The role of the family in delinquency causation: an interactional view

American society traditionally has held the family responsible for the socialization and social control of children, and when youngsters get into trouble the causal finger of blame is pointed at the family. No wonder then that a recurrent issue within the study of delinquent behavior has been the precise etiological role of the family. This thesis begins with an historical examination of the different approaches taken in the sociological study of delinquency and the family. This research investigated whether interactive effects are important in conceptualizing and understanding the family\u27s etiological role. The concept of interaction is based upon the assumption that variables may not have causal efficacy within themselves, entirely independent of other variables. Variable interaction occurs when the effect of an independent variable varies depending on the value of another independent variable. This study utilized questionnaire data gathered as a part of the Richmond Youth Study by the Survey Research Center (University of California, Berkeley) in 1965. The original stratified random sample consisted of 5,545 junior and senior high school students. While this sample included both male and female, black and nonblack adolescents, the present analysis focused on the 1,588 nonblack subsample. Survey data was available on a wide variety of youth-related issues, including self-reported delinquent activity and family conditions. This study analyzed the interactive effects of five family dimensions in relation to four other causal variables commonly associated with delinquency involvement: community social disorganization delinquent friends, attachment to peers, and delinquent definitions. Analysis of variance, a multivariate statistical model, was used to distinguish significant independent and interactive effects. Identified interactive effects were then examined through tabular analysis in order to provide a more precise understanding of how these variables interact in affecting delinquency involvement. Finally, the general notions of variable interaction which are implied by existing theories were assessed. The data analysis revealed that family factors influenced delinquency in different ways. The level of an adolescent\u27s attachment to father was found to be independently related to delinquent activity after controlling for all other effects (independent and interactive). Paternal discipline had an interactive effect on delinquency such that the type of paternal discipline influenced the effect that community social disorganization and number of delinquent friends had on delinquency; in turn, paternal discipline was significantly related to delinquency involvement under certain conditions of these same variables. The other three family factors, however, did not have a significant independent or interactive effect on delinquency involvement. These findings suggest that causal explanation and research dealing solely with direct, independent effects may minimize and oversimplify the causal role of certain family factors. At least a small portion of the family\u27s influence on delinquency involvement is through interactive effects with non-familial variables. Existing theories have failed to actively consider such interactive effects. Furthermore, the general notions of variable interaction which are implied by current theories failed to find support in the data of the present study. Thus, future theory and research would likely benefit from consideration of interactive effects

The effects of light and nutrients on Caulerpa taxifolia and growth

Caulerpa taxifolia, an invasive species elsewhere in the world, is native to Moreton Bay where its distribution has been increasing in recent years. In Australia, dense beds of C. taxifolia are predominantly found in areas of low light and high nutrients (low water quality). Monitoring data from Moreton Bay suggests that native C. taxifolia is not directly replacing seagrass, but that there is a successional trend of seagrass loss and subsequent C. taxifolia colonization. The current study examined responses of C. taxifolia in relation to changes in environmental conditions using ambient water quality and a light/nutrient manipulative experiment. In the ambient water quality experiment we found that C. taxifolia grew significantly faster in areas with higher light (lower turbidity). The manipulative experiment demonstrated that nutrients stimulate C. taxifolia growth, however, light availability and seasonality appear to influence the response of C. taxifolia growth to nutrients in Moreton Bay. These findings suggest that C. taxifolia is unlikely to colonize seagrass beds in areas with high light and low nutrients; however, in areas with moderate light and moderate to high nutrients C. taxifolia and seagrass are likely to coexist

Performance of non-native species within marine reserves

Conservation of biodiversity is a major aim of marine reserves; however the effects of reserves on non-native species, a major threat to biodiversity globally, is not widely known. Marine reserves could resist non-native species due to enhanced native diversity and biomass that heightens biotic resistance. Or non-native species could be enhanced by reserves by at least three mechanisms, including protection from harvesting, increased fishing pressure outside reserves facilitating invasions at a regional scale and increasing the exposure of reserves to more potential invaders, and increased propagule pressure from human visitation. We exhaustively searched the literature and found 13 cases that contained quantitative data on non-native species inside and outside marine reserves. In no cases did reserves resist non-native species. Of the seven cases where reserves were established prior to the arrival of the non-native species, five had no effect on the non-native species and two enhanced non-native species. Of the six cases where reserves were established in areas that had pre-existing non-native species, two had no effect on the non-native species and four enhanced the non-native species. These results suggest that while non-native species do equally well or better within marine reserves, too few data are currently available to draw broad, general conclusions regarding the effects of marine reserves on non-native species. Management plans for marine reserves rarely include guidelines for preventing or managing non-native species. If the trends we have detected here are supported by future studies, non-native species should be a priority for management of marine reserves

Water temperature and benthic light levels drive horizontal expansion of Caulerpa taxifolia in native and invasive locations

Caulerpa taxifolia is a marine alga native to tropical and subtropical regions, and invasive in temperate regions worldwide. The aim of this study was to quantify the impacts of water temperature, benthic light and nutrient enrichment on horizontal expansion of C. taxifolia, in the absence of competition from other benthic flora. Field experiments were undertaken in 1 native C. taxifolia population (Moreton Bay, Australia) and 2 invasive C. taxifolia populations (Pittwater and Port River Estuary, Australia). Manipulative experiments were conducted across a range of seasons and different shading and nutrient treatments to determine the effects of water temperature, benthic light dose and nutrient enrichment on horizontal expansion (stolon extension rate). Nitrogen and phosphorus enrichment had negligible effects on stolon extension rate at all locations, suggesting that nutrient conditions at the study sites were saturating for C. taxifolia. Shading significantly reduced stolon extension in Pittwater, and season/water temperature significantly affected stolon extension in Port River Estuary; only in Moreton Bay were both shading and season/water temperature significant. When all data were pooled in a general linear model, water temperature and average daily benthic light dose (log-transformed) significantly affected stolon extension, but nutrient enrichment did not. Site, season and the interaction between water temperature and benthic light dose also improved model performance, indicating that site-specific factors which varied between seasons also affected the measured stolon extension. Overall, our results indicate that C. taxifolia growth increased with light disproportionately at higher temperatures

The seagrasses of Moreton Bay Quandamooka: Diversity, ecology and resilience

Seagrasses are a dominant feature in the seascape of Moreton Bay. They host numerous animals and provide the region with a wide range of ecosystem services that we are only beginning to better understand. In the past 20 years, the focus of seagrass research in Moreton Bay has shifted towards predictive modelling based on comprehensive ecological understanding. There are seven species of seagrasses in Moreton Bay that persist across a wide range of environmental conditions from muddy sediments in the western Bay to the cleaner, sandier waters of the eastern Bay adjacent to Moreton (Moorgumpin) and Stradbroke (Minjerribah) Islands. There has been an encouraging recovery of meadows in some of the more degraded parts parts of the Bay, yet with an ever-increasing human population in South East Queensland, the threats to seagrasses still require continued research effort and careful management. This paper reviews the current understanding of Moreton Bay’s seagrass meadows and provides recommendations for future research

Seagrasses of Moreton Bay Quandamooka: Diversity, ecology and resilience

Seagrasses are a dominant feature in the seascape of Moreton Bay. They host numerous animals and provide the region with a wide range of ecosystem services that we are only beginning to better understand. In the past 20 years, the focus of seagrass research in Moreton Bay has shifted towards predictive modelling based on comprehensive ecological understanding. There are seven species of seagrasses in Moreton Bay that persist across a wide range of environmental conditions from muddy sediments in the western Bay to the cleaner, sandier waters of the eastern Bay adjacent to Moreton (Moorgumpin) and Stradbroke (Minjerribah) Islands. There has been an encouraging recovery of meadows in some of the more degraded parts parts of the Bay, yet with an ever-increasing human population in South East Queensland, the threats to seagrasses still require continued research effort and careful management. This paper reviews the current understanding of Moreton Bay’s seagrass meadows and provides recommendations for future research