Planothidium Lanceolatum Research Articles

ESTUDIO DEL VALOR INDICADOR DE LAS COMUNIDADES DE ALGAS BENTÓNICAS: UNA PROPUESTA DE EVALUACIÓN Y APLICACIÓN EN EL RÍO MAGDALENA, CIUDAD DE MÉXICO

The application and development of environmental laws governing watershed management requires identification of biological indicators, parameters and measures to establish its ecological status, for which the present study aims to characterize the ecological indicator value of stream benthic algae in an urban area of Mexico City. Six sites of the Magdalena river were studied in the most contrasting seasons: dry-warm, rainy and dry-cold. At each site the physicochemical parameters of water were recorded and 10 samples were collected: Five with visible algal growths and five with diatoms. The environmental quality of each site was determined by the trophic status and its confirmation with the richness and benthic algal diversity, through a canonical correspondence analysis and the calculation of the indicator value of species (IndVal). According to the trophic status, three groups of sites were recognized. The first group (G1) was assessed as reference of the oligotrophic conditions and presented 11 species with the highest IndVal, protruding: Encyonema silesiacum, Gomphonema parvulum, Navicula cryptocephala, Planothidium lanceolatum, Vaucheria bursata, Placoma regulare and Nostoc parmelioides. A second group (G2) was associated with 15 species considered detectors, which were tolerant to increased nutrients in at least one season, such as Diatoma mesodon and Prasiola mexicana. The third group (G3) included sites with species that had a wide range of tolerance to pollution: Fistulifera saprophila , Nitzschia minuta , Nitzschia palea , Nitzschia recta and Phormidium autumnale. The species IndVal of Magdalena River has established reference sites of good environmental quality and those that are altered by human activities, therefore they are recommended as the first step in a methodological proposal for a long-term biomonitoring through a biological index.

Diatoms as water quality indicators in the upper reaches of the Great Fish River, Eastern Cape, South Africa

This study focused on the spring-fed upper reaches of the economically important Great Fish River with the aim of determining if diatoms could be used for biomonitoring in semi-arid conditions in southern Africa. Five sites were monitored monthly from 2010 to 2012. Of the 269 diatom taxa belonging to 51 genera identified, the dominant taxa were mostly those considered to be pollution-tolerant: Amphora pediculus, Craticula buderi, Fragilaria biceps, Nitzschia frustulum, Nitzschia paleacea, Planothidium lanceolatum and Rhopalodia gibba. A number of diatom-based numerical indices were used to infer water quality, including the generic diatom index, the specific pollution sensitivity index, the biological diatom index, and percentage pollution-tolerant valves, which forms part of the UK trophic diatom index. All index scores showed the Great Fish River to be impacted, and showed significant correlations of diatom species abundance with pH, NO3-N, electrical conductivity, NH4-N and CaCO3. Analysis revealed EC and NO3-N as the main environmental drivers affecting diatom community composition, followed by pH and PO4-P. The percentage of diatom deformities at all sites was high, at 3.5%. Diatom indices showed the river to be impacted by decades of agricultural activity, which was confirmed by chemical water analysis. Thus diatom indices can be used for biomonitoring in semi-arid areas.

Achnanthoid diatoms (Bacillariophyta) of relict Lake Mogilnoye (Kildin Island, Barents Sea)

New data on morphology of nine monoraphid diatom species from the order Achnanthales found in late summer in the uppermost brackish-water layer of the unique subpolar meromictic Lake Mogilnoye at salinity to 4 ‰ and temperature about 10 °С are presented. Four taxa, Cocconeis cf. neothumensis var. marina, Planothidium lanceolatum, P. minutissimum and Psammothidium bioretii, are recorded for the first time in the lake. New taxa, Planothidium alekseevae sp. nov., P. asymmetricum sp. nov. and P. delicatulum f. minor f. nova, are described. The lectotype of P. delicatulum is designated.

Changes in the epipelic diatom assemblage in nutrient rich streams due to the variations of simultaneous stressors

Benthic diatoms are often used for assessing environmental conditions, such as water quality and habitat conditions in stream and river systems. Although laboratory experiments have shown that each diatom species have different levels of tolerance to different stressors, few studies have been conducted in laboratory settings that analyze the responses of the diatom assemblage to the effects of multiple simultaneous variables. The aim of this study was to evaluate some structural responses (such as species composition and diversity) of the diatom assemblage on a short time scale to the effects of the simultaneous increase in four variables that are directly linked to the environmental changes affecting the Pampean streams: turbidity, nutrients (phosphorous and nitrogen), water velocity and temperature. To this end we conducted a five-week laboratory experiment using artificial channels where we simulated two environmental conditions (LOW and HIGH) employing epipelic biofilm from a mesotrophic stream. The results obtained in the experiment show that the structure of the diatom assemblage in the epipelic biofilm is affected by the simultaneous modification of temperature, water velocity, nutrient concentration and turbidity. These modifications in the assemblage included moderate decreases in diversity, small decreases in the proportion of species sensitive to eutrophication and saprobity, moderate increases in the IDP (Pampean Diatom Index) values and moderate changes in the percentages of the stalked growth-forms. The relative abundance of species such as Luticola mutica, Navicula cryptocephala and Navicula lanceolata were negatively affected by both treatments; other species such as Planothidium lanceolatum, Caloneis bacillum, Encyonema minutum, Humidophila contenta, Luticola kotschyi, Nitzschia amphibia, Navicula veneta, Pinnularia subcapitata var. subcapitata were positively affected by the HIGH treatment; and Nitzschia fonticola was positively affected by both treatments. The results suggest that, in the very short term of the bioassay conducted, the diatom assemblage can modify its structure to respond in a sensitive manner to the abrupt changes in multiple physical–chemical variables.

Genetic and physiological responses of three freshwater diatoms to realistic diuron exposures.

This study examined the effects of diuron on strains of three major freshwater diatom species, Eolimna minima, Nitzschia palea and Planothidium lanceolatum. These species are frequently recorded in the Morcille River, where diuron runs off during phytosanitary treatments of the vineyards around. Here, there were three diatom exposure groups for each species: 0, 1 and 10 μg/L diuron during a 14-day laboratory assessment. Diuron water concentration, cell number, photosynthetic activity and gene expression were assessed at 6 h and 2, 7 and 14 days after contamination. Diuron exposure altered photosynthetic activity in that the optimal quantum yield of photosystem II (PSII) decreased between 40 and 50% and, for P. lanceolatum at 10 μg/L, there was complete inhibition. Genetic responses indicated diuron effects on both photosystem II and mitochondrial metabolism in all three species at both diuron exposure levels. Thus, analysis of the expression of psaA, d1, cox1, nad5 and 12s could be an early biomarker to detect pesticide pollution. Overall, this study revealed differences in diuron sensitivity among the three species: E. minima and N. palea appeared to be more tolerant than P. lanceolatum. These results suggest that the development of molecular tools, and more precisely of biomarkers, will aid in early assessment of contamination and water quality.

Taxonomy, distribution and autecology of Planothidium bagualensis sp. nov. (Bacillariophyta) a common monoraphid species from southern Brazilian rivers

A new species in the genus Planothidium is described, Planothidium bagualensis sp. nov., from rivers of the Rio Pardo hydrographical basin, Rio Grande do Sul, southern Brazil. This account is based on light and scanning electron microscopy. This rather common species was misidentified in previous studies conducted in Brazil as belonging to either a group of species related to Planothidium lanceolatum and its varieties, or Planothidium frequentissimum. The presence of a cavum (“hood”) in the rapheless valve, however, clearly separates it from P. lanceolatum sensu stricto which has only a sinus (“rimmed depression”); the wider and longer cells of P. bagualensis, besides having ultrastructural differences, sets it apart from P. frequentissimum. Planothidium bagualensis is widely reported in freshwater environments of southern Brazil. The species reached up to 45% of relative abundance in epilithic samples from eutrophic lotic environments of the Rio Pardo hydrographical basin. Traditional weighted-averaging approaches (WA) were applied to model phosphates (P), chemical oxygen demand (COD), total dissolved solids and pH optima. P. bagualensis is formally described and the literature reviewed to delimitate its distribution. Published photomicrographs corresponding to Planothidium lanceolatum sensu stricto from South America were up to date only found in the Andean Cordillera (Chile and Bolivia), but until now this taxon has never been illustrated in Brazil.

DIATOMS (BACILLARIOPHYCEAE) IN RIVERS AND STREAMS AND ON CULTIVATED SOILS OF THE PODKARPACIE REGION IN THE YEARS 2007–2011

Diatoms Bacillariophyceae are a specialized, systematic group of algae, living in different types of ecosystems, and they are very good indicators of water quality. Recently, detailed studies have been carried out in the territory of the Podkarpacie Province on the diversity of diatoms in running waters. The area of study covers mostly the catchment of the biggest rivers of the province (mainly the Wislok River) and cultivated soils. Running waters in the Podkarpacie Province are characterized by a huge species richness of diatoms, 738 different taxa have been found so far. The highest number of taxa was noted in the Wislok River (400), while the Żolynianka and Rozanka streams and the Mleczka were also characterized by huge diversity (from 200 to over 350 taxa). In the majority of studied sites diatoms of alkaline (pH>7) and nutrient rich (eutrophic) waters dominated: Navicula lanceolata, N. gregaria, N. capitatoradiata, Nitzschia palea, N. dissipata ssp. dissipata, Achnanthidium minutissimum var. minutissimum, A. pyrenaicum, Amphora pediculus, Diatoma vulgaris, Rhoicosphenia abbreviata, Planothidium lanceolatum, Cocconeis pediculus and C. placentula var. lineata. About 150 taxa were indentified on cultivated soils, among which the largest populations were formed by Hantzschia amphioxys, Mayamaea atomus, Nitzschia palea, N. pusilla, Pinnularia obscura and Stauroneis thermicola.

Biosorption of metals (Cd, Cu and Zn) by the freshwater diatom Planothidium lanceolatum: a laboratory study

Biosorption, the naturally occurring physiochemical process which passively concentrates and binds contaminants to cellular structures, can be used in biological systems for the removal of metal ions from polluted waters. It also has the potential to achieve better performance at lower cost than conventional wastewater treatment technologies. The aim of this study was to characterize the ability of the freshwater diatom Planothidium lanceolatum (Brébisson) Lange-Bertalot to biosorb cadmium (Cd), copper (Cu) and zinc (Zn) from aqueous solutions. This diatom is one of the most dominant microalgae in the Tensift River, Marrakech region, Morocco, into which industrial wastewaters are often discharged directly, without pretreatment. As the water from this river is used for irrigation, it represents a potential risk to the environment and human health. The choice of these three heavy metals is based on their high concentrations in mining waste and industrial wastewaters. Our results indicate that the biosorption of metals by P. lanceolatum increased with the initial concentration of metal ions in the medium up to 100–130 mg L−1. The maximum biosorbed metal ion concentrations were 104, 81 and 41 mg per 16×108 diatom cells L−1 for Zn, Cu and Cd, respectively. The maximum uptake of metals was obtained at pH 6.0 for Cu and at pH 8.0 for Cd and Zn. An increase in the biosorption of P. lanceolatum was observed with an increase in temperature from 15 to 25†C. The biosorption of all three metal ions followed the Langmuir isotherm. Competitive biosorption of Cd, Cu and Zn ions was also achieved. Fourier transform infrared spectroscopy revealed the different metal-binding functional groups on the diatom surface that are able to react with metals in the medium. The results suggest that P. lanceolatum can be used as a biosorbent for the efficient removal of heavy metals from aqueous solutions at temperature and pH values close to average values in the Tensift River.

Analysis of the type material of Achnanthidium lanceolatum Brébisson ex Kützing (Bacillariophyta) with the description of two new Planothidium species from the Antarctic Region.

The type material of Achnanthidium lanceolatum (transferred in 1999 to the genus Planothidium) is investigated to reveal the identity of several Planothidium populations from the Antarctic Region. The morphology and the ultrastructure was analysed using light and scanning electron microscopy. The results of this analysis revealed the presence of two so far undescribed Planothidium species in the investigated Antarctic material. Both species are described as new to science: P. rost- rolanceolatum Van de VijVer, KopaloVa et zidaroVa sp. nov. and P. subantarcticum Van de VijVer et c.e.Wetzel sp. nov. The new species can be differentiated based on differences in valve outline and the shape and size of the central area. Planothidium lanceolatum is formally lectotypified. Notes on the ecology and distribution of the new Antarctic species are added.

Biomarker imaging of single diatom cells in a microbial mat using time-of-flight secondary ion mass spectrometry (ToF-SIMS)

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a surface sensitive MS technique that offers a new way of studying lipid biomarkers at the microscopic level, without the need to destroy the physical integrity of the sample by extraction. We applied ToF-SIMS to a cryosection of a microbial mat and compared the results with ToF-SIMS and gas chromatography–MS (GC–MS) analysis of extracts from the same material. A wide range of lipid biomarkers was identified with ToF-SIMS in the microbial mat cryosection. Spectra and ion images revealed that individual biomarkers, including fatty acids, mono-, di- and triacylglycerols, carotenoids and chlorophyll were localized with diatom cells identified as Planothidium lanceolatum using optical microscopy. This diatom species can thus be regarded as a major lipid source within the microbial mat system. The results underpin the idea that ToF-SIMS has the potential to become an important technique for future biomarker studies, in particular for the clear cut assignment of biomarkers to distinctive morphological structures and specific microorganisms within complex biogeochemical samples.

Knowledge to Ecological Preferences in a Tropical Epiphytic Algae to Use with Eutrophication Indicators

In Ayapel floodplain periphyton associated to macrophyte roots on the basis of material was collected in fourteen sampling sites in nine moments of compilation. From the analysis of the samples were recorded 550 algal species, of which 56% were diatoms. Furthermore it was valued relative abundances of taxa and the average physicochemical variables to identify the optimal values and tolerance ranges of species. In the case of nitrates optimal value was below 2 mg/L for all algae except for Actinella sp. and Euastrum sinuosum which optimal values were close to zero with low variability. Regarding all species the algal nitrite concentration showed optimum values below 2 mg/L except Encyonema minutum and E. sinuosum whose optimum were 0.4 and 0.5 mg/L respectively. About nitrogen as ammonia was repeated the above situation, i.e. optimum values below 2 mg/L except for E. minutum and E. sinuosum. Respect to phosphorus the species with optimum greater than 0.6 mg/L are the diatoms, in contrast, the lowest values were optimal for E. sinuosum and Actinella sp. From the viewpoint of bioindication high abundance of Synedra goulardii indicates high transparency, Ulnaria ulna and Planothidium lanceolatum indicate lower concentration of dissolved oxygen and water temperature between 29°C - 30°C, Actinella aff. robusta, E. minutum, Cylindrospermopsis raciborski, Lyngbya cf. limnetica, Eunotia naegueli, Navicula cryptocephala, Diadesmis confervaceae, Frustulia rhomboides and Aulacoseira granulata.(For more information,please refer to the PDF.)

Benthic diatom assemblages and their response to human stress in small-sized volcanic-siliceous streams of central Italy (Mediterranean eco-region)

The river typology ‘volcanic rivers’ represents a unique typology in the Mediterranean eco-region in Europe but its type-specific diatom assemblages are still poorly investigated. The main aims of this study were (i) to analyse the diatom diversity of this river type, (ii) to investigate the relationships between diatom diversity and environmental variables and (iii) to identify the characterizing diatom community structure of different environmental groups. To this end, we selected 13 streams located in central Italy, belonging to a single river type and covering the whole quality range from human impacted sites to those in ‘reference conditions’. Most frequent and abundant diatom species found were Cocconeis placentula var. lineata, Planothidium lanceolatum, Rhoicosphenia abbreviata and Amphora pediculus. Species richness in reference and less impacted sites was not higher than in intermediate and heavily degraded ones, but non-metric multidimensional scaling (N-MDS) analysis revealed a substantial difference among their diatom community structure. The indicator species analysis defined the characteristic species of three environmental groups identified by N-MDS. The findings of this study represent a contribution to the knowledge on diatom communities of Mediterranean volcanic-siliceous rivers and provide information for a data-driven implementation of the Water Framework Directive in Italy for this specific river typology.

Toxicity and biosorption of chromium from aqueous solutions by the diatom Planothidium lanceolatum (Brébisson) Lange-Bertalot

The present study reports the ability of the diatom Planothidium lanceolatum (Brebisson) LangeBertalot (P. lanceolatum) to remove hexavalent chromium [Cr(VI)] from aqueous solutions in batch system under varying ranges of pH, contact time and initial ion concentrations by the determination Cr(VI) toxic effects and biosorption by this species. The results show a significant growth of P. lanceolatum for Cr concentrations up to 10 mg L -1 . The growth rate decreases as a function of increasing concentrations of Cr(VI). The cultures made with Tensift River water (Marrakech, Morocco) developed in the presence of Cr(VI) concentrations from 0 to 4 mg L -1 . But the culture with tannery effluent water grew with concentrations from 0 to 0.152 mg L -1 . The IC50 calculated is 8.7 mg L -1 for the artificial growth medium tested which is more than that calculated with river water (3.85 mg L -1 ) and tannery effluent water (0.075 mg L -1 ). The biosorption of Cr increases with the decrease of pH. The biosorption capacity calculated from the Langmuir isotherm was 93.45 mg Cr(VI).g diatoms -1 at an initial concentration of 0.4 g dried diatoms per liter with an initial Cr(VI) concentration of 20 mg L -1 . The wide ecological valence of this diatom to pollution parameters and the seasonal pattern of its life cycle are the main factors that make the biomonitoring of Cr(VI) by this species feasible.

Impact of the herbicide metolachlor on river periphytic diatoms: Experimental comparison of descriptors at different biological organization levels

A microcosm experiment was carried out in order to test the effect of the herbicide metolachlor on river periphytic diatoms and to find potential diatom bioindicators of contamination. Effects were investigated at different biological organization levels (biofilm, diatom community, population and individual levels). The colonization of glass substrates by natural biofilm in artificial streams did not vary quantitatively between control and contaminated conditions (5 and 30 μg.L− 1 ). However, non-parametric multivariate analysis of variance revealed a significant difference between contaminated and control diatom communities with regard to species composition. The difference was due to the greater development of probably tolerant species in the presence of the herbicide (e.g. , Planothidium frequentissimum, Planothidium lanceolatum, Amphora montana, Surirella brebissonii and Nitzschia gracilis ). An increase in the occurrence of abnormal forms was observed in relation to metolachlor concentration. In particular, up to 8% of the frustules of the species Surirella angusta exhibited prominent deformities. Monospecific acute toxicity tests were then performed on two species to estimate toxicity parameters based on growth inhibition. These tests also confirmed the teratogenic effect of the herbicide on S. angusta . This study shows that low concentrations of metolachlor in natural streams may significantly alter diatom community structure and that abnormal diatom forms should be taken into account in water contamination assessment.

Distribution of phytoplankton in a German lowland river in relation to environmental factors

In comparison to lentic systems, the species composition and community structure of phytoplankton in lotic habitats are still poorly understood. We investigated the spatial and temporal dynamics of the phytoplankton community in a German lowland river, the Kielstau catchment, and the relationships with environmental variables. Among the 125 taxa observed, Desmodesmus communis, Pediastrum duplex and Discostella steligera were dominant species at lentic sites while Tabellaria flocculosa, Euglena sp., Planothidium lanceolatum, Cocconeis placentula and Fragilaria biceps dominated at lotic sites. Remarkable spatial and temporal variations of the phytoplankton community were revealed by non-metric multidimensional scaling. Canonical correspondence analysis indicated that physical factors (e.g. hydrological variables) and major nutrients [e.g. total phosphorus, dissolved inorganic nitrogen (DIN)] were of equal importance controlling the variation in structure of riverine phytoplankton assemblages. Weighted averaging regression and cross-calibration produced strong models for predicting DIN, water temperature (WT) and total suspended solid (TSS), which enabled the selection of algal taxa as potentially sensitive indicators: for DIN, Ulnaria ulna var. acus, U. ulna, D. communis and Euglena sp.; for WT: D. steligera, Scenedesmus dimorphus, D. communis and Euglena sp.; for TSS, Nitzschia sigmoidea, D. communis and Oscillatoria sp. The results from this relatively small survey indicate the need for further monitoring to gain a better understanding of riverine phytoplankton and to capitalize on the environmental indicator capacity of the phytoplankton community.

DIATOM BIODIVERSITY OF SPRINGS IN THE BERCHTESGADEN NATIONAL PARK (NORTH-EASTERN ALPS, GERMANY), WITH THE ECOLOGICAL AND MORPHOLOGICAL CHARACTERIZATION OF TWO SPECIES NEW TO SCIENCE

Diatom assemblages were investigated in 9 springs of the Berchtesgaden National Park (carbonate substratum; north-eastern Alps, Germany), by collecting individual samples from the main substrata (stones, bryophytes, surface sediment), and measuring an extensive number of environmental variables. Overall, 104 taxa belonging to 39 genera were found. The highest number of taxa observed in any one sample was 37. The Shannon-Wiener Diversity Index varied between 1.2 and 2.4. The most frequent (counted in ≥ 4 samples) and abundant (maximum relative abundance > 5%) species were Achnanthidium minutissimum, Meridion circulare, Diatoma mesodon, Eucocconeis laevis, Navicula leistikowii, Denticula tenuis, Encyonema sublangebertalotii sp. nov., Planothidium lanceolatum, Achnanthidum pyrenaicum, Eunotia arcubus, Navicula cataracta-rheni, Rossithidium petersenii, Achnanthidum dolomiticum, Diploneis krammeri, Navicula cryptotenella, and Reimeria sinuata. The proportion of species belonging to one of the threat categories of the Red List for central Europe was 54%, and included species belonging to category 3 (“Endangered”): Eucocconeis flexella, Navicula moenofranconica, N. wildii, and Rossithidium petersenii. Two species new two science were discovered and described; one species was transferred to the genus Sellaphora (S. perhibita comb, nov.), and its ultrastructure was documented in detail. Encyonema sublangebertalotii sp. nov. resembles widely distributed species such as E. minutum and E. lange-bertalotii from which it can be distinguished by the outline (in particular the endings), dimensions, external raphe course and areolae density. Moreover, it appears to be mainly epiphytic in oligo(meso)trophic springs. Oligotrophic conditions might be important also for the second new species, Eunotia glacialispinosa sp. nov. which can be easily distinguished from similar species by its dimensions, striae and areolae density, distal raphe course, and by the presence of the characteristic spines. In Berchtesgaden it occurred exclusively in a specific spring type (seepages), and was found to develop also in comparable habitats (e.g. small dystrophic lake in a fen) by examining materials from several countries in the North of Europe. All these habitats had slightly alkaline or acidic pH but never presented ombrotrophic conditions. The comparison with a carbonate National Park located at the southern margin of the Alps (Dolomiti Bellunesi) revealed many similarities but also interesting differences mostly linked to the geographic distribution of specific spring types.

Using change-point analysis and weighted averaging approaches to explore the relationships between common benthic diatoms and in-stream environmental variables in mid-atlantic highlands streams, USA

Diatoms are increasingly being used in the bioassessment of aquatic systems. However, autecological information for many common taxa is incomplete. We explored the potential of classification (CT) and regression tree (RT) approaches to identify the hierarchical interaction among water quality variables in predicting the relative abundance of ten common stream diatom taxa in the Mid-Atlantic Highlands ecoregion. RT analysis was also used to identify environmental change points corresponding to major shifts in species abundances. We also used traditional weighted-averaging approaches (WA) to model taxon pH and total phosphorus (TP) optima. RT and WA approaches provided different, yet complementary, information on the complex relationships between common stream diatoms and environmental variables. Both RT and CT highlighted the interaction of stream acidity (pH, acid neutralizing capacity (ANC)), and TP in structuring the stream diatom assemblage. For the RT of taxa, where pH was an important predictor, higher pH predicted higher relative abundances. In contrast, higher TP predicted lower relative abundances for some diatom taxa (e.g., Achnanthidium minutissimum (Kutz.) Czarnecki), while predicting higher relative abundances for other taxa (e.g., Planothidium lanceolatum (Breb.) Round & Bukht., Gomphonema parvulum (Kutz.) Kutz.). The environmental change point for pH derived from RT analysis was lower than WA optima for all species. We suggest that RT change point analysis can be used to complement traditional WA optima approaches, especially when diatom taxa’s abundances are affected by interactive environmental factors, to provide more refined information on stream diatom environmental preferences.

Tareena Billabong - a palaeolimnological history of an ever-changing wetland, Chowilla Floodplain, lower Murray - Darling Basin, Australia

A 427-cm sediment core was extracted from Tareena Billabong, a Murray River floodplain wetland in the extreme south-west of New South Wales, Australia. Analysis of fossil diatoms and pollen, sediment 210Pb and 137Cs profiles and radiocarbon and luminescence dating reveal that Tareena Billabong has undergone substantial environmental change in its ~5000-year history. Shortly after its formation, the billabong was a freshwater lagoon with a diatom flora dominated by Synedra ulna and Planothidium lanceolatum. An increase in Aulacoseira granulata, a river plankton dominant today, reflects two phases of increased connectivity with the Murray River in the mid to late Holocene. A shift to lagoonal taxa after ~3000 years BP is attributed to water balance and river-flow changes, possibly associated with regional climate change. Importantly, it appears to have undergone an extended phase of increasing turbidity, and possibly wetland salinity, commencing ~3000 years BP. Sedimentation increased at least 15-fold in the European phase. Billabong salinity increased markedly soon after European settlement, reaching a peak in the late 1800s AD. While regulation then increased the degree of connection between the billabong with the River in the 1920s AD, salinity levels remained high. Increased salinity is revealed by increases in the diatom taxa Amphora spp., Cyclotella meneghiniana, Gyrosigma acuminatum, Planothidium delicatulum and Tryblionella hungarica and by declines in Casuarinaceae, Eucalyptus, Myriophyllum and Cyperaceae pollen. Tareena Billabong was subjected to considerable environmental pressures from the early stages of European settlement in terms of sediment load, hydrological change and salinity.

Moss-inhabiting diatom communities from Heard Island, sub-Antarctic

In this paper, we list 192 diatom taxa, collected from bryophyte samples from Heard Island (52°05′S, 73°30′E). The Heard Island diatom flora shows a marked similarity to those of the Crozet and Kerguelen archipelagos, and is quite dissimilar to the moss-dwelling diatom flora of Macquarie and Amsterdam Island. Based on species composition, three main groups of samples could be discerned. Each group represents a different habitat. Samples dominated by Diadesmis ingeae, Pinnularia borealis and several Psammothidium species seem to prefer the driest habitats. A special form of this community was found in shaded areas. Samples from wet habitats such as flush areas and pools were dominated by species such as Adlafia bryophila, Sellaphora tumida, Fragilaria capucina and Planothidium lanceolatum. An intermediate group was observed in more acid, but terrestrial, conditions, characterised by Eunotia paludosa and Chamaepinnularia soehrensis var. muscicola. These community patterns are similar to those found on other sub-Antarctic islands, and we suggest that a group of typical sub-Antarctic species and communities exists.

Distribution of benthic diatoms in relation to environmental variables in lowland streams

The composition (% relative abundance) of diatom assemblages from soft bottom sediments was studied at 75 sites situated in 46 rivers, brooks, and ditches in the islands of Hiiumaa and Saaremaa and in the lowland of West Estonia. Although the total number of recorded taxa was 205, the studied diatom assemblages consisted of 54, 55, 48, and 50 constant species in the drainage basin of Moonsund, the Gulf of Riga, Hiiumaa, and Saaremaa, respectively. The habitats of the dominating taxa were heterogenous and the most widespread species were Achnanthidium minutissimum, Martyana martyi, Meridion circulare, Cocconeis placentula, Planothidium lanceolatum, and Amphora pediculus. The Shannon–Weaver diversity (H′) index varied from 2.09 to 4.63. Multivariate analyses were used to identify the environmental variables governing the composition and structure of the benthic diatom assemblage. Principal Component Analysis (PCA) and Redundancy Analysis (RDA), based on 56 most abundant taxa, indicated differences in the composition and structure of diatom assemblages between different drainage basins as well as between the upper and lower stream courses. In the headwaters there prevailed small epipsammic diatoms (Martyana, Planothidium, Staurosira, Staurosirella). Different motile epipelic species from the genera Amphora, Navicula, Nitzschia, etc. were distributed abundantly in the lower courses of the streams. There was a positive correlation between order of the stream site and trophic level of water (R=0.35; p<0.05). Along a river system, the increasing order of the stream was accompanied by higher trophic level of water.