RESUMO
Riverine floodplains are highly productive habitats that often act as nurseries for fish but are threatened by flow regulation. The Fitzroy River in northern Australia is facing development, but uncertainty exists regarding the extent to which floodplain habitats deliver benefits to fish, particularly given the brevity of seasonal floodplain inundation. We investigated the growth rate of young-of-year bony bream (Nematalosa erebi) in main channel and ephemeral floodplain habitats using age derived from otolith daily increments. We also investigated potential mechanisms influencing growth and modelled the consequences of differential growth rate on survival. Our results revealed higher growth occurred exclusively on the floodplain and that zooplankton biomass was the best predictor of growth rate. Modelling indicated that elevated growth rate in high-growth floodplain pools (top 25th percentile) could translate into substantial increases in survivorship. The positive effect of zooplankton biomass on growth was moderated under highly turbid conditions. Temperature had a minor influence on growth, and only in floodplain habitats. Our results indicate ephemeral floodplain habitats can deliver substantial growth and survival benefits to young-of-year fish even when floodplain inundation is brief. This study highlights the need to ensure that water policy safeguards floodplain habitats due to their important ecological role.
Assuntos
Ecossistema , Rios , Animais , Peixes/fisiologia , Austrália , Biomassa , ZooplânctonRESUMO
Fisheries and natural water resources across the world are under increasing pressure from human activity, including fishing and irrigated agriculture. There is an urgent need for information on the climatic/hydrologic drivers of fishery productivity that can be readily applied to management. We use a generalized linear mixed model framework of catch curve regression to resolve the key climatic/hydrological drivers of recruitment in Barramundi Lates calcarifer using biochronological (otolith aging) data collected from four river-estuary systems in the Northern Territory, Australia. These models were then used to generate estimates of the year class strength (YCS) outcomes of different water abstraction scenarios (ranging from 10% to 40% abstraction per season/annum) for two of the rivers in low, moderate, and high discharge years. Barramundi YCS displayed strong interannual variation and was positively correlated with regional monsoon activity in all four rivers. River-specific analyses identified strong relationships between YCS and several river-specific hydrology variables, including wet and dry season discharge and flow duration. Water abstraction scenario models based on YCS-hydrology relationships predicted reductions of >30% in YCS in several cases, suggesting that increased water resource development in the future may pose risks for Barramundi recruitment and fishery productivity. Our study demonstrates the importance of the tropical monsoon as a driver of Barramundi recruitment and the potential for detrimental impacts of increased water abstraction on fishery productivity. The biochronological and statistical approaches we used have the potential to be broadly applied to inform policy and management of water resource and fisheries.
Assuntos
Pesqueiros , Perciformes , Animais , Humanos , Hidrologia , Northern Territory , Rios , ÁguaRESUMO
The relationship between detritivore diversity and decomposition can provide information on how biogeochemical cycles are affected by ongoing rates of extinction, but such evidence has come mostly from local studies and microcosm experiments. We conducted a globally distributed experiment (38 streams across 23 countries in 6 continents) using standardised methods to test the hypothesis that detritivore diversity enhances litter decomposition in streams, to establish the role of other characteristics of detritivore assemblages (abundance, biomass and body size), and to determine how patterns vary across realms, biomes and climates. We observed a positive relationship between diversity and decomposition, strongest in tropical areas, and a key role of abundance and biomass at higher latitudes. Our results suggest that litter decomposition might be altered by detritivore extinctions, particularly in tropical areas, where detritivore diversity is already relatively low and some environmental stressors particularly prevalent.
Assuntos
Biota , Ecossistema , Rios , Animais , Biodiversidade , Biomassa , Tamanho Corporal , Chironomidae/fisiologia , Clima , Ephemeroptera/fisiologia , Insetos/fisiologia , Folhas de Planta/química , Floresta Úmida , Rios/química , Rios/microbiologia , Rios/parasitologia , Rios/virologia , Clima Tropical , TundraRESUMO
Running waters contribute substantially to global carbon fluxes through decomposition of terrestrial plant litter by aquatic microorganisms and detritivores. Diversity of this litter may influence instream decomposition globally in ways that are not yet understood. We investigated latitudinal differences in decomposition of litter mixtures of low and high functional diversity in 40 streams on 6 continents and spanning 113° of latitude. Despite important variability in our dataset, we found latitudinal differences in the effect of litter functional diversity on decomposition, which we explained as evolutionary adaptations of litter-consuming detritivores to resource availability. Specifically, a balanced diet effect appears to operate at lower latitudes versus a resource concentration effect at higher latitudes. The latitudinal pattern indicates that loss of plant functional diversity will have different consequences on carbon fluxes across the globe, with greater repercussions likely at low latitudes.
RESUMO
Rivers around the world are threatened by altered flow due to water resource development. Altered flow can change food webs and impact riverine energetics. The Fitzroy River, in northern Australia, is targeted for development but uncertainty remains about the sources of carbon supporting the food web, particularly in the lowlands-the region most likely to be impacted by water extraction. This study used stable isotopes to investigate if algal biofilm is the main carbon source sustaining fish in lowland habitats. We also sought evidence that large-bodied migratory fish were transporting remote carbon around the system. Our results revealed that local algal biofilm carbon was the dominant source of energy sustaining fish in wet season floodplain habitats, but that fish in main-channel pools during the dry season were increasingly dependent on other carbon sources, such as leaf litter or phytoplankton. We found no evidence that large-bodied fish were transporting remote carbon from the floodplain or estuary into the lower main-channel of the river. We recommend that water planners take a precautionary approach to policy until sufficient food web evidence is amassed.
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Natural river floodplains are among the Earth's most biologically diverse and productive ecosystems but face a range of critical threats due to human disturbance. Understanding the ecological processes that support biodiversity and productivity in floodplain rivers is essential for their future protection and rehabilitation. Fish assemblage structure on tropical river floodplains is widely considered to be driven by dispersal limitation during the wet season and by environmental filtering and interspecific interactions during the dry season. However, the individual-level movement behaviours (e.g. site attachment, nomadism, homing) that regulate dispersal of fish on floodplains are poorly understood. We combined radiotelemetry and remote sensing to examine the movement behaviour of two large-bodied fishes (barramundi Lates calcarifer, forktail catfish Neoarius leptaspis) over the flood cycle in a tropical river-floodplain system in northern Australia to: (a) quantify movement responses in relation to dynamic habitat resources at a landscape scale; and (b) determine the extent of spatial 'reshuffling' of individual fish following the wet season. Both species altered their behaviour rapidly in response to changes in the availability and distribution of aquatic habitat, with most individuals undertaking extensive movements (up to ~27 km from the tagging location) on the inundated floodplain during the wet season. Although there was considerable individual variation in movement patterns, overall barramundi distributions closely tracked the extent of floodplain primary productivity, whereas catfish distributions were most closely associated with the extent of flooded area. Most individuals of both species exhibited homing back to previously occupied dry season refugia during the wet-to-dry transition, even though other potential refugia were available in closer proximity to wet season activity areas. We postulate that homing behaviour modulates temporal variation in fish assemblage composition and abundance and limits the transfer of aquatic-derived energy and nutrients into terrestrial food webs by reducing fish mortality on drying floodplains. Our study demonstrates the importance of quantifying individual-level behaviour across the three stages of dispersal (emigration, inter-patch movement, immigration) for our understanding of how animal movement influences energetic subsidies and other large-scale ecosystem processes.
Assuntos
Ecossistema , Rios , Animais , Austrália , Peixes , Cadeia Alimentar , HumanosRESUMO
In gape-limited predators, gape size restricts the maximum prey size a predator is capable to ingest. However, studies investigating the energetic consequences of this relationship remain scarce. In this study, we tested the hypothesis that gape-size variability influences individual body condition (a common proxy for fitness) in one of the largest freshwater teleost predators, the barramundi. We found that individual barramundi with larger gapes relative to body size had higher body condition values compared to conspecifics with smaller gapes. Body condition was highest soon after the wet season, a period of high feeding activity on productive inundated floodplains, and body condition decreased as the dry season progressed when fish were restricted to dry season remnant habitats. The increased condition obtained during the wet season apparently offsets weight loss through the dry season, as individuals with large gapes were still in better condition than fish with small gapes in the late-dry season. Elucidation of the links between intraspecific variability in traits and performance is a critical challenge in functional ecology. This study emphasizes that even small intraspecific variability in morphological trait values can potentially affect individual fitness within a species' distribution.
Assuntos
Perciformes , Comportamento Predatório , Animais , Tamanho Corporal , Peixes , BocaRESUMO
Global patterns of biodiversity have emerged for soil microorganisms, plants and animals, and the extraordinary significance of microbial functions in ecosystems is also well established. Virtually unknown, however, are large-scale patterns of microbial diversity in freshwaters, although these aquatic ecosystems are hotspots of biodiversity and biogeochemical processes. Here we report on the first large-scale study of biodiversity of leaf-litter fungi in streams along a latitudinal gradient unravelled by Illumina sequencing. The study is based on fungal communities colonizing standardized plant litter in 19 globally distributed stream locations between 69°N and 44°S. Fungal richness suggests a hump-shaped distribution along the latitudinal gradient. Strikingly, community composition of fungi was more clearly related to thermal preferences than to biogeography. Our results suggest that identifying differences in key environmental drivers, such as temperature, among taxa and ecosystem types is critical to unravel the global patterns of aquatic fungal diversity.
Assuntos
Fungos , Microbiota , Rios/microbiologia , Folhas de Planta/microbiologia , Análise EspacialRESUMO
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth's biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented "next-generation biomonitoring" by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.
Assuntos
Ciclo do Carbono/fisiologia , Ecossistema , Monitoramento Ambiental/métodos , Rios/microbiologia , Temperatura , Atividades Humanas , HumanosRESUMO
Andropogon gayanus Kunth. is a large African tussock grass invading Australia's tropical savannas. Invasion results in more intense fires which increases the mortality rate of adult woody plants. Invasion may also affect community structure by altering the recruitment potential of woody plants. We investigated the effects of A. gayanus invasion on ground-level microclimate, and the carbon assimilation potential and recruitment potential of two Eucalyptus species. We compared microclimatic variables from the early wet-season and into the mid-dry season to coincide with the period of growth of A. gayanus. We assessed Eucalyptus recruitment by monitoring seedling establishment, growth and survival of experimentally sown seed, and estimating seedling density resulting from natural recruitment. A. gayanus invasion was associated with increased grass canopy height, biomass and cover. Following invasion, the understorey microclimate had significantly reduced levels of photon flux density, increased air temperatures and vapour pressure deficit. The conditions were less favourable for woody seedling with aboveground biomass of seedlings reduced by 26% in invaded plots. We estimated that invasion reduced daily carbon assimilation of woody seedlings by ~30% and reduced survivorship of Eucalyptus seedlings. Therefore, A. gayanus invasion reduces recruitment potential, contributing to the transformation of savanna to a grassland ecosystem.
Assuntos
Ecossistema , Espécies Introduzidas , Poaceae , Árvores , Austrália , Biodiversidade , Biomassa , Estações do Ano , Plântula , Clima TropicalRESUMO
Food web subsidies from external sources ("allochthony") can support rich biological diversity and high secondary and tertiary production in aquatic systems, even those with low rates of primary production. However, animals vary in their degree of dependence on these subsidies. We examined dietary sources for aquatic animals restricted to refugial habitats (waterholes) during the dry season in Australia's wet-dry tropics, and show that allochthony is strongly size dependent. While small-bodied fishes and invertebrates derived a large proportion of their diet from autochthonous sources within the waterhole (phytoplankton, periphyton, or macrophytes), larger animals, including predatory fishes and crocodiles, demonstrated allochthony from seasonally inundated floodplains, coastal zones or the surrounding savanna. Autochthony declined roughly 10% for each order of magnitude increase in body size. The largest animals in the food web, estuarine crocodiles (Crocodylus porosus), derived ~80% of their diet from allochthonous sources. Allochthony enables crocodiles and large predatory fish to achieve high biomass, countering empirically derived expectations for negative density vs. body size relationships. These results highlight the strong degree of connectivity that exists between rivers and their floodplains in systems largely unaffected by river regulation or dams and levees, and how large iconic predators could be disproportionately affected by these human activities.
Assuntos
Cadeia Alimentar , Rios , Animais , Tamanho Corporal , Ecossistema , PeixesRESUMO
Protected areas remain a cornerstone for global conservation. However, their effectiveness at halting biodiversity decline is not fully understood. Studies of protected area benefits have largely focused on measuring their impact on halting deforestation and have neglected to measure the impacts of protected areas on other threats. Evaluations that measure the impact of protected area management require more complex evaluation designs and datasets. This is the case across realms (terrestrial, freshwater, marine), but measuring the impact of protected area management in freshwater systems may be even more difficult owing to the high level of connectivity and potential for threat propagation within systems (e.g. downstream flow of pollution). We review the potential barriers to conducting impact evaluation for protected area management in freshwater systems. We contrast the barriers identified for freshwater systems to terrestrial systems and discuss potential measurable outcomes and confounders associated with protected area management across the two realms. We identify key research gaps in conducting impact evaluation in freshwater systems that relate to three of their major characteristics: variability, connectivity and time lags in outcomes. Lastly, we use Kakadu National Park world heritage area, the largest national park in Australia, as a case study to illustrate the challenges of measuring impacts of protected area management programmes for environmental outcomes in freshwater systems.
Assuntos
Conservação dos Recursos Naturais/métodos , Água Doce , Animais , Biodiversidade , Conservação dos Recursos Naturais/tendências , Ecossistema , Poluição Ambiental/prevenção & controle , Espécies Introduzidas , Northern Territory , Parques Recreativos , PlantasRESUMO
Biotic communities are shaped by adaptations from generations of exposure to selective pressures by recurrent and often infrequent events. In large rivers, floods can act as significant agents of change, causing considerable physical and biotic disturbance while often enhancing productivity and diversity. We show that the relative balance between these seemingly divergent outcomes can be explained by the rhythmicity, or predictability of the timing and magnitude, of flood events. By analyzing biological data for large rivers that span a gradient of rhythmicity in the Neotropics and tropical Australia, we find that systems with rhythmic annual floods have higher-fish species richness, more stable avian populations, and elevated rates of riparian forest production compared with those with arrhythmic flood pulses. Intensification of the hydrological cycle driven by climate change, coupled with reductions in runoff due to water extractions for human use and altered discharge from impoundments, is expected to alter the hydrologic rhythmicity of floodplain rivers with significant consequences for both biodiversity and productivity.
Assuntos
Biodiversidade , Aves/fisiologia , Ecossistema , Peixes/fisiologia , Inundações , Florestas , Animais , Austrália , Mudança Climática , México , Rios , América do SulRESUMO
Comparative studies of plant resource use and ecophysiological traits of invasive and native resident plant species can elucidate mechanisms of invasion success and ecosystem impacts. In the seasonal tropics of north Australia, the alien C4 perennial grass Andropogon gayanus (gamba grass) has transformed diverse, mixed tree-grass savanna ecosystems into dense monocultures. To better understand the mechanisms of invasion, we compared resource acquisition and usage efficiency using leaf-scale ecophysiological and stand-scale growth traits of A. gayanus with a co-habiting native C4 perennial grass Alloteropsis semialata. Under wet season conditions, A. gayanus had higher rates of stomatal conductance, assimilation, and water use, plus a longer daily assimilation period than the native species A. semialata. Growing season length was also ~2 months longer for the invader. Wet season measures of leaf scale water use efficiency (WUE) and light use efficiency (LUE) did not differ between the two species, although photosynthetic nitrogen use efficiency (PNUE) was significantly higher in A. gayanus. By May (dry season) the drought avoiding native species A. semialata had senesced. In contrast, rates of A. gayanus gas exchange was maintained into the dry season, albeit at lower rates that the wet season, but at higher WUE and PNUE, evidence of significant physiological plasticity. High PNUE and leaf (15)N isotope values suggested that A. gayanus was also capable of preferential uptake of soil ammonium, with utilization occurring into the dry season. High PNUE and fire tolerance in an N-limited and highly flammable ecosystem confers a significant competitive advantage over native grass species and a broader niche width. As a result A. gayanus is rapidly spreading across north Australia with significant consequences for biodiversity and carbon and retention.
RESUMO
The food web is one of the oldest and most central organising concepts in ecology and for decades, food chain length has been hypothesised to be controlled by productivity, disturbance, and/or ecosystem size; each of which may be mediated by the functional trophic role of the top predator. We characterised aquatic food webs using carbon and nitrogen stable isotopes from 66 river and floodplain sites across the wet-dry tropics of northern Australia to determine the relative importance of productivity (indicated by nutrient concentrations), disturbance (indicated by hydrological isolation) and ecosystem size, and how they may be affected by food web architecture. We show that variation in food chain length was unrelated to these classic environmental determinants, and unrelated to the trophic role of the top predator. This finding is a striking exception to the literature and is the first published example of food chain length being unaffected by any of these determinants. We suggest the distinctive seasonal hydrology of northern Australia allows the movement of fish predators, linking isolated food webs and potentially creating a regional food web that overrides local effects of productivity, disturbance and ecosystem size. This finding supports ecological theory suggesting that mobile consumers promote more stable food webs. It also illustrates how food webs, and energy transfer, may function in the absence of the human modifications to landscape hydrological connectivity that are ubiquitous in more populated regions.
Assuntos
Ecossistema , Cadeia Alimentar , Rios , Estações do Ano , Distribuição Animal , Animais , Austrália , Isótopos de Carbono/análise , Geografia , Isótopos de Nitrogênio/análise , Análise de Regressão , Especificidade da EspécieRESUMO
BACKGROUND: Widespread invasion by non-native plants has resulted in substantial change in fire-fuel characteristics and fire-behaviour in many of the world's ecosystems, with a subsequent increase in the risk of fire damage to human life, property and the environment. Models used by fire management agencies to assess fire risk are dependent on accurate assessments of fuel characteristics but there is little evidence that they have been modified to reflect landscape-scale invasions. There is also a paucity of information documenting other changes in fire management activities that have occurred to mitigate changed fire regimes. This represents an important limitation in information for both fire and weed risk management. METHODOLOGY/PRINCIPAL FINDINGS: We undertook an aerial survey to estimate changes to landscape fuel loads in northern Australia resulting from invasion by Andropogon gayanus (gamba grass). Fuel load within the most densely invaded area had increased from 6 to 10 t ha(-1) in the past two decades. Assessment of the effect of calculating the Grassland Fire Danger Index (GFDI) for the 2008 and 2009 fire seasons demonstrated that an increase from 6 to 10 t ha(-1) resulted in an increase from five to 38 days with fire risk in the 'severe' category in 2008 and from 11 to 67 days in 2009. The season of severe fire weather increased by six weeks. Our assessment of the effect of increased fuel load on fire management practices showed that fire management costs in the region have increased markedly (â¼9 times) in the past decade due primarily to A. gayanus invasion. CONCLUSIONS/SIGNIFICANCE: This study demonstrated the high economic cost of mitigating fire impacts of an invasive grass. This study demonstrates the need to quantify direct and indirect invasion costs to assess the risk of further invasion and to appropriately fund fire and weed management strategies.
Assuntos
Andropogon/crescimento & desenvolvimento , Conservação dos Recursos Naturais/métodos , Incêndios/prevenção & controle , Espécies Introduzidas , Medição de RiscoRESUMO
High levels of hydrological connectivity during seasonal flooding provide significant opportunities for movements of fish between rivers and their floodplains, estuaries and the sea, possibly mediating food web subsidies among habitats. To determine the degree of utilisation of food sources from different habitats in a tropical river with a short floodplain inundation duration (~2 months), stable isotope ratios in fishes and their available food were measured from three habitats (inundated floodplain, dry season freshwater, coastal marine) in the lower reaches of the Mitchell River, Queensland (Australia). Floodplain food sources constituted the majority of the diet of large-bodied fishes (barramundi Lates calcarifer, catfish Neoarius graeffei) captured on the floodplain in the wet season and for gonadal tissues of a common herbivorous fish (gizzard shad Nematalosa come), the latter suggesting that critical reproductive phases are fuelled by floodplain production. Floodplain food sources also subsidised barramundi from the recreational fishery in adjacent coastal and estuarine areas, and the broader fish community from a freshwater lagoon. These findings highlight the importance of the floodplain in supporting the production of large fishes in spite of the episodic nature and relatively short duration of inundation compared to large river floodplains of humid tropical regions. They also illustrate the high degree of food web connectivity mediated by mobile fish in this system in the absence of human modification, and point to the potential consequences of water resource development that may reduce or eliminate hydrological connectivity between the river and its floodplain.
Assuntos
Peixes/fisiologia , Cadeia Alimentar , Rios , Animais , Inundações , Oceanos e Mares , Dinâmica Populacional , Queensland , Movimentos da ÁguaRESUMO
1. Despite implications for top-down and bottom-up control and the stability of food webs, understanding the links between consumers and their diets remains difficult, particularly in remote tropical locations where food resources are usually abundant and variable and seasonal hydrology produces alternating patterns of connectivity and isolation. 2. We used a large scale survey of freshwater biota from 67 sites in three catchments (Daly River, Northern Territory; Fitzroy River, Western Australia; and the Mitchell River, Queensland) in Australia's wet-dry tropics and analysed stable isotopes of carbon (δ(13) C) to search for broad patterns in resource use by consumers in conjunction with known and measured indices of connectivity, the duration of floodplain inundation, and dietary choices (i.e. stomach contents of fish). 3. Regression analysis of biofilm δ(13) C against consumer δ(13) C, as an indicator of reliance on local food sources (periphyton and detritus), varied depending on taxa and catchment. 4. The carbon isotope ratios of benthic invertebrates were tightly coupled to those of biofilm in all three catchments, suggesting assimilation of local resources by these largely nonmobile taxa. 5. Stable C isotope ratios of fish, however, were less well-linked to those of biofilm and varied by catchment according to hydrological connectivity; the perennially flowing Daly River with a long duration of floodplain inundation showed the least degree of coupling, the seasonally flowing Fitzroy River with an extremely short flood period showed the strongest coupling, and the Mitchell River was intermediate in connectivity, flood duration and consumer-resource coupling. 6. These findings highlight the high mobility of the fish community in these rivers, and how hydrological connectivity between habitats drives patterns of consumer-resource coupling.
Assuntos
Peixes , Cadeia Alimentar , Rios , Animais , Biofilmes , Carbono/química , Carbono/metabolismo , Isótopos de Carbono/análise , Dieta , Conteúdo Gastrointestinal/química , Invertebrados/química , Northern Territory , Queensland , Análise de Regressão , Estações do Ano , Especificidade da Espécie , Clima Tropical , Movimentos da Água , Austrália OcidentalRESUMO
A 24-yr-old woman was found dead in her home from apparent propofol "toxicity." Her blood level of propofol was 4.3 microg/mL. She had no history of drug abuse and no evidence of such behavior at autopsy. The medical examiner and police investigators felt that she died from probable homicide. Attention was focused on a male registered nurse acquaintance, who had acquired propofol and other drugs in the course of his regular duties in a surgical intensive care unit. This is the first reported case of murder with propofol.
Assuntos
Anestésicos Intravenosos/intoxicação , Homicídio , Propofol/intoxicação , Abuso de Substâncias por Via Intravenosa , Anestésicos Intravenosos/administração & dosagem , Anestésicos Intravenosos/sangue , Rotulagem de Medicamentos , Overdose de Drogas , Evolução Fatal , Feminino , Humanos , Injeções Intravenosas , Masculino , Propofol/administração & dosagem , Propofol/sangue , Suicídio , Adulto JovemRESUMO
The wet/dry tropics of the Australian savannas are particularly prone to fire due to the highly seasonal rainfall and accumulation of grassy fuels. The effect of an early dry season wildfire (May, 1998) on the water quality of a seasonally flowing stream (December-June) was examined for a lowland savanna forest in Kakadu National Park (northern Australia) which had remained unburnt for 10 years. The water quality variables assessed were: total and volatile suspended sediment, phosphorus, nitrogen, iron and manganese. Compared to three years of pre-fire water quality data and 5 years of stream flow data, there was no detectable impact of the wildfire on the volume of stream flow, mean concentrations and the total mass transported by the stream for each water quality variable, except possibly nitrogen. The limited effect on water quality is attributed primarily to the timing of the wildfire and the low intensity relative to fires later in the dry season (September). The retention of canopy cover and the accumulation of leaf litter following the wildfire, and the catchment's gently undulating terrain all contributed to the negligible impact on water quality. Early dry season fires appear to be a viable management option for reducing accumulated fuel loads and hence reducing the risk of destructive wildfires later in the dry season.