Browsing by Author "Wen, L"
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- ItemCarbon uptake in surface water food webs fed by paleogroundwater(American Geophysical Union, 2019-04-05) Mazumder, D; Saintilan, N; Hollins, SE; Meredith, KT; Jacobsen, GE; Kobayashi, T; Wen, LThe use of 14C to elucidate sources of carbon within freshwater aquatic ecosystems is challenging the assumption that modern autochthonous carbon dominates energy flows. We measured the uptake of old carbon through several trophic levels of a wetland fed by groundwater of the Great Artesian Basin, Australia, the largest artesian basin in the world. Stable isotopes (δ13C and δ15N) and radiocarbon (14C) were used to quantify food chain links and connection between groundwater and surface water food webs. Our results suggest that old groundwater was the dominant carbon source even at the highest trophic levels, with predatory fish returning apparent carbon ages of up to 11 ka. Stable isotope analysis (δ13C and δ15N) identified trophic links between fish, aquatic insects, and algae with smaller contributions from particulate organic matter to the food webs. As natural mound springs and associated wetlands are the only source of reliable water during dry periods over vast areas of the western Great Artesian Basin, the result has potential implications for the interpretation of archaeological artefacts associated with indigenous passage within the interior. ©2019. ANSTO, Macquarie University, Commonwealth of Australia.
- ItemFood webs in freshwater floodplain wetlands inundated with environmental flows during drought conditions(Australian Nuclear Science and Technology Organisation, 2010-08-09) Mazumder, D; Johansen, MP; Saintilan, N; Iles, J; Knowles, L; Kobayashi, T; Wen, LIn the present study we used δS13C and δS15N stable isotope ratios in basal sources, primary producers, and a variety of invertebrate and fish consumers to gain better understanding of the sources of energy and trophic positions for aquatic species at floodplain water bodies within Yanga wetlands, Murrumbidgee floodplain, Australia. We compared δ13C and δ15N data from conditions of higher water levels and volumes that occurred in summer following a managed environmental flow, with data from winter conditions of lower water levels and volumes. Mass-balance mixing models were used to examine relative food source contributions to consumer diet. We also employed probabilistic simulation modelling to better understand trends of trophic positions, diet shifts and varying contributions from sources to consumers in water bodies of the Yanga wetlands. The data indicated contraction in the trophic position of Hypseleotris spp. in winter consistent with shrinking water volumes that induced greater competition, particularly between endemic Hypseleotris spp and and exotic Cyprinus carpio, for overlapping, and more limited varieties of food sources. Data indicated that the δ13C values for fish and insects from the low-water sampling period were typically -2-4%0 depleted compared to the corresponding high-water values. The δ13C values for one basal source (algae) depleted up to 25%0 between the sampling periods, while a second basal source (SOM) depleted less than 4%0. This study provided modelling results that indicated shifts in energy source and trophic position related to water fluctuations were consistent between adjacent water bodies and changes in food availability increased competition among species that may adversely impact population of endemic species.
- ItemHydrological connectivity and ecological functional processes in inland floodplain wetlands: nutrient and carbon cycling(Australian Society for Limnology, 2013-12-03) Wassens, S; Ralph, TJ; Ryder, DS; Saintilan, N; Mazumder, D; Wen, L; Hunter, S; Kobayashi, TFloodplain wetlands have intricate multi-channeled networks and unpredictable wet and dry phases related to variable hydrological regimes and geomorphic processes such as sedimentation and erosion. Hydrological reconnection of river channels with outer floodplain and wetland habitats initiates mobilisation and transformation of nutrients and carbon in inland floodplain wetlands. In this study, we aim to show habitat-dependent patterns of mobilisation and transformation of nutrients (total and dissolved nitrogen and phosphorus) and dissolved organic carbon (DOC) following environmental water releases, based on the available data from the Murrumbidgee Wetlands, Macquarie Marshes and Gwydir Wetlands. In general, concentrations of nutrients and DOC are lower within channels and higher on the floodplain and in wetlands where shallow inundation and mixing of topsoil with water occurs. Higher concentrations of nutrients and DOC on the floodplain represent a combination of supply from channels coupled with in situ releases from the water-soil interface. The volume, timing, depth, rate of rise and fall, and spatial distribution of water being introduced to floodplain wetlands influence the amount and distribution of nutrients and carbon in these systems. Rates of ecological functional processes such as primary productivity and respiration (or decomposition) are closely related to concentrations of nutrients and DOC. We propose a nutrient-DOC framework, combined with hydrological regimes and geomorphic processes, to better predict and understand the relationship between hydrological connectivity and ecological responses of inland floodplain wetlands. © The Authors
- ItemImpoundment constraint of fish niche diversity in a temperate Australian river(Springer, 2016-02-02) Mazumder, D; Williams, RJ; Wals, C; Wen, L; Saintilan, NDams constitute a major threat to aquatic ecosystems world-wide by modifying habitat and impairing opportunities for many freshwater fish. Subsequently, there can be a loss in fish diversity and change in the species distributions and population structure that ultimately contribute to changes in trophic structure and ecosystem function. In this study, stable isotope analysis (SIA) was used to compare trophic interaction and niche space of five fish species residing upstream and downstream of a significant barrier (Tallowa Dam) on the Shoalhaven River in south-eastern Australia. Significant reduction in niche space was found among predator/prey species residing in upstream habitat, implying limited dietary opportunity. Mixing calculations for Macquaria novemaculeata confirmed ontogenetic differences upstream and downstream of the dam. Causal mechanisms for this variability in trophic structure include habitat modification and/or discontinuity in river connectivity. SIA provides a useful tool for demonstrating the effect of barriers and/or impoundments on aquatic ecosystems, and for developing future monitoring programmes to evaluate restoration strategies.
- ItemIncorporation of local dissolved organic carbon into floodplain aquatic ecosystems(Springer Nature Limited, 2021-03-31) Saintilan, N; Kelleway, JJ; Mazumder, D; Kobayashi, T; Wen, LEnvironmental flow releases in lowland Australian rivers are currently timed to avoid high-carbon production on floodplains. Moreover, return flows (water draining from floodplains back into rivers) are avoided if there exists a risk of introducing deoxygenated “blackwater” into the main channel. This concern has restricted the range of possible watering scenarios being considered by environmental flow managers. We utilised a series of blackwater flows in the lower Murrumbidgee floodplain, Australia, in 2016 and 2017 to determine the origin and trophic contribution of blackwater dissolved organic carbon (DOC) in a floodplain wetland. We demonstrate a consistent difference in the isotope signature of blackwater DOC compared to both dissolved inorganic carbon (DIC) and river water DOC, explained by the greater contribution of floodplain vegetation (including the river red gum Eucalyptus camaldulensis) to blackwater DOC. Stable carbon isotope signatures suggest a contribution of blackwater to algal production, whereby microbial-mediated conversion of blackwater DOC into DIC may create opportunities for primary autotrophic productivity. This carbon signature was incorporated by the common yabby Cherax destructor. In the main river channel, C. destructor, the native gudgeon Hypseleotris spp. and the introduced European carp Cyprinus carpio may utilise the same basal carbon source. The use of small to moderate floodplain inundation with return flow to the river, properly monitored, would ameliorate the risk of hypoxia while providing the benefit of floodplain-derived DOC and associated increases to in-stream productivity. © The Author(s), under exclusive licence to Springer Nature B.V. 2021
- ItemInherent variation in carbon and nitrogen isotopic assimilation in the freshwater macro-invertebrate Cherax destructor(CSIRO Publishing, 2016-01-05) Mazumder, D; Wen, L; Johansen, MP; Kobayashi, T; Saintilan, NIndividual variability in diet source selection has often been cited as the main factor for intra-specific variation of isotopic signatures among food-web consumers. We conducted a laboratory study to test how well the individual variability of the δ13C and δ15N ratios in the muscle of an omnivore consumer (yabby: Cherax destructor) corresponded to the variability of various diet types and diet combinations. We found that C. destructor muscle isotope signatures varied in concert with the composition of single-source diets, and that this variability was low. However, when fed the same proportional mixture of multiple diet sources, comparatively high isotopic variability was observed among specimens. Results suggest that a substantial component of isotopic variability in wild populations may be owing to inherent differences in uptake, absorption, and sequestration among individuals, which is distinct from behaviourally driven individualised diet selection. Considering the potential of such individual variability in assimilation to be present in many different consumer populations, we suggest further testing for a range of species and inclusion of this source of variation, for interpretation of isotopic data for trophic ecology. © CSIRO 1996-2020
- ItemIsotopic and modelling studies of food web structure in wet and dry conditions, Yanga wetlands NSW, Australia(CSIRO, 2010-05-11) Mazumder, D; Johansen, MP; Saintilan, N; Iles, J; Knowles, L; Kobayashi, Y; Wen, LFloodplain wetlands provide habitat for a diverse range of aquatic biota, as well as performing other important ecosystem functions such as transformation of nutrients, providing breeding and nursery grounds for numerous species. Overall productivity and biodiversity of floodplain wetlands are closely linked with water availability, and in particular to the reliable reoccurrence of water inflows. Alteration of wetland inflow and outflow regimes can greatly impact the functioning of food-webs through biodiversity loss, diversion of energy flow and ecosystem functionality. In the present study stable isotope ratios (δ13C and δ15N) of primary producers, sediment organic matter (SOM) and a variety of invertebrate and fish species are used to gain better understanding of the food-web relations at various waterholes in wetter and drier conditions in Yanga National Park, in the lower Murrumbidgee floodplain. Mass-balance mixing models were used to examine relative food source contributions to consumer diet. We also employed probabilistic simulation software to better understand trends of trophic positions, diet shifts and varying contributions from sources to consumers in waterholes of the Yanga wetlands. We compared δ13C and δ15N data from wetter (greater surface water area and depth) conditions in February, with data from the drier (smaller surface water area an depth) conditions in August. The data indicated contraction in the trophic position of Hypseleotris spp. (carp guudgeon) in August consistent with shrinking waterholes where species were forced into competing for overlapping, and a more limited variety, of food sources. In particular the endemic Hypseleotris spp. appears to be forced into greater competition with the exotic C. carpio (carp). Data also indicated that energy source of consumer species varied with changing water levels among all waterholes. The drier (August) δ13C values for fish and insects were typically shifted ~1-3‰ lower than the corresponding wetter (February) values. These shifts appear to correspond to depletion in the δ13C algal values, and appear to indicate a greater proportional contribution of δ13C from algae to the δ13C in consumers. This study provides δ13C and δ15N values for endemic and exotic aquatic species in Australian semi-arid wetlands. It provides modelling results indicating shifts in energy source and trophic position relative to water fluctuations and indicates increased competition among similar species that may adversely impact endemic species populations.
- ItemIsotopic tools for better management of aquatic environment and resources(Australasian Environment Isotope Conference, 2015-07-08) Mazumder, D; Saintilan, N; Kobayashi, T; Wen, L; Rogers, K; Hollins, SE; Johansen, MP; Walsh, C; Narimbi, J; Sammut, JWater is a vital resource that is under ever-increasing demand from population and industry growth, agricultural development, and environmental allocations that are crucial to sustain the natural ecosystems upon which we all rely. Analysis of naturally-occurring stable isotopes (d13C and d15N) have emerged as powerful techniques for addressing research and management-related questions in ecology and aquaculture. Our work on coastal wetlands has identified carbon and nutrient dynamics, the sequestration potential of saltmarsh and mangrove systems, and anthropogenic impacts on aquatic food chains. We compared trophic position and dietary sources in freshwater wetlands during a severe El Nino drought (2007) and following a subsequent series of wetter than average La Nina years (2013), and identified that food chains expand and contract with oscillations in climate phase in the absence of new sources of carbon. We applied isotopic tools in aquaculture, which is the fastest growing food-producing sector in Australia and around the world and accounts for one-third of global fish production. However, production and profitability from inland and coastal aquaculture are often low due to environmental constraints and the increasing cost of production. Our work to develop low-cost feeding strategies for PNG fish farmers suggests operational costs can be reduced by carefully utilising production inputs or changing the ingredients used in feed formulations. These results provide insights for further applications of stable isotopes in the aquatic ecosystem studies.
- ItemProductivity influences trophic structure in a temporally forced aquatic ecosystem(John Wiley & Sons, Inc., 2017-07-06) Mazumder, D; Saintilan, N; Wen, L; Kobayashi, T; Rogers, KPrevious studies on the relationship between ecosystem productivity, size and food-chain length have been restricted to comparisons between locations. We examined the effect of temporal variability in productivity on trophic structure of a floodplain ecosystem, hypothesising that during the wet-flood pulses, the increased resource availability might lead to higher food-chain lengths. We examined multiple common sampling locations and species during a severe El Niño drought which followed a consecutive series of historically wet La Niña years, comparing trophic position and dietary sources. While carbon stable isotopes showed no significant difference between the two phases, nitrogen stable isotopes indicated that most species were feeding higher in the food chain in the wet phase. The results suggest that oscillations in climate phase-driven changes have effects on food-chain lengths through changes in productivity, without the introduction of new sources of carbon or changes to the composition of higher-order predators. © 2017 John Wiley & Sons, Inc.
- ItemA stable isotope approach to determine herbivorous diets of wintering geese at Dongting Lake, China(Beijing ICP, 2016-06) Guan, L; Mazumder, D; Yang, XX; Wen, L; Wang, YY; Lei, JL; Lei, GCThe East Dongting Lake National Nature Reserve in China is listed as a Ramsar Wetlands due to its global significance for migratory waterbird conservation, especially for the geese. For example, more than 90% of East Asian population of the vulnerable Lesser White-fronted Goose(Anser erythropus), and large numbers of Bean Goose(Anser fabilis) and Greater White-fronted Goose(Anser albifrons) over winter here every year from October to the next March. However, the habitats and food quality of the wintering geese have been threatened by hydrological alternation due to the operation of the Three Gorges Dam. Understanding the diets of these geese is fundamental for their conservation. We used the stable isotopic ratios of the body tissues of three predominant goose species(i.e. Ans?er erythropus, Anser fabilis and Anser albifrons) and their potential diet items(6 grass species), and applied smooth transition autoregressive(SIAR) mixing models to quantify the contribution of different food items to their diets. The results showed that the δ13C values of the blood samples were significantly different from those of feather, and the difference was consistent for the three kinds of geese. These results indicated that clear dietary shifts from their breeding place at the Arctic to the wintering place at Dongting Lake. The δ13C values of the blood samples of the geese showed there were no significant difference(ANOVA, p=0.265) suggesting that they share the same food sources at Dongting Lake. Moreover, the multiple-source mixing models(i.e. SIAR model) indicated that no single plant had a contribution greater than 35% to the diet of geese at 0.95 confident levels(0.50 and 0.95 credibility intervals of the posterior distributions range from 0.24-0.25 and 0.32-0.34, respectively). The results indicated that the geese had no preference for a particular plant. The findings suggested that the features at patch level(e.g. vegetation greenness and development stage) but not plant species might be the decisive factor in the habitat selection of the geese. Therefore, the management actions aiming to maintain habitat quality were critical for the waterbird conservation in Dongting Lake. © Beijing ICP 2016
- ItemA stable isotope approach to determine herbivory diets of wintering geese at Dongting lake, China(University of New South Wales and Australian Nuclear Science and Technology Organisation, 2015-07-09) Guan, L; Mazumder, D; Yang, XX; Wen, L; Lei, JL; Wang, YY; Lei, GCNot provided to ANSTO Library.
- ItemTrophic shifts involving native and exotic fish during hydrologic recession in floodplain wetlands(Springer Nature Limited, 2011-12-28) Mazumder, D; Johansen, MP; Saintilan, N; Iles, J; Kobayashi, T; Knowles, L; Wen, LStable isotopes (δ13C and δ15N) and gut contents were analysed for two species of co-occurring native and exotic fish in three shallow water bodies within an Australian riparian wetland system. During a period of hydrologic recession we found depletions in δ13C of up to −25‰ for algae and −2‰ for sediment organic matter (SOM). The native Hypseleotris sp. (carp gudgeon) and the exotic Cyprinus carpio (common carp) were depleted in δ13C up to −3.2‰, indicating that the SOM was the dominant dietary source of carbon for the two species of fish in both high- and the receded low-water conditions. In the low-water conditions, however, there was a five-fold increase in the occurrence of insects in the gut of the exotic C. carpio and the trophic positions of C. carpio and Hypseleotris sp. were more similar in all three water bodies than at high-water conditions. Our results indicate that there were shifts in dietary sources and trophic positions during hydrologic recession and provide evidence that flow reductions in wetland systems can increase the dietary overlap between native and exotic fishes. © Society of Wetland Scientists 2011
- ItemVegetation persistence and carbon storage: implications for environmental water management for Phragmites australis(American Geophysical Union, 2015-07-14) Whitaker, K; Rogers, K; Saintilan, N; Mazumder, D; Wen, L; Morrison, RJEnvironmental water allocations are used to improve the ecological health of wetlands. There is now increasing demand for allocations to improve ecosystem productivity and respiration, and enhance carbon sequestration. Despite global recognition of wetlands as carbon sinks, information regarding carbon dynamics is lacking. This is the first study estimating carbon sequestration for semiarid Phragmites australis reedbeds. The study combined aboveground biomass assessments with stable isotope analyses of soils and modeling of biomass using Normalized Digital Vegetation Index (NDVI) to investigate the capacity of environmental water allocations to improve carbon storage. The study considered relationships between soil organic carbon (SOC), carbon sources, and reedbed persistence in the Macquarie Marshes, a regulated semiarid floodplain of the Murray-Darling Basin, Australia. SOC storage levels to 1 m soil depth were higher in persistent reedbeds (167 Mg ha−1) than ephemeral reedbeds (116–138 Mg ha−1). In situ P. australis was the predominant source of surface SOC at persistent reedbeds; mixed sources of surface SOC were proposed for ephemeral reedbeds. 13C enrichment with increasing soil depth occurred in persistent and ephemeral reedbeds and may not relate to flow characteristics. Despite high SOC at persistent reedbeds, differences in the rate of accretion contributed to significantly higher rates of carbon sequestration at ephemeral reedbeds (approximately 554 and 465 g m−2 yr−1) compared to persistent reedbeds (5.17 g m−2 yr−1). However, under current water regimes, rapid accretion at ephemeral reedbeds cannot be maintained. Effective management of persistent P. australis reedbeds may enhance carbon sequestration in the Macquarie Marshes and floodplain wetlands more generally. © 2015 American Geophysical Union