Floodplain wetlands are among the most productive and biodiverse ecosystems on Earth and provide a major subsidy of food resources for consumers in river systems. The basal energy source for those consumers in many systems comes from aquatic algal production influenced by different characteristics of the floodplain environment. Our aim was to estimate relationships between algal productivity and environmental variables in the channels and wetlands of the Mitchell River floodplain in tropical Australia. We measured physical, chemical, and biological variables in a range of different wetland types (palustrine, lacustrine, and riverine) and different habitat types (emergent macrophytes, floating macrophytes, submerged macrophytes, and open water). The most productive areas were found among riverine wetlands and submerged habitats. The statistical models showed that habitat type and turbidity alone can predict algal productivity with reasonable accuracy (pseudo-R 2 = 0.35, n = 63). Importantly, those attributes can be measured using remote sensing, and hence the model can be used to predict algal productivity over wider spatial scales and identify important "hotspot" areas of primary productivity that sustain aquatic food webs. Through this approach we can inform current conservation and water planning frameworks to manage the impact of human development on the productivity of wetlands at large spatial scales.

Rationale: Stable isotope analysis of leaf material has many applications including assessment of plant water-use efficiency and paleoclimatology. To facilitate interpretations of small shifts in the carbon isotope composition (δ 13 C) of leaves, accurate and repeatable results are required. Pre-sample homogenisation is essential to ensure a representative sample is analysed, but can also introduce error. Methods: We investigate how different grinding methods (freezer-milling and ball-milling) affect the carbon content and δ 13 C of tree leaves from a wetland in Queensland, Australia, commenting on how increased temperature, sample contamination, sample loss, or poor homogenisation may impact results. Results: No alteration of leaf δ 13 C is observed due to different milling methods, although there may be a significant increase in %C of samples processed using ball-milling. Conclusions: We suggest %C variability is possibly due to contamination from abraded plastic vials or insufficient homogenisation during ball-milling, with no significant impact on δ 13 C. Overall, we suggest that intermittent ball-milling may be the best solution to reduce costs, preparation time and use of liquid nitrogen, aiming to achieve complete homogenisation using the shortest possible duration of milling.

Groundwater systems, traditionally considered lifeless conduits of water Boulton 2008, Schulz et al. 2013), are now known to provide critical habitat for a diverse range of fauna collectively called stygofauna. Stygofauna communities can have significant conservation value as exemplified by rela tively high levels of endemism and biodiversity. Despite this the biogeography and taxonomic diversity of stygofauna communities largely remains undocumented. This paper describes the development and interrogation of a statewide database of 755 samples from 582 sites, and reviews the current knowledge of stygofauna biodiversity and biogeography across Queensland (northeastern Australia).Queensland is known to host 24 described families of stygofauna with stygofauna composition broadly consistent with other regions around the world. However Queensland assemblages tend to be unusually rich in both oligochaetes (16% cf. 2%) and syncarids (12% cf. 4%). Associations between stygofauna taxonomic richness and key environmental variables were consistent with many general as sumptions of habitat suitability. However there were also notable exceptions, including stygofauna records from: groundwater 60 meters below ground level; groundwater with electrical conductivity above 50,000 μS/cm, and; both highly acidic (pH 3.5) and alkaline (pH 10.3) environments. These exceptions clearly demonstrate that strict adherence to general assumptions about habitat suitability when planning sam pling activities may mask the true diversity of groundwater ecosystems.

Lake sediments are important archives of past climate variability and lake responses to climate. In order to accurately infer past climates, it is necessary to understand, and account for, the ecological processes that affect the record of indicators preserved in lake sediment. This is particularly the case with respect to the concentration of carbon and nitrogen (TOC, TN, and calculated C:N), and the stable isotope composition of organic matter preserved in lake sediments. These are common, yet ambiguous, tracers of environmental change. Ideally, palaeoenvironmental reconstructions using the concentration and isotope composition of organic matter should be grounded in a detailed understanding of the sources of the organic material. This study documents the history and evolution of Blue Lake, an environmentally and culturally important oligotrophic, groundwater window lake on North Stradbroke Island, Queensland, Australia. We utilise organic matter δ 13 C, TOC, TN, and C:N from a 2.4 metre sediment core with a basal age of 7.5 cal kyr BP, to investigate changing organic matter sources as a measure of the climate sensitivity of Blue Lake. This interpretation is supported by data from contemporary algae, aquatic and terrestrial plants, and catchment soils. We show that lake nutrient dynamics drove an increase in algal biomass at 4.2 cal kyr BP. This change coincides with a widely documented intensification of the El Niño-Southern Oscillation, which we infer to have influenced lake nutrient concentrations by reducing groundwater throughflow. Climatic changes resulted in marked changes in lake primary productivity, despite relatively little turnover of the lake diatom flora and catchment vegetation. This suggests that south-east Queensland dune lakes are sensitive to climate changes and helps to refine past and future palaeoclimate research using sediments from these lakes. It also indicates that increased nutrient concentrations in Blue Lake may result from projected changes in 21 st Century climate.

No abstract