Biology Reference
In-Depth Information
addition of more than one reference site into any comparative study (Hanson et al. 2010),
however superficially attractive, has significant resource implications (Amiard-Triquet and
Rainbow 2009). An alternative to the use of multiple reference sites may be to use historical
data (Hanson et al. 2010). However, special attention must be paid to the fact that historical
data may include temporal variations such as those due to global warming or increasing
input of emerging contaminants.
16.2.4 Use of Modeling to Establish Baseline Values of Biomarkers
Is it possible to be free from the need for a reference site(s) by determining a baseline for
comparison, as for example, for chemical concentrations in bivalves used in Mussel Watch
program?
OSPAR documents prepared with assistance of the International Council for the
Exploration of the Sea provide a number of baseline values determined in samples from
reference sites such as for MT and EROD in fish liver, δ-aminolevulinic acid dehydratase
in fish blood, and lysosomal stability (OSPAR Commission 2007). For vitellogenin (VTG)
in male fish or Scope for Growth (SfG), provisional background values are indicated. More
recently (OSPAR 2011), the question of baseline values has been examined for AChE activ-
ity, frequency of micronuclei, and DNA damage determined by using the Comet assay.
It does seem preferable to assess the normal physiological ranges of biomarkers at refer-
ence sites. Accordingly, Xuereb et al. (2009a) determined a AChE basal activity of 8.4 nmol
min −1 for the amphipod Gammarus fossarum (male with a weight ranging from 15 to 20 mg),
corresponding to the AChE annual mean value obtained for the Morcille River, France, a
station unimpacted by anthropogenic activities. In the absence of any significant seasonal
effect on G. fossarum AChE activity, the maximal and minimal threshold values were 7.4
and 9.5 nmol min −1 , corresponding to the 95% confidence intervals. Thus, a mean AChE
activity lower than the minimal threshold value could be interpreted as resulting from a
neurotoxic effect. A similar approach was used to assess the value of the base level of DNA
damage measured using the Comet assay in adult male amphipods originating from four
sites located upstream of contaminant sources. From all experiments, a mean value of 3.1%
(95% confidence interval, 2.7-3.6% tail DNA) was determined (Lacaze et al. 2011a). This
low range results from the lack of significant spatial and temporal variations in the DNA
damage level. Deviation from the mean of four different sites on the Swedish Baltic coast
with low anthropogenic impact was established for a large number of biomarkers (blood
variables, VTG in male plasma, EROD, and glutathione reductase in liver) determined in
perch Perca fluviatilis (Hanson et al. 2010).
Hagger et al. (2010) investigated the seasonal responses of a battery of biomarkers Neutral
Red Retention (NRR, heart rate, feeding rate) at different levels of biological organization
in mussels Mytilus edulis collected from a reference estuary in Devon, UK. By integrating
biomarker responses in a biomarker response index and creating an index of health, these
authors consider that it is possible to limit the natural variability of individual responses.
To improve water quality biomonitoring by using in situ feeding assays, attempts at
modeling the influence of confounding factors were recently made following on from the
previous work of Maltby et al. (2002) or Moreira et al. (2006). The influence of natural fac-
tors (body size, temperature, and conductivity for G. fossarum studied by Coulaud et al.
2011; temperature, salinity, and sediment grain size for Hydrobia ulvae tested by Krell et
al. 2011) were first quantified under laboratory conditions. Then, it is possible to test the
influence of each factor by using classical statistical models (multiple regression model,
analysis of variance), and to evaluate the suitability of the model by comparing feeding
Search WWH ::




Custom Search