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Water Conductivity (water + conductivity)
Selected AbstractsElectrosensory avoidance of metal obstacles by the paddlefishJOURNAL OF FISH BIOLOGY, Issue 2 2000C. Gurgens Paddlefish Polyodon spathula detected and avoided obstacles with an exposed metallic surface but not plastic objects. An aluminium obstacle was avoided from significantly greater minimum approach distances than were any of the other obstacles. No significant difference was detected between the plastic and plastic-covered aluminium obstacles, while control values were significantly less than for all obstacle types. Avoidance distances measured at different water conductivities were not significantly different. Fish collided frequently with the plastic and plastic-covered aluminium obstacles, and with the control site, suggesting that these obstacles were not detected by the electrosensory apparatus. The aluminium obstacle was avoided successfully in all test runs. The unambiguous avoidance behaviour elicited by the aluminium obstacle suggests that large metallic structures, such as locks and dams, have the potential to interfere with paddlefish migrations. ©2000 The Fisheries Society of the British Isles [source] Distribution of benthic diatoms in U.S. rivers in relation to conductivity and ionic compositionFRESHWATER BIOLOGY, Issue 8 2003Marina Potapova Summary 1We quantified the relationships between diatom relative abundance and water conductivity and ionic composition, using a dataset of 3239 benthic diatom samples collected from 1109 river sites throughout the U.S.A. [U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program dataset]. This dataset provided a unique opportunity to explore the autecology of freshwater diatoms over a broad range of environmental conditions. 2Conductivity ranged from 10 to 14 500 ,S cm,1, but most of the rivers had moderate conductivity (interquartile range 180,618 ,S cm,1). Calcium and bicarbonate were the dominant ions. Ionic composition, however, varied greatly because of the influence of natural and anthropogenic factors. 3Canonical correspondence analysis (CCA) and Monte Carlo permutation tests showed that conductivity and abundances of major ions (HCO + CO, Cl,, SO, Ca2+, Mg2+, Na+, K+) all explained a statistically significant amount of the variation in assemblage composition of benthic diatoms. Concentrations of HCO + CO and Ca2+ were the most significant sources of environmental variance. 4The CCA showed that the gradient of ionic composition explaining most variation in diatom assemblage structure ranged from waters dominated by Ca2+ and HCO + CO to waters with higher proportions of Na+, K+, and Cl,. The CCA also revealed that the distributions of some diatoms correlated strongly with proportions of individual cations and anions, and with the ratio of monovalent to divalent cations. 5We present species indicator values (optima) for conductivity, major ions and proportions of those ions. We also identify diatom taxa characteristic of specific major-ion chemistries. These species optima may be useful in future interpretations of diatom ecology and as indicator values in water-quality assessment. [source] Is fish condition correlated with water conductivity?JOURNAL OF FISH BIOLOGY, Issue 1 2003G. H. Copp There were no correlations between fish condition (K) and water conductivity in 14 species of 0+ year fishes in the River Great Ouse, U.K., catchment. Values of K increased with increasing distance from river source in dace Leuciscus leuciscus and roach Rutilus rutilus. [source] Morphology and Anatomy of Shoot, Root, and Propagation Systems in Hoffmannseggia glaucaPLANT BIOLOGY, Issue 6 2007T. A. Kraus Abstract: Hoffmannseggia glauca is a perennial weed that has tubers and root-borne buds. Some authors only consider root tubers without mentioning root-borne buds, while others consider that more anatomic studies become necessary to determine the origin of these structures and to interpret their behaviour. The objectives are: to study the growth form of the plant in order to analyze the ontogeny of its propagation organs, and to study its shoot and root anatomical characters that affect water conductivity. Hoffmannseggia glauca was collected in Argentina. Development of its shoot and root systems was observed. Shoots and roots were processed to obtain histological slides. Macerations were prepared to study vessel members. Primary and lateral roots originate buds that develop shoots at the end of the first year. In winter, aerial parts die and only latent buds at soil surface level and subterranean organs remain. In the following spring, they develop innovation shoots. Roots show localized swellings (tuberous roots), due to a pronounced increase of ray thickness and parenchymatous proliferation in the root center. Root vessel members are wider than those of aerial and subterranean shoots. Early development of an extensive root system, presence of root borne buds, anatomic and physiological specialization of innovation shoots, capability of parenchymatous rays to originate buds and tuberous roots, and high water transport efficiency in subterranean organs lead Hoffmannseggia glauca to display higher colonization potential than other species. [source] Precautionary rules for exotic trout aquaculture in fishless shallow lakes of Patagonia: minimizing impacts on the threatened hooded grebe (Podiceps gallardoi)AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2010Julio L. Lancelotti Abstract 1.Conflicts between habitat use and conservation are inherent to the management of wetlands. A major challenge for their management is to preserve habitat while addressing the demands from multiple users. In southern Patagonia (Argentina), a growing aquaculture activity based on rainbow trout introductions in shallow lakes is generating concerns about the effects on the waterbird fauna, including some endemic species. 2.Generalized linear models (GLM) were used to analyse data on the endemic hooded grebe (Podiceps gallardoi) collected over a diverse set of lakes to: (1) build presence-absence models as a function of environmental variables; (2) assess current and potential overlap with trout aquaculture; (3) explore the power of alternative lake assignment algorithms based on habitat variables to segregate critical habitat and aquaculture activities; and (4) explore the correlation between the probability of grebe presence and their abundance in given lakes. 3.Hooded grebe presence is clearly correlated with macrophyte cover, lake area, and water conductivity. Medium size lakes, with a combination of emerging macrophytes, adjacent to open water areas had the highest probability of both hooded grebe presence and abundance. 4.Different lake allocation scenarios are identified that could grant significant protection to hooded grebes without substantial losses for trout producers. The a priori probability to hold hooded grebe, assigned by the model based on lake characteristics, provides a tool that can be used by managing authorities to derive precautionary management rules to regulate aquaculture and to preserve primary hooded grebe habitat. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||