Freshwater shrimps (Macrobrachium depressimanum and Macrobrachium jelskii) as biomonitors of Hg availability in the Madeira River Basin, Western Amazon

Abstract

Total mercury (THg) concentrations mea-sured in two freshwater shrimp species( M a c ro b r a c h i u m d e p re s s i m a n u m a n d Macrobrachium jelskii ) showed a relationship withthe location of artisanal and small-scale gold min-ing (ASGM) from the Madeira River Basin, West-ern Amazon. Between August 2009 and May 2010,212 shrimp samples were collected in the conflu-ence of the Madeira River with three of its tribu-taries (Western Amazon). THg concentration wasquantified in the exoskeleton, hepatopancreas andmuscle tissue of the shrimps by cold vapor atomicabsorption spectrophotometry. There were no sig-nificant differences between the two shrimp specieswhen samples came from the Madeira River, but Hg concentrations were significantly lower in a tributary outside the influence of the gold miningarea. Average THg concentrations were higher inthe hepatopancreas (up to 160.0 ng g − 1 ) and lower in the exoskeleton and muscle tissue (10.0 – 35.0 ng g − 1 and < 0.9 – 42.0 ng g − , respectively).Freshwater shrimps from the Madeira River re-spond to local environmental levels of Hg and can be considered as biomonitors for environmental Hgat this spatial scale. These organisms are important for moving Hg up food webs including those that harbor economic significant fish species and thusenhancing human exposure.