Metal bioaccumulation through food web pathways in Port Curtis

"Port Curtis is an international trades port supporting major local industries as well as a large commercial and recreational fishing industry. Previous studies in the harbour (CRC Coastal Zone, 2005), have determined that despite relatively low metal concentrations in the water column there appears to be some accumulations of some metals in the marine organisms that inhabit the harbour. Aquatic animals can absorb metals through exposure in sediments and the water column but also via their diet, through metals accumulated in their food source. This route of exposure was investigated in this study."--p. i

Transplanted oysters and resident mud crabs as biomonitors in Spillway Creek

Transplanted oysters and resident mud crabs were used as biomonitoring tools to assess spatial differences in fluoride and metal (aluminium (AI), arsenic (As), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), nickel (Ni), selenium (Se) and zinc (Zn)) concentrations in Spillway Creek. Oysters obtained from an oyster lease from an uncontaminated area were deployed for a three month period at four sites within Spillway Creek and two external control sites. After retrieval, oysters (soft tissue) were analysed for concentrations of fluoride and nine metals. Between site comparisons included oysters from the oyster lease. Mud crabs were collected from the same sites over a two week period immediately prior to oyster retrieval and assessed for the presence of rust spot shell disease. Hepatopancreas (liver) and muscle tissues of mud crabs were also analysed for fluoride and metal concentrations and between site comparisons made. Concentrations of fluoride and metals in oysters and mud crabs were also compared to food guidelines. The mud crab results were also compared to the findings of a previous study 'Fluoride and metals in Spillway Creek Crustacea' (Andersen et al., 2001). Analyses of water metal and fluoride concentrations in Spillway Creek were also undertaken by BSL on one occasion. Despite elevated concentrations of fluoride in water samples closer to the discharge channel there were no between site differences in fluoride accumulations in oysters. Concentrations were, however, elevated in mud crab muscle from mud crabs closer to the discharge channel compared to sites near the mouth of Spillway Creek and the external reference sites, althoug.lJ. the site separation was not statistically significant. A similar trend of fluoride accumulation in mud crab muscle was evident in the previous study. Although mean concentrations in mud crab hepatopancreas tended to be more elevated in the Spillway Creek sites these were not significantly different to reference sites. Concentrations in mud crab muscle were not at such a level as to pose a human health risk from the consumption of mud crab meat. Nickel was elevated in Spillway oysters closer to the discharge suggesting exposure to bioavailable nickel, however a reverse trend of accumulation was evident for copper, zinc and to a lesser extent iron. Lilly Island oysters often had some of the highest metal concentrations, with oysters from the lease area often the lowest. Wild Cattle appeared to be a suitable control site. There also appeared to be an accumulation of selenium in mud crabs closer to the discharge channel. Apart from selenium there appeared to be no site trend for metal accumulations in mud crab tissue, which was similar to the fmdings of the previous study. Metal concentrations in mud crabs or oysters were not outside the boundaries of current food guidelines. There also appeared to be no relationship between water metal concentrations sampled on one occasion and biota metal concentrations. Water concentrations in Spillway Creek are known to be variable and the findings highlight the benefits of biologically monitoring, representing average ambient bioavailable contaminant concentrations over a time period. The differences in fluoride and metal concentrations in oysters and mud crabs in this study are likely to be due to a combination of their accumulation strategies and the nature of the exposure being pulse rather than continuous

Antioxidant enzymes as biomarkers of environmental stress in oysters in Port Curtis

The estuarine embayment of Port Curtis is Queensland's largest multi-cargo port and the fifth largest port in Australia. It supports major industries in the Gladstone area including the world's largest alumina refinery and Australia's largest aluminium smelter. Because the estuary is one of the Coastal CRC's three key study areas, research by the CRC contaminants team focused firstly on identifying contaminants of concern in a screening-level risk assessment. Although enrichment of some metals in marine organisms was recorded, subsequent projects focused on assessment of organism health to determine if environmental harm had occurred. There was a need to demonstrate a relationship between exposure to a contaminant and an adverse ecological effect. The objective of the current study was to examine the use of biomarkers as a measure of pollution-induced stress in oysters (Saccostrea glomerata) transplanted into Port Curtis from a clean area. Biomarkers are defined as a biological response that can be related to exposure to an environmental contaminant. In a broad context they can include measuring such endpoints as reproduction and growth, or behavioural changes; however, the biomarkers chosen in this study measured effects at a cellular level. Exposure to pollutants causes the production of potent oxidants and free radicals capable of damaging important cell components such as proteins and DNA. In response, the cell initiates antioxidant enzyme systems and produces free radical scavengers in order to prevent cellular injury and maintain cell homeostasis. The induced biomarker response can then be measured and related to measured concentrations of the contaminant the oyster is exposed to