ORCID Profile
0000-0002-5917-9792
Current Organisation
University of Saskatchewan
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Natural Resource Management | Ecosystem Function | Ecological Applications | Environmental Management |
Coastal and Estuarine Flora, Fauna and Biodiversity | Fresh, Ground and Surface Water Flora, Fauna and Biodiversity
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/MF09126
Abstract: Biomagnification of mercury (Hg) leads to high concentrations in fish and subsequent health risks for fish-eaters. Despite the global concern afforded to Hg over the past 40 years, little attention has been paid to this toxic heavy metal in Australia in general, and tropical northern Australia in particular. This review examines past Hg research in Australia and explores seven hypotheses as to why so little research and monitoring has been conducted in northern rivers and estuaries. We rule out the possibility that fishing intensity (an indicator of potential Hg exposure in humans) is lower in Australia than in other countries with more intensive Hg research programs. Instead, we hypothesise that low atmospheric deposition, owing to prevailing wind direction and few local point sources, coupled with highly productive waterbodies, contributes to low Hg bioaccumulation and hence the reduced interest in measuring Hg. Outstanding questions regarding Hg in northern Australia include the assessment of atmospheric deposition rates of Hg, the trophic level and growth and food consumption rates of consumers such as large-bodied fishes, linkages between fire regimes and Hg availability, and the capacity for in situ Hg methylation in tropical systems.
Publisher: Wiley
Date: 22-04-2012
DOI: 10.1002/ECO.1270
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/MF12114
Abstract: The present study indicates the critical role of hydrologic connectivity in floodplain waterholes in the wet–dry tropics of northern Australia. These waterbodies provide dry-season refugia for plants and animals, are a hotspot of productivity, and are a critical part in the subsistence economy of many remote Aboriginal communities. We examined seasonal changes in water quality and aquatic plant cover of floodplain waterholes, and related changes to variation of waterhole depth and visitation by livestock. The waterholes showed declining water quality through the dry season, which was exacerbated by more frequent cattle usage as conditions became progressively drier, which also increased turbidity and nutrient concentrations. Aquatic macrophyte biomass was highest in the early dry season, and declined as the dry season progressed. Remaining macrophytes were flushed out by the first wet-season flows, although they quickly re-establish later during the wet season. Waterholes of greater depth were more resistant to the effects of cattle disturbance, and seasonal flushing of the waterholes with wet-season flooding homogenised the water quality and increased plant cover of previously disparate waterholes. Therefore, maintaining high levels of connectivity between the river and its floodplain is vital for the persistence of these waterholes.
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/MF10211
Abstract: Despite prior studies showing good agreement between fin and muscle isotope ratios in temperate fishes, the non-lethal method of fin s ling has yet to become a standard technique in isotopic food-web studies, and the relationship between the two tissues has never been tested in the tropics. We hypothesised that fin and muscle δ13C and δ15N would be strongly correlated in tropical fishes, thus allowing non-lethal s ling of these species. To test this hypothesis, we analysed fin and muscle tissues from 174 tropical fishes representing 27 species from the Mitchell River, Queensland, Australia. Fin tissue was a strong predictor of muscle-tissue δ13C (r2 = 0.91 for all species) and was slightly enriched in 13C (0.9‰), consistent with the results of studies on temperate species. Fin tissue was a poorer predictor of muscle-tissue δ15N (r2 = 0.56 for all species) although the mean difference between the tissues was small ( .1‰). Differences were smallest in the largest fish, possibly because the elemental composition (%N) of fin more closely resembled that of muscle. These measurements provide more impetus for increased use of fin tissue as a non-destructive means of testing hypotheses about fish food webs in the tropics and elsewhere.
Publisher: Wiley
Date: 26-12-2014
DOI: 10.1002/RRA.2630
Publisher: Wiley
Date: 10-01-2013
DOI: 10.1002/RRA.2554
Publisher: Wiley
Date: 08-12-2014
DOI: 10.1111/AEC.12212
Publisher: Wiley
Date: 02-06-2020
DOI: 10.1111/JFB.14372
Publisher: Elsevier BV
Date: 02-2012
DOI: 10.1016/J.SCITOTENV.2011.11.022
Abstract: Little is known about the threat of mercury (Hg) to consumers in food webs of Australia's wet-dry tropics. This is despite high concentrations in similar biomes elsewhere and a recent history of gold mining that could lead to a high degree of exposure for biota. We analysed Hg in water, sediments, invertebrates and fishes in rivers and estuaries of north Queensland, Australia to determine its availability and biomagnification in food webs. Concentrations in water and sediments were low relative to other regions of Hg concern, with only four of 138 water s les and five of 60 sediment s les above detection limits of 0.1μgL(-1) and 0.1μgg(-1), respectively. Concentrations of Hg in fishes and invertebrates from riverine and wetland food webs were well below international consumption guidelines, including those in piscivorous fishes, likely due to low baseline concentrations and limited rates of biomagnification (average slope of log Hg vs. δ(15)N=0.08). A large fish species of recreational, commercial, and cultural importance (the barramundi, Lates calcarifer), had low concentrations that were below consumption guidelines. Observed variation in Hg concentrations in this species was primarily explained by age and foraging location (floodplain vs. coastal), with floodplain feeders having higher Hg concentrations than those foraging at sea. These analyses suggest that there is a limited threat of Hg exposure for fish-eating consumers in this region.
Publisher: Springer Science and Business Media LLC
Date: 31-01-2018
DOI: 10.1038/S41598-018-19918-6
Abstract: The trophic position of a top predator, synonymous with food-chain length, is one of the most fundamental attributes of ecosystems. Stable isotope ratios of nitrogen ( δ 15 N) have been used to estimate trophic position of organisms due to the predictable enrichment of 15 N in consumer tissues relative to their diet. Previous studies in crocodilians have found upward ontogenetic shifts in their ‘trophic position’. However, such increases are not expected from what is known about crocodilian diets because ontogenetic shifts in diet relate to taxonomic categories of prey rather than shifts to prey from higher trophic levels. When we analysed dietary information from the literature on the four Amazonian crocodilians, ontogenetic shifts in dietary-based trophic position (TP diet ) were minimal, and differed from those estimated using δ 15 N data (TP SIA ). Thus, ontogenetic shifts in TP SIA may result not only from dietary assimilation but also from trophic discrimination factors (TDF or Δ 15 N) associated with body size. Using a unique TDF value to estimate trophic position of crocodilians of all sizes might obscure conclusions about ontogenetic shifts in trophic position. Our findings may change the way that researchers estimate trophic position of organisms that show orders of magnitude differences in size across their life span.
Publisher: Wiley
Date: 08-05-2020
DOI: 10.1111/EFF.12553
Publisher: Wiley
Date: 14-11-2011
Publisher: Wiley
Date: 21-11-2011
DOI: 10.1111/J.1365-2656.2011.01925.X
Abstract: 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.
Publisher: Wiley
Date: 16-05-2008
DOI: 10.1111/J.1365-2656.2008.01394.X
Abstract: 1. Lipids have more negative delta(13)C values relative to other major biochemical compounds in plant and animal tissues. Although variable lipid content in biological tissues alters results and conclusions of delta(13)C analyses in aquatic food web and migration studies, no standard correction protocol exists. 2. We compared chemical extraction and mathematical correction methods for freshwater and marine fishes and aquatic invertebrates to better understand impacts of correction approaches on carbon (delta(13)C) and nitrogen (delta(15)N) stable isotope data. 3. Fish and aquatic invertebrate tissue delta(13)C values increased significantly following extraction for almost all species and tissue types relative to nonextracted s les. In contrast, delta(15)N was affected for muscle and whole body s les from only a few freshwater and marine species and had a limited effect for the entire data set. 4. Lipid normalization models, using C : N as a proxy for lipid content, predicted lipid-corrected delta(13)C for paired data sets more closely with parameters specific to the tissue type and species to which they were applied. 5. We present species- and tissue-specific models based on bulk C : N as a reliable alternative to chemical extraction corrections. By analysing a subset of s les before and after lipid extraction, models can be applied to the species and tissues of interest that will improve estimates of dietary sources using stable isotopes.
Publisher: Public Library of Science (PLoS)
Date: 16-07-2018
Publisher: Wiley
Date: 03-2015
DOI: 10.1890/14-0991.1
Abstract: 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 ersity. We show that the relative balance between these seemingly ergent 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 bio ersity and productivity.
Publisher: Wiley
Date: 14-06-2017
DOI: 10.1111/FWB.12952
Publisher: Springer Science and Business Media LLC
Date: 21-09-2016
Publisher: Wiley
Date: 22-03-2013
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1016/J.ENVINT.2017.02.008
Abstract: Cumulative environmental impacts driven by anthropogenic stressors lead to disproportionate effects on indigenous communities that are reliant on land and water resources. Understanding and counteracting these effects requires knowledge from multiple sources. Yet the combined use of Traditional Knowledge (TK) and Scientific Knowledge (SK) has both technical and philosophical hurdles to overcome, and suffers from inherently imbalanced power dynamics that can disfavour the very communities it intends to benefit. In this article, we present a 'two-eyed seeing' approach for co-producing and blending knowledge about ecosystem health by using an adapted Bayesian Belief Network for the Slave River and Delta region in Canada's Northwest Territories. We highlight how bridging TK and SK with a combination of field data, interview transcripts, existing models, and expert judgement can address key questions about ecosystem health when considerable uncertainty exists. SK indicators (e.g., bird counts, mercury in fish, water depth) were graded as moderate, whereas TK indicators (e.g., bird usage, fish aesthetics, changes to water flow) were graded as being poor in comparison to the past. SK indicators were predominantly spatial (i.e., comparing to other locations) while the TK indicators were predominantly temporal (i.e., comparing across time). After being populated by 16 experts (local harvesters, Elders, governmental representatives, and scientists) using both TK and SK, the model output reported low probabilities that the social-ecological system is healthy as it used to be. We argue that it is novel and important to bridge TK and SK to address the challenges of environmental change such as the cumulative impacts of multiple stressors on ecosystems and the services they provide. This study presents a critical social-ecological tool for widening the evidence-base to a more holistic understanding of the system dynamics of multiple environmental stressors in ecosystems and for developing more effective knowledge-inclusive partnerships between indigenous communities, researchers and policy decision-makers. This represents new transformational empirical insights into how wider knowledge discourses can contribute to more effective adaptive co-management governance practices and solutions for the resilience and sustainability of ecosystems in Northern Canada and other parts of the world with strong indigenous land tenure.
Publisher: Springer Science and Business Media LLC
Date: 28-11-2016
DOI: 10.1007/S00442-016-3786-Z
Abstract: Food web subsidies from external sources ("allochthony") can support rich biological ersity 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.
Publisher: Public Library of Science (PLoS)
Date: 06-06-2018
Publisher: Springer Science and Business Media LLC
Date: 09-10-2011
DOI: 10.1007/S00442-011-2148-0
Abstract: 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.
Publisher: University of Chicago Press
Date: 03-2014
DOI: 10.1086/674632
Publisher: Wiley
Date: 07-08-2012
Publisher: Public Library of Science (PLoS)
Date: 12-06-2013
Publisher: Wiley
Date: 13-05-2022
DOI: 10.1002/PAN3.10335
Abstract: River rhythmicity refers to the periodic, recurrent phenomena of a riverscape that are synchronized with the rise and fall of river water, creating regimes of river time. River rhythmicity can serve as a lens into the temporal dimension of river formation and socio‐ecological dynamics that are of great interest to many disciplines. In this paper, we introduce river rhythmicity as a conceptual and analytical framework to unify riparian human communities, academic disciplines and water agencies in approaching research and management of rivers. We also explore how the disruptions to riverine rhythms that are experienced by river‐dwelling communities, and are often visible in river discharge data through time, reconfigure, hinder or sever relationships between people and rivers. To ground our discussion in practical, lived experience, we provide brief descriptions of regimes of river time to demonstrate how rhythmic patterns established with rivers in north‐central Canada and Amazonian Colombia shape the lives of two of our co‐authors. By prioritizing holistic accounts of river rhythms, we can elucidate a fuller range of phenomena and their dynamic interactions, revealing riverscape features that are highly valued by local communities yet not often visible to any one discipline. Rhythmicity provides a conceptual framework to help address several challenges facing river conservation and water allocation dilemmas. By emphasizing relationality, it serves to (a) move beyond a biophysical framing of human‐nature connectedness by demonstrating that dynamic processes and relationships are constitutive of rivers, not derivative of them (b) enhance understanding of how the temporal dimensions of riverine relationships and river dwelling are experienced (c) highlight the socio‐cultural consequences of changes to river time and (d) centre socially embedded relationships with rivers forged from generations of observations of care and reciprocity. Read the free Plain Language Summary for this article on the Journal blog.
Publisher: The Royal Society
Date: 04-2022
Abstract: Supporting the recovery of large carnivores is a popular yet challenging endeavour. Estuarine crocodiles in Australia are a large carnivore conservation success story, with the population having extensively recovered from past heavy exploitation. Here, we explored if dietary changes had accompanied this large population recovery by comparing the isotopes δ 13 C and δ 15 N in bones of crocodiles s led 40 to 55 years ago (small population) with bones from contemporary in iduals (large population). We found that δ 13 C and δ 15 N values were significantly lower in contemporary crocodiles than in the historical cohort, inferring a shift in prey preference away from marine and into terrestrial food webs. We propose that an increase in intraspecific competition within the recovering crocodile population, alongside an increased abundance of feral ungulates occupying the floodplains, may have resulted in the crocodile population shifting to feed predominantly upon terrestrial food sources. The number of feral pigs consumed to sustain and grow crocodile biomass may help suppress pig population growth and increase the flow of terrestrially derived nutrients into aquatic ecosystems. The study highlights the significance of prey availability in contributing to large carnivore population recovery.
Publisher: Public Library of Science (PLoS)
Date: 03-03-2016
Publisher: Wiley
Date: 2015
DOI: 10.1890/14-0991.1.SM
Start Date: 10-2021
End Date: 09-2024
Amount: $391,000.00
Funder: Australian Research Council
View Funded Activity