Despite advances in water resources management and planning, the São Francisco River Basin in Bra... more Despite advances in water resources management and planning, the São Francisco River Basin in Brazil has suffered from systematic drought problems in recent years, leading to severe human and environmental water security threats. This paper aims to track the water security for different periods and its relations with the changes in physical and natural asset conditions. The paper explores how investment planning to mitigate the water security threats and explore opportunities to increase the value of investments. The paper finds that grey infrastructure has regulated threats from increasing in the downstream of the river basin, however, continuous increase in water security threats in the upstream of the basin threatens water security downstream. This is evident from the spatial connectivity and unidirection externalities. As the capacity to further increase in grey investment is reaching its limit in the downstream, the increases in green infrastructure investment upstream, especia...
Managing receiving-water quality, ecosystem health and ecosystem service delivery is challenging ... more Managing receiving-water quality, ecosystem health and ecosystem service delivery is challenging in regions where extreme rainfall and runoff events occur episodically, confounding and often intensifying land-degradation impacts. We synthesize the approaches used in river, reservoir and coastal water management in the event-driven subtropics of Australia, and the scientific research underpinning them. Land-use change has placed the receiving waters of Moreton Bay, an internationally-significant coastal wetland, at risk of ecological degradation through increased nutrient and sediment loads. The event-driven climate exacerbates this issue, as the waterways and ultimately Moreton Bay receive large inputs of nutrients and sediment during events, well above those received throughout stable climatic periods. Research on the water quality and ecology of the region's rivers and coastal waters has underpinned the development of a world-renowned monitoring program and, in combination with catchment-source tracing methods and modeling, has revealed the key mechanisms and management strategies by which receiving-water quality, ecosystem health and ecosystem services can be maintained and
δ15N values of plants and animals are being increasingly used to identify the flow of nitrogen th... more δ15N values of plants and animals are being increasingly used to identify the flow of nitrogen through aquatic ecosystems. The δ15N values of crops, riparian trees, emergent and submerged aquatic vegetation in streams from both cleared (agricultural) and forested (rainforest) catchments were sampled. Riparian and aquatic plants had similar δ15N values in forested streams,suggesting a similar source of inorganic nitrogen.In cleared catchments, however, aquatic plants had δ15N values 4–8‰ higher than adjacent riparian vegetation and aquatic plants from streams in forested catchments. The elevated δ15N values of aquatic vegetation in streams with cleared catchments suggest that these plants either have access to a different source of N than those in undisturbed catchments or that high rates of microbial decomposition and nutrient cycling in the cleared catchments influence the δ15N value of available N. This also suggests that the aquatic plants in disturbed catchments are incorporatin...
Understanding the sources of sediment, organic matter and nitrogen (N) transferred from terrestri... more Understanding the sources of sediment, organic matter and nitrogen (N) transferred from terrestrial to aquatic environments is important for managing the deleterious off-site impacts of soil erosion. In particular, investigating the sources of organic matter associated with fine sediment may also provide insight into carbon (C) and N budgets. Accordingly, the main sources of fine sediment, organic matter (indicated by total organic carbon), and N are determined for three nested catchments (2.5 km 2 , 75 km 2 , and 3076 km 2) in subtropical Australia. Source samples included subsoil and surface soil, along with C3 and C4 vegetation. All samples were analysed for stable isotopes (δ 13 C, δ 15 N) and elemental composition (TOC, TN). A stable isotope mixing model (SIAR) was used to determine relative source contributions for different spatial scales (nested catchments), climatic conditions and flow stages. Subsoil was the main source of fine sediment for all catchments (82%, SD = 1.15) and the main N source at smaller scales (55-76%, SD = 4.6-10.5), with an exception for the wet year and at the larger catchment, where surface soil was the dominant N source (55-61%, SD = 3.6-9.9), though contributions were dependent on flow (59-680 m 3 /s). C3 litter was the main source of organic C export for the two larger catchments (53%, SD = 3.8) even though C4 grasses dominate the vegetation cover in these catchments. The sources of fine sediment, organic matter and N differ in subtropical catchments impacted by erosion, with the majority of C derived from C3 leaf litter and the majority of N derived from either subsoil or surface soil. Understanding these differences will assist management in reducing sediment, organic matter and N transfers in similar subtropical catchments while providing a quantitative foundation for testing C and N budgets.
Although considerable knowledge has been gathered regarding the role of fish in cycling and trans... more Although considerable knowledge has been gathered regarding the role of fish in cycling and translocation of nutrients across ecosystem boundaries, little information is available on how the energy obtained from different ecosystems is temporally allocated in fish bodies. Although in theory, limitations on energy budgets promote the existence of a trade-off between energy allocated to reproduction and somatic growth, this trade-off has rarely been found under natural conditions. Combining information on RNA:DNA ratios and carbon and nitrogen stable-isotope analyses we were able to achieve novel insights into the reproductive allocation of diamond mullet (Liza alata), a catadromous, widely distributed herbivorous-detritivorous fish. Although diamond mullet were in better condition during the wet season, most reproductive allocation occurred during the dry season when resources are limited and fish have poorer body condition. We found a strong trade-off between reproductive and somatic investment. Values of δ 13 C from reproductive and somatic tissues were correlated, probably because δ 13 C in food resources between dry and wet seasons do not differ markedly. On the other hand, data for δ 15 N showed that gonads are more correlated to muscle, a slow turnover tissue, suggesting long term synthesis of reproductive tissues. In combination, these lines of evidence suggest that L. alata is a capital breeder which shows temporal uncoupling of resource ingestion, energy storage and later allocation to reproduction.
Australian dryland rivers are acknowledged as being among the most variable and unpredictable in ... more Australian dryland rivers are acknowledged as being among the most variable and unpredictable in the world in terms of their flow regimes. Although renowned for their spectacular floods over vast and complex floodplains, rivers exist for much of the time as discrete waterholes, which are important refugia for aquatic biota. Recent work has shown that waterholes are filled by surface flows and there is little evidence of groundwater contributions. The permanence of these refugia is largely determined by waterhole morphology and evaporative loss, and some waterholes can clearly persist for 2 years or more without surface flow connection. As a consequence, the spatial distribution of refugia for aquatic biota is determined not only by the physical template but also by the duration of dry spells and the timing of flow events. Flow variability also has a major influence on aquatic production in these systems and ultimately influences food availability for fish and other consumers. During dry spells, aquatic food webs in waterholes are largely supported by algal production in the shallow littoral zone. At the other extreme, during floods, the boom of aquatic production on floodplains provides an immense food resource. However, there are many occasions when in-channel flows (flow pulses) result in periods where neither of these sources of production is likely to be available. Although such flow pulses are essential for the physical persistence and connectivity of waterholes, we propose that they may lead to food limitation and stress for populations of fish and other consumers. Water resource development in dryland rivers often leads to an increase in the frequency and duration of flow pulses, due to reduced floods and elevated base flows. This increase in the 'bits in between' natural boom or bust conditions may help to explain the observed decline in ecosystem health in dryland river systems with significant water resource development.
Aspects of invertebrate drift were investigated in four small rainforest streams in south-eastern... more Aspects of invertebrate drift were investigated in four small rainforest streams in south-eastern Queensland. Hourly sampling in two streams revealed low drift rates and no distinct diel patterns. This may have been a consequence of the low flows experienced during the study period. The drift was dominated by Simuliidae, Chironomidae and to a lesser extent Tasmanocoenis sp. (Caenidae) and Cheumatopsyche sp. 6 (Hydropsychidae). Additional studies were undertaken to examine why some individuals of particular taxa drift while others (of the same taxa) remain in or on the substratum. Analysis of the relative gut fullness of simuliid and chironomid larvae showed that a higher proportion of non-drifting individuals had full or nearly full guts compared with those in the drift. Hungrier individuals of these two taxa may enter the drift as a food searching mechanism. An analysis of limb loss of hexapod nymphs indicated that a disproportionate number of individuals in the drift had one or mo...
Tourists can adversely influence the ecology of oligotrophic lakes by increasing algal production... more Tourists can adversely influence the ecology of oligotrophic lakes by increasing algal production via direct nutrient inputs and/or re-suspension of sediments. To assess the influence of tourists on food web dynamics, we used the natural abundance of stable isotopes of carbon and nitrogen to calculate the relative importance of autochthonous and allochthonous carbon sources to littoral zone food webs across five variously visited perched dune lakes on Fraser Island, Australia. The relative importance of autochthonous (phytoplankton and periphyton) carbon to littoral zone consumers was highly variable across taxa and lakes. Despite the potential influence of algal biomass, ambient nutrient concentrations and tannin concentrations on the contribution of autochthonous carbon to littoral zone food webs, none of these variables correlated to the per cent contribution of autochthonous carbon to consumer diets. Instead, autochthonous sources of carbon contributed more to the diets of aquat...
Recent studies of the genetic structure of stream-dwelling organisms have suggested that ®ne-scal... more Recent studies of the genetic structure of stream-dwelling organisms have suggested that ®ne-scale patterns are the consequence of patchy recruitment from a small number of matings and limited in-stream dispersal. Predictions of this hypothesis were tested by spatial and temporal analysis of the genetic structure of populations of a stream may¯y (Bungona sp.: Baetidae) in subtropical streams in southeastern Queensland. Signi®cant departures from Hardy±Weinberg proportions occurred more often than would be predicted by chance alone and no consistent pattern was observed across sites, loci or sampling times. As in previous studies, the largest dierentiation was observed at the smallest spatial scale (reaches within streams) on most sampling occasions. These data provide additional support for a patchy recruitment hypothesis. Despite the ®ne-scale population structure, there was evidence of widespread adult dispersal across the study region, especially between streams and subcatchments within the same block of continuous dense forest.
1. Globally, tropical floodplains are highly productive ecosystems. This is largely due to predic... more 1. Globally, tropical floodplains are highly productive ecosystems. This is largely due to predictable seasonal rains providing replenishing floodwaters that stimulate nutrient turnover which, in turn, substantially boosts both primary and secondary productivity. This is associated with concomitant shifts in the types of primary producers and associated food webs. 2. The Magela Creek floodplain on Kakadu National Park in northern Australia is one of the most studied tropical freshwater ecosystems in Australia, and provides an opportunity to collate and examine information on organic carbon sources and pathways through food webs to gain a fundamental understanding of how these systems may function. 3. We reviewed biophysical information published since the early 1980s to construct an assessment of the carbon resources for the channel and floodplain. 4. We conclude that macrophytes, largely in the form of grasses and aquatic plants, produce the greatest above-ground biomass on the Magela Creek floodplain. Although macrophytes provide suitable substrata for the attachment of epiphytes, they do not appear to be an important carbon source for aquatic consumers themselves. Nevertheless, macrophytes do provide critical seasonal food and habitat structure for other producers and consumers on the floodplain, such as the abundant magpie geese. 5. We developed a generalised conceptual food web and carbon budget contrasting the "wet" and "dry" seasons for the Magela Creek system, as a representative of tropical seasonal floodplain systems. Running title-Wet & Dry contrasts in carbon resources on a tropical floodplain 2 6. Our conceptual model of tropical floodplains indicates that knowledge of the seasonal and spatial links and exchanges between the floodplain and the river is critical in understanding ecosystem function.
1. Biodiversity, water quality and ecosystem processes in streams are known to be influenced by t... more 1. Biodiversity, water quality and ecosystem processes in streams are known to be influenced by the terrestrial landscape over a range of spatial and temporal scales. Lumped attributes (i.e. per cent land use) are often used to characterise the condition of the catchment; however, they are not spatially explicit and do not account for the disproportionate influence of land located near the stream or connected by overland flow. 2. We compared seven landscape representation metrics to determine whether accounting for the spatial proximity and hydrological effects of land use can be used to account for additional variability in indicators of stream ecosystem health. The landscape metrics included the following: a lumped metric, four inverse-distance-weighted (IDW) metrics based on distance to the stream or survey site and two modified IDW metrics that also accounted for the level of hydrologic activity (HA-IDW). Ecosystem health data were obtained from the Ecological Health Monitoring Programme in Southeast Queensland, Australia and included measures of fish, invertebrates, physicochemistry and nutrients collected during two seasons over 4 years. Linear models were fitted to the stream indicators and landscape metrics, by season, and compared using an information-theoretic approach. 3. Although no single metric was most suitable for modelling all stream indicators, lumped metrics rarely performed as well as other metric types. Metrics based on proximity to the stream (IDW and HA-IDW) were more suitable for modelling fish indicators, while the HA-IDW metric based on proximity to the survey site generally outperformed others for invertebrates, irrespective of season. There was consistent support for metrics based on proximity to the survey site (IDW or HA-IDW) for all physicochemical indicators during the dry season, while a HA-IDW metric based on proximity to the stream was suitable for five of the six physicochemical indicators in the post-wet season. Only one nutrient indicator was tested and results showed that catchment area had a significant effect on the relationship between land use metrics and algal stable isotope ratios in both seasons. 4. Spatially explicit methods of landscape representation can clearly improve the predictive ability of many empirical models currently used to study the relationship between landscape, habitat and stream condition. A comparison of different metrics may provide clues about causal pathways and mechanistic processes behind correlative relationships and could be used to target restoration efforts strategically.
This study examined genetic variation within and among populations of the caddis fly Tasiagma cil... more This study examined genetic variation within and among populations of the caddis fly Tasiagma ciliata (Tasimiidae: Trichoptera) from rainforest streams in southeast Queensland, Australia. 2. Very low levels of genetic differentiation at large spatial scales, between subcatchments and between catchments, indicated that dispersal by the winged adults is widespread. However, significant genetic differentiation at the smallest spatial scale examined, within reaches in a single stream, suggested limited movement by larvae within streams. 3. A patchy distribution of deviations from Hardy-Weinberg equilibrium and differences in patterns among allozyme loci suggested that populations in particular reaches were the result of only a few matings. 4. These results are surprising, given the large numbers of larvae present within a single reach. We suggest that stochastic effects of recruitment may underlie much of the spatial and temporal variation in population numbers in these rainforest streams.
/ Recent research has emphasized the importance of riparian ecosystems as centers of biodiversity... more / Recent research has emphasized the importance of riparian ecosystems as centers of biodiversity and links between terrestrial and aquatic systems. Riparian ecosystems also belong among the environments that are most disturbed by humans and are in need of restoration to maintain biodiversity and ecological integrity. To facilitate the completion of this task, researchers have an important function to communicate their knowledge to policy-makers and managers. This article presents some fundamental qualities of riparian systems, articulated as three basic principles. The basic principles proposed are: (1) The flow regime determines the successional evolution of riparian plant communities and ecological processes. (2) The riparian corridor serves as a pathway for redistribution of organic and inorganic material that influences plant communities along rivers. (3) The riparian system is a transition zone between land and water ecosystems and is disproportionately plant species-rich when compared to surrounding ecosystems. Translating these principles into management directives requires more information about how much water a river needs and when and how, i.e., flow variables described by magnitude, frequency, timing, duration, and rate of change. It also requires information about how various groups of organisms are affected by habitat fragmentation, especially in terms of their dispersal. Finally, it requires information about how effects of hydrologic alterations vary between different types of riparian systems and with the location within the watershed.
We suggest that fluvial ecosystems are legitimate users of water and that there are basic ecologi... more We suggest that fluvial ecosystems are legitimate users of water and that there are basic ecological principles guiding the maintenance of long-term ecological vitality. This article articulates some fundamental relationships between physical and ecological processes, presents basic principles for maintaining the vitality of fluvial ecosystems, identifies several major scientific challenges and opportunities for effective implementation of the basic ecological principles, and acts as an introduction to three specific articles to follow on biodiversity, biogeochemistry, and riparian communities. All the objectives, by necessity, link climate, land, and fresh water. The basic principles proposed are: (1) the natural flow regime shapes the evolution of aquatic biota and ecological processes, (2) every river has a characteristic flow regime and an associated biotic community, and (3) aquatic ecosystems are topographically unique in occupying the lowest position in the landscape, thereby integrating catchment-scale processes. Scientific challenges for the immediate future relate to quantifying cumulative effects, linking multidisciplinary knowledge and models, and formulating effective monitoring and assessment procedures. Additionally, forecasting the ecological consequences of changing water regimes is a fundamental challenge for science, especially as environmental issues related to fresh waters escalate in the next two to three decades.
Intensive recreational use of oligotrophic lakes can lead to increases in epilimnetic nutrient co... more Intensive recreational use of oligotrophic lakes can lead to increases in epilimnetic nutrient concentrations (through direct inputs from urine or re-suspension of sediments) and the development of undesirable algal blooms. Despite these adverse ecological responses to tourist activities, many lake monitoring programs do not address tourist nutrient inputs at appropriate spatial and temporal scales. This paper presents results of investigations aimed at detecting the effects of nutrient inputs to perched dune lakes on Fraser Island, principally through within-lake comparisons of nutrient and algal variables. Nutrient concentrations and algal biomass were measured in heavily visited (disturbed) and inaccessible (reference) sites within five perched dune lakes on Fraser Island, Australia, during the summer of 1999/2000. Whilst nutrient and phytoplankton chlorophyll a concentrations did not differ between sites, periphyton chlorophyll a concentrations were occasionally significantly hi...
... Mosisch, Fran Sheldon, Frances D'Souza and James Udy, Fiona Balc... more ... Mosisch, Fran Sheldon, Frances D'Souza and James Udy, Fiona Balcombe, Jo Clapcott, Stephen Balcombe, Vanessa Fry, Nick Marsh, Mick Smith and Michelle Winning for their assistance over the years. Some have since moved ...
Despite advances in water resources management and planning, the São Francisco River Basin in Bra... more Despite advances in water resources management and planning, the São Francisco River Basin in Brazil has suffered from systematic drought problems in recent years, leading to severe human and environmental water security threats. This paper aims to track the water security for different periods and its relations with the changes in physical and natural asset conditions. The paper explores how investment planning to mitigate the water security threats and explore opportunities to increase the value of investments. The paper finds that grey infrastructure has regulated threats from increasing in the downstream of the river basin, however, continuous increase in water security threats in the upstream of the basin threatens water security downstream. This is evident from the spatial connectivity and unidirection externalities. As the capacity to further increase in grey investment is reaching its limit in the downstream, the increases in green infrastructure investment upstream, especia...
Managing receiving-water quality, ecosystem health and ecosystem service delivery is challenging ... more Managing receiving-water quality, ecosystem health and ecosystem service delivery is challenging in regions where extreme rainfall and runoff events occur episodically, confounding and often intensifying land-degradation impacts. We synthesize the approaches used in river, reservoir and coastal water management in the event-driven subtropics of Australia, and the scientific research underpinning them. Land-use change has placed the receiving waters of Moreton Bay, an internationally-significant coastal wetland, at risk of ecological degradation through increased nutrient and sediment loads. The event-driven climate exacerbates this issue, as the waterways and ultimately Moreton Bay receive large inputs of nutrients and sediment during events, well above those received throughout stable climatic periods. Research on the water quality and ecology of the region's rivers and coastal waters has underpinned the development of a world-renowned monitoring program and, in combination with catchment-source tracing methods and modeling, has revealed the key mechanisms and management strategies by which receiving-water quality, ecosystem health and ecosystem services can be maintained and
δ15N values of plants and animals are being increasingly used to identify the flow of nitrogen th... more δ15N values of plants and animals are being increasingly used to identify the flow of nitrogen through aquatic ecosystems. The δ15N values of crops, riparian trees, emergent and submerged aquatic vegetation in streams from both cleared (agricultural) and forested (rainforest) catchments were sampled. Riparian and aquatic plants had similar δ15N values in forested streams,suggesting a similar source of inorganic nitrogen.In cleared catchments, however, aquatic plants had δ15N values 4–8‰ higher than adjacent riparian vegetation and aquatic plants from streams in forested catchments. The elevated δ15N values of aquatic vegetation in streams with cleared catchments suggest that these plants either have access to a different source of N than those in undisturbed catchments or that high rates of microbial decomposition and nutrient cycling in the cleared catchments influence the δ15N value of available N. This also suggests that the aquatic plants in disturbed catchments are incorporatin...
Understanding the sources of sediment, organic matter and nitrogen (N) transferred from terrestri... more Understanding the sources of sediment, organic matter and nitrogen (N) transferred from terrestrial to aquatic environments is important for managing the deleterious off-site impacts of soil erosion. In particular, investigating the sources of organic matter associated with fine sediment may also provide insight into carbon (C) and N budgets. Accordingly, the main sources of fine sediment, organic matter (indicated by total organic carbon), and N are determined for three nested catchments (2.5 km 2 , 75 km 2 , and 3076 km 2) in subtropical Australia. Source samples included subsoil and surface soil, along with C3 and C4 vegetation. All samples were analysed for stable isotopes (δ 13 C, δ 15 N) and elemental composition (TOC, TN). A stable isotope mixing model (SIAR) was used to determine relative source contributions for different spatial scales (nested catchments), climatic conditions and flow stages. Subsoil was the main source of fine sediment for all catchments (82%, SD = 1.15) and the main N source at smaller scales (55-76%, SD = 4.6-10.5), with an exception for the wet year and at the larger catchment, where surface soil was the dominant N source (55-61%, SD = 3.6-9.9), though contributions were dependent on flow (59-680 m 3 /s). C3 litter was the main source of organic C export for the two larger catchments (53%, SD = 3.8) even though C4 grasses dominate the vegetation cover in these catchments. The sources of fine sediment, organic matter and N differ in subtropical catchments impacted by erosion, with the majority of C derived from C3 leaf litter and the majority of N derived from either subsoil or surface soil. Understanding these differences will assist management in reducing sediment, organic matter and N transfers in similar subtropical catchments while providing a quantitative foundation for testing C and N budgets.
Although considerable knowledge has been gathered regarding the role of fish in cycling and trans... more Although considerable knowledge has been gathered regarding the role of fish in cycling and translocation of nutrients across ecosystem boundaries, little information is available on how the energy obtained from different ecosystems is temporally allocated in fish bodies. Although in theory, limitations on energy budgets promote the existence of a trade-off between energy allocated to reproduction and somatic growth, this trade-off has rarely been found under natural conditions. Combining information on RNA:DNA ratios and carbon and nitrogen stable-isotope analyses we were able to achieve novel insights into the reproductive allocation of diamond mullet (Liza alata), a catadromous, widely distributed herbivorous-detritivorous fish. Although diamond mullet were in better condition during the wet season, most reproductive allocation occurred during the dry season when resources are limited and fish have poorer body condition. We found a strong trade-off between reproductive and somatic investment. Values of δ 13 C from reproductive and somatic tissues were correlated, probably because δ 13 C in food resources between dry and wet seasons do not differ markedly. On the other hand, data for δ 15 N showed that gonads are more correlated to muscle, a slow turnover tissue, suggesting long term synthesis of reproductive tissues. In combination, these lines of evidence suggest that L. alata is a capital breeder which shows temporal uncoupling of resource ingestion, energy storage and later allocation to reproduction.
Australian dryland rivers are acknowledged as being among the most variable and unpredictable in ... more Australian dryland rivers are acknowledged as being among the most variable and unpredictable in the world in terms of their flow regimes. Although renowned for their spectacular floods over vast and complex floodplains, rivers exist for much of the time as discrete waterholes, which are important refugia for aquatic biota. Recent work has shown that waterholes are filled by surface flows and there is little evidence of groundwater contributions. The permanence of these refugia is largely determined by waterhole morphology and evaporative loss, and some waterholes can clearly persist for 2 years or more without surface flow connection. As a consequence, the spatial distribution of refugia for aquatic biota is determined not only by the physical template but also by the duration of dry spells and the timing of flow events. Flow variability also has a major influence on aquatic production in these systems and ultimately influences food availability for fish and other consumers. During dry spells, aquatic food webs in waterholes are largely supported by algal production in the shallow littoral zone. At the other extreme, during floods, the boom of aquatic production on floodplains provides an immense food resource. However, there are many occasions when in-channel flows (flow pulses) result in periods where neither of these sources of production is likely to be available. Although such flow pulses are essential for the physical persistence and connectivity of waterholes, we propose that they may lead to food limitation and stress for populations of fish and other consumers. Water resource development in dryland rivers often leads to an increase in the frequency and duration of flow pulses, due to reduced floods and elevated base flows. This increase in the 'bits in between' natural boom or bust conditions may help to explain the observed decline in ecosystem health in dryland river systems with significant water resource development.
Aspects of invertebrate drift were investigated in four small rainforest streams in south-eastern... more Aspects of invertebrate drift were investigated in four small rainforest streams in south-eastern Queensland. Hourly sampling in two streams revealed low drift rates and no distinct diel patterns. This may have been a consequence of the low flows experienced during the study period. The drift was dominated by Simuliidae, Chironomidae and to a lesser extent Tasmanocoenis sp. (Caenidae) and Cheumatopsyche sp. 6 (Hydropsychidae). Additional studies were undertaken to examine why some individuals of particular taxa drift while others (of the same taxa) remain in or on the substratum. Analysis of the relative gut fullness of simuliid and chironomid larvae showed that a higher proportion of non-drifting individuals had full or nearly full guts compared with those in the drift. Hungrier individuals of these two taxa may enter the drift as a food searching mechanism. An analysis of limb loss of hexapod nymphs indicated that a disproportionate number of individuals in the drift had one or mo...
Tourists can adversely influence the ecology of oligotrophic lakes by increasing algal production... more Tourists can adversely influence the ecology of oligotrophic lakes by increasing algal production via direct nutrient inputs and/or re-suspension of sediments. To assess the influence of tourists on food web dynamics, we used the natural abundance of stable isotopes of carbon and nitrogen to calculate the relative importance of autochthonous and allochthonous carbon sources to littoral zone food webs across five variously visited perched dune lakes on Fraser Island, Australia. The relative importance of autochthonous (phytoplankton and periphyton) carbon to littoral zone consumers was highly variable across taxa and lakes. Despite the potential influence of algal biomass, ambient nutrient concentrations and tannin concentrations on the contribution of autochthonous carbon to littoral zone food webs, none of these variables correlated to the per cent contribution of autochthonous carbon to consumer diets. Instead, autochthonous sources of carbon contributed more to the diets of aquat...
Recent studies of the genetic structure of stream-dwelling organisms have suggested that ®ne-scal... more Recent studies of the genetic structure of stream-dwelling organisms have suggested that ®ne-scale patterns are the consequence of patchy recruitment from a small number of matings and limited in-stream dispersal. Predictions of this hypothesis were tested by spatial and temporal analysis of the genetic structure of populations of a stream may¯y (Bungona sp.: Baetidae) in subtropical streams in southeastern Queensland. Signi®cant departures from Hardy±Weinberg proportions occurred more often than would be predicted by chance alone and no consistent pattern was observed across sites, loci or sampling times. As in previous studies, the largest dierentiation was observed at the smallest spatial scale (reaches within streams) on most sampling occasions. These data provide additional support for a patchy recruitment hypothesis. Despite the ®ne-scale population structure, there was evidence of widespread adult dispersal across the study region, especially between streams and subcatchments within the same block of continuous dense forest.
1. Globally, tropical floodplains are highly productive ecosystems. This is largely due to predic... more 1. Globally, tropical floodplains are highly productive ecosystems. This is largely due to predictable seasonal rains providing replenishing floodwaters that stimulate nutrient turnover which, in turn, substantially boosts both primary and secondary productivity. This is associated with concomitant shifts in the types of primary producers and associated food webs. 2. The Magela Creek floodplain on Kakadu National Park in northern Australia is one of the most studied tropical freshwater ecosystems in Australia, and provides an opportunity to collate and examine information on organic carbon sources and pathways through food webs to gain a fundamental understanding of how these systems may function. 3. We reviewed biophysical information published since the early 1980s to construct an assessment of the carbon resources for the channel and floodplain. 4. We conclude that macrophytes, largely in the form of grasses and aquatic plants, produce the greatest above-ground biomass on the Magela Creek floodplain. Although macrophytes provide suitable substrata for the attachment of epiphytes, they do not appear to be an important carbon source for aquatic consumers themselves. Nevertheless, macrophytes do provide critical seasonal food and habitat structure for other producers and consumers on the floodplain, such as the abundant magpie geese. 5. We developed a generalised conceptual food web and carbon budget contrasting the "wet" and "dry" seasons for the Magela Creek system, as a representative of tropical seasonal floodplain systems. Running title-Wet & Dry contrasts in carbon resources on a tropical floodplain 2 6. Our conceptual model of tropical floodplains indicates that knowledge of the seasonal and spatial links and exchanges between the floodplain and the river is critical in understanding ecosystem function.
1. Biodiversity, water quality and ecosystem processes in streams are known to be influenced by t... more 1. Biodiversity, water quality and ecosystem processes in streams are known to be influenced by the terrestrial landscape over a range of spatial and temporal scales. Lumped attributes (i.e. per cent land use) are often used to characterise the condition of the catchment; however, they are not spatially explicit and do not account for the disproportionate influence of land located near the stream or connected by overland flow. 2. We compared seven landscape representation metrics to determine whether accounting for the spatial proximity and hydrological effects of land use can be used to account for additional variability in indicators of stream ecosystem health. The landscape metrics included the following: a lumped metric, four inverse-distance-weighted (IDW) metrics based on distance to the stream or survey site and two modified IDW metrics that also accounted for the level of hydrologic activity (HA-IDW). Ecosystem health data were obtained from the Ecological Health Monitoring Programme in Southeast Queensland, Australia and included measures of fish, invertebrates, physicochemistry and nutrients collected during two seasons over 4 years. Linear models were fitted to the stream indicators and landscape metrics, by season, and compared using an information-theoretic approach. 3. Although no single metric was most suitable for modelling all stream indicators, lumped metrics rarely performed as well as other metric types. Metrics based on proximity to the stream (IDW and HA-IDW) were more suitable for modelling fish indicators, while the HA-IDW metric based on proximity to the survey site generally outperformed others for invertebrates, irrespective of season. There was consistent support for metrics based on proximity to the survey site (IDW or HA-IDW) for all physicochemical indicators during the dry season, while a HA-IDW metric based on proximity to the stream was suitable for five of the six physicochemical indicators in the post-wet season. Only one nutrient indicator was tested and results showed that catchment area had a significant effect on the relationship between land use metrics and algal stable isotope ratios in both seasons. 4. Spatially explicit methods of landscape representation can clearly improve the predictive ability of many empirical models currently used to study the relationship between landscape, habitat and stream condition. A comparison of different metrics may provide clues about causal pathways and mechanistic processes behind correlative relationships and could be used to target restoration efforts strategically.
This study examined genetic variation within and among populations of the caddis fly Tasiagma cil... more This study examined genetic variation within and among populations of the caddis fly Tasiagma ciliata (Tasimiidae: Trichoptera) from rainforest streams in southeast Queensland, Australia. 2. Very low levels of genetic differentiation at large spatial scales, between subcatchments and between catchments, indicated that dispersal by the winged adults is widespread. However, significant genetic differentiation at the smallest spatial scale examined, within reaches in a single stream, suggested limited movement by larvae within streams. 3. A patchy distribution of deviations from Hardy-Weinberg equilibrium and differences in patterns among allozyme loci suggested that populations in particular reaches were the result of only a few matings. 4. These results are surprising, given the large numbers of larvae present within a single reach. We suggest that stochastic effects of recruitment may underlie much of the spatial and temporal variation in population numbers in these rainforest streams.
/ Recent research has emphasized the importance of riparian ecosystems as centers of biodiversity... more / Recent research has emphasized the importance of riparian ecosystems as centers of biodiversity and links between terrestrial and aquatic systems. Riparian ecosystems also belong among the environments that are most disturbed by humans and are in need of restoration to maintain biodiversity and ecological integrity. To facilitate the completion of this task, researchers have an important function to communicate their knowledge to policy-makers and managers. This article presents some fundamental qualities of riparian systems, articulated as three basic principles. The basic principles proposed are: (1) The flow regime determines the successional evolution of riparian plant communities and ecological processes. (2) The riparian corridor serves as a pathway for redistribution of organic and inorganic material that influences plant communities along rivers. (3) The riparian system is a transition zone between land and water ecosystems and is disproportionately plant species-rich when compared to surrounding ecosystems. Translating these principles into management directives requires more information about how much water a river needs and when and how, i.e., flow variables described by magnitude, frequency, timing, duration, and rate of change. It also requires information about how various groups of organisms are affected by habitat fragmentation, especially in terms of their dispersal. Finally, it requires information about how effects of hydrologic alterations vary between different types of riparian systems and with the location within the watershed.
We suggest that fluvial ecosystems are legitimate users of water and that there are basic ecologi... more We suggest that fluvial ecosystems are legitimate users of water and that there are basic ecological principles guiding the maintenance of long-term ecological vitality. This article articulates some fundamental relationships between physical and ecological processes, presents basic principles for maintaining the vitality of fluvial ecosystems, identifies several major scientific challenges and opportunities for effective implementation of the basic ecological principles, and acts as an introduction to three specific articles to follow on biodiversity, biogeochemistry, and riparian communities. All the objectives, by necessity, link climate, land, and fresh water. The basic principles proposed are: (1) the natural flow regime shapes the evolution of aquatic biota and ecological processes, (2) every river has a characteristic flow regime and an associated biotic community, and (3) aquatic ecosystems are topographically unique in occupying the lowest position in the landscape, thereby integrating catchment-scale processes. Scientific challenges for the immediate future relate to quantifying cumulative effects, linking multidisciplinary knowledge and models, and formulating effective monitoring and assessment procedures. Additionally, forecasting the ecological consequences of changing water regimes is a fundamental challenge for science, especially as environmental issues related to fresh waters escalate in the next two to three decades.
Intensive recreational use of oligotrophic lakes can lead to increases in epilimnetic nutrient co... more Intensive recreational use of oligotrophic lakes can lead to increases in epilimnetic nutrient concentrations (through direct inputs from urine or re-suspension of sediments) and the development of undesirable algal blooms. Despite these adverse ecological responses to tourist activities, many lake monitoring programs do not address tourist nutrient inputs at appropriate spatial and temporal scales. This paper presents results of investigations aimed at detecting the effects of nutrient inputs to perched dune lakes on Fraser Island, principally through within-lake comparisons of nutrient and algal variables. Nutrient concentrations and algal biomass were measured in heavily visited (disturbed) and inaccessible (reference) sites within five perched dune lakes on Fraser Island, Australia, during the summer of 1999/2000. Whilst nutrient and phytoplankton chlorophyll a concentrations did not differ between sites, periphyton chlorophyll a concentrations were occasionally significantly hi...
... Mosisch, Fran Sheldon, Frances D'Souza and James Udy, Fiona Balc... more ... Mosisch, Fran Sheldon, Frances D'Souza and James Udy, Fiona Balcombe, Jo Clapcott, Stephen Balcombe, Vanessa Fry, Nick Marsh, Mick Smith and Michelle Winning for their assistance over the years. Some have since moved ...
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Papers by Stuart Bunn