Accumulation of metals by toadfish from sediment and infauna: Are fish what they eat?

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 (r2 = 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 (r2 = 0.32–0.73; P < 0.001, n = 55) and infauna (r2 = 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.