdo Dry Valley Region, Antarctica

Numerous ephemeral streams flow within the McMurdo Dry Valley Region of Antarctica that transport glacial meltwater to perennially ice-covered, closed-basin lakes during the austral summer. The diurnal behavior for two Taylor Valley streams of different character was examined during the summer of 2010-11. Andersen Creek is a short, 1st-order proglacial stream, whereas Von Guerard Stream is a long, high-order stream with an extensive hyporheic zone that has a substantial cyanobacterial algal mat community in its middle reaches. Both streams display strong daily cycles for temperature, electrical conductivity, dissolved oxygen, and pH. Conductivity varies in concert with flow, with solute dilution occurring during the daily high-flow pulse. Dissolved oxygen co-varies strongly with pH at Andersen Creek but not for Von Guerard Stream. Each stream has a distinct geochemical character that for Andersen Creek is a direct reflection of its glacial source, unmodified by secondary effects, whereas that for Von Guerard Stream is modulated by its resident algal mat community and through extensive hyporheic zone interaction and exchange.

Impacts of permafrost degradation on a stream in Taylor Valley, Antarctica

The McMurdo Dry Valleys (MDV) of Antarctica are an ice-free landscape that supports a complex, microbially dominated ecosystem despite a severely arid, cold environment (<5cm water equivalent/y, −18°C mean annual air temperature). Recent observations of permafrost degradation in the coastal zones of the MDV suggest that this region is nearing a threshold of rapid landscape change. In 2012, substantial thermokarst development was observed along several kilometers of the west branch of Crescent Stream in Taylor Valley mostly in the form of bank failures, whereas the adjacent east branch was unaffected. The objective of this study was to quantify the changes to the stream banks of the west branch of Crescent Stream and to determine the impacts on the composition of the stream bed material. Three annually repeated terrestrial LiDAR scans were compared to determine the rates of ground surface change caused by thermokarst formation on the stream bank. The areal extent of the thermokarst was shown to be decreasing; however, the average vertical rate of retreat remained constant. Field measurements of bed materials indicated that the west branch and the reach downstream of the confluence (of east and west branches) consistently contained more fines than the unaffected east branch. This suggests that the finer bed material is a result of the thermokarst development on the west branch. These finer bed material compositions are likely to increase the mobility of the bed material, which will have implications for stream morphology, stream algal mat communities, and downstream aquatic ecosystems.

Primary producers and nutrient loading in Silver Springs, FL, USA

The characteristics and dynamics of primary producer communities of Silver Springs was examined to compare with that observed by Odum [Odum, H.T., 1957. Trophic structure and productivity of Silver Springs, Florida. Ecol. Monogr. 27, 55–112.] as a means of evaluating the impacts of changes that have occurred over time. The Silver Springs ecosystem is considered an ecosystem at risk, where nitrate levels have more than doubled over the past 50 years. The spatial and temporal abundance and distribution of above-sediment primary producers in Silver Springs, FL, USA, was estimated on a system-wide basis using a GIS platform. The results of study suggest that while the Sagittaria component of Silver Springs has remained relatively stable, epiphyte and benthic algal mat community biomass has expanded, particularly benthic forms, like Lyngbya. However, we argue for caution in weighing the significance of long-term comparisons of system-wide biomass in light of considerable spatial heterogeneity in aquatic primary producer communities.

Legionella Species Diversity in an Acidic Biofilm Community in Yellowstone National Park

Legionella species are frequently detected in aquatic environments, but their occurrence in extreme, acidic, geothermal habitats has not been explored with cultivation-independent methods. We investigated a predominately eukaryotic algal mat community in a pH 2.7 geothermal stream in Yellowstone National Park for the presence of Legionella and potential host amoebae. Our analyses, using PCR amplification with Legionella-specific primers targeting 16S rRNA genes, detected four known Legionella species, as well as Legionella sequences from species that are not represented in sequence databases, in mat samples and cultivated isolates. The nonrandom occurrence of sequences detected at lower (30 degrees C) and higher (35 to 38 degrees C) temperatures suggests that natural thermal gradients in the stream influence Legionella species distributions in this mat community. We detected only one sequence, Legionella micdadei, from cultivated isolates. We cultured and sequenced partial 18S rRNA gene regions from two potential hosts, Acanthamoeba and Euglena species.

The spring energy budget of the algal mat community in a Crimean hypersaline lake determined by microcalorimetry

The energy contents (standing stock) of the floating mat formed by the green alga Cladophora sivaschensis and the energy transfers through it were quantified for a shallow hypersaline lake (at Cape Khersones, Crimea, Ukraine) during the spring months. Appropriate direct calorimetric techniques were applied to: (i) measure the heat energy dissipated by the mat community and by the free bacterioplankton in the water column below it; and (ii) differentiate between the heat flows by the heterotrophic and the phototrophic components of the community. It was shown that Cladophora biomass reached a peak of 579.5 g C m–2, contributing more than 99.6% of the total mat community. Throughout the spring, the total bacterial energy transfer (6 to 23 mW m–2) was as little as 1.1 to 2.6% of the total heat dissipated by the microplankton community. The rest of the estimated heat energy (584 to 1488 mW m–2) was associated with Cladophora metabolism. In the spring community: (i) the rate of biomass accumulation in the lake photic layer significantly exceeded its heterotrophic mineralisation; (ii) the efficiency of the microbial loop was too low to process even a minor part of the accumulated organic matter. The microcalorimetric technique was shown to be a highly promising approach for further studies of natural microbial mats and biofilms, biological systems with complex metabolism that involves not only aerobic processes but also anaerobic catabolism under local hypoxic/microxic conditions.

Microbially mediated sulphide production in a thermal, acidic algal mat community in Yellowstone National Park.

Our objective in this study was to characterize prokaryotic sulphide production within the oxygenic, predominantly eukaryotic algal mat in an acidic stream, Nymph Creek, in Yellowstone National Park (YNP). We used microsensors to examine fluctuations in H2S and O2 concentrations over time through the vertical aspect of the approximately 3 mm mat in a 46-48 degrees C region of the creek. We also used analyses of PCR-amplified 16S rRNA gene sequences obtained from denaturing gradient gels, and PCR-amplified sequences of a functional gene associated with microbial sulphate respiration (dsrA) to characterize the bacterial community in the same region of the mat. During midday, photosynthesis rates were high within the first 500 micro m interval of the mat and high oxygen concentrations (600% air saturation) penetrated deeply (>1800 micro m) into the mat. During early evening and night, oxygen concentrations within the first 1100 micro m of the mat decreased over time from 60% air saturation (a.s) to 12% a.s. A precipitous decline in oxygen concentration occurred at a depth of 1100 micro m in all night measurements and anoxic conditions were present below 1200 micro m. Within this anoxic region, sulphide concentrations increased from nearly 0 micro M at 1200 micro m depth to 100 micro M at 2400 micro m depth. Enrichment cultures inoculated with Nymph Creek mat organisms also produced H2S. Sequence analyses of 16S rRNA and dsrA genes indicated the presence of at least five bacterial genera including species involved in dissimilative sulphate or sulphur reduction.

Productivity and species composition of algal mat communities exposed to a fluctuating thermal regime

Algal mat communities growing in thermal effluents of production nuclear reactors at the Savannah River Plant, near Aiken, SC, are exposed to large temperature fluctuations resulting from reactor operations. Rates of primary production and species composition were monitored at 4 sites along a thermal gradient in a trough microcosm to determine how these large temperature fluctuations affected productivity and algal community structure. Blue-green algae (cyanobacteria) were the only phototrophic primary producers growing in water above 45°C. These thermophiles were able to survive and apparently adapt to ambient temperatures when the reactor was shut down. The algal mat communities exposed to <45°C were composed of blue-green and eukaryotic algae that adapted rapidly to ambient temperatures. An increase in the percentage extracellular release (PER) of(14)C-labeled dissolved organic compounds and a decrease in primary production were observed during periods of thermal fluctuation. The results show that the dominant phototrophs in this artificially heated aquatic habitat have been selected for their ability to survive large temperature fluctuations and are similar to those of natural hot springs.

Paleoenvironmental Analysis of Joachim Dolomite (Middle Ordovician), North Arkansas: ABSTRACT

The Joachim Dolomite (Middle Ordovician) crops out in an east-west trending belt across north-central Arkansas. This formation is the oldest of four members composing the post-St. Peter Ordovician carbonate sequence, which was deposited during an overall marine transgression. These units prograded in response to progressively deeper epeiric conditions caused by a relative rise in sea level near the low-relief, positive Ozark Dome. The Joachim Dolomite ranges in thickness from 1 to 25 m and contains four units in a shoaling-upward sequence: subtidal basal sheet unit, subtidal bank unit, sublittoral sheet unit, and intertidal-supratidal veneer unit. These units represent an offlapping sequence of subtidal to intertidal to supratidal environmental zones. Marine sedimentation caused carbonate banks to shoal and prograde seaward, producing a local marine regression. Algal mat communities promoted carbonate bank progradation by forming a cohesive mat that stabilized substrates and resisted wave scour. These algal mats created cryptalgal fabrics, cryptalgal columnar structures and stratigraphic sequences analogous to those End_Page 1566------------------------------ observed in Shark Bay, Western Australia. The Joachim Dolomite is a dolostone intermixed with variable quantities of detrital quartz grains. Halite hoppers present in the intertidal veneer unit suggest that the initial dolomitization of the sediments was induced by evaporative pumping of metahaline and hypersaline water into the prograding carbonate banks. Later, successive influxes of mixed meteoric-marine and meteoric waters converted the marine protodolomite matrix into dolomicrite and eliminated the primary marine porosity. End_of_Article - Last_Page 1567------------

Growth of Heterotrophic Bacteria and Algal Extracellular Products in Oligotrophic Waters

The unexpected observation of 200 to 400 coliform bacteria per 100 ml in an unpolluted pristine stream was studied within Grand Teton National Park, Wyo. The high numbers of waterborne bacteria occurred in mid- to late summer at a location where there was a coincidental bloom of an algal mat community. Periphyton samplers were used to measure the algal growth that coincided with the increase in number of bacteria. Laboratory studies followed the growth of various coliform bacteria in the supernatant obtained from a Chlorella culture isolated from the mat community. Mixed natural bacterial populations from the stream and pure cultures of water-isolated fecal and nonfecal coliforms increased by two to three orders of magnitude at 13 degrees C when grown in the algal supernatant. Radioactive algal products were obtained by feeding an axenic Chlorella culture C-labeled bicarbonate under laboratory cultivation at 13 degrees C with illumination. Radioactive organic material from the algae became incorporated into the particulate fraction of pure cultures of coliform bacteria as they reproduced and was later released as they died.

Some thoughts on metallogenesis and evolution of the Arabian-Nubian Shield

On the basis of ultrastructural, biochemical and genetic studies, bacteria and blue green algae (Kingdom Monera, all prokaryotes) differ unambiguously from the eukaryotic organisms (Fungi, plants sensu stricto) and protists or protoctists, (Copeland, 1956). The gap between eukaryotes and prokaryotes is recognized as the most profound evolutionary discontinuity in the living world. This gap is reflected in the fossil record. Fossil remains of Archaean and Proterozoic Aeons primarily consist of prokaryotes and the Phanerozoic is overwhelmingly characterized by fossils of the megascopic eukaryotic groups, both metazoa and metaphyta. Based on the morphological interpretation of microscopic objects structurally preserved in Precambrian cherts, the time of appearance of remains of eukaryotic organisms in the fossil record has been claimed to be as early as 2.7 · 109 years ago, (Kaźmierczak, 1976). Others suggest chronologies varying between 1.7 to 1.3 · 109 (Schopf et al., 1973) or a time approaching 1.3 · 109 years (Cloud, 1974).There is general agreement that many of the Ediacaran faunas, which have been dated at about 680 m.y. are fossils of megascopic soft-bodied invertebrate animals. Since all invertebrates are eukaryotic, the ca. 680 m.y. date for deposition of these animal assemblages may represent the earliest appearance of eukaryotic organisms. But the question remains as to whether there is definitive evidence for eukaryotic cells before this “benchmark” of the late Precambrian.An excellent discussion of this particular problem as especially relating to acritarchs extending from rocks of Upper Riphean through Vendian and into the basal Cambrian is presented in recent studies by Vidal (1974, 1976) in Late Precambrian microfossils from the Visingsö rocks of southern Sweden.Previous work on the laboratory silicification of wood and algal mat communities (Leo and Barghoorn, 1976) suggested that further analysis of “artificial fossils” might be of aid in the interpretation of fossil morphology toward the ultimate solution of this problem. Thus the procedure developed by one of us (ESB) for laboratory wood silicification was adapted to various smaller objects.By successive immersions of wet cellular aggregates, colonies of various organisms and abiotic organic microspheres in tetraethyl orthosilicate, silicified cells and structures are produced which bear an interesting resemblance to ancient chert-embedded microfossils. Our observation of these microorganisms and proteinoid microspheres silicified in the laboratory as well as of degrading microorganisms, both eukaryotic and prokaryotic, have led us to conclude that many, if not all, of the criteria for assessing fossil eukaryotic microorganisms are subject to serious criticism in interpretation. We studied a large variety of prokaryotic algae, some eukaryotic algae, fungi, protozoa, and abiotic organic microspheres stable at essentially neutral pH. In some cases, degradation and/or silicification systematically altered both size and appearances of microorganisms. By the use of monoalgal cultures of blue-green algae, features resembling nuclei, chloroplasts, tetrads, pyrenoids, and large cell size may be simulated. In many cases individual members of these cultures show so much variation that they may be mistaken as belonging to more than one species. The size ranges for silicified prokaryotic and eukaryotic algae overlap. Several prokaryotes routinely yielded spherical or filamentous structures that resembled large cells. Because of genuine large sizes (e.g., Prochloron), shrinkage, systematic alteration or congregation of unicells to form other structures we find sizes to be of very limited use in determining whether an organism of simple morphology was prokaryotic or eukaryotic. Although some “prebiotic proteinoid microspheres” (of Fox and Harada, 1960) are impossible to silicify with our laboratory methods, those stable at neutral pH (Hsu and Fox, 1976) formed spherical objects that morphologically resemble silicified algae or fungal spores. Many had internal structure. We conclude that even careful morphometric studies of fossil microorganisms are subject to many sources of misinterpretation. Even though it is a logical deduction that eukaryotic microorganisms evolved before Ediacaran time there is no compelling evidence for fossil eukaryotes prior to the late Precambrian metazoans.

On the experimental silicification of microorganisms II. On the time of appearance of eukaryotic organisms in the fossil record

Abstract On the basis of ultrastructural, biochemical and genetic studies, bacteria and blue green algae (Kingdom Monera, all prokaryotes) differ unambiguously from the eukaryotic organisms (Fungi, plants sensu stricto ) and protists or protoctists, (Copeland, 1956). The gap between eukaryotes and prokaryotes is recognized as the most profound evolutionary discontinuity in the living world. This gap is reflected in the fossil record. Fossil remains of Archaean and Proterozoic Aeons primarily consist of prokaryotes and the Phanerozoic is overwhelmingly characterized by fossils of the megascopic eukaryotic groups, both metazoa and metaphyta. Based on the morphological interpretation of microscopic objects structurally preserved in Precambrian cherts, the time of appearance of remains of eukaryotic organisms in the fossil record has been claimed to be as early as 2.7 · 10 9 years ago, (Kaźmierczak, 1976). Others suggest chronologies varying between 1.7 to 1.3 · 10 9 (Schopf et al., 1973) or a time approaching 1.3 · 10 9 years (Cloud, 1974). There is general agreement that many of the Ediacaran faunas, which have been dated at about 680 m.y. are fossils of megascopic soft-bodied invertebrate animals. Since all invertebrates are eukaryotic, the ca. 680 m.y. date for deposition of these animal assemblages may represent the earliest appearance of eukaryotic organisms. But the question remains as to whether there is definitive evidence for eukaryotic cells before this “benchmark” of the late Precambrian. An excellent discussion of this particular problem as especially relating to acritarchs extending from rocks of Upper Riphean through Vendian and into the basal Cambrian is presented in recent studies by Vidal (1974, 1976) in Late Precambrian microfossils from the Visingso rocks of southern Sweden. Previous work on the laboratory silicification of wood and algal mat communities (Leo and Barghoorn, 1976) suggested that further analysis of “artificial fossils” might be of aid in the interpretation of fossil morphology toward the ultimate solution of this problem. Thus the procedure developed by one of us (ESB) for laboratory wood silicification was adapted to various smaller objects. By successive immersions of wet cellular aggregates, colonies of various organisms and abiotic organic microspheres in tetraethyl orthosilicate, silicified cells and structures are produced which bear an interesting resemblance to ancient chert-embedded microfossils. Our observation of these microorganisms and proteinoid microspheres silicified in the laboratory as well as of degrading microorganisms, both eukaryotic and prokaryotic, have led us to conclude that many, if not all, of the criteria for assessing fossil eukaryotic microorganisms are subject to serious criticism in interpretation. We studied a large variety of prokaryotic algae, some eukaryotic algae, fungi, protozoa, and abiotic organic microspheres stable at essentially neutral pH. In some cases, degradation and/or silicification systematically altered both size and appearances of microorganisms. By the use of monoalgal cultures of blue-green algae, features resembling nuclei, chloroplasts, tetrads, pyrenoids, and large cell size may be simulated. In many cases individual members of these cultures show so much variation that they may be mistaken as belonging to more than one species. The size ranges for silicified prokaryotic and eukaryotic algae overlap. Several prokaryotes routinely yielded spherical or filamentous structures that resembled large cells. Because of genuine large sizes (e.g., Prochloron ), shrinkage, systematic alteration or congregation of unicells to form other structures we find sizes to be of very limited use in determining whether an organism of simple morphology was prokaryotic or eukaryotic. Although some “prebiotic proteinoid microspheres” (of Fox and Harada, 1960) are impossible to silicify with our laboratory methods, those stable at neutral pH (Hsu and Fox, 1976) formed spherical objects that morphologically resemble silicified algae or fungal spores. Many had internal structure. We conclude that even careful morphometric studies of fossil microorganisms are subject to many sources of misinterpretation. Even though it is a logical deduction that eukaryotic microorganisms evolved before Ediacaran time there is no compelling evidence for fossil eukaryotes prior to the late Precambrian metazoans.

Three new species ofSchizothrix Kützing (Cyanophyta) from marine algal mats

Three new species of the genusSchizothrix (Cyanophyta) have been described:Sch. gracilis, Sch. splendida andSch. constricta. They are significant members of many algal mat communities in marine shallow water and intertidal environments.

Algal Mats, Cryptalgal Fabrics, and Structures, Hamelin Pool, Western Australia: ABSTRACT

Cryptalgal sediments and structures in Hamelin Pool, Western Australia, are formed by interactions between blue-green algae, which trap and bind sediment particles, and a variety of mechanical and diagenetic processes. The algae form a cohesive mat that tends to cover intertidal, supratidal, and some shallow subtidal surfaces. The mat is differentiated into seven intergradational types as an expression of variations in algal species present, ratio of filamentous to unicellular forms, quantity of mucilaginous matrix, life habits, and quantity and nature of the host sediment. The distribution of mat types is controlled by environmental factors such as elevation of substrate, drainage, depth and nature of interstitial groundwater, and sediment influx. In tidal flats with gen le gradients, there is a broad zonation of mat types, whereas the mat is highly differentiated and has a condensed, patchy development of types on headlands and locations with irregular topography. The sediments trapped and/or bound by the algal-mat communities are imprinted with distinctive fabrics. These fabrics, which can be related to specific mat types, reflect a complex interaction between the algae and processes of sedimentation and diagenesis. Important factors in the development of fabric are surface texture and internal structure of the mat, rate and frequency of sediment influx, and processes such as oxidation, cementation, and lithification. Changes in mat type with changes in environmental conditions (e.g., shoaling and sediment influx) lead to the development of successions of fabrics in the sediment pile. The mat-sediment complex is shaped by physical factors into a variety of structures: (1) extensive flat-lying sheets, (2) ridge and rill structure, (3) rings and crescents, (4) linked ellipsoids and columns, (5) discrete ellipsoidal and circular columns, and (6) calyx and tiered calyx structures. The size range of structures varies from a few centimeters to several meters; confluent and branched structures also are common. The gross morphology of the structures is largely independent of the mat type (or types) involved in the primary trapping and/or binding processes. Major environmental factors involved in shaping of structures are waves, currents, substrate gradient, and long-term sea-level change; minor factors include burial, exhumation, growth of epiphytes, activity of browsing organisms, gas evolution, corrosion, precipitation, desiccation, and variation in sediment type. These factors also influence the external surface texture of structures.

Isolation and Characterization of Keto‐Carotenoids from the Neutral Extract of Algal Mat Communities of a Desert Soil

The carotenoid pigments of surficial algal mat communities of a California absolute subtropical desert were isolated and characterized principally by means of high resolution mass spectrometry. The pigments were all oxidized keto‐types, predominantly canthaxanthin, its isomers, and echinone. The carotenoid pattern suggests that the mats represent an old climax ecosystem in which the algal cells at the time of collection were starved for nitrogen.

Succession in Algal Mat Communities at Three Different Nutrient Levels

The effect of three different levels of phosphates and nitrates on temporal variation of structural and functional parameters was studied in algal mat communities in microcosms. The experimental units contained 1 liter of water collected from a farm pond. Microcosms receiving the largest input of nutrients were highest in biomass and pigments, but no greater in net production and respiration than microecosystems receiving an intermediate level of nutrients. These four variables remained low in systems receiving the lowest level of nutrients. The ratio of production to respiration approached unity at all nutrient levels. Production/biomass and production/chlorophyll (i.e., assimilation number) ratios generally decreased with time and leveled off at all nutrient levels. No effects on the pigment diversity ratio, D430/D665 attributable to nutrients were observed.

Aliphatic hydrocarbons and fatty acids of some marine and freshwater microorganisms.

Gas chromatography and combined gas chromatography-mass spectrometry have been used to study the fatty acids and hydrocarbons of a bacterium from the Pacific Ocean, Vibrio marinus, a freshwater blue-green alga, Anacystis nidulans, and algal mat communities from the Gulf of Mexico. Both types of microorganisms (bacteria and algae) showed relatively simple hydrocarbon and fatty acid patterns, the hydrocarbons predominating in the region of C-17 and the fatty acids in the range of C-14 to C-18. The patterns of V. marinus were more comparable to those of the algal populations than to patterns reported for other bacteria. An incomplete correlation between fatty acids and hydrocarbons in both types of organisms was observed, making it difficult to accept the concept that the biosynthesis of hydrocarbons follows a simple fatty acid decarboxylation process.

Fatty Acids in Blue-Green Algal Mat Communities

The concentrations of the major fatty acids were determined for the varied layers of an algal mat community. The living mat contains substantial amounts of the unsaturated acids, while the underlying layers become progressively depleted in unsaturated molecules. A similar progressive increase in the ratio of saturated to unsaturated acids was detected in a sediment core from a hypersaline lagoon.