Marine Ecosystems under Toxic Pressure - Vulnerability of Coastal Ecosystems and Adaptation - page 13

1.3.2. On an individual level
Disturbance in cellular physiology generally manifests itself by the
effects on the survival, growth, reproduction and indeed the behavior
of individuals. It is also at an individual level that contamination
occurs. This does not depend only on the chemical form of the
contaminants, from which it has wrongly been thought possible to
define “the” bioavailability [GOU 13], but above all on the specific
details of an individual's life history.
1.3.2.1. How specific and individual variability influences
contamination
The biological and ecological characteristics of individuals are
implicated at all stages of the contamination process and the biological
response: exposure, absorption, elimination and eventual
compensation for the product's effects. In the first place, the duration
of contact between the organism and contaminated environment
depends on the number and duration of the developmental stages
undergone during the lifecycle, as well as the presence of defense
mechanisms over the course of this cycle [SPR 05]. The habitat and
feeding method determine the organism's behavior and influence its
level of exposure [KOI 92].
The biological and ecological characteristics of species are
moreover involved in the kinetics of the organism's contamination
[ESC 02]. In effect, the speed at which a contaminant is absorbed
depends on the intensity of the exchanges between the organism and
its environment. This absorption speed can be described using food
assimilation rates [CAN 02] and the exchange surface between the
organism and environment. This exchange surface is generally
represented by the ratio between the surface of the body and its
volume (S/V) [ESC 02]. In this ratio, assessment of the body surface
takes account of the toxin's different absorption routes: the
integument, the digestive tract and the respiratory surfaces [WEI 04].
For two organisms of similar size, the higher the S/V ratio, the more
rapid the kinetics of the toxin's absorption [KOI 92]. In practice, it is,
therefore, mainly the mode of feeding and the respiratory system (gills