Ld. Hylander et al., Fish mercury concentration in the Alto Pantanal, Brazil: influence of season and water parameters, SCI TOTAL E, 261(1-3), 2000, pp. 9-20
The tropical flood plain Pantanal is one of the world's largest wetlands an
d a wildlife sanctuary. Mercury (Hg) emissions from some upstream gold mini
ng areas and recent findings of high natural Hg levels in tropical oxisols
motivated studies on the Hg cycle in the Pantanal. A survey was made on tot
al Hg in the most consumed piscivorous fish species from rivers and floodpl
ain lakes in the north (Caceres and Barao de Melgaco) and in the south part
of Alto Pantanal (around the confluence of the Cuiaba and Paraguai rivers)
. Samples were collected in both the rainy and dry seasons (March and Augus
t 1998) and included piranha (Serrasalmus spp.), and catfish (Pseudoplatyst
oma coruscans, pintado, and Pseudoplatystoma fasciatum, cachara or surubim)
. There was only a small spatial variation in Hg concentration of the 185 a
nalyzed fish samples from the 200 x 200 km large investigation area, and 90
% contained total Hg concentration below the safety limit for regular fish
consumption (500 ng g(-1)). Concentration above this limit was found in bot
h Pseudoplatystoma and Serrasalmus samples from the Baia Sia Mariana, the o
nly acid soft-water lake included in this study, during both the rainy and
dry seasons. Concentration above this limit was also found in fish outside
Baia Sia Mariana during the dry season, especially in Rio Cuiaba in the reg
ion of Barao de Melgaco. The seasonal effect may be connected with decreasi
ng water volumes and changing habitat during the dry season. The results in
dicate that fertile women should restrict their consumption of piscivorous
fishes from the Rio Cuiaba basin during the dry season. Measures should be
implanted to avoid a further deterioration of fish Hg levels. (C) 2000 Else
vier Science B.V. All rights reserved.