Epilithic Research Articles

Estructura de la taxocenosis de diatomeas y su relación con variables ambientales en tres cuencas de la provincia de San Luis (Argentina)

La composición y distribución de las asociaciones de algas en ecosistemas lóticos son el resultado de condiciones en el medio ambiente y en particular pueden reflejar su estructura y funcionamiento.El objetivo de este trabajo fue estudiar la relación de la riqueza, abundancia y diversidad de las especies de diatomeas con las características ambientales en tres cuencas de la provincia de San Luis. Para ello se seleccionaron 14 sitios de muestreo en tres cuencas: en la cuenca del río Conlara siete sitios, otros tres en la cuenca del río Quinto y finalmente cuatro en la cuenca del Bebedero. En cada sitio de muestreo se registraron parámetros hidráulicos y fisicoquímicos. Se colectaron muestras epilíticas que fueron obtenidas por raspado de pequeñas rocas del fondo. La estructura de la comunidad estuvo caracterizada por el predominio de las diatomeas pennales que se destacaron tanto cualitativa como cuantitativamente. Las variaciones de parámetros fisicoquímicos influyeron en la composición específica de las taxocenosis y permitieron establecer dos grupos de especies: el primero constituido por Nitzschia palea, Melosira varians, Navicula tripunctata y Halamphora veneta que se vincularon a arroyos de mayor número de orden y mayor conductividad. Mientras que Geissleria decussis, Epithemia sorex y Cymbella affinis constituyeron el segundo grupo relacionado con mayor caudal y pH, en tanto que Navicula radiosa y Rophalodia gibba estuvieron asociadas a la altitud y concentración del oxígeno disuelto, respectivamente. Una referencia florística confiable de diatomeas permite hacer diagnósticos fundamentados sobre el estado ecológico de los arroyos, así como para establecer programas de monitoreo en la provincia.

Disentangling the taxonomy and morphology of Ectropothecium (Bryophyta: Hypnaceae s.l .) with comments on its generic relationships, and Neoptychophyllum , a new name for the genus Ptychophyllum

Ectropothecium is a genus of Hypnaceae, consisting of epiphytic or lithophytic species that are mainly distributed in tropical and subtropical forests. With 233 currently accepted species, the genus has one of the most difficult taxonomies among pleurocarpous mosses. Delimitation of Ectropothecium has been challenging because of morphological convergence between closely related genera within the Hypnaceae, namely Hypnum , Isopterygium , Taxiphyllum , and Vesicularia . Redefining the generic limits is based on reassessment of seven critically important morphological features, i.e., branching pattern, pseudoparaphyllium type, leaf shape, laminal cell surface, alar cell formation, capsule size, and exothecial cell walls. Microscopic images of morphological and anatomical important features are used to show generic characteristics. The five closely related genera are morphologically distinct, but oftentimes difficult to separate apart without considering several features at the same time. The generic delineation of Ectropothecium is provided. Neoptychophyllum (Hypnaceae), a new name is proposed for the genus Ptychophyllum , an illegitimate homonym and a previous generic synonym of Ectropothecium .

Short communication:Study on epilithic diatoms in the kozluk creek (Arapgir-Malatya, Turkey)

Short communication:Study on epilithic diatoms in the kozluk creek (Arapgir-Malatya, Turkey)

Testate Amoeba Communities of Epilithic Mosses and Lichens: New Data from Russia, Switzerland and Italy

The testate amoebae (TA) of many potential habitats around the world have been barely investigated but data on species presence and abundance is essential to answering big questions about microbial biogeography and the diversity of protist life. One such habitat lacking basic data is epilithic mosses and lichens with only a small number of samples analysed in previous studies and no systematic attempt to understand potential environmental controls. We use a large dataset (n = 81) from sites in Russia, Switzerland and Italy to demonstrate that testate amoebae in this habitat are both abundant and diverse. The community of our samples was dominated by ubiquitous taxa and differed between the northern (Russia) and southern (Switzerland and Italy) sites, perhaps due to differences in climate or air quality. Community composition, concentration and diversity were explained by moisture content but not by elevation above the ground surface and there were no significant differences between communities of mosses and lichens. Surprisingly our data showed a significant difference between communities of epiphytic and epilithic lichens in the same region sampled at the same time. Our study adds to the evidence that moisture availability is a critical factor in structuring testate amoeba communities across habitats and highlights the paucity of knowledge of TA in many environments.

Qualitative study of epilithic algal diversity spectrum in Lidder stream of Lidder Valley (Kashmir Himalayas)

The present study was carried out in Lidder stream in Lidder Valley of Kashmir Himalayas, to show a typical taxonomic composition of epilithic algae. The epilithic algal community was represented by 144 taxa belonging to four classes namely, Bacillariophyceae with104 species (72%), Chlorophyceae with 19 species (13%), Cyanophyceae with 12 species (8%), Euglenophyceae with 4 species (3%) and Phylum Protozoa with 3 species (2%) while classes Chrysophyceae and Dinophyceae contributed 1 species (1%) each. Bacillariophyceae was represented by some dominant forms like Navicula (16 species), Nitzschia (11 species), Cymbella (9 species) and Gomphonema (7 species). Among blue green algae (Cyanophyceae), genus Spirulina recorded 3 species and Merismopedia registered 2 species. While in Chlorophyceae, the highest number of species was documented by genus Cosmarium (3 species), moreover Closterium, Euastrum and Ulothrix registered 2 species each. Bacillariophyceae was the predominant class at all the sites with the highest contribution of 104 species at sites S1c, S2d, S2g and S4 (first year) and S1a, S1b, S2d, S2e, S2f, S2g, and S4 (second year) while the lowest of 98 species was recorded at site S3 during the entire study, the rest groups were moderately to least represented. Key words: Taxonomic, epilithic algae, Lidder Valley, Kashmir, Himalayas.

TWENTY-THREE YEARS OF GROWTH MEASUREMENTS ON THE CRUSTOSE LICHEN CALOPLACA AURANTIA IN THE CENTRAL NEGEV DESERT

ABSTRACT Over a period of 23 years, growth rates of primarily circular thalli of the crustose epilithic lichen Caloplaca aurantia (Pers.) Hellb. var. aurantia Poelt were measured in the highlands of the Negev Desert near Avdat. Thalli with an area greater than 3 to 4 cm2have reached the “linear phase” of growth, i.e., they show an almost constant annual increment in their radius. In an average of 11 samples, this growth amounted to 0.371 mm yr−1. In order to determine the width of the marginal annulus which contributes to the extension growth of the lichen, different portions of the center of some of the thalli were removed. A remaining annulus with a width of 12 mm provides sufficient assimilates for unimpaired centrifugal growth, which was not the case with an annulus 6 mm in width. Thalli of Diploschistes calcareus (Mull. Arg.) Stein., another crustose lichen species, showed an annual radial growth increment of 0.17 mm yr−1; however, data from only two samples could be collected. From diameter and grow...

Comparative performance of diatom indices in aquatic pollution assessment.

The use of epilithic diatoms as indicators of river water quality was evaluated in two streams of south Turkey. Diatoms as well as physical and chemical variables were sampled monthly between May, 2002 and April 2003 at six sites that can represent the streams. A total of 110 diatom taxa belonging to 32 genera were found. The most tolerant taxa to organic pollution were Nitzschia palea (Kutzing) W. Smith., Craticula accomoda (Hustedt) D.G. Mann., Gomphonema parvulum (Kutzing) Kutzing,Navicula atomus (Kutzing) Grunow, Navicula cryptocephala Kutzing. These species were dominant at the organically polluted stations. The performance of three types of benthic diatom index was compared (Swiss Diatom Index (DI-CH), Trophic Index (TI) and Saprobic Index (SI)). The indices were significantly correlated with dissolved oxygen, chloride, biological oxygen demand (BOD5), and concentrations of nutrients (NO3-N, NO2-N, NH4-N, and PO4-P). DI-CH, TI and SI had high correlations with thephysicochemical variables but DI-CH and TI were more reliable than the SI. We concluded that in these rivers, DI-CH and TI could be more useful than SI. Based on the significant correlation with nutrients and organic pollution variables this study suggests that SI, TI and DI-CH are integrating the effects of organic pollution. Key words: Diatom indices, pollution assessment, Turkey.

Epilithic diatom assemblages in rivers draining into Golfo Dulce (Costa Rica) and their relationship to water chemistry, habitat characteristics and land use

Epilithic diatom assemblages from neotropical streams draining into Golfo Dulce (Costa Rica) were studied to determine how diatoms were related to measured environmental conditions. Twenty-three sites, affected by different land use practices, were selected and monitored for 21 months. Water chemistry was characterized by moderate specific conductivity (100 - 300 µS/cm), neutral to alkaline pH and moderate to high values of soluble reactive phosphorus (10-70 µg/L). Anthropogenic impact was reflected in lower oxygen saturation, elevated nitrogen compounds and measured sedi- ment load. A diverse diatom flora of 212 taxa was found. Patterns in the diatom distri- bution in relation to environmental variables, as revealed by canonical correspondence analysis, showed that riparian shading, pH, conductivity, current velocity and turbidity were the most important measured factors in determining species composition. The re- lationship between conductivity and pH was sufficiently strong to develop weighted- averaging regression and calibration models. Optima and tolerances of the most com- mon diatom taxa are presented.

Epilithic algal strategies in a reservoir with periodic water-level changes

(1997). Epilithic algal strategies in a reservoir with periodic water-level changes. SIL Proceedings, 1922-2010: Vol. 26, No. 2, pp. 458-462.

Epilithic lichens on the floor of the Taylor Valley, Ross Dependency, Antarctica

Epilithic lichens on the floor of the Taylor Valley, Ross Dependency, Antarctica

Effects of Increasing Water Temperatures and Flow Rates on Epilithic Fauna in a Cooling-Water Discharge Basin

Description de la composition et des variations saisonnieres des communautes epilithiques d'un bassin de reception des eaux de refroidissement d'une centrale nucleaire suedoise.Les prelevements ont ete effectues toutes les 3 semaines pendant un an a des temperatures s'etageant jusqu'a 10˚ audessus des temperatures naturelles