Bioenergetics of blue swimmer crab (

Stock enhancement is a contemporary management method employed to support fisheries productivity. Blue swimmer crab (Portunus armatus) is a widely distributed species that has been identified as a candidate for stock enhancement; however, the release strategy and ecological impact of releases have not yet been assessed. Here, we (1) quantify the bioenergetics of blue swimmer crab, (2) estimate consumption rates, and (3) develop these relationships in a stocking model to assess appropriate release densities and associated trophic impacts. Static respirometry was used to measure the resting metabolic rate (RMR) of blue swimmer crab at three temperatures (19, 24, and 29°C). RMR was found to increase with temperature (Q10 = 2.32), and was 73% higher when crabs were at a premoult or moulting stage. Parameters derived from respirometry experiments were applied to estimate blue swimmer crab stocking density in a south-eastern Australian estuary, by adapting an existing production-based simulation model. The model estimated a median stocking density of ~1.2 crabs per 100 m2. A sensitivity analysis showed that the growth rate was the most influential parameter in this model, showing the importance of this parameter when assessing stocking scenarios.</jats:p

Bismuth(III) complexes derived from α-amino acids: the impact of hydrolysis and oxido-cluster formation on their activity against Helicobacter pylori

Eight bismuth(III) complexes derived from a variety of α-amino acids covering a range of physico-chemical properties (L-phenylalanine (Phe), L-proline (Pro), L-methionine (Met), L-cysteine (Cys), D,L-serine (Ser), L-tyrosine (Tyr), L-aspartic acid (Asp) and L-glutamic acid (Glu)) have been synthesised, characterised, and evaluated for their activity against Helicobacter pylori. The optimal synthetic procedure utilises [Bi(OtBu)3], giving the complexes [BiL3] (L = Phe 1, Pro 2, Met 3, Ser 5, Tyr 6) and [Bi2L3] (L = Cys 4, Asp 7, Glu 8) cleanly and in good yield. However, the synthesis is sensitive to both temperature and moisture. The solubility and stability of the bismuth(III) complexes was investigated using ESI-MS. Almost all compounds (except for [Bi(Phe)3] and [Bi(Pro)3]) were found to be partially or completely soluble in aqueous solution giving a pH 2.5–5.0, indicating the presence of free α-amino acid and hydrolysis of the bismuth(III) complexes to polynuclear bismuth oxido-clusters. The results of the bactericidal studies against Helicobacter pylori demonstrate that this hydrolysis process impacts significantly on the observed Minimum Inhibitory Concentration (MICs) which are increased substantially, often by many orders of magnitude, when the complexes are initially prepared in water rather than DMSO

Flow events drive patterns of phytoplankton distribution along a river-estuary-bay continuum

Freshwater flow events drive phytoplankton productivity in subtropical coastal river systems. However, few studies have the necessary temporal and spatial resolution to fully characterise the effect of events on the distribution of phytoplankton across the full river-estuary-bay continuum. The present study characterised the response of phytoplankton to high-flow events in an Australian subtropical system; and identified the primary drivers of this response. During high-flow events, the concentration of phytoplankton chlorophyll a (Chl a) initially declined in the estuary, a response primarily driven by the shortened water-residence time. In the bay, phytoplankton growth in the near-shore zone was light limited; however, nutrients stimulated phytoplankton growth on the seaward edge of the river plume. During the post-high-flow phase, the concentration of Chl a in the freshwater reaches peaked downstream, where catchment-derived nutrients accumulated. In the estuary, elevated nutrient loads stimulated phytoplankton growth upstream and downstream of the light-limited zone. In the bay, nitrogen availability declined, and Chl a declined with an increasing distance offshore. The phytoplankton response to events documented in the present study can be used to identify when and where phytoplankton in subtropical systems may be strongly influenced by changes in the magnitude of nutrient, sediment and freshwater loads associated with high-flow events which result from anthropogenic pressures within the catchment