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Interacting Effects (interacting + effects)
Selected AbstractsInteracting effects of CO2 partial pressure and temperature on photosynthesis and calcification in a scleractinian coralGLOBAL CHANGE BIOLOGY, Issue 11 2003Stéphanie Reynaud Abstract We show here that CO2 partial pressure (pCO2) and temperature significantly interact on coral physiology. The effects of increased pCO2 and temperature on photosynthesis, respiration and calcification rates were investigated in the scleractinian coral Stylophora pistillata. Cuttings were exposed to temperatures of 25°C or 28°C and to pCO2 values of ca. 460 or 760 ,atm for 5 weeks. The contents of chlorophyll c2 and protein remained constant throughout the experiment, while the chlorophyll a content was significantly affected by temperature, and was higher under the ,high-temperature,high- pCO2' condition. The cell-specific density was higher at ,high pCO2' than at ,normal pCO2' (1.7 vs. 1.4). The net photosynthesis normalized per unit protein was affected by both temperature and pCO2, whereas respiration was not affected by the treatments. Calcification decreased by 50% when temperature and pCO2 were both elevated. Calcification under normal temperature did not change in response to an increased pCO2. This is not in agreement with numerous published papers that describe a negative relationship between marine calcification and CO2. The confounding effect of temperature has the potential to explain a large portion of the variability of the relationship between calcification and pCO2 reported in the literature, and warrants a re-evaluation of the projected decrease of marine calcification by the year 2100. [source] Interacting effects of management and environmental variability at multiple scales on invasive species distributionsJOURNAL OF APPLIED ECOLOGY, Issue 6 2009Jeffrey M. Diez Summary 1. The distribution and abundance of invasive species can be driven by both environmental variables and land management decisions. However, understanding these relationships can be complicated by interactions between management actions and environmental variability, and differences in scale among these variables. The resulting ,context-dependence' of management actions may be well-appreciated by ecologists and land managers, but can frustrate attempts to apply general management principles. 2. In this study, we quantify the effects of land management and environmental variability at different scales on the occurrence and abundance of Hieracium pilosella, a major agricultural weed in New Zealand. We used a hierarchical study design and analysis to capture relevant scales of variation in management actions and environmental heterogeneity, and test hypotheses about how these factors interact. 3. We show that fertilizing and grazing interact with environmental gradients at the scale of management application (farm paddocks) to influence the establishment and local abundance of H. pilosella. 4. We further show that H. pilosella's relationships with fine-scale abiotic and biotic factors are consistent with expected mechanisms driven by larger-scale management actions. Using data on occurrence and local abundance, we tease apart which factors are important to establishment and subsequent local spread. 5.Synthesis and applications. A major challenge for environmental scientists is to predict how invasive species may respond to ongoing landscape modifications and environmental change. This effort will require approaches to study design and analysis that can accommodate complexities such as interacting management and environmental variables at different scales. Management actions will be more likely to succeed when they explicitly account for variation in environmental context. [source] Interacting effects of dietary lipid level and temperature on growth, body composition and fatty acid profile of rohu, Labeo rohita (Hamilton)AQUACULTURE NUTRITION, Issue 6 2004K. Mishra Abstract Three isonitrogenous (320 g kg,1 crude protein, casein and gelatine) semi-purified diets with 80 (L8), 130 (L13) and 180 (L18) g kg,1 lipid (sunflower oil at increasing levels and cod liver oil fixed at 50 g kg,1) at three digestible energy levels (12 096, 13 986 and 15 876 kJ kg,1 dry weight) and were tested, in triplicate, on rohu fingerlings (3.2 ± 0.08 g) at two different temperatures (21 and 32 °C). Fish were fed to apparent satiation, twice daily, at 09.00 and 15.00 h, 7 days a week for 56 days. Maximum growth was obtained at a lipid level of 80 g kg,1 (L8) at 21 °C (439.37%) and 130 g kg,1 (L13) at 32 °C (481.8%). In general growth rate was higher at 32 °C than at 21 °C at all lipid levels. Tissue monounsaturated fatty acid (MUFA) contents decreased with increasing lipid level at 32 °C, but the reverse occurred at 21 °C. At 21 °C, Polyunsaturated fatty acid (PUFA) level increased significantly (P > 0.05) over initial values, but was affected insignificantly by dietary lipid level. At 32 °C, fish fed diet L13 had more n-3 fatty acid (FA) in liver and muscle than the other two dietary groups while at 21 °C, both liver and muscle FA profiles exhibited significant change (P > 0.05) in n-3 and n-6 FA content which corresponded to variation in percent addition of dietary lipid. However, n-3/n-6 ratio was higher for fish fed diet L13 at 32 °C and diet L8 at 21 °C and may be correlated with fish growth. [source] Differences in sino-atrial and atrio-ventricular function with age and sex attributable to the Scn5a+/, mutation in a murine cardiac modelACTA PHYSIOLOGICA, Issue 1 2010K. Jeevaratnam Abstract Aim:, To investigate the interacting effects of age and sex on electrocardiographic (ECG) features of Scn5a+/, mice modelling Brugada syndrome. Methods:, Recordings were performed on anaesthetized wild-type (WT) and Scn5a+/, mice and differences attributable to these risk factors statistically stratified. Results:,Scn5a+/, exerted sex-dependent effects upon sino-atrial function that only became apparent with age. RR intervals were greater in old male than in old female Scn5a+/,. Atrio-ventricular (AV) conduction was slower in young female mice, whether WT and Scn5a+/,, than the corresponding young male WT and Scn5a+/,. However, PR intervals lengthened with age in male but not in female Scn5a+/, giving the greatest PR intervals in old male Scn5a+/, compared with either old male WT or young male Scn5a+/, mice. In contrast, PR intervals were similar in old female Scn5a+/, and in old female WT. QTc was prolonged in Scn5a+/, compared with WT, and female Scn5a+/, compared with female WT. Age-dependent alterations in durations of ventricular repolarization relative to WT affected male but not female Scn5a+/,. Thus, T-wave durations were greater in old male Scn5a+/, compared with old male WT, but indistinguishable between old female Scn5a+/, and old female WT. Finally, analysis for combined interactions of genotype, age and sex demonstrated no effects on P wave and QRS durations and QTc intervals. Conclusion:, We demonstrate for the first time that age, sex and genotype exert both independent and interacting ECG effects. The latter suggest alterations in cardiac pacemaker function, atrio-ventricular conduction and ventricular repolarization greatest in ageing male Scn5a+/,. [source] The effects of fluvial processes and habitat heterogeneity on distribution, growth and densities of juvenile Atlantic salmon (Salmo salar L.), with consequences on abundance of the adult fishECOLOGY OF FRESHWATER FISH, Issue 4 2002R. J. Gibson Abstract,,,The required freshwater habitats of juvenile Atlantic salmon (Salmo salar) are, in general, well known, but vary in quality, related to interacting effects of several variables, which may depend on different parts of a river system. Examples are given of ranges of densities and growth that can be found at various sites in eastern Canada, illustrating the biological and physico-chemical factors affecting production of juvenile salmon. Relative growth rates can indicate habitat quality and population densities. Salmon parr have negative effects on brook trout in riffle habitats. The effects of migrations within the river and of changes with stream succession on juvenile salmon production are illustrated with examples from a Newfoundland river. Migration of age-classes can be quantified from ,self-thinning' curves. Lakes have enhancing effects on downstream fluvial habitats, and, at least in Newfoundland, and probably in many boreal areas, the lacustrine proportion of the basin can be used as an index for deriving estimates of required spawning escapement. The factors described should be taken into account for more refined estimates of river production and management of the salmon resource. [source] Several components of global change alter nitrifying and denitrifying activities in an annual grasslandFUNCTIONAL ECOLOGY, Issue 4 2006R. BARNARD Summary 1The effects of global change on below-ground processes of the nitrogen (N) cycle have repercussions for plant communities, productivity and trace gas effluxes. However, the interacting effects of different components of global change on nitrification or denitrification have rarely been studied in situ. 2We measured responses of nitrifying enzyme activity (NEA) and denitrifying enzyme activity (DEA) to over 4 years of exposure to several components of global change and their interaction (increased atmospheric CO2 concentration, temperature, precipitation and N addition) at peak biomass period in an annual grassland ecosystem. In order to provide insight into the mechanisms controlling the response of NEA and DEA to global change, we examined the relationships between these activities and soil moisture, microbial biomass C and N, and soil extractable N. 3Across all treatment combinations, NEA was decreased by elevated CO2 and increased by N addition. While elevated CO2 had no effect on NEA when not combined with other treatments, it suppressed the positive effect of N addition on NEA in all the treatments that included N addition. We found a significant CO2,N interaction for DEA, with a positive effect of elevated CO2 on DEA only in the treatments that included N addition, suggesting that N limitation of denitrifiers may have occurred in our system. Soil water content, extractable N concentrations and their interaction explained 74% of the variation in DEA. 4Our results show that the potentially large and interacting effects of different components of global change should be considered in predicting below-ground N responses of Mediterranean grasslands to future climate changes. [source] Effects of temperature and food quality on anuran larval growth and metamorphosisFUNCTIONAL ECOLOGY, Issue 5 2002D. Álvarez Summary 1Anurans exhibit high levels of growth-mediated phenotypic plasticity in age and size at metamorphosis. Although temperature and food quality exert a strong influence on larval growth, little is known about the interacting effects of these factors on age and size at metamorphosis. 2Plasticity in growth rates, maximum larval mass, mass loss, larval period and size at metamorphosis was examined in Iberian Painted Frogs (Discoglossus galganoi Capula, Nascetti, Lanza, Bullini & Crespo 1985) under different combinations of temperature and diet quality. 3Temperature and diet had strong effects on the maximum size reached by tadpoles throughout the premetamorphic stages. Larval body mass varied inversely with temperature. The effect of diet depended on temperature; larvae fed on a ,carnivorous' diet (rich in protein and lipids) achieved a larger size than larvae offered an ,herbivorous' diet (rich in carbohydrates) at 17 °C but not at 12 or 22 °C. 4Larval period was insensitive to diet composition, and varied only with temperature. Primarily the interacting effects of food quality and temperature affected size at metamorphosis. Size at metamorphosis varied inversely with temperature under the plant- and the animal-based diets. However, the carnivorous diet resulted in bigger metamorphs at 17 and 22 °C, but did not influence final mass at 12 °C. Maximum size over the larval period explained most of the variation in mass loss after the premetamorphic growing phase. [source] The response of heterotrophic activity and carbon cycling to nitrogen additions and warming in two tropical soilsGLOBAL CHANGE BIOLOGY, Issue 9 2010DANIELA F. CUSACK Abstract Nitrogen (N) deposition is projected to increase significantly in tropical regions in the coming decades, where changes in climate are also expected. Additional N and warming each have the potential to alter soil carbon (C) storage via changes in microbial activity and decomposition, but little is known about the combined effects of these global change factors in tropical ecosystems. In this study, we used controlled laboratory incubations of soils from a long-term N fertilization experiment to explore the sensitivity of soil C to increased N in two N-rich tropical forests. We found that fertilization corresponded to significant increases in bulk soil C concentrations, and decreases in C loss via heterotrophic respiration (P< 0.05). The increase in soil C was not uniform among C pools, however. The active soil C pool decomposed faster with fertilization, while slowly cycling C pools had longer turnover times. These changes in soil C cycling with N additions corresponded to the responses of two groups of microbial extracellular enzymes. Smaller active C pools corresponded to increased hydrolytic enzyme activities; longer turnover times of the slowly cycling C pool corresponded to reduced activity of oxidative enzymes, which degrade more complex C compounds, in fertilized soils. Warming increased soil respiration overall, and N fertilization significantly increased the temperature sensitivity of slowly cycling C pools in both forests. In the lower elevation forest, respired CO2 from fertilized cores had significantly higher ,14C values than control soils, indicating losses of relatively older soil C. These results indicate that soil C storage is sensitive to both N deposition and warming in N-rich tropical soils, with interacting effects of these two global change factors. N deposition has the potential to increase total soil C stocks in tropical forests, but the long-term stability of this added C will likely depend on future changes in temperature. [source] Climatology of cloud-to-ground lightning in Georgia, USA, 1992,2003INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2005Mace L. Bentley Abstract A 12-year climatology of lightning cloud-to-ground flash activity for Georgia revealed the existence of three primary regions of high lightning activity: the area surrounding the Atlanta Metropolitan Statistical Area, east-central Georgia along the fall line, and along the Atlantic coast. Over 8.2 million ground flashes were identified during the climatology. July was the most active lightning month and December was the least active. Annual, seasonal, and diurnal distributions of cloud-to-ground flashes were also examined. These patterns illustrated the interacting effects of land cover, topography, and convective instability in enhancing lightning activity throughout Georgia. A synoptic analysis of the ten highest lightning days during the summer and winter revealed the importance of frontal boundaries in organizing convection and high lightning activity during both seasons. The prominence of convective instability during the summer and strong dynamical forcing in the winter was also found to lead to outbreaks of high lightning activity. Copyright © 2005 Royal Meteorological Society. [source] RECENT ADVANCES IN FERTILIZATION ECOLOGY OF MACROALGAE,JOURNAL OF PHYCOLOGY, Issue 1 2002Bernabé SantelicesArticle first published online: 19 FEB 200 Our understanding of natural patterns of fertilization in seaweeds has increased substantially over the last 10 years due to new approaches and methods to characterize the nature and frequency of fertilization processes in situ, to recognize the conditions and mechanisms enhancing fertilization success, and to anticipate population and community consequences of the patterns of natural fertilization. Successful reproduction in many species depends on a delicate juxtaposition of abiotic and biotic conditions. Important abiotic factors are those triggering gamete release (e.g. single or interacting effects of light quality and water movement) and those affecting gamete viability or concentrations (e.g. salinity effects on polyspermy blocks; gamete dilution due to water movement). Examples of important biotic components are synchronous gamete release, efficiency of polyspermy-blocking mechanisms, population density of sexually fertile thalli, interparent distances, and male-to-female ratios. Field data indicate fertilization frequencies of 70%,100% in broadcasting-type seaweeds (e.g. fucoids) and 30%,80% in brooding-type (red) algae. Red algal values are higher than previously thought and challenge presently accepted explanations for their complex life histories. Important population and community questions raised by the recent findings relate to the magnitude of gene flow and exchange occurring in many micropopulations that seemingly breed during periods of isolation, the physiological basis and population effects of male-to-male competition and sexual selection during fertilization of brooding seaweeds, and the effects of massive gamete release, especially in holocarpic seaweeds, on benthic and planktonic communities. Comparative studies in other algal groups are now needed to test the generality of the above patterns, to provide critical pieces of information still missing in our understanding of natural fertilization processes, and to elucidate the evolutionary consequences of the different modes of reproduction (e.g. brooders vs. broadcasters). [source] Reproductive success and helper effects in the cooperatively breeding grey-crowned babblerJOURNAL OF ZOOLOGY, Issue 3 2007C. J. Blackmore Abstract Cooperative breeding, where some individuals help to raise offspring that are not their own, is a relatively rare social system in birds. We studied the breeding biology of a declining cooperative breeder, the grey-crowned babbler Pomatostomus temporalis, with the aim of isolating the social factors that affect its reproductive success. Most breeding pairs were assisted by philopatric offspring, although pairs could breed successfully without helpers. Females laid up to four clutches (usually three eggs per clutch) per season. Male (but not female) helpers increased the number of young fledged from individual nests and the likelihood of re-nesting, resulting in higher seasonal fledgling production. Helper effects on brood size and fledgling production were greater in the second year of the study, which was also characterized by higher nest failure. This suggests that helpers enhance reproduction more in poor conditions. Our study demonstrates the interacting effects of social and ecological factors on reproductive success, and that retention of offspring is not always beneficial for the breeders in cooperative species. [source] When (not) to indulge in ,puffery': the role of consumer expectations and brand goodwill in determining advertised and actual product qualityMANAGERIAL AND DECISION ECONOMICS, Issue 6 2000Praveen K. Kopalle We analyze why some firms advertise product quality at a level different from the actual quality of a product. By considering the interacting effects of product quality and advertising, we develop a dynamic model of consumer expectations about product quality and the development of brand goodwill to determine the optimal values for the decision variables. The model parameters are determined based on prior literature and we use numerical techniques to arrive at the solution. We then derive conditions under which a firm will find it optimal to overstate or understate product quality. The results suggest that quality may be overstated in markets characterized by high price sensitivity, low quality sensitivity, low brand loyalty, and high source credibility, suggesting the need for vigilance on the part of consumers, upper level managers and regulatory authorities in such market conditions. This is important because current regulatory resources are insufficient to reduce deceptive advertising practices (Davis JJ. 1994. Ethics in advertising decision-making: implications for reducing the incidence of deceptive advertising. Journal of Consumer Affairs28: 380,402). Further, the law of deceptive advertising prohibits some advertising claims on the ground that they are likely to harm consumers or competitors (Preston IL, Richards JI. 1993. A role for consumer belief in FTC and Lanham Act deceptive advertising cases. American Business Law Journal31: 1,29). Also, Nagler (1993. Rather bait than switch: deceptive advertising with bounded consumer rationality. Journal of Public Economics51: 359,378) shows that deceptive advertising causes a net social welfare loss and a public policy effectively preventing deception will improve social welfare. Copyright © 2000 John Wiley & Sons, Ltd. [source] Interaction of landscape and life history attributes on genetic diversity, neutral divergence and gene flow in a pristine community of salmonidsMOLECULAR ECOLOGY, Issue 23 2009DANIEL GOMEZ-UCHIDA Abstract Landscape genetics holds promise for the forecasting of spatial patterns of genetic diversity based on key environmental features. Yet, the degree to which inferences based on single species can be extended to whole communities is not fully understood. We used a pristine and spatially structured community of three landlocked salmonids (Salvelinus fontinalis, Salmo salar, and Salvelinus alpinus) from Gros Morne National Park (Newfoundland, Canada) to test several predictions on the interacting effects of landscape and life history variation on genetic diversity, neutral divergence, and gene flow (m, migration rate). Landscape factors consistently influenced multispecies genetic patterns: (i) waterfalls created strong dichotomies in genetic diversity and divergence between populations above and below them in all three salmonids; (ii) contemporary m decreased with waterway distance in all three species, while neutral genetic divergence (,) increased with waterway distance, albeit in only two taxa; (iii) river flow generally produced downstream-biased m between populations when waterfalls separated these, but not otherwise. In contrast, we expected differential life history to result in a hierarchy of neutral divergence (S. salar > S. fontinalis > S. alpinus) based on disparities in dispersal abilities and population size from previous mark-recapture studies. Such hierarchy additionally matched varying degrees of spatial genetic structure among species revealed through individual-based analyses. We conclude that, whereas key landscape attributes hold power to predict multispecies genetic patterns in equivalent communities, they are likely to interact with species-specific life history attributes such as dispersal, demography, and ecology, which will in turn affect holistic conservation strategies. [source] Top-down and bottom-up control in an eelgrass,epiphyte systemOIKOS, Issue 5 2008Sybill Jaschinski Nutrient supply and the presence of grazers can control primary producers in aquatic ecosystems, but the relative importance of bottom-up and top-down effects remains inconclusive. We conducted a mesocosm experiment and a field study to investigate the independent and interactive effects of nutrient enrichment and grazing on primary producers in an eelgrass bed Zostera marina. Nutrient treatments consisted of ambient or enriched (2× and 4× ambient) concentrations of inorganic nitrogen and phosphate. Grazer treatments consisted of presence or absence of field densities of the common isopod Idotea baltica. We found strong and interacting effects of nutrients and grazing on epiphytes. Epiphyte biomass and productivity were enhanced by nutrient enrichment and decreased in the presence of grazers. The absolute amount of epiphyte biomass consumed by grazers increased under high nutrient supply, and thus, nutrient effects were stronger in the absence of grazing. The effects of grazers and fertilisation on epiphyte composition were antagonistic: chain-forming diatoms and filamentous algae profited from nutrient enrichment, but their proportions were reduced by grazing. Eelgrass growth was positively affected by grazing and by nutrient enrichment at moderate nutrient concentrations. High nutrient supply reduced eelgrass productivity compared to moderate nutrient conditions. The monthly measured field data showed a nitrogen limitation for epiphytes and eelgrass in summer, which may explain the positive effect of nutrient enrichment on both primary producers. Generally, the field data suggested the possibility of seasonally varying importance of bottom-up and top-down control on primary producers in this eelgrass system. [source] | |||||||||||||