Fuel from within: Can resuspended organic Phosphorus stimulate harmful Cyanobacteria Blooms in Western Lake Erie?

Lake Erie, the shallowest of the Laurentian Great Lakes, has been historically plagued with summertime blooms of potentially toxic cyanobacteria (Microcystis spp.) that originate in the shallow western part of the lake (average depth 10 m). The onset of Microcystis blooms often follow wind-driven resuspension events, indicating that internal loading of growth limiting nutrients (mainly phosphorus, P) may stimulate cyanobacterial growth. We hypothesize that wind-driven sediment resuspension releases particulate P (PP) in the form of organic (POP) or inorganic phosphorus (PIP), fueling cyanobacterial growth in the water. To test this hypothesis, we exposed replicate sediment cores from two sites in the western basin of Lake Erie (WE04, WE08) to increasing shear stress using an erosion chamber. Our results indicate site-specific differences in the release of PP from experimentally resuspended sediments. Sediment from the deeper site (WE4; high sand content) released lower levels of PP compared with the shallower site (WE8; high silt content). Laboratory culture experiments determined Microcystis can effectively access sediment bound organic P as a growth source. Growth rates were determined with Microcystis cultures amended with POP and PIP as well as dissolved inorganic P (DIP) and dissolved organic P (DOP). DIP growth rates were highest followed by DOP, POP, and PIP respectively. Potential activities of alkaline phosphatase enzymes that are used by cyanobacteria to remineralize inorganic P from organic P complexes, also increased during the erosion experiments and in the POP cultures. Our results indicate the potential for internal loading of PP following wind-driven resuspension event to promote blooms of Microcystis in the western basin of Lake Erie

The Indigenous population of Cape York Peninsula, 2001-2016

Recent projections made by the Australian Bureau Statistics (ABS) of Indigenous populations resident in various regions of north Australia included a set of estimates for Cape York Peninsula. These were found to be substantially at odds with the results for adjacent regions such as the West Arnhem and Gulf regions of the Northern Territory. The Cape York projections produced population growth rates that were substantially lower than those recorded for other regions, with projected numbers in certain age groups actually declining over the forecast period to 2016. Two factors were regarded as responsible for this outcome: · a deficient 1996 estimated resident population (ERP), and · a lack of regionally-derived age-specific fertility rates (ASFRs). This paper seeks to redress these shortcomings by presenting an alternative and improved set of 1996 population estimates, and by applying regionally-derived ASFRs to projections from this base year. The basic strategy employed in constructing alternative population estimates was to identify other regional population counts that had some claim to credibility in terms of their coverage of the Indigenous population within the region at specified points in time. A number of such sources were identified, and each was assessed for suitability as an element in a proxy count

Benchmarking ABS Population Estimates for Queensland Aboriginal and Torres Strait Islander Communities

Concerns have been expressed for some time by Indigenous community leaders, government agencies, and local service providers about the accuracy of demographic data for those Aboriginal and Torres Strait Islander communities in Queensland depicted in Figure 1. The main issue has been a claim of undercounting by the five-yearly census. Surprisingly, only one study exists (Martin and Taylor 1996) which can claim to directly test the validity of a census count for a remote Indigenous community. One conclusion of this study was that the enumeration strategy adopted by the ABS for use in remote Indigenous communities was structured in such a way as to increase the likelihood of omitting young people, the more mobile and more socially marginal. This was considered to be a by-product of the attempt to assign individuals to households as mainstream constructs in situations where inter-household and inter-community mobility is the norm (Martin and Taylor 1996). At the same time, it should be noted that independent observation of the 2001 enumeration in Aurukun revealed that when sufficient and appropriate personnel are in place, and where a team commitment to counting all individuals is sustained, a satisfactory population count can be achieved (Martin 2002). The difficulty, it seems, is in ensuring that these pre-conditions are achieved at all places, and at each census (Martin et al 2002)

'Changing places: Indigenous population movement in the 1990s'

This paper presents selected measures of Indigenous population mobility using 1996 Census data and compares these with equivalent measures for the non-Indigenous population. There are two parts to the exercise. The first comprises an examination of relative propensities to move according to the age and sex distribution of movers, their labour force status and income distribution. The second is an analysis of the contribution of mobility to spatial redistribution of the Indigenous population

The mobility status of Indigenous Australians

This paper provides, for the first time, comparative national parameters of Indigenous population mobility. Using a customised 54 region internal migration matrix from the 1991 Census, preliminary findings are presented in regard to three broad perspectives on mobility. First, an analysis is provided of the relative propensity for Indigenous people to migrate. Secondly, the effects of migration on spatial redistribution are examined, particularly in regard to regional patterns of net migration gain and loss and the relative balance of population flows between metropolitan and non-metropolitan areas. Finally, the pattern of inter-regional migration flows is explored with a view to defining spatial networks of movement. Although Indigenous people are found to migrate at the same rate as the rest of the population, it is clear that their mobility behaviour is quite different from that of the general population. In particular, the pattern of Indigenous spatial interaction is found to be a far more localised phenomenon. A number of policy implications are identified in relation to the limitations of census data for migration analysis in remote areas, the variable effect of mobility on regional population change, and the estimation of client populations for the Aboriginal and Torres Strait Islander Commission (ATSIC) regional councils in the face of widespread mobility

Estimating intercensal Indigenous employment change, 1991-96

The 1996 Census count of Indigenous Australians included a substantial number of individuals who were not recorded as Indigenous by the previous census. This paper considers the implications of this for interpreting change in employment numbers and provides a methodology for reconciling census data. This task is urgent because policy makers rely heavily on census data to measure outcomes and establish trends. At face value, results from the 1996 Census present a good news story - an increase of 25,000 people in work, representing a 44 per cent growth since 1991. Such growth is scarcely credible in the context of previously observed Indigenous employment trends as well as what is known about the performance of the labour market generally. How then is it to be interpreted

The relative mobility status of Indigenous Australians: Setting the research agenda

A project under way at the Centre for Aboriginal Economic Policy Research aims to establish, for the first time, comparative national parameters of Indigenous population mobility with particular reference to four distinct mobility perspectives, namely: the overall propensities to migrate, the net effect of migration on spatial redistribution, patterns of migration flow and resulting spatial networks, and the spatio-temporal sequence of individual movements over the life course. The first step in this process, presented here, involves a comprehensive review of the scope and content of existing research on Indigenous and non-Indigenous population mobility. This summary examination is necessary to identify gaps in understanding and thereby outline likely priorities for future research. The results show that quite different concerns and methodologies are evident in the literature on Indigenous population mobility compared with that pertaining to the movement of the Australian population generally. This, in part, reflects the often distinct cultural, demographic and economic contexts in which mobility occurs, but it is also indicative of a variable disciplinary bias in the analysis of migration. Major deficiencies are revealed in understanding some of the basic facets of Indigenous movement propensities and spatial redistribution relative to what is known for the rest of the population. As far as information regarding migration flows and the sequence of population movements is concerned, this deficit is commonly shared. In order to overcome these gaps in understanding standard techniques of migration analysis using census data are proposed. This paper considers the determinants of employment income for Indigenous Australians compared with non-Indigenous Australians. Ordinary Least Square (OLS) regression techniques are applied to 1991 Census data to consider the question: does the lower income of these Indigenous people reflect differences in their factor endowments (like education) rewarded in the labour market, or are they rewarded differently for the same set of endowments than are non-Indigenous Australians. The results show that the main source of lower incomes for Indigenous Australians was their smaller endowment of human capital characteristics. The paper concludes with a discussion of the policy implications of these results

Enumerating the Aboriginal population of remote Australia: Methodological and conceptual issues

Despite claims of underenumeration of Indigenous people, a basic problem in establishing the demography of remote Indigenous populations remains the lack of well documented and adequately controlled independent checks against census data. This paper attempts to provide such verification by comparing population counts and age distributions from the last two ABS enumerations of the Aboriginal population of Aurukun, Cape York Peninsula, with the results of detailed ethnographic surveys of the same population. Significant undercount of young adults and children is noted. Consideration of the ethnographic realities of remote Indigenous communities indicates methodological and conceptual deficiencies in the current ABS remote area enumeration strategy and a number of strategies for addressing these issues are proposed

Case study methodologies and a wider appreciation of development planning

This article describes a case study research and training method currently being developed by the authors with the support of OECD, UNESCO and the EEC. This method is intended for personnel actively involved in urban planning and development although the method may be adapted for use in a variety of planning and management contexts. In short. the central concern is with the provision of learning systems for helping planners and those in cognate disciplines achieve a deeper understanding and thereby contribute to an improve­ment in their urban management ability. This may be particularly appropriate in countries concerned with "public accountability," and "public Involvement" in the planning and development processes