Comparative accumulation of Cd-109 and Se-75 from water and food by an estuarine fish (Tetractenos glaber)

Abstract

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 (14 kBq L-1 of Cd-109 and 24 kBq L-1 of Se-75) and food (ghost shrimps; Trypaea australiensis: 875 Bq g(-1) Cd-109 and 1130 Bq g(-1) Se-75) for 25 days (uptake phase), followed by exposure to radionuclide-free water or food for 30 days (loss phase). Toadfish accumulated Cd-109 predominantly from water (85%) and Se-75 predominantly from food (62%), although the latter was lower than expected. For both the water and food exposures, Cd-109 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 Cd-109 uptake. This may be attributed to toadfish drinking large volumes of water to maintain osmoregulation. By the end of the loss phase, Cd-109 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, Se-75 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. © 2007, Elsevier Ltd.