Contribution of microspatial factors to benthic diatom communities

Large rivers are worldwide under severe pressure and there is a lack of information on large river restoration. The present paper represents a meta-analysis of available data on river rehabilitation projects performed at the Austrian Danube River consisting of six rehabilitation projects addressing 19 sites. The overall goal was to analyse the response of fish assemblages to different rehabilitation types based on (1) morphological type (“Instream Habitat Enhancement”, “backwater Enhancement”, “extended Enhancement”), (2) length of rehabilitation measure (3) time after construction (4) applied monitoring design. Biological metrics evaluated included number of fish species and relative density, habitat guilds and Leitbild species. In total, number of species increases by 55% comparing rehabilitated with unrestored sites. The number of species of all habitat guilds is higher after rehabilitation. The proportion of rheophilic species increased and the community evolved toward a more type-specific community, according to the Leitbild. Significant differences between measure types were not detected. The rehabilitation success depends mainly on its spatial extent. Highest positive response of number of rheophilic species is achieved by a length >3.9 km. The results show that habitat rehabilitation of large rivers is effective if the spatial extent of the measure is in accordance with river size.     

Contribution to the ecology ofMarsilea quadrifolia L.

Data are presented on the aboveground and underground biomass of the speciesMarsilea quadrifolia and on the water regime and soil conditions in a habitat of this species in Central Europe (Czechoslovakia).     

Contribution to the environmental ecology of Cryptogramma crispa (L.) R. Br. ex Hooker in the Alps

We studied the habitat characteristics in a number of Cryptogramma crispa stations throughout the Alps. Our objectives were: (1) to define the environmental ecology of C. crispa in the southern part of its distributional area in Europe; (2) to test the reliability of ecological indicator values of soil reaction, nutrient and dispersion status, light and temperature for this species. The habitats of C. crispa mostly consisted in coarse-grained stable screes (on rock slide deposits, talus cones, talus sheets, stone fields and moraines), within a broad elevation range with maximum frequency in the subalpine and lower alpine vegetation belts. At higher altitudes, C. crispa was mostly found on South-exposed slopes with high potential irradiance, whereas at low altitude it was most abundant on North-exposed rather gentle slopes formed of big boulders. The screes colonized by C. crispa were formed of acid metamorphic rocks or igneous rocks and had a coarse texture. The soil accumulated in the spaces among boulders had sandy texture and acidic reaction, with medium to high carbon and total nitrogen contents. Calcium lacks entirely in the soil. Our field data gave support to the Ellenberg–Landolt ecological indicator values of light and temperature, but not to those of soil reaction and soil nutrient content, for which some changes are proposed.     

Approaches to investigating the ecology of plasmids in marine bacterial communities

To better understand prokaryotic gene flux in marine ecosystems and to determine whether or not environmental parameters can effect the composition and structure of plasmid populations in marine bacterial communities, information on the distribution, diversity, and ecological traits of marine plasmids is necessary. This mini-review highlights recent insights gained into the molecular diversity and ecology of plasmids occurring in marine microbial communities.     

Contribution of vitamin A deficiency to calculogenic risk factors of urine: studies in children.

Studies in experimental animals showed that vitamin A deficiency enhanced the severity of urinary calculi disease. In India, children with low socioeconomic status are the major victims of bladder stone disease, and vitamin A deficiency is also more prevalent among these children. However, no systematic study is available to correlate the vitamin A-deficient status of children with their predisposition to urinary calculi disease. Vitamin A-deficient and normal boys were the subjects of this study. Twenty-four-hour samples of urine were collected from all the children at the beginning of the study and after normalizing the vitamin A status of the deficient children. Important risk factors were estimated in urine. Plasma vitamin A levels were also measured in these children. Among the deficient group, only children with plasma vitamin A levels of 15 micrograms and lower exhibited calcium oxalate crystalluria. Most importantly, abnormal crystalluria was observed in all children whose plasma vitamin A levels were 13 micrograms/dl or less. Compared to normal children the urine of vitamin A-deficient children showed the following changes: (a) reduced concentration of crystal growth inhibitors, namely citrate and glycosaminoglycans; (b) a decline in inhibitory activity toward calcium oxalate crystal growth; and (c) enhanced excretion of high risk factors, namely calcium and oxalate. Correction of vitamin A status normalized the above abnormal properties of urine. The results of this study strongly support the hypothesis that the vitamin A-deficient state is one of the factors that can enhance the risk of urolithiasis in susceptible populations.     

Contribution to the ecology and seed germination ofCucumis callosus

Ecology and germination behaviour of the seeds of two categories ofCucumis callosus Cogn. has been studied here. The seeds were found to be rigid in their requirement of light and temperature for germination. Red and far-red lights were found to affect germination and a phytochrome system appeared to be present. Temperature was found to have a significant effect on seed germination.     

Contribution of vegetative anatomy to the systematics of the Zygophyllaceae R.Br

SHEAHAN, M. C. & CUTLER, D. F., 1993. Contribution of vegetative anatomy to the systematics of the Zygophyllaceae R.Br. The Zygophyllaceae sensu lato are a heterogeneous family of trees, shrubs and herbs growing in arid and semi-arid areas of the world. There has been disagreement about the systematic status of some groups within the family, and the position of Balanites has also been disputed. The vegetative anatomy of the family was examined to see if it could throw light on current systems of classification. The anatomy of 37 species in 19 genera is described, and the results of tests of C₄ activity in 27 species are given. There is anatomical evidence to support the exclusion of Balanites into a separate family, and some groups (Engler's Peganoideae and Nitrarioideae) have characteristics which set them apart from the rest of the family. This is in accordance with other analyses of the family based on morphological, palynological and biochemical studies. There is also evidence that the tribuloid genera Tribulus, Kallstroemia and Kelleronia should be separated from the zygophylloid genera, at least at subfamily level; however, Neoluederitzia and Sisyndite should remain in the Zygophylloideae. Brief reference is made to relationships with other families in the Geraniales.     

The structural aspect in the ecology of sea-grass communities

Summary 1. Sea-grasses are aquatic angiosperms which are completely adapted to life in the marine environment. They belong to 2 families, the Potamogetonaceae with 9 marine genera and the Hydrocharitaceae with 3 marine genera.2. All sea-grasses satisfy the following indispensable conditions for a successful existence in the sea: (a) high salt tolerance, (b) ability to grow when fully submerged, (c) well-developed rhizomes, (d) hydrophilous pollination, and (e) sufficient competitive power in the marine environment.3. Plant taxa which fulfill the first 4 conditions excellently, but have a reduced competition capacity, are unable to establish themselves successfully in the marine environment and are restricted to poikilohaline environments, such as brackish waters and continental salt waters. Moreover, some of these taxa occur in instable fresh-water environments.4. Within the group of the sea-grasses 6 different growth-forms can be distinguished: parvozosterids, magnozosterids, syringodiids, enhalids, halophilids and amphibolids.5. The growth-forms are linked with the environmental conditions: they show a distinct horizontal zonation and in the succession series they follow each other in a fixed sequence.6. The structure of the communities is also dependent on the dominating growthforms. The communities of parvozosterids and halophilids are very simple in structure. The magnozosterid vegetations show some differentiation. In the enhalid and amphibolid communities a marked stratification occurs, as an upper layer, characterized by photophilous epiphytes on the leaves, and a lower layer with sciophilous epiphytes on the rhizomes can be distinguished.7. Sea-grass communities alter the physical environment by stabilizing the bottom, slackening the water movements and increasing the sedimentation.8. Sea-grass vegetations form a food resource for many marine organisms and water fowl, and are also of some importance as shelter and nurseries for a number of animal species.

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Der strukturelle Aspekt in der Ökologie von Seegras-Gemeinschaften

Kurzfassung Seegräser sind aquatische Angiospermen, welche vollkommen an das Leben im Meer angepaßt sind. Sie gehören zu zwei Familien, den Potamogetonaceen mit 9 und den Hydrocharitaceen mit 3 marinen Gattungen. Für das Leben im Meer sind sie gut ausgerüstet mit Eigenschaften, die unbedingt für eine erfolgreiche Existenz erforderlich sind: hohe Salztoleranz, Fähigkeit, ganz untergetaucht zu gedeihen, Vorhandensein gut entwickelter Rhizome, hydrophile Bestäubung und ein ausreichendes Konkurrenzvermögen. Eine erfolgreiche Ansiedlung im Meer ist bereits ausgeschlossen, wenn die zuletzt erwähnte Eigenschaft nicht vorhanden ist. Es gibt nämlich eine Reihe von Gattungen, die in ihrer Beziehung zur Umwelt, insbesondere zum Salzgehalt, eine viel größere Toleranz besitzen als die Seegräser, aber ungenügend konkurrenzfähig sind gegenüber stenobionten Wasserpflanzen. Diese Gattungen sind beschränkt auf poikilohaline Gewässer und unstabile Süßwasserbiotope. Die Gesellschaften dieser Pflanzen werden zur Klasse der Ruppietea gestellt. Die echten Seegrasgesellschaften werden zusammengefaßt in der Klasse Zosteretea. Diese Gesellschaften sind noch ungenügend studiert worden; daher wird ihre Struktur von vielen Pflanzensoziologen nicht korrekt beurteilt. Der Verfasser bereitet eine Monographie über die Seegräser vor; er hatte Gelegenheit, alle bis jetzt bekannten Arten gründlich zu untersuchen und die Wichtigkeit ihrer morphologischen Merkmale für die Ökologie zu prüfen. Es stellte sich heraus, daß unter den Seegräsern 6 Wuchsformen unterschieden werden können, welche charakterisiert sind durch das Verästelungssystem, die Blattform und die Natur der Blattscheiden. Jede Wuchsform hat ihren eigenen Platz in der Zonierung und in der Sukzessionsreihe, und jede bedingt im großen und ganzen die Struktur der von ihr konstituierten Pflanzengesellschaft.

     

Contribution to the taxonomy and ecology of the Azorean benthic marine algae

Algal zonation patterns were studied in two sites (Caloura, south coast and Ribeirinha, north coast) of the island of Sao Miguel, Azores. At each site two stations were studied and the transects revealed the occurrence of two distinct and well established algal zones. In the first zone, daily immersed and emersed by the tide, the algae were growing in a dense and short tangle forming a mat, referred to as algal turf. In the second zone, which was wet most of the time, the algae were larger and frondose. A list of the species of benthic marine algae occurring on the algal turf of each station is given. Of the total of 47 species found, eight are new for the Azores and another 13 species are recorded for the first time for Sao Miguel. Gigartina acicularis (Roth) Lamouroux and articulate coralline algae (Corallina oficinalis Linnaeus and Jania spp.) were the more common species. Seasonal variation of the algal turf was studied and related to mean monthly values of air and sea water temperatures, insolation and hours of light. The zonation patterns and composition of algal species were compared with those from other open rocky shores.     

Systems ecology,people ecology,and the anthropology of fishing communities

Ecological approaches within maritime anthropology are reviewed, particularly those concerned with resource management in fisheries and characterized by certain assumptions of systems ecology. The systems ecology approach used in anthropology exhibits certain problems, including the assumption of equilibria, the tendency to restrict analyses to immediate and natural environmental relations, and the reification of analytical systems. Under the rubric of people ecology, data from research among commercial fishermen of Fogo Island, Newfoundland, are used to explore an alternative that emphasizes people rather than systems as starting points for study, and underscores the role of larger social and political processes in affecting local man — environment relations.