Zinc in fish, crabs, oysters, and mangrove flora and fauna from Cleveland Bay

Zinc in muscle tissue from 28 species of fish, three species of sharks and rays, two species of squid and cuttlefish, and three species of crustacea c ollected from Cleveland Bay, together with some measurements made on oyster s and mangrove flora and fauna are reported, In the fish species the mean Z n concentration in muscle tissue was 4.83+/-2.82 mug/g wet weight, slightly lower than zinc measurements (7 mug/g wet weight) made in 14 fish species collected from the bay in 1975, Zinc in sharks and rays ranged from 3.5 to 7.2 mug/g wet wt, in squid and cuttlefish 13-16 mug/g wet wt, and in crusta cea levels ranged from 14 to 18 mug/g wet wt. Zinc levels in fish varied be tween species with concentrations well below the ANZECC Maximum Residue Lim it of zinc in seafood (150 mug/g wet wt), Although lower zinc concentration s were found in oysters collected from the Townsville Harbour area (2080 mu g/g wet wt), compared with previous measurements made 25 years ago at this site, these levels are still above the Maximum Residue Limit for zinc in oy sters (1000 mug/g wet wt). Concentrations of zinc in oysters from Orpheus I sland (2547 mug/g wet wt), about 74 km away from industrial and urban activ ity, are also above the safe guideline values. Horseshoe Bay oysters transp lanted to Ross Creek accumulated zinc at a rate of about 100 mug/g of oyste r tissue per week, suggesting that dissolved zinc levels at this site are e levated, and that oysters rapidly accumulate zinc, Highest concentrations o f zinc in mangrove leaves (30-65 mug/g dry wt) occurred in Osbornia octodon ta, Exocaria agalocha, and Aegialitus annulata, compared with Ceriops tagal , and Avicennia marina (5-10 mug/g dry wt). No significant difference in zi nc concentration occurred between leaves and litter fall for most of these species, with the sole exception of Exocaria, which showed almost a twofold increase in concentration. In seven species of mangrove fauna levels of zi nc were very uniform and close to 50 mug/g (dry wt) Telescopium telescopium from the mouth of the Ross Estuary was the exception with levels at 400 mu g/g (dry wt). (C) 2000 Elsevier Science Ltd. All rights reserved.