Habitat Zones Research Articles

Mapping and Understanding the Role of Seabed Morphology in Relation to Beluga Whale (Delphinapterus leucas) Hotspots and Habitat Use in the Mackenzie Estuary, NT

The Tarium Niryutait Marine Protected Area within the Mackenzie Estuary provides a critical summer habitat for the Eastern Beaufort Sea (EBS) beluga whales (Delphinapterus leucas). Given the lack of seabed characterization in the Mackenzie Estuary, there is a need to characterize key features and governing processes that may influence or drive beluga habitat use. Thus, we sample and describe the Mackenzie Estuary seabed and examine the influence of ice conditions, fluvial processes and wave interactions to define seabed processes and spatially defined habitats. Lastly, we examine how beluga selects specific seabed characteristics or habitat types. Seabed mapping, sediment sampling and delineation of seafloor features are used to define the seabed habitat. The majority of the seabed consists of medium to coarse-grained silt and is void of any bathymetric variations and disturbances. Five seabed habitat zones were defined: (1) featureless and flat, (2) scours and disturbed, (3) sandy shoal, (4) deep channel and (5) longshore bars. Beluga observations analysed retrospectively from 1972 to 1992 were associated with the featureless and flat seabed habitat 72% of the time. However, a preference for the sandy shoal habitat provides some indication there are substrates in the estuary which are suitable for whales to rub against (to scrape off moulting skin), supporting the hypothesis there are certain habitats that may attract belugas during the annual moult.

Using Recreation‐Grade Side‐Scan Sonar to Produce Classified Maps of Submerged Aquatic Vegetation

AbstractThe routine assessment and monitoring of aquatic habitat characteristics, such as submerged aquatic vegetation (SAV), is a fundamental tool in fisheries management. The relative low cost and availability of recreation‐grade side‐scan sonar (SSS) systems has made capturing high‐resolution (<10 cm) underwater imagery a practical and viable tool for improving these assessments. Using Humminbird SSS and a boat‐mounted transducer, we determined our ability to produce classified maps of SAV within three reservoirs in Texas. Sonar recordings of photic zone habitat were collected and processed into georeferenced mosaic images by using SonarTRX SSS software for use in geographical information systems (GISs). The resulting raster images were interpreted to identify and map SAV, and a classification scheme was developed. Random‐point data was also used to develop a traditional error matrix and an accuracy assessment for each classified map. In the three reservoirs, 485 ha were classified, including 298 ha of SAV. The area estimates for 11 of 12 classes fell within the 95% CIs that were estimated from concurrent random‐point surveys. Overall classification accuracy ranged from 78% to 88% for the three reservoirs. The methods that were developed demonstrate an accurate procedure for calculating SAV coverage and producing a high‐quality map product for distribution to stakeholders.

The Eurasian steppe belt in time and space: Phylogeny and historical biogeography of the false flax (Camelina Crantz, Camelineae, Brassicaceae)

Stretching 8000 km from the Pannonian basin and the Danube delta in the West to the Manchuria region in the East and reaching up to 1000 km in width, the Eurasian steppe belt is the vastest steppe region worldwide. However, our knowledge about the temporal and spatial patterns of floral origin and evolution of the Eurasian Steppe is limited and inconclusive. Case studies on typical steppe flora may help us close such gaps. The study subject of this project was Camelina – a taxon which occupies open dry habitats in temperate zones of Eurasia. To infer the evolutionary history of this genus, maximum likelihood optimisation in RAxML and Bayesian Inference approach were carried out, based on the nuclear external transcribed spacer region. Furthermore, we performed a secondarily calibrated time estimation analysis using Bayesian optimisation in BEAST to infer potential influence of climatic shifts and paleogeographic events on the distribution patterns of Camelina and carried out an ancestral area reconstruction analysis using a Bayesian Binary Method. Our study resulted in a well-supported phylogeny that corresponds with the species morphology and uncovered several genetically distinct inter- and intraspecific lineages which appear to correlate geographically. Time divergence estimation argue for the diversification of Camelina to have taken place in the Middle East around the transition from Pliocene to Pleistocene (3-2 mya), and its historical biogeography to have been under a strong influence of several glacial periods and their palaeoclimatic and palaeoenvironmental consequences. Its young age also explains the subtle morphological character differences among species and high interspecific hybridisation potential. We further discuss the rediscovery of wild Camelina sativa populations and propose the external transcribed spacer as a ribotype identifying region for young and rapidly evolving core eudicot lineages.

Исследование ресурсных зон поселений Кисловодской котловины

The publication focuses on 2018 findings of a comprehensive soil-archaeological survey of the multi-temporal settlements catchment within Kislovodsk Depression. The most in-depth study was conducted in the vicinity of Podkumskoye 3 fortification (5th — 8th centuries AD), where 100 soil sections were laid along a regular network with 50 m step at different distances from the habitat zone. In the soil sections, archaeological material was recorded layer by layer, the description of soil profiles and sampling for chemical and microbiological tests were carried out. The samples were tested for active microbial biomass, urease activity, saprotrophs, magnetic susceptibility and phosphates.
 This paper deals only with the findings of ceramics as a marker of farming practiced by ancient and medieval people living in this site. In total, about 2,380 fragments of pottery with a total weight of about 9 kg were discovered. A preliminary analysis of the spatial distribution of ceramics was carried out using the geostatistical module of ArcGIS software. It clearly showed different areas of farming in the Koban and Early Alanian areas. Now, the team is working on the analysis of the obtained material and soil samples for the detailed reconstruction of the site catchment in terms of farming.

Spatial distribution of flow currents and habitats in artificial buffer zones for ecosystem-based coastal engineering

As the process of urbanization progresses, coastal engineering are posing serious threat to the local ecosystems. The poorly designed coastal engineering will have irreversible effects on local ecosystems, such as the biodiversity declination, the connectivity destruction and the ecosystems deterioration. Therefore, it is very necessary to improve the concept of ecosystem-based coastal engineering design. In strict accordance with the notion of eco-seawall, in this research, the hydrodynamic change in 20 engineering scenarios was discussed and determined the spatial distribution of suitable habitats for aquatic species, which defined as the niche of aquatic organisms in the dimension of hydrodynamic. This research was conducted by carrying out pilot-scale experiment with an aim to enhance the traditional coastal engineering in terms of (a) measuring the intensity of hydrodynamic variations by adding artificial beach or buffer zone (b) determining the overtopping risks in varying working conditions (c) visualizing the distribution of optimal habitat areas with hydrodynamic parameters as eco-niche dimension. As revealed by the results, four working conditions pose low overtopping risk and exhibit uniform distribution of flow (No.1, No.2, No.8 and No.14). Additionally, the suitable habitats distribution have been visualized for 4 types of working condition with safety structure. A conclusion can be drawn that there are significantly fewer unsuitable habitat areas in the No.14 scenario as compared to other schemes. In general, this research is conducive to improving the development of ecosystem-based coastal engineering.

Habitat heterogeneity determines plant species richness in urban stormwater ponds

Urbanisation is seen as one of the most important drivers for species extinction. The aim of our study was to compare vascular plant species richness of 35 artificial urban stormwater ponds (STOPON) designed to control water flow, with 35 control ponds (CONTROL) in the surrounding landscape. For both plot types, we gathered a variety of environmental parameters to determine the drivers of plant species richness. Based on the results, we discuss the relevance of STOPON for biodiversity conservation in urban areas and give recommendations for biodiversity-friendly construction and pond management.Our study showed that the environmental conditions clearly varied between STOPON and CONTROL. STOPON were especially larger than CONTROL; as a consequence, the aquatic, semi-aquatic and terrestrial zones had a greater extent at STOPON. Accordingly, the overall and mean number of aquatic, salt-tolerating aquatic and threatened plant species was higher at STOPON than at CONTROL. However, species density of all three plant indicator groups did not differ among the two plot types.The greater plant species richness of STOPON was driven by a higher habitat heterogeneity which was especially explained by (i) the genuine effect of habitat area on habitat heterogeneity, (ii) the existence of three similarly large habitat zones (terrestrial, semi-aquatic, aquatic) and (iii) the regular management, which represses shading plants, creates open soil and activates the soil seed bank. Due to the high species richness of threatened plant species STOPON play an important role in biodiversity conservation in urban areas.

Passive ambient comfort and the interaction of vernacular strategies and devices in arid zone habitat design: case of Biskra, Algeria

ABSTRACTUp until the industrial revolution, energy consumption was relatively linear, and almost exclusively renewable. The exponential industrial and economic development that began with the industrial revolution became increasingly energy-intensive, and since the switch to fossil fuels that energy consumption has been based on non-renewable resources. Satisfying the energy needs of the present without harming future generations remains a complicated problem, especially at the habitat level. This article proposes a methodology for building designers, building upon research on converging towards a global optimum, more specifically, it investigates the feasibility of integrating mezzanines and vaults as vernacular devices to improve the energy performance of buildings in arid zones, while to ensuring the comfort of the occupants. This level of comfort and energy performance is based on the morphological structure of the proposed building type. Combined, these devices result in a higher reduction of thermal in energy ratio load of up to 20.84%. These reductions in energy needs were achieved by applying the methodology developed for the architectural design of a building located in Biskra, Algeria, a design that takes into account both the comfort aspects of the occupants and the need for reduced energy consumption.

Habitat species pools shape algal and bacterial communities and their correlations.

Understanding of community ecology is scale dependent. When the scale definition changes from subjectively defined "regional species pools" to "habitat species pools", heterogeneity differences occur for microbial communities. However, given the environmental gradients differences among habitats, responses of other organisms and interspecific correlations to habitat species pools may also be heterogeneous. This hypothesis is supported by our research about algal and bacterial communities among four different habitats in littoral zones. In our results, both the algal and bacterial community compositions varied along habitat species pools. Furthermore, at community level, significant correlation was only found between bacterioplankton and phytoplankton in pelagic habitat. And at individual level, the covariant trends between habitat generalists in algal and bacterial communities varied among habitats. Our results indicated that habitat-specific patterns can not only influence the habitat species pools, but also shape the interspecies interaction, and this should be considered in the further study of algae-bacterial correlation.

Passive Ambient Comfort and Correlation of Strategies and Vernacular Devices for Habitat Design in Arid Zones: The Case of Biskra, Algeria

Current concerns focus on the need to reduce energy consumption in construction and over the lifespan of buildings. A major objective is to create affordable housing. However, reducing the energy needs of the present without harming the needs of future generations remains difficult to put into practice, especially at the level of habitats in arid zones. In this research, a housing design assistance process for building designers is proposed, with the aim of converging towards a global optimum for the correlation and integration of vernacular devices and strategies in an optimized way. This will allow the integration of energy performance indicators and user comfort, in order to ultimately optimize, for this case study, the morphogenesis of residential buildings based on the morphological structure of a proposed building in Biskra, Algeria. This last developed process is articulated on various combinations distinguished for the case of the integration of devices and strategies, which allow maximum energy saving while ensuring the comfort of the occupants. As part of this research, this integration constituted a major challenge and made it possible to achieve a reduction in energy ratio of up to 25.11% compared to the standard building and the objectives of the research.

Causal relationships of Raphidiopsis (formerly Cylindrospermopsis) dynamics with water temperature and N:P-ratios: A meta-analysis across lakes with different climates based on inferential modelling

Raphidiopsis raciborskii is a tropical toxic cyanobacterium that is rapidly expanding to diverse lake habitats in different climate zones by sophisticated adaptation mechanisms.This meta-analysis investigated correlations of R. raciborskii with water temperature and N:P (nitrogen to phosphorus)-ratios across four lakes with different climates and trophic states by means of long-term time series and the hybrid evolutionary algorithm HEA. The results have shown that in the lakes with temperate and Mediterranean climate, R. raciborskii is strongly correlated with water temperature since germination and growth rely on rising water temperatures in spring. In contrast, there was a weaker correlation with water temperature in subtropical and tropical lakes where pelagic populations of R. raciborskii are overwintering, and are present all year round. However, the highest abundances of R. raciborskii coincided with highest water temperature for the Mediterranean, subtropical and tropical lakes, whilst in the temperate Langer See the highest abundances of R. raciborskii occurred at 24.1 °C, even though temperatures of up to 27 °C were recorded in 2013 and 2014. The correlation of R. raciborskii with N:P-ratios proved to be strongest for the meso- to eutrophic Lake Kinneret (r2 = 0.8) and lowest for the eutrophic Lake Paranoa (r2 = 0.16). However, the assumption has been confirmed that R. raciborskii is growing fastest when waters are N-limited regardless of trophic states. In terms of phenology, the temperate and Mediterranean lakes displayed “fastest growth” in spring and early summer. In contrast, the growing season in subtropical and tropical lakes lasted from spring to autumn most likely because of overwintering populations, and growing importance of direct and indirect biotic regulating factors such as competition, grazing, remineralisation of nutrients along warming climate. In order to carry out a meta-analysis of time series across four different lakes, HEA served as powerful tool resulting in inferential models with predictive capacity for population dynamics of R. raciborskii just driven by water temperature or N:P-ratios, whilst coefficients of determination r2 served as criteria for hypotheses testing.

Rapid assessment of the riparian zone habitat of river.

Some riparian areas of the country are in danger of deterioration due to uncontrolled exploitation coupled with loose implementation of environmental protection policies and regulations. Muleta River, a major watershed in Bukidnon, Philippines, was assessed to determine the present condition of its riparian habitat. Abiotic and biotic conditions of the river were assessed. Other factors including land cover, population density, and river geomorphologic characteristics contributing to the river condition were also evaluated. Results revealed that Muleta Watershed is in sub-optimal condition signifying favorable condition for floral and faunal habitat. However, considerable degradation in some isolated cases was likewise spotted. Biotic condition has shown greater degradation approaching marginal condition compared to the abiotic condition which is yet in the upper sub-optimal condition. It was found out that the midstream portion of the watershed is the most disturbed, followed by the downstream area and lastly by the upstream portion. The extent of agricultural cultivation is found as one of the significant factors affecting the health of the riparian habitat areas. It is recommended that riparian protection policies must be formulated and implemented to abate, if not prevent, the impact of anthropogenic interventions resulting to overexploitation in the riparian areas especially in midstream portion of the river.

Aquatic Vegetation and Invertebrate Communities of Big Stone National Wildlife Refuge

Abstract Observed degradation of aquatic systems at Big Stone National Wildlife Refuge, located in west-central Minnesota, have been associated with sediment-laden inflows from riverine systems. To support management, a study was conducted during 2013–2014 with overall goals of characterizing the aquatic invertebrate and vegetation communities of the Big Stone National Wildlife Refuge and exploring relations between these communities and various water-quality parameters. Sample sites were located along an observed vegetation gradient and assigned to three predetermined habitat zones for comparison purposes: upstream, transition, and downstream. Of the 12 species of aquatic vegetation that were identified, invasive narrowleaf cattail Typha angustifolia dominated the upstream zone (observed at >90% of sample locations), coontail Ceratophyllum demersum and narrowleaf cattail were most common in the transition zone (collected or observed at 100 and 83% of sample locations, respectively), and coontail and narrowleaf pondweed Potamogeton strictifolius were most common in the downstream zone (collected at 100 and 64% of sample locations, respectively). Measured values for the water-quality parameters varied among dates, reflecting the continually fluctuating nature of riverine systems. Based on general observations across sample dates, turbidity and dissolved oxygen concentrations were greatest in the upstream zone sample sites, while oxidation-reduction potential was greatest in the downstream zone sites. There were 115 unique aquatic invertebrate taxa identified to varying levels of taxonomic resolution. Results suggested that there were overall differences in invertebrate biomass among the sample dates, but that there were no strong trends among the sample zones. Aquatic invertebrates and vegetation communities, along with the water-quality parameters, varied temporally and showed irregular relations among the sample zones. These general observations emphasize the importance of temporally and spatially intensive sampling to account for natural variation. Moreover, short- and long-term streamflow and water-level information obtained for this study demonstrated substantial variability that must be considered when conducting biotic inventories and monitoring water quality, as well as when using such data to assess management options. Periodic monitoring of wetlands and associated streamflows, along with sediment loads and water quality of inflows, should allow Big Stone National Wildlife Refuge staff to identify habitat degradation and potential contributing factors, and to develop strategies to achieve specific management objectives and goals.

Detecting Indicator Taxa Associated with Benthic Organic Enrichment Using Different Video Camera Orientations

Sutherland, T.F.; Sterling, A.M.; Shaw, K.L.; Blasco, N.N.J., and Bradford, M.J., 2019. Detecting indicator taxa associated with benthic organic enrichment using different video camera orientations. Journal of Coastal Research, 35(2), 467–479. Coconut Creek (Florida), ISSN 0749-0208.Two video cameras mounted on a remotely operated vehicle (ROV) were used to generate paired forward-facing (FF) and downward-facing (DF) observations of benthic epifauna along 10 single transects at eight marine finfish aquaculture sites in British Columbia, Canada. The abundance of mat-forming primary indicators of organic enrichment, such as sulphide-oxidizing bacteria and opportunistic polychaete complexes (OPC), were quantified through percentage coverage estimates. Coverage estimates for sulphide-oxidizing bacteria were strongly correlated between the FF and DF orientations across all substrate types. The occurrence of OPC was limited to a single mixed-substrate site, which provided the strongest FF vs. DF relationship within this study. In contrast to sulphide-oxidizing bacteria, epifaunal abundance (count data) revealed strong relationships between camera orientations for fine sediments and mixed sediments and a weaker relationship observed for vertical rock wall environments. Similar observations occurred for estimates of both sessile (dominated by plumose anemones) and motile taxa guilds comprising the total epifaunal community. Weaker relationships associated with the rock wall substrate are likely due to alternating blackout periods experienced by each camera orientation as the ROV passes vertical or ledge habitat zones. Overall, a combination of FF and DF video orientations may provide more robust abundance estimates for settings that are characterized by various substrate grades and structural and/or mat-forming taxa.

Mosaic environments shape the distribution of Neotropical freshwater ichthyoplankton

AbstractDam presence results in heterogeneous aquatic environments that probably favour segregation of ichthyoplankton developmental stages. Therefore, the present study tested the hypothesis that dams in the Upper Uruguay River create heterogeneous aquatic environments favouring segregation of ichthyoplankton developmental stages and also separate species with different reproductive tactics. Ichthyoplankton were captured bimonthly during 2002–2015 in 25 sampling stations grouped by fluviometric characteristics. Sampling was performed at night, with cylindrical–conical plankton nets and light traps. After quantifying ichthyoplankton, we identified larvae to the lowest possible taxonomic level and classified them based on developmental stage and reproductive tactics. Egg abundance was higher in lotic environments, preflexion individuals were more abundant in transitional lotic/lentic environments, and the flexion stage was predominant in lentic environments. Larval assemblages consisted mainly of sedentary species or those with short reproductive migrations. Species with similar reproductive tactics occurred in different environments. In conclusion, we provided evidence demonstrating that mosaic environments in the Upper Uruguay River are important for life cycle completion of different fish species. These distinct habitat zones allow for successful spawning and offspring development, thus guaranteeing recruitment.

Spatial and temporal analysis of beta diversity in the Barro Colorado Island forest dynamics plot, Panama

BackgroundEcologists are interested in assessing the spatial and temporal variation in ecological surveys repeated over time. This paper compares the 1985 and 2015 surveys of the Barro Colorado Forest Dynamics plot (BCI), Panama, divided into 1250 (20 m × 20 m) quadrats.Methods, spatial analysisTotal beta diversity was measured as the total variance of the Hellinger-transformed community data throughout the BCI plot. Total beta was partitioned into contributions of individual sites (LCBD indices), which were tested for significance and mapped.Results, spatial analysisLCBD indices indicated the sites with exceptional community composition. In 1985, they were mostly found in the swamp habitat. In the 2015 survey, none of the swamp quadrats had significant LCBDs. What happened to the tree community in the interval?Methods, temporal analysisThe dissimilarity in community composition in each quadrat was measured between time 1 (1985) and time 2 (2015). Temporal Beta Indices (TBI) were computed from abundance and presence-absence data and tested for significance. TBI indices can be decomposed into B = species (or abundances-per-species) losses and C = species (or abundances-per-species) gains. B-C plots were produced; they display visually the relative importance of the loss and gain components, through time, across the sites.Results, temporal analysisIn BCI, quadrats with significant TBI indices were found in the swamp area, which is shrinking in importance due to changes to the local climate. A published habitat classification divided the BCI forest plot into six habitat zones. Graphs of the B and C components were produced for each habitat group. Group 4 (the swamp) was dominated by species (and abundances-per-species) gains whereas the five other habitat groups were dominated by losses, some groups more than others.ConclusionsWe identified the species that had changed the most in abundances in the swamp between T1 and T2. This analysis supported the hypothesis that the swamp is drying out and is invaded by species from the surrounding area. Analysis of the B and C components of temporal beta diversity bring us to the heart of the mechanisms of community change through time: losses (B) and gains (C) of species, losses and gains of individuals of various species. TBI analysis is especially interesting in species-rich communities where we cannot examine the changes in every species individually.

Growth of salt-secretor and non-salt secretor mangrove seedlings with varying salinity and their relations to habitat zonation

The growth of six mangrove seedlings under varying salinity was studied concerning the habitat zonation. Healthy and mature propagules and seeds of selected mangroves, Rhizophora apiculata, R. stylosa, Ceriops tagal, Avicennia marina, A. alba, and Acanthus ilicifolius were collected from North Sumatran mangroves. Mangrove seedlings were grown for three months in 0.0%, 0.5%, 1.5%, 2.0% and 3.0% salinity concentration. The growth of mangrove seedlings emerged to show variation among the species. The growth of two salt secretor species of A. marina and A. alba were increased in the occurrence of salt with maximum activation at 2.0%. This escalation was reduced once salt concentration was increased above 2.0%. By contrast, two non-salt secretor species of R. apiculata and R. stylosa significantly expanded to 1.5% salinity, at that moment decreasing by accumulative salts. A salt secretor species of Ac showed the less salt tolerant of mangrove species. ilicifolius and a nonsalt-secretor of C. tagal, which their optimum growth was at 0.5% salinity. The tolerance of mangrove species to salt concentration tracked the sequence of Av. marina and Av. alba (most foreshore species) >R. stylosa and R. apiculata>C. tagal>Ac. ilicifolius (most landward species), which is following the natural species distribution and habitat zones.

Clonal integration increases growth performance and expansion of Eichhornia crassipes in littoral zones: A simulation study

Clonal integration can improve the spread and growth of invasive plants in response to various disturbances. However, little is known about its role in floating aquatic clonal plants that expand from aquatic into terrestrial habitats in littoral zones. Thus, in this study, we simulated the expansion of the invasive clonal aquatic plant Eichhornia crassipes from aquatic to terrestrial habitats through two modes of clonal integration. We subjected E. crassipes parent plants and offspring ramets to three levels of natural light in terrestrial habitats: 100%, 60%, and 10%. The stolon connections were either severed or kept intact. Our findings showed that clonal integration had positive effects on plants exposed to shade in the terrestrial habitats and produced negative effects on plants in the aquatic habitats. Overall, clonal integration significantly increased whole-plant growth performance. Parent plants and offspring ramets in the terrestrial environments can enhance their adaptability to shade by increasing the maximum quantum yield of photosystem II and chlorophyll content. Clonal integration can support the expansion of E. crassipes from aquatic into terrestrial habitats with limited light conditions through significantly elevated growth traits. Thus, E. crassipes has a high ability for clonal integration and may be a potential threat to littoral zone ecosystems.

A below-the-present late Holocene relative sea level and the glacial isostatic adjustment during the Holocene in the Malay Peninsula

This study has reconstructed the Holocene relative sea-level history in the relatively tectonically stable Malay Peninsula with two specific objectives: quantifying the sea-level indicative meanings of mangrove sediments and producing new high-quality sea-level index points. In this study, a wetland on the east coast of the Peninsula was extensively surveyed; the elevational relationship between habitat zones and their pollen and diatom assemblages was established; and a number of indicative meanings were precisely quantified for this wetland. This quantified relationship is extrapolated to other coastal sites of the Peninsula for re-calibration of previously published mangrove-based sea-level data. The reconstructed sea-level history from the new and re-calibrated data demonstrates a period of rapid sea-level rise at a rate of 15.8 ± 3.9 mm/a between 10,500 cal a BP at −35.0 ± 4.3 m and 9000 cal a BP at −14.2 ± 1.6 m. The rate of rising sea level was gradually reduced to zero from 9000 to 5000 cal a BP, and by the end of this period the relative sea level reached a highstand of c. 3.3 ± 0.2 m. Over the past 5000 years relative sea level fell to its lowest point at −0.6 ± 0.1 m by 800 cal a BP. This far-field sea-level history has been driven by the global ice-volume change and glacial isostatic adjustment, and it matches well with the modelled ice-volume equivalent sea level.

Vegetation Dynamics and Species Diversity in a Saharan Oasis, Egypt

The present study provides an analysis of the floristic composition, habitat types, vegetation structure and species diversity, elucidating the role of the environmental factors that affect species distribution in Kharga Oasis, Western Desert, Egypt. The vegetation was sampled from 89 permanently visited stands in 12 sites situated along N - S line transect across the oasis, and extending for about 185 km to cover as much as possible the physiognomic variation in habitats. Four main habitats were recognized and forming concentric zones (from inside to outside): farmlands and date-palm orchards represent the inner zone, the waste-salinized lands (not saltmarshes) in the middle zone, and the surrounding (bounding) desert in the outer zone. A total of 122 species from 35 families and 102 genera represented the flora of the study area. Poaceae, Asteraceae and Fabaceae were the major families, which constituted 47% of the total flora. Classification using Bray-Curtis cluster analysis produced 4 vegetation groups (A - D); each can be linked to a certain habitat. The arrangement of habitat zones along the first DCA axis can be noticed: outer zone (bounding desert), middle zone (waste-salinized lands) and inner zone (arable lands). On the other hand, farmlands and date-palm orchard groups were separated from each other along the second DCA axis. The relationship between the vegetation and soil variables was studied using Canonical Correspondence Analysis (CCA); it was indicated the most important environmental gradients those control the vegetation composition and the distribution pattern of species in Kharga Oasis, which were mainly related to gradients in soil moisture content and fine fractions. The present situation of Kharga Oasis urges the conservation of some old historic wells and the naturally growing open dom-palm forests before vanishing due to high human activities in the area.

Distribution, abundance and activity of geosmin and 2-methylisoborneol-producing Streptomyces in drinking water reservoirs

While cyanobacteria have been widely recognised as the most common cause of geosmin and 2-methylisoborneol related taste and odour (T&O) episodes in drinking water supplies, many reported occurrences could not be attributed to these organisms. The Streptomyces genus of soil bacteria also includes producers of these compounds, however their potential role in such occurrences is poorly understood and often disregarded on the basis that they are terrestrial rather than aquatic organisms, with their detection in water samples assumed to reflect the presence of dormant spores rather than metabolically active vegetative cells. Using qPCR and a differential cell lysis technique for DNA extraction, allowing distinction of spores from vegetative cells, the aim of this study was to determine the distribution, abundance and potential activity of Streptomyces species across a range of aquatic and marginal habitat zones in two drinking water reservoirs, including: exposed soil, submerged sediments, plant debris and emergent macrophytes at the margins; marginal and offshore surface waters; deep offshore waters; and offshore benthic sediments. Marginal substrates including soil, sediment and plant debris were identified as the dominant habitat zones for Streptomyces, (concentrations up to 1.1 × 107 cells g−1) supporting the concept of ‘wash-in’ from the margins due to run-off or water level rise following rainfall, as the likely pathway for Streptomyces induced T&O in reservoirs. However, vegetative cells were also found to comprise a substantial proportion of Streptomyces populations in the reservoir water mass itself (>90% in some surface and bottom water samples), suggesting the potential for these bacteria to be metabolically active in the water and therefore contribute to in situ production of T&O metabolites.