Ryan Jay Keith Dunn

Modelling copper uptake by Saccostrea glomerata with diffusive gradients in a thin film measurements

Environmental context. Organisms, like commercially available rock oysters, can be used to measure the uptake of contaminants (e.g. trace metals) and thereby provide a relative measure of water quality between sites or of water quality changes over time. However, these measurements cannot be directly compared with water quality guidelines, which require water concentrations and not tissue concentrations, to provide an absolute indication of water quality. The present study found that the amount of copper accumulated in oyster tissue was proportional to water copper concentrations measured by passive sampler devices, thereby allowing oyster copper accumulation to be interpreted in terms of biologically-available copper water concentrations and to be compared with the water quality guidelines. Abstract. Copper bioaccumulation in transplanted oysters, Saccostrea glomerata, was compared with measurements of water concentrations. Tissue copper measurements were positively correlated with acid-soluble copper concentrations (n = 6, r = 0.874, P = 0.023) and with DGT (diffusive gradients in a thin film)-accumulated copper mass at two sites (n = 9, r = 0.967, P < 0.001; n = 9, r = 0.888, P = 0.001) where continual bioaccumulation occurred. The more significant correlations are likely due to the time-integrated nature of DGT measurements, despite the biomonitor measuring different copper species. This empirical relationship allowed S. glomerata-available copper concentrations (0.70–1.6 μg L–1) to be modelled across 14 sites and produced a highly significant correlation (r = 0.787, P = 0.001) with DGT-labile copper measurements (0.10–0.49 μg L–1). This approach allowed biomonitor measurements to be compared with water quality guidelines and would further expand the use of biomonitors for aquatic monitoring if widely replicated.

Salt Fluxes within a Very Shallow Subtropical Estuary

Abstract This article describes the transport processes and net salt flux within a shallow estuarine system, with particular reference to the Coombabah Lake–Creek system in Queensland, Australia. Observations of currents and salinity at two locations within Coombabah Lake provided a basis for assessing the relative importance of various transport processes within a very shallow (water depth <1 m) subtropical estuary. The instantaneous velocity and salinity data were decomposed into time-averaged means and time-varying components and were used to quantify the salt flux components attributed to various physical processes. In this study, advection by residual flow, which contributed 65% of the total salt flux, was identified as the dominant process in transporting salt. The advective flux also determined the direction of the net salt flux within this shallow estuarine system. This study concludes that the net salt flux varies spatially and temporarily with hydromorphological and meteorological conditions.

Sediment Dynamics of a Very Shallow Subtropical Estuarine Lake

ABSTRACT Ali, A.; Lemckert, C.J.; Zhang, H., and Dunn, R.J.K., 2014. Sediment dynamics of a very shallow subtropical estuarine lake. Estuaries are of immense importance to many communities. The characteristics of estuarine flow and sediment conditions are important, since they play a critical role in the functionality and health of these systems. This study investigated sediment dynamics of a very shallow subtropical estuarine system: Coombabah Lake, southern Moreton Bay (Australia). Total suspended solid concentrations, turbidity, salinity, and tide levels were measured at eight stations within the lake. In situ current velocity and meteorological data were also collected during the study period, and data were analysed to determine the dominant sediment dynamic processes within the lake. Sediment transport was simulated using a three-dimensional numerical model to better understand the influence of various physical processes. Influence of sea-level rise on the sedimentary dynamic processes was also examined. Results of the study identified that sediment dynamics were dominated by advection processes driven by the influence of tides, with wind and wave forcing playing minor roles during the study period. Model simulations agreed well with the collected field data. The influence of sea-level rise within the system was predicted to reduce the turbidity of the system, and presumably increase primary productivity.

Gold Coast Broadwater: Southern Moreton Bay, Southeast Queensland (Australia)

The Gold Coast Broadwater, a large shallow estuarine water body, is a central feature of the Gold Coast City in Southeast Queensland (Australia) and forms the southern part of Moreton Bay. The Broadwater has undergone dramatic changes over the past few decades, including the construction of an extensive number and network of artificial waterways that account for up to 90 % of Australias canal estates. Positioned in one of the fastest growing regions in the developed world, urbanisation surrounding the Broadwater will continue. The region has important biodiversity values that have led to areas of the Broadwater being listed as an international Ramsar site and inclusion to international migratory bird agreements. The Broadwater provides a vital function in the provision of feeding, spawning and nursery sites for recreationally and commercially important finfish species. Key to the protection of the Broadwater is a reduction of pollutant loads from urban and agricultural stormwater run-off, golf courses and industrial infrastructure/areas and replacement of natural habitats with urban development. Collectively, initiatives undertaken by regulatory authorities have been successful to date and demonstrate that future conservation requires the integration of multidisciplinary science and proactive management driven by the high ecological, economical and community values placed on the Broadwater and adjoining waterways.

Macroinfauna Dynamics and Sediment Parameters of a Subtropical Estuarine Lake—Coombabah Lake (Southern Moreton Bay, Australia)

ABSTRACT Dunn, R.J.K.; Lemckert, C.J.; Teasdale, P.R., and Welsh, D.T., 2013. Macroinfauna dynamics and sediment parameters of a subtropical estuarine lake—Coombabah Lake (Southern Moreton Bay, Australia). The distribution, composition, density, and biomass of benthic macrofauna within estuarine environments typically exhibit significant variations attributable to heterogeneity in and interactions between physical, biological, and chemical processes. The spatial and temporal dynamics of benthic macroinfauna assemblages and physicochemical sediment parameters within the intertidal mudflats of a subtropical estuarine lake (Coombabah Lake, Southern Moreton Bay) were studied at four sites from August 2006 to April 2007. No significant seasonal changes were observed at any site for all physical sediment parameters. The northern sample sites were characterised by fine- to medium-grained to moderately to poorly sorted sediments and the southern sample sites by fine-grained to moderately well to well-sorted. A total of 1029 individuals representing species from three orders, including deposit feeding and filter feeding macroinfaunal groups, were collected. The highest combined species densities occurred in the fine-grained southern sites, with the greatest combined species density occurring at Site 4 during winter. Amphipods (Victoriopisa australiensis) and polychaete worms (Simplisetia aequisetis) dominated the lake-wide faunal community with V. australiensis, representing 49% of the total retrieved macroinfauna. Significant correlations between mean macroinfauna densities, biomassDW, sediment parameters, and seasonal maximum monthly temperatures were identified during the study. Seasonal trends in combined site densities were observed at each of the lake sites, with the highest combined density occurring during winter. Spatial and temporal variations might also be partially explained by the predation pressures of fish and migratory wading birds within the lake, with the seasonal presence of migratory wading birds coinciding with the minimum observed macroinfauna densities at each sample site.