Biology Reference
In-Depth Information
Two months after the
Sea Empress
disaster, DNA adducts in the gills of the shanny
Lipophrys pholis
sampled at the spillage zone were still at a level of 470/10
9
nucleotides,
whereas the total hydrocarbons in sediments detected at the same site was 22 ± 4 μg g
-1
dry
weight (d.w.). The high levels of DNA adducts in ovaries, testis, and liver augured adverse
effects on reproduction and progeny output. High levels of DNA adducts were also quan-
tified in the sole (
Pleuronectes platessa
) and the dab (
Limanda limanda
), even 16 months after
the wreck (Table 13.1). Surprisingly, DNA adducts were absent in soft tissues of mussels
and sponges.
On the other hand, after the
Erika
wreck, high levels of DNA adducts were measured
in the digestive gland of mussels (
Mytilus edulis
), although these were three times lower
than in the liver of fish (
Solea solea
) (Table 13.1). The highest values were recorded at Pointe
Chemoulin and Baie de Bourgneuf, the sites most impacted by the oil spill (Amat et al.
2006). The range of PAH concentrations (16 PAH congeners) in mussels was 200-1500 ng g
-1
(d.w. soft tissues) at impacted sites, versus 20-200 ng g
-1
d.w. in apparently nonimpacted
sites.
Generally speaking, DNA adducts in fish livers are also biomarkers used in the biomoni-
toring of estuaries and rivers (Table 13.1). High values have been recorded at Southampton,
in the Thames, the Tyne, and the Clyde, in comparison with the rivers Mersey and Alde
in England, the Forth in Scotland, and Belfast in Northern Ireland (Lyons et al. 2004). In
France, the Baie de Seine was compared to the reference site of the Baie de Somme (Akcha
et al. 2003, 2004). The levels of DNA adducts in fish livers sampled in 2001 in Baie de
Seine were rather low (about 10 adducts/10
9
nucleotides). Levels were slightly higher in
adults than in juveniles, and in males compared to females. On the other hand, records in
freshwater mussels (
Dreissena polymorpha
) sampled in the Seine river (15-40 adducts/10
9
nucleotides) in 2002 indicated exposure to genotoxic pollutants, possibly PAHs. The latter
were quantified in mussel tissues at high concentrations at polluted sites compared to the
reference site (Le Goff et al. 2006). Temporal variations were registered, and 1 year later
(2003) DNA adduct levels were lower (<10 adducts/10
9
nucleotides), as were the PAH con-
centrations in the mussels (Rocher et al. 2006).
Levels of DNA adducts in gills of
M. edulis
were found in the same range at polluted sites
on the coasts of Iceland, Norway and Sweden (10-20 adducts/10
9
nucleotides), for instance,
in Reykjavik harbor (Ericson et al. 2002; Skarphédinsdóttir et al. 2007). Gill DNA adduct lev-
els were found to be higher in mussels in the intertidal zone compared to the subtidal zone,
the difference being largest in winter (Skarphédinsdóttir et al. 2005). This was explained
by a higher pollution level of the surface microlayer, an additional stress for intertidal mus-
sels under the effect of the tidal cycle, and photoactivation of hydrocarbons, such as PAHs,
known to be rendered more toxic by sunlight and ultraviolet (UV) radiation. DNA adduct
levels in mussels were higher in gills than in the digestive gland (Skarphédinsdottir et al.
2007) as already shown in
Mytilus galloprovincialis
on Mediterranean coasts by Pisoni et al.
(2004). In fish, the difference was not so clear, with higher adduct levels in the liver than
in the gills at different sites of the Baltic Sea (Ericson et al. 1998), whereas the inverse was
found in the Venice lagoon (Venier and Zampieron 2005).
The comparison of adduct levels between studies requires consideration of the adduct
enrichment method used before chromatographic separation of
32
P-nucleotides. Indeed,
the comparison of the same samples indicated that results differed according to whether
enrichment was achieved by digestion with nuclease P1 or by extraction in pure butanol
(Harvey et al. 1999; Venier and Zampieron 2005).
As a whole, these data validate the measurement of DNA adducts in fish as a dosimetry
biomarker of exposure to genotoxic pollutants. The levels of hepatic DNA adducts correlate
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