Scientists from the Australian Nuclear Science and Technology Organisation (ANSTO) have performed the first radiotracer studies on Australian marine fish species, using techniques that can provide information about how trace metals move through the food chain in Australian waterways. The study aims to give scientists a better idea of the impact of trace metal pollution in marine ecosystems.
Postdoctoral Research Fellow at ANSTO, Dr Gillian Peck, has studied how the trace metals selenium and cadmium are accumulated by a common Australian marine fish species - Favonigobius lateralis or long-finned goby.
Dr Peck said the scientists are using radioactive isotopes of selenium (75Se) and cadmium (109Cd) in the laboratory to study how quickly the fish take up these metals following exposure to radio-labelled food. ANSTO facilities are then used to measure which tissues they accumulate in, and how long it takes the fish to lose these metals once the exposure is stopped.
"Radiotracer studies are a critical step in gaining an improved and quantified understanding of how metals are transferred and accumulate in fish tissues and the rates at which these processes occur," said Dr Peck.
"Our studies have shown that both cadmium and selenium accumulate in the goby; however, the accumulation was most marked in the reproductive tissues. The uptake of selenium from radio-labelled food into the reproductive tissue was up to a factor of six higher than other tissues, and cadmium uptake was a factor of four higher during a short term exposure period of 16 days. Transfer of both
cadmium and selenium into the eggs or roe carried by the females was also demonstrated."
Cadmium and selenium can accumulate in the environment from industrial pollution. Sediments containing these trace metals can be washed into lakes where they are consumed by organisms such as bi-valves and invertebrates, and are passed on through the food chain. Dr Peck is continuing this research and pilot studies on the sand whiting, (Sillago ciliata), a species important to both the commercial and recreational fishing industries.
Previous studies have demonstrated that elevated trace metal concentrations in fish can affect reproductive success. Trace metals accumulated in the ovaries of adult females are transferred to offspring via egg yolk. This form of exposure can be detrimental to egg and larvae survival and development.
These findings led to the NSW-Environmental Protection Authority undertaking a study to assess the environmental effects of metals in sediments from Lake Macquarie, north of Sydney, which led to continuing studies by ANSTO.
"We anticipate that investigating these pathways and processes will provide a benchmark for future Australian studies," said Dr Peck. "The knowledge gained from these studies is important for managing our environment and ensuring the ecological health of our marine ecosystems for our future generations."