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Water pH (water + ph)
Selected AbstractsShifts in the ecological behaviour of plant species between two distant regions: evidence from the base richness gradient in miresJOURNAL OF BIOGEOGRAPHY, Issue 2 2008Petra Hájková Abstract Aim, Water pH and conductivity are known to be major environmental factors controlling the species composition of nutrient-poor wetlands. Based on the analysis of two large data sets of species co-occurrence, sampled along the entire pH/calcium gradient, we explored whether species exhibit similar or different ecological behaviour in the two regions. Location, West Carpathians (central Europe) and Bulgaria (south-eastern Europe), situated 800 km apart. Bulgaria represents a range margin for many mire species. Methods, The probability of occurrence of the 41 most common species along the pH and conductivity gradients was assessed using logistic regression fitted by means of generalized additive models. The species optimum and amplitude were determined. To check the possible effect of competitive release, we estimated where the potential maximum number of species (maximum overlap in realized niches) occurs along the base richness gradient. Results, Most of the 41 frequently occurring species showed a significant response to water pH and ln-transformed conductivity (approximating total mineral richness) in both regions. Eight species showed a shift in pH optimum greater than one unit, while 12 species showed the same or a larger shift along the conductivity gradient. Nearly all these striking shifts were connected to an extension of species tolerance towards mineral-poor acid habitats in Bulgaria, which causes links between species and measured factors to be conspicuously weaker in Bulgaria than in the West Carpathians. Regarding ecological amplitude, 24 species exhibited a wider tolerance to water conductivity in the West Carpathians, whereas 17 species exhibited a wider tolerance in Bulgaria. Main conclusions, A distinctive variation in the realized niche was observed in a large portion of the species examined. Niche shifts between local populations of the same species were similar to those of closely related vicariant species. Ecotypic adaptation within species is a possible explanation for this pattern. Other possible explanations (competitive release, specific habitat conditions, compensation for climate) seem to be less justified. The local populations of rich-fen species may have adapted to mineral-poor acid conditions in the high crystalline mountains of Bulgaria during dry periods of pleniglacials. Nomenclature,Marhold & Hindák (1998); for Balkan elements not included in this source, Andreev et al. (1992). [source] Performance evaluation of concurrent rice,fish,prawn culture with and without cull harvestingAQUACULTURE RESEARCH, Issue 9 2010Rajeeb K Mohanty Abstract This study was carried out in farmers' fields for three experimental culture cycles to evaluate the performance of rice,fish,prawn culture. The treatments carried out were deepwater rice mono-cropping (R), and rice,fish,prawn culture with cull harvesting (R,FC) and without cull harvesting (R,F). Water pH and total alkalinity were significantly higher (P<0.05) in R,FC than in R,F, while the concentrations of total suspended solids, plankton and chlorophyll a were higher in R,F. Cull harvesting in R,FC had no marked influence on the concentrations of dissolved oxygen, NH4+, nitrite, nitrate and phosphate compared with the R,F treatment. The significantly higher fish and prawn yields (P<0.05) and species-wise faster individual growth performance in R,FC than in R,F were probably due to periodic cull harvesting, which minimized the competition for food and space as well as physiological stress at reduced density. The paddy yield and percentage increase in paddy yield over rice mono-crop was significantly higher (P<0.05) in R,FC (25%), followed by R,F (16.9%), probably due to lower chlorophyll a (36.7 mg m,3) and plankton density (1.4 × 104 L,1), which minimized the competition for nutrients with rice plants. The highest rice equivalent yield (38.5), output value,cultivation cost ratio (1.56) and enhanced net return (28%) in deepwater rice,fish culture were recorded when cull harvesting was practiced. [source] A rapid technique for assessing the suitability of areas for invasive species applied to New Zealand's riversDIVERSITY AND DISTRIBUTIONS, Issue 2 2008Cathy Kilroy ABSTRACT Early responses to incursions of non-indigenous species (NIS) into new areas include modelling and surveillance to define the organisms' potential and actual distributions. For well-studied invasive species, predictive models can be developed based on quantitative data describing environmental tolerances. In late 2004, an invasive freshwater diatom Didymosphenia geminata, an NIS for which we had no such quantitative data, was detected in a New Zealand river. We describe a procedure used to rapidly develop a classification of suitability for all New Zealand's rivers, based on two sources of information. First, from a review of the limited available literature and unpublished data, we determined that temperature, hydrological and substrate stability, light availability, and water pH were the most important environmental gradients determining D. geminata's broad-scale distribution and capacity for establishing and forming blooms in rivers. The second information source was a GIS-based river network developed for a national classification of New Zealand's rivers, with associated data describing environmental characteristics of each section of the network. We used six variables that were available for every section of the network as surrogates for the environmental gradients that determine suitability. We then determined the environmental distance of all the river sections in the network from our assessment of the optimal conditions conducive to D. geminata blooms. The analysis suggested that > 70% of New Zealand's river sections (stream order > 3) fell into the two highest suitability categories (on a five-point scale). At the time of writing, D. geminata had spread to 12 catchments, all of which were within these two categories. The technique is applicable in initial responses to incursions of NIS where quantitative information is limited, and makes optimal use of available qualitative information. Our assessment contributed to evaluations of the potential ecological, social, and economic impacts of D. geminata and is currently being used to stratify site selection for ongoing surveillance. [source] The influence of stream invertebrate composition at neighbouring sites on local assemblage compositionFRESHWATER BIOLOGY, Issue 2 2005R. A. SANDERSON Summary 1. The composition of freshwater invertebrate assemblages at a location is determined by a range of physico-chemical and biotic factors in the local environment, as well as larger-scale spatial factors such as sources of recruits. We assessed the relative importance of the species composition of local neighbourhoods and proximal environmental factors on the composition of invertebrate assemblages. 2. Macroinvertebrate assemblages were sampled at 188 running-water sites in the catchment of the River Rede, north-east England. A total of 176 species were recorded. 3. Environmental data, in the form of 13 biotic and abiotic measurements that described stream physical structure, aquatic vegetation and water characteristics, were recorded for each site. Detrended correspondence analysis was then used to simplify nine of these stream environmental variables to create an index of stream structure. 4. The species composition of the invertebrate assemblages was related to the environmental variables, using an information theoretic approach. The impact of the species composition of neighbouring sites on each site was determined using Moran's I and autoregressive modelling techniques. 5. Species composition was primarily associated with water pH and stream structure. The importance of the species composition of neighbouring sites in determining local species assemblages differed markedly between taxa. The autoregressive component was low for Coleoptera, intermediate for Trichoptera and Plecoptera, and high for Ephemeroptera. 6. We hypothesise that the observed differences in the autoregressive component amongst these orders reflects variation in their dispersal abilities from neighbouring sites. [source] Potential sources of food hazards in emerging commercial aquaculture industry in sub-Saharan Africa: a case study for UgandaINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2009Ananias Bagumire Summary A study was conducted to assess sources of food hazards in Uganda's emerging commercial aquaculture industry based on Hazard Analysis Critical Control Point (HACCP), focusing on inputs, their sources and farm-practices on ten representative commercial farms. Critical control points (CCPs) were identified to reveal potential hazards that would jeopardise any export trade. Site selection, water quality, fertiliser, fish seed, fish rearing facilities, feeds, and post-harvest practices were the main CCPs identified. Animal manure was used to generate plankton as pond fertiliser in nine of the ten surveyed farms and veterinary drugs were not found in any of the ten farms, which is starkly different from aquaculture in indutrialised countries. Potential sources of hazards from water were mainly: municipal waste flow which was more likely on five of the ten farms, domestic waste (four farms), agricultural run-off (three farms), and low water pH (three farms). Fish fry and fingerlings from other farms, feeds formulated on-farm from unapproved sources, chemical products, uncontrolled fish predators, and domestic animal and human activities were the other potential sources of hazards. A complete application of HACCP is recommended for producing safe products that meet the strict market standards of developed countries. [source] Deterministic assembly of land snail communities according to species size and dietJOURNAL OF ANIMAL ECOLOGY, Issue 4 2010Brandon Schamp Summary 1.,We investigated whether coexisting snail species in 145 treeless fen communities in the Western Carpathian Mountains differed more in size and diet than would be expected by chance, as predicted for traits commonly associated with competition and differential resource acquisition under limiting similarity theory. 2.,Contrary to expectations, coexisting snail species were no more different in body size than expected by chance under a null model. However, variation in body size played a significant role in structuring snail communities: coexisting snail species were significantly more similar with respect to body size. 3.,We developed two new test statistics to expand our investigation of limiting similarity to include diet, a nominal trait. We tested whether communities of snails were characterized by a greater richness of diet, and whether different diets were represented more or less evenly within communities. Communities of snails were significantly less evenly distributed than expected by chance, with detritivores being over-represented relative to predatory strategies. 4.,We also examined the effect of water pH and conductivity, herbaceous cover, and bryophyte and vascular plant richness, on these trends by examining how the effect size of our tests varied across these gradients. Convergence in species size increased with increasing habitat pH. Specifically, smaller snail species were over-represented in fen communities in general, and this effect was accentuated in increasingly calcareous fens. 5.,Theory predicts that traits related strongly to environmental conditions are more likely to be convergent. Our findings support this suggestion, as small snail species have an advantage in tolerating freezing conditions over winter when refuges are limited. 6.,These results add to the growing body of literature demonstrating that variation in body size and diet play a strong role in structuring communities, although frequently in ways not predicted by limiting similarity theory. Finally, our results increase our understanding of how species are assembled non-randomly into communities with respect to important traits. [source] Effects of sand and process water pH on toluene diluted heavy oil in water emulsions in turbulent flowAICHE JOURNAL, Issue 1 2009Chandra W. Angle Abstract The presence of sand in heavy oil production is known to enhance oil recovery. Sand can also be detrimental depending on the properties of the sand,water interface. In this process, the water soluble material interacts with both sand and oil droplets and affects emulsion stability. The formation and stability of heavy oil-in-water emulsions during turbulent flow using batch process stirred-tank mixing of oil, sand, and water were investigated at three pH. Size distributions were measured by laser diffraction. High-speed video photomicrography was used to observe the process during mixing. Results showed that the presence of sand enhanced formation of stable, fine emulsion at basic pH 8.5. When the pH of the water was reduced below 6.5 both sand and droplets surface properties changed, the emulsions became less stable and coalescence was apparent. The sand grains acted as coalescers at low pH and enhanced breakage at high pH. © Her Majesty the Queen in Right of Canada, as represented by the Minister of Natural Resources, 2008 AIChE J, 2009 [source] Occurrence of Vibrio vulnificus in mussel farms from the Varano lagoon environmentLETTERS IN APPLIED MICROBIOLOGY, Issue 4 2010L. Beneduce Abtract Aims:, Monitoring the occurrence of the human pathogen Vibrio vulnificus in a mussel farm located in the lagoon of Varano (Italy). Methods and Results:, A total of 72 samples of mussel, water and sediment, collected from two locations of Varano lagoon in the Gargano peninsula, during a 7- month survey, were analysed. Isolation and PCR characterization of six V. vulnificus environmental genotype strains revealed that this pathogen was isolated when with T was above 22°C and salinity ranged between 22·7 and 26·4,. No significant correlation of the occurrence of V. vulnificus with water pH or salinity was observed. Moreover, 8% of mussel samples were found to be contaminated by V. vulnificus. All of that positive mussel samples originated from the same sampling station. Conclusion:, It is suggested that warmer season are risky to eat raw or undercooked bivalve molluscs in the local area. Significance and Impact of the Study:, To increase knowledge about environmental conditions that may affect the occurrence of waterborne pathogen Vibrio vulnificus in seafood. [source] | |||||||||||||