Suspended sediments in fluvial systems originate from a myriad of diffuse and point sources, with the relative contribution from each source varying over time and space. The process of sediment fingerprinting focuses on developing methods that enable discrete sediment sources to be identified from a composite sample of suspended material. This review identifies existing methodological steps for sediment fingerprinting including fluvial and source sampling, and critically compares biogeochemical and physical tracers used in fingerprinting studies. Implications of applying different mixing models to the same source data are explored using data from 41 catchments across Europe, Africa, Australia, Asia, and North and South America. The application of seven commonly used mixing models to two case studies from the US (North Fork Broad River watershed) and France (Bléone watershed) with local and global (genetic algorithm) optimization methods identified all outputs remained in the acceptable range of error defined by the original authors. We propose future sediment fingerprinting studies use models that combine the best explanatory parameters provided by the modified Collins (using correction factors) and Hughes (relying on iterations involving all data, and not only their mean values) models with optimization using genetic algorithms to best predict the relative contribution of sediment sources to fluvial systems.
Of all ecosystems, freshwaters support the most dynamic and highly concentrated biodiversity on Earth. These attributes of freshwater biodiversity along with increasing demand for water mean that these systems serve as significant models to understand drivers of global biodiversity change. Freshwater biodiversity changes are often attributed to hydrological alteration by water-resource development and climate change owing to the role of the hydrological regime of rivers, wetlands and floodplains affecting patterns of biodiversity. However, a major gap remains in conceptualising how the hydrological regime determines patterns in biodiversity's multiple spatial components and facets (taxonomic, functional and phylogenetic). We synthesised primary evidence of freshwater biodiversity responses to natural hydrological regimes to determine how distinct ecohydrological mechanisms affect freshwater biodiversity at local, landscape and regional spatial scales. Hydrological connectivity influences local and landscape biodiversity, yet responses vary depending on spatial scale. Biodiversity at local scales is generally positively associated with increasing connectivity whereas landscape-scale biodiversity is greater with increasing fragmentation among locations. The effects of hydrological disturbance on freshwater biodiversity are variable at separate spatial scales and depend on disturbance frequency and history and organism characteristics. The role of hydrology in determining habitat for freshwater biodiversity also depends on spatial scaling. At local scales, persistence, stability and size of habitat each contribute to patterns of freshwater biodiversity yet the responses are variable across the organism groups that constitute overall freshwater biodiversity. We present a conceptual model to unite the effects of different ecohydrological mechanisms on freshwater biodiversity across spatial scales, and develop four principles for applying a multi-scaled understanding of freshwater biodiversity responses to hydrological regimes. The protection and restoration of freshwater biodiversity is both a fundamental justification and a central goal of environmental water allocation worldwide. Clearer integration of concepts of spatial scaling in the context of understanding impacts of hydrological regimes on biodiversity will increase uptake of evidence into environmental flow implementation, identify suitable biodiversity targets responsive to hydrological change or restoration, and identify and manage risks of environmental flows contributing to biodiversity decline.
Summary Biological indicators have been widely used in Australian riverine systems to assess the effectiveness of past and current management. The short generation time, sessile nature, responsiveness to environmental conditions and the availability of sound, quantitative methodologies make biofilms suitable as a monitoring tool in these systems. This paper describes biofilm structure, function and development through the processes of succession and disturbance. Biofilms are assemblages of algae, fungi and microorganisms which cover rocks, wood and sediments in aquatic systems. A review of biofilm collection and processing techniques using relevant Australian and international studies reveals a large literature on many structural and functional biofilm attributes. Studies using structural attributes such as biomass and diversity to examine water quality impacts and invertebrate grazers dominate the Australian literature. More recently, studies have used functional biofilm attributes such as metabolism and foodweb interactions. Monitoring programs that combine structural and functional biofilm attributes will allow the best assessment of impacts in riverine systems. Biofilm functional parameters provide an integrated, long‐term measure of ecosystem function, with structural attributes such as biomass and diversity allowing historical comparisons with previously recorded datasets. Monitoring programs such as these with a well‐founded scientific base and defined management outcomes will expand our knowledge of river function and contribute to the restoration of Australian river systems.
BackgroundDams are important to ensure food security and promote economic development in sub-Saharan Africa. However, a poor understanding of the negative public health consequences from issues such as malaria could affect their intended advantages. This study aims to compare the malaria situation across elevation and proximity to dams. Such information may contribute to better understand how dams affect malaria in different eco-epidemiological settings.MethodsLarval and adult mosquitoes were collected from dam and non-dam villages around the Kesem (lowland), Koka (midland), and Koga (highland) dams in Ethiopia between October 2013 and July 2014. Determination of blood meal sources and detection of Plasmodium falciparum sporozoites was done using enzyme-linked immunosorbent assay (ELISA). Five years of monthly malaria case data (2010–2014) were also collected from health centers in the study villages.ResultsMean monthly malaria incidence was two- and ten-fold higher in the lowland dam village than in midland and highland dam villages, respectively. The total surface area of anopheline breeding habitats and the mean larval density was significantly higher in the lowland dam village compared with the midland and highland dam villages. Similarly, the mean monthly malaria incidence and anopheline larval density was generally higher in the dam villages than in the non-dam villages in all the three dam settings. Anopheles arabiensis, Anopheles pharoensis, and Anopheles funestus s.l. were the most common species, largely collected from lowland and midland dam villages. Larvae of these species were mainly found in reservoir shoreline puddles and irrigation canals. The mean adult anopheline density was significantly higher in the lowland dam village than in the midland and highland dam villages. The annual entomological inoculation rate (EIR) of An. arabiensis, An. funestus s.l., and An. pharoensis in the lowland dam village was 129.8, 47.8, and 33.3 infective bites per person per annum, respectively. The annual EIR of An. arabiensis and An. pharoensis was 6.3 and 3.2 times higher in the lowland dam village than in the midland dam village.ConclusionsThis study found that the presence of dams intensifies malaria transmission in lowland and midland ecological settings. Dam and irrigation management practices that could reduce vector abundance and malaria transmission need to be developed for these regions.
Integrative research has been the dominant theme in this Special Issue, demonstrated by contemporary examples of effective collaborations and solutions for the successful engagement of scientists in the policy and management arena. Evident in these papers is the increasing use of the term ‘best available science’ (BAS) as a basis for well-informed resource management decisions. The term is used to engender credibility and trust among stakeholders and promotes greater awareness, communication, involvement, transparency and understanding among research, policy and management communities. However, there remains no clear statement of the properties of BAS or guidance on its practical application in the decision-making process. We define the attributes that underpin BAS and examine the issues of uncertainty, risk and communication as key challenges to successful integrative management. We advocate an interdisciplinary process that facilitates understanding of discipline-based knowledge structures, articulates uncertainty and risk about the scientific information, and promotes engagement and trust among the generators and users of information. Ultimately, successful management of aquatic ecosystems will rely on scientists, managers and decision makers who have the skills and courage to apply the best science available and not wait for the best science possible.
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