Assessment of the impact of dams on aquatic food webs using stable isotopes: Current progress and future challenges.

Dams have disrupted natural river systems worldwide and although population and community level effects on aquatic biota have been well documented, food web responses remain poorly understood and difficult to characterize. The application of stable isotope analysis (SIA) provides a means to assess the effect of dams on food webs. Here we review the effect of dams on aquatic food webs using SIA, aiming to detect knowledge gaps in the field of dam impacts on aquatic food webs and propose a conceptual framework to help formulate hypotheses about dam impacts on food webs guided by food web theory.

Fingerprinting eukaryotic metabolism across the animal kingdom using position-specific isotope analysis (PSIA) C/C measurements.

Despite differences in their overall metabolism, eukaryotes share a common mitochondrial biochemistry. We investigated how this fundamental biochemistry supports overall metabolism using a high-resolution carbon isotope approach, position-specific isotope analysis. We measured carbon isotope C/C cycling in animals, focusing on amino acids that are formed in mitochondrial reactions and are most metabolically active.

Benthic-pelagic mixing of trace elements in estuarine food webs.

Trace element accumulation pathways are important in many ecological and toxicological studies on aquatic organisms, yet these pathways are often poorly understood. To study the influence of diet and environment on the trace element composition of species within estuarine food webs, we performed a community level assessment of 28 trace elements (including major and minor elements) in common fish and prawn taxa across four estuaries, and in fish, prawn, and other invertebrate taxa within a single estuary. Despite sediment substrates from the four estuaries having distinctly different geochemical compositions, food web samples showed no separation by estuary, but clear separation by taxa.

Connectivity of fish communities in a tropical floodplain river system and predicted impacts of potential new dams.

Longitudinal and lateral connectivity is important for mobile aquatic species in rivers for reproductive migrations, recruitment, gene flow and access to food resources across habitat types. Water resource developments such as dams and levees may disrupt these connections, causing river fragmentation and loss of access to highly productive habitats such as floodplain wetlands. We used sulfur stable isotopes as a tracer to estimate patterns of fish movement in an unregulated river in tropical northern Australia, taking advantage of observed spatial variation in sulfur isotope values of their food resources across the catchment.

Uptake and accumulation of cadmium, manganese and zinc by fisheries species: Trophic differences in sensitivity to environmental metal accumulation.

Fishery targeted species living in estuaries face multiple anthropogenic pressures including habitat contamination. However, trace metal concentrations in aquatic organisms can be highly variable, making it difficult to interpret accumulation responses. Understanding sources for metal accumulation in these organisms and their biokinetics is important for management of local fisheries and ensuring safety and quality of consumed seafood, particularly in urbanised areas.

Catchment soils supply ammonium to the coastal zone - Flood impacts on nutrient flux in estuaries.

Erosion of soil from catchments during floods can deliver large quantities of sediment to the coastal zone. The transformations and processes of nutrient release from catchment soils during flooding are not well understood. To test the hypothesis that catchment soils supply nutrients to the coastal zone, we examined nutrient release and transformation following wetting of soils formed from three distinct rock types (basalt, granite and sandstone) with fresh and marine water.