Seasonal fluctuations of DDTs and PCBs in zooplankton and fish of Lake Maggiore (Northern Italy)

Concentrations of DDTs and PCBs were determined in the zooplankton and in three different fish species
(shad, whitefish and roach) collected seasonally during 2009 and 2010 in three sites in Lake Maggiore, a
south-alpine lake that has been contaminated by DDT since 1996. As previously observed in 2008, even
during 2009 DDTs concentrations were higher in zooplankton than in fish, probably due to the very
unstable situation of the lake still influenced by local inputs. The situation changed in 2010, when all
DDT compounds increased in fish to levels much higher than those measured in zooplankton. Biomagnification
was statistically demonstrated for pp0DDE in all the three fish species, indicating a probable signal
of recovery of the lake.
Although with respect to total PCBs we observed that the contamination levels varied across time periods
and across fish species, biomagnification was evident from zooplankton to fish both in 2009 and in
2010. As concern individual PCBs, biomagnification from zooplankton to all three fish species was significant
for PCB 153 and PCB 138.