Global Distribution of Radionuclides (¹³⁷Cs and⁴⁰K) in Marine Mammals

Abstract

Concentrations of anthropogenic radionuclides were measured in the muscle of marine mammals collected from various locations all over the world, and the global distribution of 137Cs in marine mammals was investigated. 40K was detected in all the specimens of marine mammals with no apparent difference between regions. An anthropogenic radionuclide, 137Cs, was detected in most of the species of marine mammals. With regard to the worldwide distribution of 137Cs, the highest concentration was noticed in the U.K. coast, followed by Lake Baikal, and decreases toward the southern sampling points. A strong positive correlation was observed between 137Cs levels in the muscle of marine mammals and the ambient seawater. Marine mammals feeding on fishes showed a higher concentration factor (CF) for 137Cs than those feeding on cephalopods. To our knowledge, this is the first report on the global distribution of 137Cs and the effect of feeding habits on the CF values of 137Cs in marine mammals.

Radiocaesium (137Cs) in marine mammals from Svalbard, the Barents Sea and the North Greenland Sea

“…From these areas harbour porpoises (Phocoena phocoena) had a mean 137 Cs activity in muscle tissue of 6.9 Bq/kg w.w. (N = 19, range from undetectable to 66.6 Bq/kg w.w.) (Watson et al, 1999). The second highest values of 137 Cs reported are from Baikal seals (Phoca sibirica) with a mean muscle value of 14.0 F 2.0 (SD) Bq/kg w.w. (N = 5, range from 12.0-17.0 Bq/kg w.w.) (Yoshitome et al, 2003). Values of 137 Cs, comparable to those reported by Watson et al (1999) and Yoshitome et al (2003) were also reported from harbour porpoises collected in the Black Sea in 1993 (N = 5, mean = 9.0 F 2.1 (SD) Bq/kg w.w.) (Kanivets et al, 1999).…”

“…The second highest values of 137 Cs reported are from Baikal seals (Phoca sibirica) with a mean muscle value of 14.0 F 2.0 (SD) Bq/kg w.w. (N = 5, range from 12.0-17.0 Bq/kg w.w.) (Yoshitome et al, 2003). Values of 137 Cs, comparable to those reported by Watson et al (1999) and Yoshitome et al (2003) were also reported from harbour porpoises collected in the Black Sea in 1993 (N = 5, mean = 9.0 F 2.1 (SD) Bq/kg w.w.) (Kanivets et al, 1999). In the Eastern Tropical Pacific specific activities in three dolphin species were above detection limits in samples from the late 1970s and early 1980s.…”

“…These were collected near nuclear weapons test sites (Calmet et al, 1992). The general decrease in values towards the south is confirmed by analyses of spinner dolphin (Stenella longirostris) samples from the Indian Ocean collected in 1990-1991 and a Weddell seal (Leptonychotes weddellii) sample from Antarctica collected in 1981 where no 137 Cs was detected (Yoshitome et al, 2003).…”

“…Yoshitome et al (2003) reported that marine mammals feeding predominantly on fish generally showed higher degrees of 137 Cs bioaccumulation than those feeding predominantly on cephalopods. Concentration factors for 137 Cs recommended by the IAEA (2004) for fish (1 Â10 2 ) are one order of magnitude higher than for cephalopods (1 Â10 1 ).…”

“…However, specific activities and concentration factors of 137 Cs for seal species in this study are similar to a mean specific activity of 0.23 F 0.04 (SD) Bq/kg w.w. and a concentration factor range of 34 to 130 for 137 Cs in muscle of mainly juvenile ringed, bearded and harp seals from Svalbard in 1999 (Carroll et al, 2002). In comparison, Rissanen et al (1997) reported specific activities of 0.4 to 0.9 Bq/kg (w.w.) with a concentration factor range of 32 to 72 in muscle of harp seals (all juvenile) from the White Sea in 1995 and 1996, while Yoshitome et al (2003) reported an average 137 Cs specific activity of 2.0 F 0.5 Bq/kg (w.w.) and a concentration factor range of 320 to 560 for ringed seals (age unknown) from the Kara Sea in 1995.…”