Cyanobacteria are commonly found in a number of temperate and tropical bioregions, and provide important roles in fuelling many nutrient poor freshwater and marine ecosystems. Although cyanobacteria commonly occur in these environments, little is known about the use of cyanobacteria as suitable organisms for toxicity studies. Here, we propose the use of the unicellular cyanobacteria Cyanobium sp., as a potential species for tropical toxicity testing using flow cytometry. Cyanobium sp. was isolated from a composite sample of sea water in Halifax Bay, North Queensland, Australia. After careful isolation, cleaning and purification, Cyanobium sp. was used to determine the toxicity of copper, cobalt, and nickel at pH 8, and ammonia at pH 7 and 8. EC 10 / 50 values were calculated using growth inhibition data determined via flow cytometry, which was found to provide rapid, accurate results, with the ability to define multiple endpoints. Cyanobium sp. was particularly sensitive to copper, cobalt and nickel, however, thrived at elevated concentrations of ammonia, irrespective of pH value. The results indicate that Cyanobium sp. is a useful test organism for tropical marine metal toxicity studies, however, is unsuitable for nutrient studies, particularly ammonia.

Nutrient bioindicators are increasingly being recognised as a diagnostic tool for nutrient enrichment of estuarine and marine ecosystems. Few studies, however, have focused on field translocation of bioindicator organisms to detect nutrient discharge from industrial waste. The brown macroalgae, Sargassum flavicans, was investigated as a potential bioindicator of nutrient-enriched industrial effluent originating from a nickel refinery in tropical north-eastern Australia. S. flavicans was translocated to a number of nutrient enriched creek and oceanic sites over two seasons and assessed for changes in stable isotope ratios of 15N and 13C within the plant tissue in comparison to reference sites. Nutrient uptake in macroalgae, translocated to the nutrient enriched sites adjacent to the refinery, increased 3–4-fold in δ15N, compared to reference sites. Using δ15N of translocated S. flavicans proved to be a successful method for monitoring time-integrated uptake of nitrogen, given the current lack of passive sampler technology for nutrient monitoring.

Few data are available on the comparative accumulation of metal(loid)s from water and food in estuarine/marine fish. Smooth toadfish (Tetractenos glaber), commonly found in estuaries in south-eastern Australia, were separately exposed to radio-labelled seawater (14kBqL(-1) of (109)Cd and 24kBqL(-1) of (75)Se) and food (ghost shrimps; Trypaea australiensis: 875Bqg(-1)(109)Cd and 1130Bqg(-1)(75)Se) for 25 days (uptake phase), followed by exposure to radionuclide-free water or food for 30 days (loss phase). Toadfish accumulated (109)Cd predominantly from water (85%) and (75)Se predominantly from food (62%), although the latter was lower than expected. For both the water and food exposures, (109)Cd was predominantly located in the gut lining (60-75%) at the end of the uptake phase, suggesting that the gut may be the primary pathway of (109)Cd uptake. This may be attributed to toadfish drinking large volumes of water to maintain osmoregulation. By the end of the loss phase, (109)Cd had predominantly shifted to the excretory organs - the liver (81%) in toadfish exposed to radio-labelled food, and in the liver, gills and kidney (82%) of toadfish exposed to radio-labelled water. In contrast, (75)Se was predominantly located in the excretory organs (gills, kidneys and liver; 66-76%) at the end of the uptake phase, irrespective of the exposure pathway, with minimal change in percentage distribution (76-83%) after the loss phase. This study emphasises the importance of differentiating accumulation pathways to better understand metal(loid) transfer dynamics and subsequent toxicity, in aquatic biota.

The importance to food‐webs of trophic cul‐de‐sacs, species that channel energy flow away from higher trophic levels, is seldom considered outside of the pelagic systems in which they were first identified. On intertidal mudflats, inputs of detritus from saltmarshes, macroalgae or microphytobenthos are generally regarded as a major structuring force underpinning food‐webs and there has been no consideration of trophic cul‐de‐sacs to date. A fully orthogonal three‐factor experiment manipulating the density of the abundant gastropod, Pyrazus ebeninus, detritus and macrobenthic predators on a Sydney mudflat revealed large deleterious effects of the gastropod, irrespective of detrital loading or the presence of predators. Two months after experimental manipulation, the standing‐stock of microphytobenthos in plots with high (44 per m2) densities of P. ebeninus was 20% less than in plots with low (4 per m2) densities. Increasing densities of P. ebeninus from low to high halved the abundance of macroinvertebrates and the average number of species. In contrast, the addition of detritus had differing effects on microphytobenthos (positively affected) and macroinvertebrates (negatively affected). Over the two‐months of our experiment, no predatory mortality of P. ebeninus was observed and high densities of P. ebeninus decreased impacts of predators on macroinvertebrate abundances. Given that the dynamics of southeast Australian mudflats are driven more by disturbance than seasonality in predators and their interactions with prey, it is likely that Pyrazus would be similarly resistant to predation and have negative effects on benthic assemblages at other times of the year, outside of our study period. Thus, in reducing microphytobenthos and the abundance and species richness of macrofauna, high abundances of the detritivore P. ebeninus may severely limit the flow of energy up the food chain to commercially‐important species. This study therefore suggests that trophic cul‐de‐sacs are not limited to the eutrophied pelagic systems in which they were first identified, but may exist in other systems as well.

Coral reefs are highly dynamic and productive marine ecosystems, providing habitat and refuge for an enormous number of species including fish, invertebrates and algae. With increased anthropogenic pressures and global climate change, many coral reefs are rapidly declining. Currently, there is limited knowledge on condition and community assemblage composition of shallow fringing coral reefs along the south-eastern coast of Queensland, Australia. With increased demand to determine existence of coastal fringing reefs by National Regional Management groups, a rapid cost effective method to determine reef composition and condition was required. The aim of this study was to determine the benthic structure and extent of two small coastal fringing reefs (Hummock Hill Reef and Stringers Reef) along the Southern Great Barrier Reef. Reef substrate assessments were carried out using a rapid assessment technique and a Point Intercept Method (PIM). The data were analysed and classified using a Geographic Information System (GIS). Percent substrate cover was calculated using a visual basic image analysis program. The Point intercept method showed higher accuracy over the rapid assessment technique (up to 15–40% difference) and was thus deemed a more suitable classification tool for reefs with high structural complexity and heterogeneity. This study focused on piloting a rapid, cost effective Point Intercept Technique using random point count methodology to document coral benthic habitat and extent over a commonly used rapid assessment method as a tool for reef coastal management and conservation. The two techniques were compared and substrate classification success, limitations and errors were discussed.

Semaphore crabs (Heloecius cordiformis), soldier crabs (Mictyris platycheles), ghost shrimps (Trypaea australiensis), pygmy mussels (Xenostrobus securis), and polychaetes (Eunice sp.), key benthic prey items of predatory fish commonly found in estuaries throughout southeastern Australia, were exposed to dissolved 109Cd and 75Se for 385 h at 30 kBq/l (uptake phase), followed by exposure to radionuclide-free water for 189 h (loss phase). The whole body uptake rates of 75Se by pygmy mussels, semaphore crabs and soldier crabs were 1.9, 2.4 and 4.1 times higher than 109Cd, respectively. There were no significant (P > 0.05) differences between the uptake rates of 75Se and 109Cd for ghost shrimps and polychaetes. The uptake rates of 109Cd and 75Se were highest in pygmy mussels; about six times higher than in soldier crabs for 109Cd and in polychaetes for 75Se – the organisms with the lowest uptake rates. The loss rates of 109Cd and 75Se were highest in semaphore crabs; about four times higher than in polychaetes for 109Cd and nine times higher than in ghost shrimps for 75Se – the organisms with the lowest loss rates. The loss of 109Cd and 75Se in all organisms was best described by a two (i.e. short and a longer-lived) compartment model. In the short-lived, or rapidly exchanging, compartment, the biological half-lives of 75Se (16–39 h) were about three times greater than those of 109Cd (5–12 h). In contrast, the biological half-lives of 109Cd in the longer-lived, or slowly exchanging compartment(s), were typically greater (1370–5950 h) than those of 75Se (161–1500 h). Semaphore crabs had the shortest biological half-lives of both radionuclides in the long-lived compartment, whereas polychaetes had the greatest biological half-life for 109Cd (5950 h), and ghost shrimps had the greatest biological half-life for 75Se (1500 h). This study provides the first reported data for the biological half-lives of Se in estuarine decapod crustaceans. Moreover, it emphasises the importance of determining metal(loid) accumulation and loss kinetics in keystone prey items, which consequently influences their trophic transfer potential to higher-order predators.

This study determined the condition and reproductive output of a common estuarine toadfish, Tetractenos glaber, in two metal contaminated and two reference estuaries near Sydney, Australia. Female toadfish from metal contaminated estuaries were smaller and younger than in reference estuaries; however, it could not be resolved whether these differences were due to direct effects of metal contamination or differences in nutritional value of prey. Lipid content in liver and gonad tissues was inversely related with levels of As, Pb, Cd and Co in sediment. In contrast, protein content in liver, gonad and muscle tissues was positively related to sediment levels of Ni and Co. Increased levels of Pb in gonads were associated with decreased oocyte diameter and density. This suggests a reduction in egg size and fecundity, which ultimately may lead to a decline in female reproductive output. Changes in fish health and reproduction caused by chemical pollutants may alter fish population and community structure.

This study determined the metal levels in sediments and tissues of a common estuarine fish, Tetractenos glaber (smooth toadfish), from two metal contaminated and two reference estuaries near Sydney, Australia. Metal levels were highest in sediments and fish from contaminated estuaries. Gonads contained the highest metal levels followed by muscle, gill and liver. Metal accumulation was gender-dependant (e.g. male gonads were >20 times higher in As than females; female gills were >30 times higher than males for Pb). Cadmium, Pb and Ni levels in fish tissues reflected sediment levels, indicating sediment and/or dietary metal uptake. Levels of As, Co, Cd & Pb in gills showed similar patterns to other tissues, suggesting that metals may have been taken up by gills through contaminated water. Similar metal patterns in tissues and sediments suggest more than one uptake pathway. This study indicates that multiple factors influence metal accumulation in fish.

Metals may have direct and indirect effects on aquatic biota at different trophic levels. This study examined the metal concentrations and nutritional value (protein and lipid content) of sediment infauna consumed by the estuarine smooth toadfish (Tetractenos glaber) at sites with varying metal contamination in the Parramatta River (Sydney Harbour), southeastern Australia, and the resulting influence on toadfish size and their tissue metal concentrations. Metal concentrations in sediments showed positive linear relationships (r 2 = 0.29–0.87; P < 0.001, n = 12) with metal concentrations in sediment infauna. Metal concentrations in toadfish tissues were also linearly and positively related to metal concentrations in both sediments (r 2 = 0.32–0.73; P < 0.001, n = 55) and infauna (r 2 = 0.27–0.72; P < 0.001, n = 55), indicating that sediment and infauna are an important metal exposure pathway for toadfish. Of the key toadfish prey items (sediment infauna), polychaetes (Marphysa sanguinea) generally had the highest metal concentrations and nutritional value followed by semaphore crabs (Heloecius cordiformis) and black mussels (Xenostrobus securis). Polychaetes from the most contaminated site generally had higher metal concentrations and higher nutritional value than those from the least contaminated site. Toadfish from the most contaminated site generally had the highest metal concentrations, and were 15% larger and 41% heavier than similarly-aged toadfish from the least contaminated site, suggesting that toadfish may be benefiting in size due to ingestion of sediment infauna of higher nutritional value.

The historical operation of manufacturing, chemical and other industries in the Sydney Harbour catchment over many decades has resulted in a legacy of high chemical contamination, such that a recent report describes Port Jackson as one of the most contaminated harbours in the world. The contaminant legacy in Homebush Bay is one on the worst in the harbour and presents a considerable management problem. Consultation with environmental managers (NSW Department of Environmental Conservation, NSW Fisheries, Sydney Olympic Park Authority) have identified that the presence of contaminated estuarine sediments present a complicated management issue in several coastal situations in NSW, including Homebush Bay. Although environmental managers are beginning to understand that elucidation of environmental processes is the key to effective ecosystem management, few tools are presently available to determine the in situ inter-relationships, rates and pathways of these events. Presently the detection of concealed contraband is based mainly on the use of X-rays, vapour and trace particle detection and sniffer dogs. Commercial X-ray systems using energies up to 9 MeV provide high resolution 2-D density images of the contents of containers and are ideally suited to the detection of metallic objects with readily identifiable shapes such as firearms and other weapons. However they are not well suited to the detection of those illicit substances that have similar densities and shapes to common substances. Dual-energy X-ray radiography has become a common screening method in applications such as the nonintrusive inspection of passenger luggage. By comparing the relative transmissions of high and low-energy X-ray beams, it is possible to build a 2D image, colour coded to indicate metal and organic materials. The limited penetration of the low energy X-rays used to provide composition information prevents the method being used on consolidated air or sea freight. However composition information has been sought recently using dual-energy X-ray radiography at very high energies (up to 10 MeV). Understanding the ecological risk imposed by contaminants in estuarine sediments requires an understanding of (1) specific trophic linkages and keystone species, (2) incident contaminant levels and, for predictions, the frequency/duration of physico-chemical processes (resuspension, desorption and transport), and (3) biological uptake/transfer mechanisms under a range of incident environmental conditions. Nuclear and isotopic techniques have a wide utility in coastal zone process studies with distinct advantages over conventional methods. Highly accurate and specific information on ecological, physical, chemical and biological processes may be obtained by selection of proxy isotopes with the appropriate properties. Nuclear tracers may be naturally occurring isotopes characteristic of the particular process under investigation, artificial and introduced as analogues of natural products, or labels on substances retrieved from nature. Here we will apply a range of nuclear and isotopic techniques to study the behaviour of metal contaminants associated with the sediments of Homebush Bay and their passage through the local food-web (Figure 2). This study has four main activities: (1) Determination of the linkages between high trophic order species and different habitat resources using δ15N and δ13C. These studies identify trophic cascades (food chains) which form the basis for selection of biota for contaminant transfer experiments. (2) A short-term (weeks - months) chronology of the surface mixed-layer of sediment cores collected from Homebush Bay will determine the rate of sedimentation and resuspension (using environmental/cosmogenic 7-beryllium). Models derived from these studies provide the levels of contaminants against which risk is assessed. (3) Site 1 Site 2 Site 3 Biokinetic studies using proxy radiotracer isotopes (eg. artificial 75Se and 109Cd for stable metals) of the uptake and trophic transfer of selected contaminants by specific estaurine biota. Here we identify the rates and extent to which contaminants are accumulated and transferred to predators/seafoods. (4) Application of an environmental risk assessment model (AQUARISK) set to criteria determined by stakeholder consensus.

Supplementary feeding to damselfish Acanthochromis polyacanthus larvae, at One Tree Island on the southern Great Barrier Reef, Australia, led to increased growth in length and enhanced condition relative to unfed control larvae, although both groups dropped in body condition (measured as total lipids) over the experimental period. Survival of fry was enhanced in fed broods, with on average 60% survival over 20 days, compared to 46% survival in unfed broods. Growth, condition and survival were neither density‐dependent nor body‐size dependent within broods. This study suggests variation in food supply may strongly influence persistence of larvae to juvenile stages, and thus influence cohort size.