Home About us Contact
|
Home About us Contact | ||
|
|
||
Pristine Site (pristine + site)
Selected AbstractsNew alk genes detected in Antarctic marine sedimentsENVIRONMENTAL MICROBIOLOGY, Issue 3 2009Emanuele Kuhn Summary Alkane monooxygenases (Alk) are the key enzymes for alkane degradation. In order to understand the dispersion and diversity of alk genes in Antarctic marine environments, this study analysed by clone libraries the presence and diversity of alk genes (alkB and alkM) in sediments from Admiralty Bay, King George Island, Peninsula Antarctica. The results show a differential distribution of alk genes between the sites, and the predominant presence of new alk genes, mainly in the pristine site. Sequences presented 53.10,69.60% nucleotide identity and 50.90,73.40% amino acid identity to alkB genes described in Silicibacter pomeroyi, Gordonia sp., Prauserella rugosa, Nocardioides sp., Rhodococcus sp., Nocardia farcinica, Pseudomonas putida, Acidisphaera sp., Alcanivorax borkumensis, and alkM described in Acinetobacter sp. This is the first time that the gene alkM was detected and described in Antarctic marine environments. The presence of a range of previously undescribed alk genes indicates the need for further studies in this environment. [source] Is structure or function a better measure of the effects of water abstraction on ecosystem integrity?FRESHWATER BIOLOGY, Issue 10 2009RUSSELL G. DEATH Summary 1. Assessments of flow abstractions in streams often focus on changes to biological communities and in-stream physical characteristics, with little consideration for changes in ecosystem functioning. It is unclear whether functional indicators of ecosystem health may be useful for assessing the impacts of reduced discharge on small streams. 2. We used weirs and diversions to reduce stream discharge by over 89% in three small New Zealand streams (11,84 L s,1), ranging in water quality from pristine to moderately impaired. 3. We used both structural (benthic invertebrates) and functional (drifting invertebrates, leaf breakdown, coarse particulate organic matter (CPOM) retention and primary productivity) measures of ecosystem integrity to compare responses to water abstraction in before-after, control-impact designed experiments during summer 2005. 4. At the pristine site, the density of invertebrates, taxon richness, Macroinvertebrate Community Index (MCI), Quantitative MCI, percentage of Ephemeroptera, Plecoptera and Trichoptera individuals and percentage of filter-feeders decreased in response to reduced flows. Only taxon richness decreased at the mildly impaired stream, and reduced discharge had no effect on the invertebrate community at the stream with the lowest water quality. 5. We found that reduced discharge had little influence on the breakdown rate of willow leaves in mesh bags over 1 month. Primary productivity was also relatively insensitive to water abstraction. However, CPOM retention increased with decreased flows. Drift propensity of invertebrates increased at two sites but only within the first few days after flow reduction. 6. Structural measures of ecosystem integrity suggested that the impacts of water abstraction differed among streams of varying water quality, probably because of differences in the sensitivity of invertebrate assemblages in the three streams. In contrast, the three functional measures tested were generally less sensitive to water abstraction impacts, although understanding how stream ecosystems respond to water abstraction clearly requires that both are considered. [source] Heavy metal pollution in Antarctica: a molecular ecotoxicological approach to exposure assessmentJOURNAL OF FISH BIOLOGY, Issue 2000C. W. Evans Trematomus bernacchii sampled from two sites at Ross Island, Antarctica, were assessed for condition (gonadal and hepatic somatic indices and condition factor), pathological state (liver and gill histology), hepatic metal (Zn, Cu, Cd and Ni) concentrations, and metallothionein induction by quantitative competitive (qc) RT-PCR. Fish from a polluted site (Winter Quarters Bay) had pathological anomalies including necrosis and periductal inflammation in their livers, and X-cell disease, epithelial hyperplasia, lamellar fusion and aneurysms in their gills. Such anomalies were less common in fish from a relatively pristine site (Backdoor Bay, Cape Royds). Fish from both sites had similar liver concentrations of Zn, Cu and Cd and qcRT-PCR revealed similar levels of hepatic metallothionein mRNA. Ni in the livers of fish from Winter Quarters Bay were higher than those in fish from Backdoor Bay, but the differences were not great enough to affect hepatic metallothionein mRNA significantly. Despite the polluted state of Winter Quarters Bay waters, it seems that the heavy metals present may have only limited impact on the health status of fish collected from this locality. This may reflect a low bioavailability of the heavy metals in Ross Island marine sediments and suggests that other factors, such as relatively high levels of organic pollutants (PAHs, PCBs) or pathogens from the nearby sewage outlet, may play a more significant role in the aetiology of pathological conditions in fish from Winter Quarters Bay. [source] Diet composition of Xenopus borealis in Taita Hills: effects of habitat and predator sizeAFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Beryl A. Bwong Abstract Frogs in the genus Xenopus are ubiquitous in sub-Saharan Africa, yet very little is recorded on their ecology. They are commonly found in anthropogenically disturbed habitats, but how do these compare to conspecifics from natural habitats? The diet of Xenopus borealis from three different sites in Taita Hills, Kenya was established based on a sample of 77 (54 females and 23 males) specimens from two disturbed and one pristine sites. Xenopus borealis from all the sites was found to be a dietary generalist, feeding predominantly on invertebrates. A total of twelve invertebrate orders both terrestrial and aquatic were recorded in addition to amphibian eggs, tadpoles and fish. Frogs from the pristine forest were smaller and had ingested more terrestrial prey items than frogs in the disturbed open habitat ponds. The stomach content (both by mass and quantity) was independent of body size. The results suggest that X. borealis is an opportunistic generalist predator which may be constrained by food availability in its natural habitat. However, disturbed habitats provide abundant food items which are enough to significantly increase the mean size of the population. Résumé Les grenouilles du genre Xenopus sont présentes partout en Afrique subtropicale, mais il existe peu de travaux sur leur écologie. On les trouve fréquemment dans des habitats perturbés par les hommes, mais comment ces grenouilles-ci se comparent-elles à leurs congénères des habitats naturels ? On a pu établir le régime alimentaire de Xenopus borealis sur trois sites différents des Taita Hills, au Kenya, d'après un échantillon de 77 individus (54 femelles et 23 mâles) de deux sites perturbés et d'un site intact. Xenopus borealis s'est avéréêtre un consommateur généraliste sur tous les sites, se nourrissant principalement d'invertébrés. On a noté la présence d'un total de 12 ordres d'invertébrés, terrestres et aquatiques, auxquels s'ajoutent des ,ufs d'amphibiens, des têtards et des poissons. Les grenouilles des forêts intactes étaient plus petites et mangeaient des proies plus terrestres que celles des points d'eau d'habitats ouverts perturbés. Le contenu stomacal (aussi bien par la masse que par la quantité) était indépendant de la taille corporelle. Les résultats suggèrent que X. borealis est un prédateur généraliste opportuniste qui peut être limité par la disponibilité de la nourriture dans son habitat naturel. Par contre, des habitats perturbés fournissent une nourriture abondante, suffisante pour augmenter significativement la taille moyenne de la population. [source] | ||||||||||