Surfers Paradise, Australia
Surfers Paradise, Australia

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Dunn R.J.K.,Griffith University | Dunn R.J.K.,Asia Pacific ASA Pty. Ltd. | Lemckert C.J.,Griffith University | Teasdale P.R.,Griffith University | Welsh D.T.,Griffith University
Journal of Coastal Research | Year: 2013

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. © 2013, the Coastal Education & Research Foundation (CERF).

Ali A.,Griffith University | Lemckert C.J.,Griffith University | Zhang H.,Griffith University | Dunn R.J.K.,Griffith University | Dunn R.J.K.,Asia Pacific ASA Pty. Ltd.
Journal of Coastal Research | Year: 2014

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. © 2014 Coastal Education and Research Foundation.

Dunn R.J.K.,Griffith University | Dunn R.J.K.,Asia Pacific ASA Pty. Ltd. | Welsh D.T.,Griffith University | Jordan M.A.,Griffith University | And 3 more authors.
Hydrobiologia | Year: 2012

A previous study has demonstrated that in sandy sediment the marine yabby (Trypaea australiensis) stimulated benthic metabolism, nitrogen regeneration and nitrification, but did not stimulate denitrification, as the intense bioturbation of the yabbies eliminated anoxic microzones amenable to denitrification. It was hypothesised that organic matter additions would alleviate this effect as the buried particles would provide anoxic microniches for denitrifiers. To test this hypothesis a 55-day microcosm (75 cm × 36 cm diameter) experiment, comprising four treatments: sandy sediment (S), sediment + yabbies (S + Y), sediment + A. marina litter (S + OM) and sediment + yabbies + A. marina litter (S + Y + OM), was conducted. Trypaea australiensis significantly stimulated benthic metabolism, nitrogen regeneration, nitrification and nitrate reduction in the presence and the absence of litter additions. In contrast, the effects of litter additions alone were more subtle, developed gradually and were only significant for sediment oxygen demand. However, there was a significant interaction between yabbies and litter with rates of total nitrate reduction and denitrification being significantly greater in the S + Y + OM than all other treatments, presumably due to the decaying buried litter providing anoxic micro-niches suitable to nitrate reduction. In addition, both T. australiensis and litter significantly decreased rates of DNRA and its contribution to nitrate reduction. © 2012 Springer Science+Business Media B.V.

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