Evidence of arsenic biomagnification in Patagonian freshwater fish and the potential influence of lipids in arsenic bioaccumulation

JUNCOS, R.; ARCAGNI, M.; RIZZO, A.; MONTAÑEZ, J.C.; ARRIB¨¦RE, M.A.; CAMPBELL, L.M.; RIBEIRO GUEVARA, S.

Buenos Aires

Encuentro; SETAC Latin America 11th Biennial Meeting; 2015

Arsenic(As) is a highly toxic element released into the aquatic environment from bothanthropogenic and natural sources, such as volcanic eruptions. Lake NahuelHuapi is the largest and deepest oligotrophic lake in North Patagonia,Argentina, located close the Southern Volcanic Zone, an active volcanic arc.Although there are no significant anthropogenic sources of pollution, differentlevels of As have been recorded in biota from this lake that has beenassociated to volcanic sources. Most studies on As trophodynamics in freshwaterfood webs reveal that total As tends to decrease with increasing trophic level.However, in marine food webs, some authors have found that lipid-soluble Astend to biomagnify. The objectives of this work were to describe Astrophodynamics in the food chains of rainbow trout, brown trout and creoleperch in Lake Nahuel Huapi, and to relate fish As concentrations to C:N ratiosas proxy of lipid content. Predatory fish and their main prey were obtainedfrom the lake and processed in the laboratory, freeze dried and analyzed byInstrumental Neutron Activation Analysis in the RA-6 research nuclear reactor(Centro At¨®mico Bariloche, Argentina) to obtain total As concentrations [As] indry weight (DW). Stable nitrogen isotope (¦Ä15N) analyses were performed toassess the trophic level for As transfer patterns descriptions in each fishfood chain. %C and %N were analyzed and C:N ratios were determined to establishthe influence of lipids in As bioaccumulation of fish. Higher [As] whereobserved in muscle of the creole perch (0.7 to 1.9 ¦Ìg g-1 DW), and lower insalmonids (0.1 to 1.0 ¦Ìg g-1 DW). A decrease of [As] with increasing trophiclevel (i.e., biodilution) was observed in the salmonids food chains, followinga pelagic-littoral transfer pattern (through the consumption of fish prey);while an increase of [As] with trophic level (i.e., biomagnification) wasobserved in the creole perch food chain, following a littoral-benthic transferpattern (through the consumption of crayfish). A positive relationship between[As] and C:N ratios was found, having creole perch the highest C:N ratios and[As], rainbow trout the lowest C:N and [As], and brown trout intermediatevalues. These results suggest that As bioaccumulation could be favored by lipidcontents in fish, with As being more likely to biomagnify in fatty fish vialittoral crayfish food chains than fish with less fat and those more reliant onpelagic sources of food.