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Tidal Zone (tidal + zone)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

An actualistic perspective into Archean worlds , (cyano-)bacterially induced sedimentary structures in the siliciclastic Nhlazatse Section, 2.9 Ga Pongola Supergroup, South Africa

GEOBIOLOGY, Issue 1 2008
N. NOFFKE
ABSTRACT Extensive microbial mats colonize sandy tidal flats that form along the coasts of today's Earth. The microbenthos (mainly cyanobacteria) respond to the prevailing physical sediment dynamics by biostabilization, baffling and trapping, as well as binding. This biotic,physical interaction gives rise to characteristic microbially induced sedimentary structures (MISS) that differ greatly from both purely physical structures and from stromatolites. Actualistic studies of the MISS on modern tidal flats have been shown to be the key for understanding equivalent fossil structures that occur in tidal and shelf sandstones of all Earth ages. However, until now the fossil record of Archean MISS has been poor, and relatively few specimens have been found. This paper describes a study location that displays a unique assemblage with a multitude of exceptionally preserved MISS in the 2.9-Ga-old Pongola Supergroup, South Africa. The ,Nhlazatse Section' includes structures such as ,erosional remnants and pockets', ,multidirected ripple marks', ,polygonal oscillation cracks', and ,gas domes'. Optical and geochemical analyses support the biogenicity of microscopic textures such as filamentous laminae or ,orientated grains'. Textures resembling filaments are lined by iron oxide and hydroxides, as well as clay minerals. They contain organic matter, whose isotope composition is consistent with carbon of biological origin. The ancient tidal flats of the Nhlazatse Section record four microbial mat facies that occur in modern tidal settings as well. We distinguish endobenthic and epibenthic microbial mats, including planar, tufted, and spongy subtypes. Each microbial mat facies is characterized by a distinct set of MISS, and relates to a typical tidal zone. The microbial mat structures are preserved in situ, and are consistent with similar features constructed today by benthic cyanobacteria. However, other mat-constructing microorganisms also could have formed the structures in the Archean tidal flats. [source]

Neues Leben im Weltnaturerbe Wattenmeer.

BIOLOGIE IN UNSERER ZEIT (BIUZ), Issue 3 2010
Globalisierung unter Wasser
Abstract Neue Untersuchungen im Wattenmeer decken eine Überflutung durch eingeschleppte Arten auf, die sich in den vergangenen Jahren vor allem im Flachwasserbereich direkt unterhalb der Gezeitenzone ausbreiten konnten. Hier sind sie Nutznießer der durch den globalen Klimawandel verursachten ansteigenden Wassertemperaturen. Entstanden ist eine diverse Lebensgemeinschaft von Algen und Wirbellosen, die sich fortlaufend weiter verändert. Neben der strukturellen Komplexität der biogenen Habitate hat besonders die funktionelle Gruppe der filtrierenden Organismen zugenommen. Insgesamt ist das gesamte Ökosystem in einen Umbruch geraten, der nicht mehr umkehrbar ist. Globalization under water: Alien species in the Wadden Sea World Heritage Recent investigations reveal an increasing number of non-native species in the Wadden Sea which profit from warmer water temperatures caused by global change. These exotic species achieve highest occurrence and densities in shallow waters near the low tide water level. In this tidal zone, a highly diverse species community of algae and invertebrates became established and will continue to alter in composition. This leads to enhanced complexity of biogenic habitats and to a prevalence of filter feeding organisms. Thus, we observe a fundamental change of the whole Wadden Sea ecosystem which is without return. [source]

Phylogeny, biogeography and the stepwise evolutionary colonization of intertidal habitat in the Liparocephalini based on morphological and molecular characters (Coleoptera: Staphylinidae: Aleocharinae)

CLADISTICS, Issue 4 2010
Kee-Jeong Ahn
A phylogenetic analysis of the tribe Liparocephalini Fenyes is presented based on morphological and molecular characters. The data set comprised 50 adult morphological characters, partial COI (907 bp), COII (366 bp) and 12S rDNA (325,355 bp), and nearly complete sequences of 18S rDNA (1768,1902 bp) for 21 species. Eighteen species of liparocephaline beetles from all eight genera and three outgroups, are included. The sequences were analysed separately and simultaneously with morphological characters by direct optimization in the program POY4 and by partitioned Bayesian analysis for the combined data. The direct optimization (DO) tree for the combined data under equal weighting, which also shows a minimum incongruence length difference value, resulted in a monophyletic Liparocephalini with the following patterns of phylogenetic relationships (outgroup ((Baeostethus, Ianmoorea) (Paramblopusa ((Amblopusa, Halorhadinus) (Liparocephalus, Diaulota))))). A sensitivity analysis using 16 different parameter sets for the combined data shows the monophyly of the liparocephalines and all its genera under all parameter sets. Bayesian analysis resulted in topological differences in comparison with the DO tree under equal weighting only in the position of the genus Paramblopusa and clade (Amblopusa + Halorhadinus), which were reversed. Historical biogeography and the stepwise evolutionary colonization of intertidal habitat in the Liparocephalini are discussed. Based on the biogeographical analyses, we hypothesize that the ancestor of the Liparocephalini occurred along the Panthallassan Ocean, the direct antecedent of the Pacific Ocean, followed by repeated dispersals to the Nearctic from the Palearctic. We also hypothesize that ancestors of the Liparocephalini appear to have arisen in the littoral zone of beaches and then colonized rocky reef areas in the low tidal zone later through high- to mid-tide zones. ,© The Willi Hennig Society 2009. [source]

Lipid biomarkers, pigments and cyanobacterial diversity of microbial mats across intertidal flats of the arid coast of the Arabian Gulf (Abu Dhabi, UAE)

FEMS MICROBIOLOGY ECOLOGY, Issue 3 2008
Raeid M.M. Abed
Abstract Variations in morphology, fatty acids, pigments and cyanobacterial community composition were studied in microbial mats across intertidal flats of the arid Arabian Gulf coast. These mats experience combined extreme conditions of salinity, temperature, UV radiation and desiccation depending on their tidal position. Different mat forms were observed depending on the topology of the coast and location. The mats contained 63 fatty acids in different proportions. The increased amounts of unsaturated fatty acids (12,39%) and the trans/cis ratio (0.6,1.6%) of the cyanobacterial fatty acid n- 18:1,9 in the higher tidal mats suggested an adaptation of the mat microorganisms to environmental stress. Chlorophyll a concentrations suggested lower cyanobacterial abundance in the higher than in the lower intertidal mats. Scytonemin concentrations were dependent on the increase in solar irradiation, salinity and desiccation. The mats showed richness in cyanobacterial species, with Microcoleus chthonoplastes and Lyngbya aestuarii morphotypes as the dominant cyanobacteria. Denaturing gradient gel electrophoresis patterns suggested shifts in the cyanobacterial community dependent on drainage efficiency and salinity from lower to higher tidal zones. We conclude that the topology of the coast and the variable extreme environmental conditions across the tidal flat determine the distribution of microbial mats as well as the presence or absence of different microorganisms. [source]