Mercury in 16 demersal sharks from southeast Australia: Biotic and abiotic sources of variation and consumer health implications

• Published in: Marine environmental research Vol. 69; no. 1; pp. 18 - 26
• Main Authors: Pethybridge, Heidi, Cossa, Daniel, Butler, Edward C.V.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2010; Elsevier; Elsevier science
• Subjects: Agnatha. Pisces; Analysis of Variance; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Australia; Biological and medical sciences; Body distribution; Body Size - physiology; Carcharhiniformes; Chimaeriformes; Consumer Health Information; Deep-sea; Female; Fundamental and applied biological sciences. Psychology; Male; Maternal transfer; Mercury; Mercury - analysis; Methylmercury; Methylmercury Compounds - analysis; Muscles - chemistry; Sea water ecosystems; Seasons; Sex Factors; Sharks - physiology; Squaliformes; Synecology; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Water Pollutants, Chemical - analysis; Australia; Oceania; Deep-sea; Carcharhiniformes; Methylmercury; Mercury; Chimaeriformes; Maternal transfer; Squaliformes; Body distribution; Benthic organism; Deep water; Heavy metal; Marine environment; Vertebrata; Health status; Mother embryonal transfer; Pisces; Chondrichthyes; Environment quality; methylmercury; maternal transfer; deep-sea; body distribution
• ISSN: 0141-1136; 1879-0291
• DOI: 10.1016/j.marenvres.2009.07.006

Total mercury (THg) and monomethylmercury (MMHg) concentrations were determined in the tissues of demersal shark (Order Squaliformes and the Families: Scyliorhinidae, Hexanchidae) and chimaera species (Families: Chimaeridae and Rhinochimaeridae) from continental shelf and slope waters off southeast Australia, including embryos, juveniles and adults. The distribution of THg in various tissues (muscle, liver, kidney and skin), examined in ten species, shows higher levels in the muscle tissue (1.49 ± 0.47 mg kg −1, ww), which accounted for between 59% and 82% of the total body burden of mercury and in the kidney (0.93 ± 0.14 mg kg −1, ww) and liver (0.61 ± 0.25 mg kg −1, ww) with lower levels observed in the skin (0.12 ± 0.06 mg kg −1, ww). Additional THg determinations were performed in the muscle tissue of five other species allowing geographical and inter-specific comparisons. Speciation analysis demonstrated that more than 90% mercury was bound in muscle tissue as MMHg with higher percentages (>95%) observed in sharks species occupying deeper environments. Species differences were observed. Highest THg levels in the muscle tissue (up to 6.64 mg kg −1 wet weight, ww) were recorded in Proscymnodon plunketi and Centrophorus zeehaani (mean values; 4.47 ± 1.20 and 3.52 ± 0.07 mg kg −1, ww, respectively). Consistent with the ongoing paradigm on mercury bioaccumulation, we systematically observed THg concentrations increasing with animal size from the embryos to the larger sharks. Embryos of Etmopterus baxteri and Centroselachus crepidater had average levels 0.28 and 0.06 mg kg −1 (ww), while adult specimens reached 3.3 and 2.3 mg kg −1 (ww), respectively. THg concentrations in Australian sharks were compared with the same genus collected in other world regions. Levels were closer to data reported for East Atlantic than for the epicontinental Mediterranean margins. At a smaller geographical scale, the habitat effect on mercury concentration in sharks seems less clear. Squalid sharks occupying shelf waters showed higher mean mercury levels relative to their size (body weight, bw) than mid-slope species (0.4–6.7 mg kg −1 bw and 0.3–2.2 mg kg −1 bw, respectively). However, local regional differences (East and South Tasmania vs. Victoria) in Hg levels were not detected for the majority of taxa examined. All species, with the exception of Figaro boardmani showed values greater than 0.5 mg kg −1 (ww) and all but four were above many international regulatory thresholds (1.0 mg kg −1, ww).