Effects of a predatory fish on a tropical detritus-based food web

In contrast to that for grazing systems, relatively little information exists for trophic cascades in detritus-based stream food webs, which are predominant in forested headwater streams. Predator–prey interactions are thought to be weak in these systems, but studies are very scarce, their results are equivocal, and they do not separate the effect of direct consumption from a behavioural response of shredders. We examined the effect of predatory fish on leaf litter breakdown in headwater tropical Australian streams at three levels: (1) the behavioural response of shredder species to predator presence as indicated by chemical cues; (2) the rates of leaf breakdown resulting from shredder activity; and (3) the relationship between shredder species richness and leaf breakdown rates. Our results suggest that predatory fish can have a trait-mediated effect on detritus-based food webs in streams, by reducing consumer activity. We identified reductions in short-term overall activity in response to the presence of predatory fish cues, comparable to those found for grazers. We also observed a visible, albeit statistically non-significant, reduction in consumption rates. Shredder species richness did not affect leaf breakdown rates, and fish presence did not modify this relationship or the differences in breakdown rates among species, suggesting that the overall reduction in leaf breakdown caused by fish presence is due to a reduction in activity in every species. Thus, our laboratory studies have shown that there can be a behavioural basis for trait-mediated trophic cascades linked to fish presence in detrital food webs in streams. However, the strength of fish effects depends on environmental circumstances, and field studies of litter breakdown in streams with and without predatory fish are required if we are to elucidate the ecological significance of our observations

Factor Analysis of the Italian Version of the Alabama Parenting Questionnaire in a Community Sample

Despite difficulties measuring parenting styles, many studies have demonstrated a significant relationship between disruptive children and certain parenting practices. One of the most frequently used scales to measure parenting styles is the Alabama Parenting Questionnaire (APQ). This scale was originally defined based on theoretical dimensions and using samples from the USA. Therefore, both factor analysis studies and its adaptation to other countries have been proposed to improve and widen its use. The aim of this study was to adapt the APQ to the Italian population. A community sample of 258 mothers and children (94 %) and 192 fathers (70 %) from 274 families with children from 10- to 14-years-old who agreed to participate and met the inclusion criteria completed the APQ. Principal components and exploratory factor analyses resulted in a unique 19-item version of the APQ for mothers, fathers, and children. This unified version has resulted in two factor categories: positive (12 items) and negative parenting (7 items). The internal consistency and goodness of fit of the model were satisfactory. Moderate and significant convergent validity were found for mothers and fathers but not for children. In fact, we found differences in validity rates among the participants. Children perceived less positive and more negative parenting than did fathers and mothers, and mothers believed that they provided more positive parenting than did other parents. In conclusion, the APQ Italian version of the parents and children global report forms are considered a suitable measure for positive and negative parenting styles with acceptable validity and reliability indice

Nutrient Dynamics in Wetlands of the Middle Paraná River Subjected to Rotational Cattle Management

The progressive degradation of wetlands has stressed the need of developing sustainable management strategies for maintaining their ecological character within the context of sustainable development. Rotational cattle grazing is a common grazing strategy in aquatic systems but its effect on nutrient dynamics in lakes is scarcely known. The objectives of this study were to evaluate if cattle produces a significant increase of TN and TP in wetlands, and if the value of these nutrients decrease after cattle are removed. Samples of water, sediment and macrophytes were collected for nutrient, organic matter and other chemical analyses. Results showed a significant increase in water nutrients during the presence of cattle, decreasing during their absence. These changes occurred surprisingly rapid, suggesting a high resilience of these systems to this impact. The presence of submerged vegetation in lakes ameliorated the effect of cattle on water nutrients, suggesting an important role of these plants in ecosystem management. Rotational management would minimize the increase of nutrients in water, maintaining the ecological integrity of wetlands.Fil: Mesa, Leticia Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Mayora, Gisela Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Saigo, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Giri, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias; Argentin

Changes in sub-fossil chironomid assemblages in two Northern Patagonian lake systems associated with the occurrence of historical fires

Patagonia is commonly seen as an exceptionally pristine area because of its wildlife and practically unpolluted waters. However, during the twentieth century the burning of natural forests was one of the most important human activities in Northern Chilean Patagonia. Some estimations indicate that three million hectares were burned during the first three decades of the century. Hence the objective of this study was to evaluate the impacts of the historical fires in Lake Burgos (458420S) and Lake Thompson (458380S) in Chilean Patagonia. The impact was measured by evaluating chironomid assemblage since they are sensitive enough to be used as an indicator of aquatic ecosystem health. Fires have a direct and drastic effect on a lake watershed but also indirectly affect a lake ecosystem, changing sedimentation patterns or increasing nutrient inputs. In the studied lakes the periods with higher prevalence of fires were identified by charcoal analysis, while organic matter and magnetic susceptibility allowed the confirmation of pre-fire and post-fire periods. The chironomid composition was evaluated through a PCA and an analysis of similarity (ANOSIM) to test the significance among periods while a Detrended Correspondence Analysis was applied to the chironomid assemblage downcore to assess compositional structure and taxa turnover. In Lake Burgos the ANOSIM test indicated significant differences between the pre-fire and fire periods (p\0.05), while in Lake Thompson differences were not significant. However, in Lake Thompson the PCA clearly separated the pre-fire from the fire period but not the fire from the post-fire periods. In both lakes chironomid composition changed in relation to the period of higher prevalence of fires, which in turn implies catchment changes, pollution, and other anthropogenic impacts. Particularly a marked change in mesotrophic/eutrophic taxa was detected, reflecting an increase in nutrient input due to deforestation. Our findings point out that the lacustrine ecosystems are still affected by the impact of fires and the subsequent increase in nutrient supply that occurred almost 50 years ago. No sign of reverting to pre-disturbance conditions was observed, which makes these lakes highly sensitive to current human-induced impacts