This newsletter details the use of symbols as a visual language. Symbols are useful for depicting unequivocal messages that transcend cultures, languages and times. The use of symbols to contruct conceptual diagrams ('thought drawings') can be an effective tool for science communication and problem solving. Conceptual diagrams help to clarify thinking and provide a communication interface between scientists and non-scientists.

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This IAN newsletter explores the assessment of nutrient sources using stable isotope signatures of various marine organisms. This technique was developed in Moreton Bay, Australia for mapping sewage plumes, and was also used to determine the extent of aquaculture effluent (shrimp ponds) and to distinguish agricultural runoff (sugar cane) from other sources. The stable isotope ratio of nitrogen in organisms can be used to determine the influence of different nitrogen sources.

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Current shrimp pond management practices generally result in elevated concentrations of nutrients, suspended solids, bacteria and phytoplankton compared with the influent water. Concerns about adverse environmental impacts caused by discharging pond effluent directly into adjacent waterways have prompted the search for cost-effective methods of effluent treatment.

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Despite evidence linking shrimp farming to several cases of environmental degradation, there remains a lack of ecologically meaningful information about the impacts of effluent on receiving waters. The aim of this study was to determine the biological impact of shrimp farm effluent, and to compare and distinguish its impacts from treated sewage effluent.

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Effluent water from shrimp ponds typically contains elevated concentrations of dissolved nutrients and suspended particulates compared to influent water. Attempts to improve effluent water quality using filter feeding bivalves and macroalgae to reduce nutrients have previously been hampered by the high concentration of clay particles typically found in untreated pond effluent. These particles inhibit feeding in bivalves and reduce photosynthesis in macroalgae by increasing effluent turbidity.

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Soil disturbance in coastal regions could be linked to a variety of deleterious environmental impacts. The existing data are preliminary, but there is sufficient evidence to raise the issue to a higher priority for both research and management.

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Rapid global expansion of the aquaculture industry has prompted the need for development of techniques for effective environmental management. In intensively farmed regions, aquaculture effluent has resulted in environmental degradation of receiving waters. The issues to be addressed include analysis of effluent water quality, determination of the ecological impact of effluent on the ecosystem, and development of remediation strategies to reduce these impacts.

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Shrimp pond effluent water can contain higher concentrations of dissolved nutrients and suspended particulates than the influent water. Consequently, there are concerns about adverse environmental impacts on coastal waters caused by eutrophication and increased turbidity. One potential method of improving effluent water quality prior to discharge or recirculation is to use bivalves to filter the effluent.

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This book is the proceedings of the Moreton Bay and Catchment conference. It is divided into nine major sections covering the environmental history of the region, geology and geomorphology, catchment rivers and lakes, water quality, marine plants, marine animals, corals, flood effects and management options. The conference was preceded by a relatively small flood, which served as an opportunity to study the impact of flood events on Moreton Bay.

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Factors limiting phytoplankton biomass in the Brisbane River and Moreton Bay

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