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On Australian semiarid floodplains, large herbivores such as kangaroos have a role in the cycling of energy (carbon) through the mechanism of feeding and defaecation of vegetative material. The degree to which kangaroos are vectors of energy within this system is not fully understood. This study describes the stable carbon isotope signature of floodplain plants and kangaroo scats at two close study sites. Kangaroos were found to deposit scats that mirrored the forage composition at each particular feeding site. Scats were 3.94‰ higher in δ13C values at the site where C4grasses were available, indicating that this grass contributed ~25–30% of the diet of these kangaroos. The difference in diet due to the relative availability of C3and C4forage, detectable in the carbon stable isotope signature of scats, is used to demonstrate that kangaroos are recycling and redistributing energy locally, rather than transporting it more broadly across the floodplain. [ABSTRACT FROM AUTHOR]

Citizen, or community, science initiatives are increasingly recognised as an effective strategy to connect society with nature, science and environmental issues. However, different approaches to the delivery of the programmes can have different impacts on participant awareness, perceptions and behaviour change—especially when working with ecosystems perceived as less popular or uncharismatic, such as coastal wetlands, mangroves and saltmarshes.Using the HSBC Blue Carbon Citizen Science Programme as a case study, we compared two groups of corporate employees from Australia and New Zealand (N = 89) who participated in either: (a) a short duration citizen science experience including educational workshops and fieldwork in a local wetland; or (b) in educational workshops‐only. Questionnaires assessed the impact on participants' knowledge and perception towards wetlands, as well as their likelihood of adopting sustainable behaviours.Results revealed that participants' knowledge and understanding of environmental concepts increased, independent of the type of experience attended. However, the citizen science experience was more effective at fostering participants' intentions to make behaviour changes, with 64% of citizen science participants implementing sustainable changes at home or work, compared to 45% of workshop‐only participants.Our results highlight the importance of immersive citizen science experiences that, even of short duration, can have a valuable role enhancing participant knowledge, perception, and importantly, intention to make long‐term behaviour changes.With the increasing challenges faced by coastal systems globally, incorporating hands‐on, immersive experiences into educational programmes can be a strategic solution to improve ocean and climate literacy, while facilitating the actions required for a sustainable future. Read the free Plain Language Summary for this article on the Journal blog. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Previous 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. [ABSTRACT FROM AUTHOR]

Stable isotopes (δC and δN) 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 δC 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 δC 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. [ABSTRACT FROM AUTHOR]

Abstract  Environmental flows were released to the Macquarie Marshes (~210,000 ha) in north-west NSW of Australia between October and December 2005, inundating an estimated 24,600 ha of floodplain area. According to the flood pulse concept, the marsh floodplains would have stored large amounts of nutrients and carbon during dry antecedent conditions, which would be released into the overlaying flood water. Field studies were conducted in mid-December 2005 at two sites, one on open floodplain woodland with a sparse canopy of River Red Gum and ground cover dominated by saltbushes and the other on open floodplain with black roly-poly. At each site, nutrients, dissolved organic carbon (DOC), planktonic bacteria and phytoplankton were monitored daily for a 6-day period from the overlaying water of a floodplain inundated by the environmental water release. Those in mesocosms deployed in situ, containing marsh floodplain sediments that had been inundated artificially, were also monitored. The mesocosm results from both the sites showed that release of nitrogen was rapid, attaining mean concentrations of total nitrogen of 3.7–14.8 mg l−1, followed by more gradual increases in total phosphorus (mean concentrations 0.6–0.8 mg l−1) and DOC (26.1–50.2 mg l−1) within the 6-day experiment; planktonic microbial communities developed concomitantly with the increasing concentrations of nutrients and DOC, attaining mean densities of (6.0–6.9) × 106 cells ml−1 of planktonic bacteria and (80.7–81.4) × 103 cells ml−1 of phytoplankton; and for each site the overall measured condition of the mesocosm tended to approach that of the Marshes, over the course of the 6-day experiment. The present study (both observational and experimental) demonstrates that the floodplain sediments in the Marshes, which have been exposed to dry antecedent conditions, release nutrients and carbon to the overlaying flood water following inundation. These resources are thought to have been stored during the dry antecedent phase in accord with the flood pulse concept. Based on the mesocosm experiment, the released nutrients and carbon are in turn most likely to be used by microbial components, such as bacteria and algae, which develop within days of inundation of the floodplain sediments. Thus, environmental flow release provides potential for floodplains to attain a series of ecological responses including initial release of inorganic nutrients and dissolved organic matter and increase in planktonic bacteria and phytoplankton. [ABSTRACT FROM AUTHOR]