ORCID Profile
0000-0003-0058-773X
Current Organisation
James Cook University
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Publisher: SAGE Publications
Date: 2017
Publisher: Cold Spring Harbor Laboratory
Date: 05-2019
DOI: 10.1101/625053
Abstract: Efforts to protect and restore tropical wetlands impacted by feral pigs ( Sus scrofa ) in northern Australia have more recently included exclusion fences, an abatement response proposing fences improve wetland condition by protecting habitat for fish production and water quality. Here we tested: 1) whether the fish assemblage are similar in wetlands with and without fences and 2) whether specific environmental processes influence fish composition differently between fenced and unfenced wetlands. Twenty-one floodplain and riverine wetlands in the Archer River catchment (Queensland) were surveyed during post-wet (June-August) and late-dry season (November-December) in 2016, 2017 and 2018, using a fyke soaked overnight (~14-15hrs). A total of 6,353 fish representing twenty-six species from 15 families were captured. There were no multivariate differences in fish assemblages between seasons, years and for fenced and unfenced wetlands (PERMANOVA, Pseduo-F .58, P .68). Late-dry season fish were considerably smaller compared to post-wet season: a strategy presumably to maximise rapid disposal following rain. At each wetland a calibrated Hydrolab was deployed (between 2-4 days, with 20min logging) in the epilimnion (0.2m), and revealed distinct diel water quality cycling of temperature, dissolved oxygen and pH (conductivity represented freshwater wetlands) which was more obvious in the late-dry season survey, because of extreme summer conditions. Water quality varied among wetlands, in terms of the daily litude, and extent of daily photosynthesis recovery, which highlights the need to consider local site conditions rather than applying general assumptions around water quality conditions for these types of wetlands examined here. Though many fish access (fenced and unfenced) wetlands during wet season connection, the seasonal effect of reduced water level conditions seems to be more over-improvised compared to whether fences are installed or not, as all wetlands supported few, juvenile, or no fish species because they had dried completed regardless of whether fences were present or not.
Publisher: Wiley
Date: 30-11-2023
DOI: 10.1111/REC.13829
Abstract: Freshwater impounded wetlands are created by artificially restricting coastal wetlands connection to tides. The decrease in salinity and altered hydrology can significantly increase greenhouse gas (GHG) emissions, specifically methane (CH 4 ). Restoration of freshwater impounded wetlands through tidal reintroduction can potentially reduce GHG emissions however, studies in tropical regions are scare. This study investigates the potential for tidal restoration of impounded freshwater coastal wetlands by comparing their GHG emissions with tidally connected mangrove and saltmarshes in the Burdekin catchment in Queensland, Australia. We found that freshwater impounded wetlands had significantly higher CH 4 emissions (3,633 ± 812 μg CH 4 m −2 hour −1 ) than mangroves (27 ± 8 μg CH 4 m −2 hour −1 ) and saltmarsh (13 ± 8 μg CH 4 m −2 hour −1 ). Soil redox, moisture, carbon, nitrogen, and bulk density were all significantly correlated to methane emissions. Conversely, freshwater impounded wetlands had significantly lower nitrous oxide (N 2 O) emissions (−0.72 ± 0.18 μg N 2 O m −2 hour −1 ) than mangroves and saltmarsh (0.35 ± 0.29 and 1.32 ± 0.52 μg N 2 O m −2 hour −1 respectively). Nevertheless, when converting to CO 2 equivalents (CO 2‐eq ), freshwater impounded wetlands emitted 91 ± 20 g CO 2‐eq m −2 hour −1 , compared to the much lower 0.8 ± 0.2 and 0.7 ± 0.2 g CO 2‐eq m −2 hour −1 emission rates for mangroves and saltmarsh. In conclusion, restoration of freshwater impounded wetlands through tidal restoration is likely to result in reduced GHG emissions.
Publisher: Wiley
Date: 25-04-2019
DOI: 10.1002/AQC.3096
Publisher: Wiley
Date: 24-09-2021
DOI: 10.1002/ECE3.8054
Abstract: Installation of feral pig ( Sus scrofa ) exclusion fences to conserve and rehabilitate coastal floodplain habitat for fish production and water quality services remains untested. Twenty‐one floodplain and riverine wetlands in the Archer River catchment (north Queensland) were surveyed during postwet (June–August) and late‐dry season (November–December) in 2016, 2017, and 2018, using a fyke net soaked overnight (~14–15 hr) to test: (a) whether the fish assemblage are similar in wetlands with and without fences and (b) whether specific environmental conditions influence fish composition between fenced and unfenced wetlands. A total of 6,353 fish representing twenty‐six species from 15 families were captured. There were no wetland differences in fish assemblages across seasons, years and for fenced and unfenced (PERMANOVA, Pseudo‐ F 0.589, p .84). Interestingly, the late‐dry season fish were far smaller compared to postwet season fish: a strategy presumably in place to maximize rapid disposal following rain and floodplain connectivity. In each wetland, a calibrated Hydrolab was deployed (between 2 and4 days, with 20 min logging) in the epilimnion (0.2 m) and revealed distinct diel water quality cycling of temperature, dissolved oxygen and pH (conductivity represented freshwater wetlands), which was more obvious in the late‐dry season survey because of extreme summer conditions. Water quality varied among wetlands in terms of the daily litude and extent of daily photosynthesis recovery, which highlights the need to consider local conditions and that applying general assumptions around water quality conditions for these types of wetlands is problematic for managers. Though many fish access wetlands during wet season connection, the seasonal effect of reduced water level conditions seems more overimprovised when compared to whether fences are installed, as all wetlands supported few, juvenile, or no fish species because they had dried completely regardless of the presence of fences.
Publisher: Elsevier BV
Date: 2023
Publisher: Cold Spring Harbor Laboratory
Date: 03-12-2020
DOI: 10.1101/2020.12.03.409607
Abstract: Feral pigs predate on freshwater turtles and damage wetland habitats in the process. Installing fences successfully averts access and damage, however, they become a barrier for freshwater turtles requiring land access during migration. We collected 161 turtles ( Chelodina rugosa , Emydura subglobosa worrelli, Myuchelys latisternum ) from twenty floodplain and riverine wetlands during post-wet (June-August) and late-dry season (November-December) surveys (2015-2018) in northern Australia. Wetlands were either fenced (150 × 150mm square, 1.05m high wire mesh) or not around the wet perimeter. Nine-seven percent of in iduals caught in either fenced or unfenced wetlands had a shell carapace width greater than mesh width, of these 44 (46%) were captured inside fenced wetlands, while 50 were caught in unfenced wetlands. The remaining 35 were smaller than 150mm and would easily pass through fence mesh. Sixty-five turtles partook in a fencing manipulative experiment. Turtles with carapace widths wider than mesh often successfully escaped through fences by lifting one side of their shell and passing diagonally. In a second experiment where a piece of vertical wire (1500mmx300mm) was removed, turtles located gates after prospecting and trying to fit through meshing areas that were too small to pass through. Nine-two percent of turtles were able to locate and pass through gates, while 8% failed to locate a gate after 2 hours. Three turtles that did not use gates, and seemed to ‘give up’ and dug into the grass. Gates applied every 4m showed an 83% passage rate, every 2m was 91%, and while every 1m was 100%. Combing field and manipulative experiments revealed that large turtles will prospect and move along a fence until they find suitable passage. Applying turtle gates every 1–4m allows almost 100% passage, and if strategically applied in travel corridors, would minimize the need for large-scale clipping efforts around entire wetlands.
Publisher: Wiley
Date: 04-05-2021
DOI: 10.1111/GCB.15642
Abstract: Australia's Great Barrier Reef (GBR) catchments include some of the world's most intact coastal wetlands comprising erse mangrove, seagrass and tidal marsh ecosystems. Although these ecosystems are highly efficient at storing carbon in marine sediments, their soil organic carbon (SOC) stocks and the potential changes resulting from climate impacts, including sea level rise are not well understood. For the first time, we estimated SOC stocks and their drivers within the range of coastal wetlands of GBR catchments using boosted regression trees (i.e. a machine learning approach and ensemble method for modelling the relationship between response and explanatory variables) and identified the potential changes in future stocks due to sea level rise. We found levels of SOC stocks of mangrove and seagrass meadows have different drivers, with climatic variables such as temperature, rainfall and solar radiation, showing significant contributions in accounting for variation in SOC stocks in mangroves. In contrast, soil type accounted for most of the variability in seagrass meadows. Total SOC stock in the GBR catchments, including mangroves, seagrass meadows and tidal marshes, is approximately 137 Tg C, which represents 9%–13% of Australia's total SOC stock while encompassing only 4%–6% of the total extent of Australian coastal wetlands. In a global context, this could represent 0.5%–1.4% of global SOC stock. Our study suggests that landward migration due to projected sea level rise has the potential to enhance carbon accumulation with total carbon gains between 0.16 and 0.46 Tg C and provides an opportunity for future restoration to enhance blue carbon.
Publisher: Elsevier BV
Date: 10-2022
Publisher: Wiley
Date: 25-02-2019
DOI: 10.1111/GCB.14537
Publisher: MDPI AG
Date: 25-11-2019
DOI: 10.3390/JMSE7120426
Abstract: Laboratory mesocosm incubations were undertaken to investigate the influence of burrowing shrimp Trypaea australiensis (marine yabby) on sediment reworking, physical and chemical sediment characteristics and nutrients in sandy sediments receiving mangrove (Avicennia marina) leaf litter. Mesocosms of sieved, natural T. australiensis inhabited sands, were continually flushed with fresh seawater and pre-incubated for 17 days prior to triplicates being assigned to one of four treatments sandy sediment (S), sediment + yabbies (S+Y), sediment + leaf litter (organic matter S+OM) and sediment + yabbies + leaf litter (S+Y+OM) and maintained for 55 days. Mangrove leaf litter was added daily to treatments S+OM and S+Y+OM. Luminophores were added to mesocosms to quantify sediment reworking. Sediment s les were collected after the pre-incubation period from a set of triplicate mesocosms to establish initial conditions prior to the imposition of the treatments and from the treatment mesocosms at the conclusion of the 55-day incubation period. Yabbies demonstrated a clear effect on sediment topography and leaf litter burial through burrow creation and maintenance, creating mounds on the sediment surface ranging in diameter from 3.4 to 12 cm. Within S+Y+OM sediments leaf litter was consistently removed from the surface to sub-surface layers with only 7.5% ± 3.6% of the total mass of leaf detritus added to the mesocosms remaining at the surface at the end of the 55-day incubation period. Yabbies significantly decreased sediment wet-bulk density and increased porosity. Additionally, T. australiensis significantly reduced sediment bio-available ammonium (NH4+bio) concentrations and altered the shape of the concentration depth profile in comparison to the non-bioturbated mesocosms, indicating influences on nutrient cycling and sediment-water fluxes. No significant changes for mean apparent biodiffusion coefficients (Db) and mean biotransport coefficients (r), were found between the bioturbated S+Y and S+Y+OM mesocosms. The findings of this study provide further evidence that T. australiensis is a key-species in shallow intertidal systems playing an important role as an ‘ecosystem engineer’ in soft-bottom habitats by significantly altering physical and chemical structures and biogeochemical function.
Publisher: Oxford University Press (OUP)
Date: 29-06-2018
Publisher: Springer Science and Business Media LLC
Date: 22-01-2021
Publisher: American Association for the Advancement of Science (AAAS)
Date: 13-05-2022
Abstract: Tidal wetlands are expected to respond dynamically to global environmental change, but the extent to which wetland losses have been offset by gains remains poorly understood. We developed a global analysis of satellite data to simultaneously monitor change in three highly interconnected intertidal ecosystem types-tidal flats, tidal marshes, and mangroves-from 1999 to 2019. Globally, 13,700 square kilometers of tidal wetlands have been lost, but these have been substantially offset by gains of 9700 km
Publisher: Wiley
Date: 10-2018
DOI: 10.1111/JFB.13742
Abstract: Acute thermal and asphyxia exposure risks for freshwater fish occupying three tropical wetland typologies were examined. Field water-quality data revealed that fish in wetlands grazed by pigs had the highest exposure risks, because they are shallow and heavily damaged by pig activities. In contrast, with the exception is dissolved oxygen (which still reached critical conditions because of aquatic vegetation respiration), deeper permanent and pig-managed wetlands provides the best opportunity for the same fish species to survive in a heavily pig-modified tropical landscape.
Publisher: Wiley
Date: 03-2022
DOI: 10.1002/WLB3.01012
Abstract: Installing conservation fences to prohibit feral animal access to wetlands can become a barrier for non‐target species of interest. We collected 161 turtles ( Chelodina rugosa , Emydura subglobosa worrelli, Myuchelys latisternum ) from twenty floodplain and riverine wetlands during post‐wet (June–August) and late‐dry season (November–December) surveys (2015–2018) in northern Australia. Wetlands were fenced (150 × 150 mm square, 1.05 m high wire mesh) or unfenced around the wet perimeter. Ninety‐seven percent of in iduals caught in either fenced or unfenced wetlands had a shell carapace width greater than mesh width, of these 44 (46%) were captured inside fenced wetlands, while 50 were caught in unfenced wetlands. The remaining 35 turtles were smaller than 150 mm and would likely pass easily through fence mesh. Sixty‐five turtles partook in a fencing manipulative experiment. Turtles with carapace widths wider than mesh often successfully escaped through fences by lifting one side of their shell and passing diagonally through the mesh. In a second experiment where a piece of vertical wire (1500 × 300 mm) was removed, turtles located ‘gates' after prospecting and fitting through meshing areas that were too small to pass. Ninety‐two percent of turtles were able to locate and pass through gates, while 8% failed to locate a gate after 2 h. Gates applied every 4 m showed an 83% passage rate, every 2 m was 91%, and every 1 m was 100%. Combing field and manipulative experiments revealed that large turtles will prospect and move along a fence until they find suitable passage, which has important consequences when considering that gates could be easily retrofitted to existing sites, as well in new fencing programs, which has enormous positive conservation benefits for turtles in an already challenging and changing floodplain environment.
Publisher: Wiley
Date: 09-2020
DOI: 10.1111/EMR.12427
Publisher: Wiley
Date: 24-03-2021
DOI: 10.1002/ECE3.7412
Abstract: Wetlands are among the most vulnerable ecosystems, stressed by habitat loss and degradation from expanding and intensifying agricultural and urban areas. Climate change will exacerbate the impacts of habitat loss by altering temperature and rainfall patterns. Wetlands within Australia's Great Barrier Reef (GBR) catchment are not different, stressed by extensive cropping, urban expansion, and alteration for grazing. Understanding how stressors affect wildlife is essential for the effective management of bio ersity values and minimizing unintended consequences when trading off the multiple values wetlands support. Impact assessment is difficult, often relying on an aggregation of ad hoc observations that are spatially biased toward easily accessible areas, rather than systematic and randomized surveys. Using a large aggregate database of ad hoc observations, this study aimed to examine the influence of urban proximity on machine‐learning models predicting taxonomic richness and assemblage turnover, relative to other habitat, landscape, and climate variables, for vertebrates dwelling in the wetlands of the GBR catchment. The distance from the nearest city was, by substantial margins, the most influential factor in predicting the richness and assemblage turnover of all vertebrate groups, except fish. Richness and assemblage turnover was predicted to be greatest nearest the main urban centers. The extent of various wetland habitats was highly influential in predicting the richness of all groups, while climate (predominately the rainfall in the wettest quarter) was highly influential in predicting assemblage turnover for all groups. Bias of survey records toward urban centers strongly influenced our ability to model wetland‐affiliated vertebrates and may obscure our understanding of how vertebrates respond to habitat loss and climate change. This reinforces the need for randomized and systematic surveys to supplement existing ad hoc surveys. We urge modelers in other jurisdictions to better portray the potential influence of survey biases when modeling species distributions.
No related grants have been discovered for Nathan Waltham.